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Background: Diffusion tensor imaging (DTI) parameters correlate with muscle fiber composition, but it is unclear how these relate to in vivo contractile function. Purpose: To determine the relationship between DTI parameters of the vastus lateralis (VL) and in vivo knee extensor contractile. Methods: Thirteen healthy, premenopausal women underwent magnetic resonance imaging of the mid‐thigh to determine patellar tendon moment arm length and quadriceps cross‐sectional area. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of the VL were determined using diffusion tensor imaging (DTI). Participants underwent an interpolated twitch (ITT) experiment before and after a fatiguing concentric‐eccentric isokinetic knee extension (60°·s−1). During the ITT, supramaximal electrical stimuli were delivered to elicit twitch responses from the knee extensors before, during, and after a maximal voluntary isometric contraction (MVIC). Knee extensor‐specific tension during twitch and MVIC were calculated from isometric torque data. Pearson's correlations were used to determine the relationship between muscle contractile properties and DTI parameters. Results: MD and RD were moderately correlated with peak twitch force and rate of force development. FA and AD were moderately inversely related to percent change in MVIC following exercise. Conclusion: MD and RD are associated with in vivo quadriceps twitch properties but not voluntary strength, which may reflect the mechanical properties of constituent fiber types. FA and AD appear to relate to MVIC strength following fatiguing exercise. [ABSTRACT FROM AUTHOR]

Studies have reported that a stiff triceps surae muscle and tendonaponeurosis and also a more compliant quadriceps muscle and tendon-aponeurosis, are related to lower oxygen cost during running. However, to date, no study has investigated in a single experiment how oxygen cost during running is related to the stiffness of the free tendons (Achilles tendon, patellar tendon) and all the superficial muscles of two major muscle groups for running (i.e., quadriceps, triceps surae). Thus, 17 male trained runners/triathletes participated in this study and visited the laboratory on three occasions. On the first day, the participants were familiarized with the tests. On the second day, the passive compression stiffness of the triceps surae muscle (i.e., gastrocnemii), Achilles tendon, quadriceps muscle (i.e., vastii, rectus femoris), and patellar tendon was non-invasively measured using a digital palpation device (MyotonPRO). In addition, an incremental test was applied to test the VO2max of the participants. Thereafter, in the third visit, after at least 48-h of rest, participants performed a 15-min run on the treadmill with a speed reflecting a velocity of 70% VO2max, to assess oxygen costs during running. The Spearman correlation showed a significant negative correlation between passive Achilles tendon compression stiffness and running oxygen consumption, with a large effect size (rρ = -0.52; CI (95%) -0.81 to -0.33; P = 0.03). Moreover, no further significant relationship between oxygen cost during running and the passive compression stiffness of the quadriceps muscle and patellar tendon, as well as the triceps surae muscle, was detected. The significant correlation indicates that a stiffer passive Achilles tendon can lead to a lower oxygen cost during running. Future studies will have to test the causality of this relationship with training methods such as strength training that are able to increase the Achilles tendon stiffness. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of plyometric training on vastus lateralis (VL) and patellar tendon size, quadriceps isokinetic strength, and vertical jump height in adolescent female volleyball players. Thirty players (age mean ± SD: 15.7 ± 1.1 years) participated in a 6-week Sportsmetrics™ plyometric training program. VL thickness, echo intensity, and patellar tendon cross-sectional area were assessed by real-time ultrasound. Isokinetic quadriceps strength and vertical jump were assessed. The VL thickness, quadriceps strength, and VJ height increased and VL–echo intensity decreased after training. We recommended that 6-week Sportmetrics plyometric training program may be implemented in adolescent female volleyball programs especially before the beginning of the volleyball season. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to examine the effects of Kinesio taping (KT) on delayed onset muscle soreness. Design: Randomized controlled study. Setting: Clinical laboratory. Participants: Fifty-four nonathletic volunteers were assigned randomly to KT (n = 27) and placebo KT (n = 27) groups. Interventions: The intense exercise protocol consisted of 100 consecutive drop jumps from a 0.60-m-high platform. Kinesio tape was applied with the fan technique on the quadriceps muscles in the KT group. The placebo KT group received the Kinesio tape with no technique and tension. Main Outcome Measure: Muscle soreness, maximal isometric quadriceps muscle strength, vertical jump height, and blood analyses (creatine kinase, lactate dehydrogenase, myoglobin, and C-reactive protein) were measured preexercise, immediately postexercise, 48 hours postexercise, and 72 hours postexercise. Results: There was a significant effect of time in all outcome measures (P < .05) except serum C-reactive protein level (P > .05). The intensity of muscle soreness was significantly lower in the KT group relative to the placebo KT group at 72 hours postexercise (P = .01). The serum creatine kinase level was significantly higher in the KT group compared with the placebo KT group at 72 hours postexercise (P = .01). There were no statistically significant differences between groups for the other outcome measures (P > .05). Conclusions: These findings indicate that KT intervention following the intense exercise protocol reduced muscle soreness. However, it had no effect on maximal quadriceps isometric strength and vertical jump height or serum lactate dehydrogenase, myoglobin, and C-reactive protein levels. Furthermore, KT application after intense exercise also increased serum creatine kinase levels. [ABSTRACT FROM AUTHOR]

Purpose: To assess pacing strategies using prescribed and self-selected interset rest periods and their influence on performance in strength-trained athletes. Methods: A total of 16 strength-trained male athletes completed 3 randomized heavy strength-training sessions (5 sets and 5 repetitions) with different interset rest periods. The interset rest periods were 3 min (3MIN), 5 min (5MIN), and self-selected (SS). Mechanical (power, velocity, work, and displacement), surface electromyography (sEMG), and subjective (rating of perceived exertion) and readiness-to-lift data were recorded for each set. Results: SS-condition interset rest periods increased from sets 1 to 4 (from 207.52 to 277.71 s; P =.01). No differences in mechanical performance were shown between the different interset rest-period conditions. Power output (210 W; 8.03%) and velocity (0.03 m-s-1; 6.73%) decreased as sets progressed for all conditions (P<.001) from set 1 to set 5. No differences in sEMG activity between conditions were shown; however, vastus medialis sEMG decreased as the sets progressed for each condition ( 1.75%; P = .005). All conditions showed increases in rating of perceived exertion as sets progressed (set 1 =6.1, set 5 = 7.9; P< .001). Participants reported greater readiness to lift in the 5MIN condition (7.81) than in the 3MIN (7.09) and SS (7.20) conditions (P < .001). Conclusions: Self-selecting interset rest periods does not significantly change performance compared with 3MIN and 5MIN conditions. Given the opportunity, athletes will vary their interset rest periods to complete multiple sets of heavy strength training. Self-selection of interset rest periods may be a feasible alternative to prescribed interset rest periods. [ABSTRACT FROM AUTHOR]

Background: Carbohydrate (CHO) mouth rinse (MR) before exercise has been shown to improve physical performance and corticospinal motor excitability. Purpose: To determine the effects of different forms of CHO MR on quadriceps muscle performance and corticospinal motor excitability. Methods: 10 subjects (5 female and 5 male; 25 [1] y, 1.71 [0.03] m, 73 [5] kg) completed 4 conditions (placebo [PLA], 6.4% glucose [GLU], 6.4% maltose [MAL], 6.4% maltodextrin [MDX]). Maximal voluntary contraction (M VIC) of the right quadriceps and motor-evoked potential (MEP) of the right rectus femoris was determined pre (10 min), immediately after, and post (10 min) 20-s MR. MEP was precipitated by transcranial magnetic stimulation during muscle contraction (50% MVIC). Results: The relative change in MEP from pre-measures was different across treatments (P = .025) but was not different across time (P = .357). MEP was greater for all CHO conditions immediately after (GLU = 2.58% [5.33%], MAL = 3.92% [3.90%], MDX = 18.28% [5.57%]) and 10 min after (GLU = 14.09% [13.96%], MAL = 8.64% [8.67%], MDX = 31.54% [12.77%]) MR than PLA (immediately after = -2.19% [4.25%], 10min = -13.41% [7.46%]). MVC was greaterfor CHO conditions immediately (GLU = 3.98% [2.49%], MAL = 5.89% [2.29%], MDX = 7.66% [1.93%]) and 10 min alter (GLU = 7.22% [2.77%], MAL = 10.26% [4.22%], MDX= 10.18% [1.50%]) MR than PLA (immediately after = -3.24% [1.50%], 10 min = -6.46% [2.22%]). Conclusions: CHO MR increased corticospinal motor excitability and quadriceps muscle after application. The form of CHO used did not influence this response. [ABSTRACT FROM AUTHOR]

Obtaining true maximum voluntary excitation appears to be more difficult in older populations than in young populations. The aims of this study were (1) to determine whether differences in maximum voluntary excitation obtained from maximum voluntary isometric contraction (MVIC) and (sub-)maximum voluntary dynamic contraction [(s-)MVDC] are age dependent, and (2) to determine how normalizing electromyographic signals to corresponding maximum voluntary excitations affects variance between participants and the likelihood of normalized signals exceeding 100%. MVIC, s-MVDC, and MVDC were recorded in 10 young women, and MVIC and s-MVDC were recorded in 19 older women. A significant age × contraction mode interaction effect was found for vastus lateralis (P =.04). In young women, MVDC elicited the highest maximum voluntary excitation for vastus lateralis and rectus femoris (P <.05). In older women, no differences in maximum voluntary excitation were found (P >.05). Normalization to dynamic contractions resulted in lower between-participant variance of electromyography amplitudes, though not for all muscles, and decreased the number of normalized signals exceeding 100% in young women. These findings indicate that differences in maximum voluntary excitation across contraction modes are age dependent. Therefore, one should be cautious when comparing normalized signals between age groups; however, overall dynamic contractions may be preferable over isometric contractions for normalization purposes. [ABSTRACT FROM AUTHOR]

Context: Reductions in objectively measured moderate to vigorous physical activity (MVPA) have been reported among individuals with anterior cruciate ligament reconstruction (ACLR). Self-reported measures of physical activity are commonly used to assess participation in physical activity after ACLR despite the lack of evidence to support the validity of such measures within this population. Objective: The objective of this research was to determine the relationships between objectively measured MVPA, self-reported physical activity, and knee function among individuals with ACLR. Setting: University laboratory. Patients (or Other Participants): Thirty-one participants with a history of ACLR (sex: 23 females and 8 males; age = 19.8 [1.4] y) and 31 matched controls (sex: 23 females and 8 males; age = 20.6 [1.7] y) enrolled in this study. Intervention(s): None. Main Outcome Measures: Participants completed self-reported physical activity using the Tegner Activity Scale and the Marx Activity Rating Scale. Participant MVPA was objectively measured using an ActiGraph wGT3X-BT accelerometer for a 7-day period during which the monitor was worn for not less than 10 hours per day. Primary outcome measures were the amount of time spent in MVPA (minutes per week) and time spent in MVPA performed in bouts of ≥10 minutes (minutes per week). Relationships between the Tegner Activity Score, Marx Activity Rating Scale, and objectively measured MVPA variables were assessed using partial Spearman's rank correlation coefficients after controlling for activity monitor wear time. Results: There were no significant relationships between objectively measured MVPA and self-reported physical activity (ρ ≤ 0.31, P ≥.05) or self-reported knee-related function (ρ ≤.41, P ≥.05) among ACLR participants. Conclusions: Objectively measured physical activity is not significantly related to self-reported physical activity or self-reported knee function among individuals with a history of ACLR. Consideration of objective and self-reported physical activity within this population may provide key insights into disconnects between perception and the reality of physical activity engagement following ACLR. [ABSTRACT FROM AUTHOR]

Context: Postoperative rehabilitation is critical to optimize outcomes after anterior cruciate ligament reconstruction (ACLR). However, the relationship between physical therapy (PT) and clinical outcomes is unclear. Objective: To describe PT characteristics following ACLR and to assess the relationships between PT characteristics, surgical procedure, and clinical outcomes. Design: Cross-sectional. Setting: Laboratory. Patients (or Other Participants): A total of 60 patients (31 females/29 males, age = 22.4 [9.2] y, height = 171.7 [9.9] cm, and mass = 70.2 [14.7] kg) with a history of primary unilateral ACLR (53.6% patellar tendon and 46.4% hamstring) participated. Intervention(s): Patients completed a performance assessment and rated subjective knee function prior to physician clearance (mean = 6.3 [1.3] mo postoperatively) and were contacted within 6 months of clearance to complete a PT questionnaire. Main Outcome Measures: PT questionnaire item response, knee extension maximum voluntary isometric contraction (MVIC) torque, peak isokinetic knee extension torque, single leg hop distance, and International Knee Documentation Committee were measured. Correlations assessed relationships between PT quantity and clinical outcomes. Independent t tests compared PT quantity and clinical outcomes based on return-to-sport status, readiness to return to sport, and surgical procedure. Results: Patients completed regular PT (2 d/wk, 25 wk, 58 visits) and were most likely to conclude when discharged by the therapist (68.3%). More than half (56.7%) returned to sport, yet most (73.3%) felt unready at discharge. Isokinetic torque was correlated with days of PT/week (r =.29, P =.03). Isokinetic torque and hop symmetry were reduced in patients who returned to sport (P <.05). Patients who felt ready to return completed fewer weeks of PT (P <.05). Patients with a patellar tendon graft completed more days of PT/week and total visits, but demonstrated lower MVIC torque, MVIC symmetry, and isokinetic symmetry (P <.05). Conclusions: Many patients felt unready to return to sport at PT discharge. PT frequency was associated with isokinetic torque, yet this relationship was small. Outcomes were reduced in patients who returned to sport, suggesting premature resumption of preinjury activity. [ABSTRACT FROM AUTHOR]

It is unknown if higher antagonist muscle coactivation is a factor contributing to greater energy expenditure of cycling in older adults. We determined how age, power output, and cadence affect energy expenditure and lower limb antagonist muscle coactivation during submaximal cycling. Thirteen younger and 12 older male participants completed 6-min trials at four power output-cadence conditions (75 W-60 rpm, 75 W-90 rpm, 125 W-60 rpm, and 125 W-90 rpm) while electromyographic and metabolic energy consumption data were collected. Knee and ankle coactivation indices were calculated using vastus lateralis, biceps femoris, gastrocnemius, and tibialis anterior electromyography data. Energy expenditure of cycling was greater in older compared with younger participants at 125 W (p =.002) and at 90 rpm (p =.026). No age-related differences were observed in the magnitude or duration of coactivation about the knee or ankle (p >.05). Our results indicated that the knee and ankle coactivation is not a substantive factor contributing to greater energy expenditure of cycling in older adults. [ABSTRACT FROM AUTHOR]

Context: Whole-body vibration (WBV) has been widely used in clinical and sport practice. These devices produce constant vibrations, originating symmetrical waves that move along the vertical axis. It is suggested that mechanical stimuli produced by high vibration can be an alternative to improve neuromuscular performance and balance in different populations. However, there is still a lack of consensus in the literature regarding neurophysiological responses in the skeletal muscle immediately after the use of WBV, specifically in individuals subjected to anterior cruciate ligament reconstruction. Objective: To investigate the immediate effects of WBV on neuromuscular performance of the quadriceps femoris and postural oscillation of individuals subjected to anterior cruciate ligament reconstruction. Design: This is a blinded randomized controlled trial. Setting: University laboratory. Participants: Forty-four men. Intervention: Participants were randomized into 2 groups: control group (n = 22, exercise protocol on the vibrating platform turned off) and WBV group (n = 22, exercises on the vibrating platform turned on, at a frequency of 50 Hz and amplitude of 4 mm). Main Outcome Measures: The volunteers underwent a dynamometric evaluation of the quadriceps femoris and electromyographic activity of vastus lateralis and vastus medialis muscles, in addition to oscillation of the center of pressure at 2 different moments: before and immediately after the intervention protocol. Results: The intragroup comparison evidenced differences between preassessments and postassessments for the variables of laterolateral amplitude, peak torque, and total work. However, no significant difference was observed in the intergroup comparison after WBV protocol. Conclusion: The use of WBV did not immediately alter the performance of the quadriceps femoris and the electromyographic activity of vastus lateralis and vastus medialis muscles. In addition, it also did not interfere with pressure center oscillation of individuals subjected to anterior cruciate ligament reconstruction. [ABSTRACT FROM AUTHOR]

Purpose: To compare the concentric and eccentric training effects on fatigue induced by eccentric and concentric protocols. Methods: A total of 22 men and women (22 [3.6] y) were assigned to concentric (GCON, n = 11) or eccentric training (GECC, n = 11). The concentric (CON) and eccentric (ECC) protocols were composed of 4 sets of 20 knee-extension/flexion repetitions. Force losses were analyzed by comparing 10 repetitions' mean torques during the protocols and by verifying the maximal voluntary contraction and rate of torque development before and after the protocols. Muscle damage was assessed using echo intensity of the vastus lateralis 48 h after the protocols. Training consisted of 6 wk of isokinetic exercise at 60°/s (concentric or eccentric) twice weekly. Results: Before training, both protocols resulted in dynamic and isometric force losses in GCON and GECC (P <.01), but the magnitude was greater after the CON protocol than after the ECC protocol (P <.001). After training, both GCON and GECC showed similar force decreases during the CON and ECC protocols (P <.01), and these changes were not different from the pretraining decreases. Regarding maximal voluntary contraction after training, GECC showed lower force decreases than GCON after ECC exercise (−13.7% vs −22.3%, respectively, P <.05), whereas GCON showed lower maximal voluntary contraction decreases after CON exercise compared with pretraining (−29.2%, P <.05). Losses in rate of torque development were similar after the protocols before and after the training regimens. No changes in echo intensity were observed after the protocols before and after training. Conclusion: Both interventions resulted in similar force decreases during fatigue protocols compared with those associated with pretraining. [ABSTRACT FROM AUTHOR]

Purpose: To investigate different sport-field properties' influence on muscle-recruitment patterns and metabolic response during a series of running and agility drills. Methods: Eleven male athletes were fitted with a standard multipurpose training shoe. The test protocol consisting of 4 high-intensity trials with 60-s rests between trials performed on 2 fields with different properties. Time-dependent field properties were measured using the American Standards for Testing and Materials protocol (F-1936). A 30-m pretest and posttest sprint determined fatigue and player performance. Electromyography (EMG) recorded muscle activity for vastus medialis, biceps femoris, gastrocnemius medial head, and tibialis anterior, and metabolic activity analyzed maximal oxygen consumption, heart rate, respiratory exchange ratio, metabolic equivalent, and energy expenditure. Results: A difference was calculated for muscle activity across trials (P =.01) for both surfaces. Muscle activity was <13% on the field with less energy return (P =.01). Metabolic components (maximal oxygen consumption, heart rate, respiratory exchange ratio, metabolic equivalent, and energy expenditure) were significantly different across trials (P =.01) but not significantly different between fields. The participants completed the agility course (5.2%) faster on the field with greater energy return, while caloric expenditure was similar between fields. Conclusions: The findings indicate that field mechanical properties influence muscle-activation patterns. The field demonstrating the greatest magnitude of energy return produces the lowest sprint and agility course times; however, performing on a field exhibiting unfamiliar mechanical properties could cause the athlete to produce atypical movement patterns that might contribute to overuse of the neuromuscular system. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates the effects of normobaric hypoxia on repeated sprint exercise (RSE) with different balance between oxidative (phosphocreatine and oxidative pathway) and glycolytic contributions. Therefore, performance and psychophysiological responses were compared during RSE to exhaustion with the same exercise-to-rest ratio (1:2) but different sprint durations (5, 10, or 20 s) either in normoxic (RSN) or hypoxic (RSH; F io 2 = 0.13) conditions. Methods: On separate visits, 10 active participants completed in random order three cycling RSN (5:10; 10:20 and 20:40) and three similar RSH sessions to exhaustion. Vastus lateralis muscle oxygenation was recorded by near-infrared spectroscopy. Blood lactate concentration, limb and breathing discomfort, and ratings of perceived exertion were measured. Results: Total sprint number was smaller in hypoxia than in normoxia for 5:10 (20.8 ± 8.6 vs 14.7 ± 3.4; P = 0.014) and 10:20 (13.7 ± 6.3 vs 8.8 ± 2.5; P = 0.018) but not 20:40 (5.6 ± 1.9 vs 5.6 ± 2.5). The fatigue index was larger in hypoxia only for 5:10 (−43.5%, P < 0.001). Irrespective of condition, blood lactate concentration increased with the sprint duration with higher values for 20:40 than 5:10 (13.1 ± 2.7 vs 11.5 ± 2.2 mmoL·L−1; P = 0.027). Limb and breathing discomfort and ratings of perceived exertion did not differ in all RSE. Muscle oxygenation was mainly impacted by sprint duration (i.e., main effect of sprint duration on [HHb] min, [tHb] max, Δ[HHb], and Δ[tHb]) but not by hypoxia. The normoxia-to-hypoxia percentage decrease for total sprint number for 5:10 was correlated with the highest power output over 5 s (R 2 = 0.55; P = 0.013) and 10 s (R 2 = 0.53; P = 0.016). Conclusions: Hypoxia impairs repeated sprint ability when the oxidative but not the glycolytic contribution is substantial. The oxidative–glycolytic balance, influenced partly by sprint duration, is key during repeated sprint in hypoxia. [ABSTRACT FROM AUTHOR]

Walking and running are based on rapid burst‐like muscle contractions. Burst‐like contractions generate a Gaussian‐shaped force profile, in which neuromuscular determinants have never been assessed. We investigated the neural and contractile determinants of the rate of force development (RFD) in burst‐like isometric knee extensions. Together with maximal voluntary force (MVF), voluntary and electrically evoked (8 stimuli at 300 Hz, octets) forces were measured in the first 50, 100, and 150 ms of burst‐like quadriceps contractions in 24 adults. High‐density surface electromyography (HDsEMG) was adopted to measure the root mean square (RMS) and muscle fiber conduction velocity (MFCV) from the vastus lateralis and medialis. The determinants of voluntary force at 50, 100, and 150 ms were assessed by stepwise multiple regression analysis. Force at 50 ms was explained by RMS (R2 = 0.361); force at 100 ms was explained by octet (R2 = 0.646); force at 150 ms was explained by MVF (R2 = 0.711) and octet (R2 = 0.061). Peak RFD (which occurred at 60 ± 10 ms from contraction onset) was explained by MVF (R2 = 0.518) and by RMS50 (R2 = 0.074). MFCV did not emerge as a determinant of RFD. Muscle excitation was the sole determinant of early RFD (50 ms), while contractile characteristics were more relevant for late RFD (≥100 ms). As peak RFD is mostly determined by MVF, it may not be more informative than MVF itself. Therefore, a time‐locked analysis of RFD provides more insights into the neuromuscular characteristics of explosive contractions. [ABSTRACT FROM AUTHOR]

Background: Noncontact anterior cruciate ligament (ACL) injuries typically occur during deceleration movements such as landing or cutting. However, conflicting data have left the kinematic mechanisms leading to these injuries unclear. Quantifying the influence of sagittal and coronal plane knee kinematics on in vivo ACL strain may help to elucidate noncontact ACL injury mechanisms. Purpose/Hypothesis: The purpose of this study was to measure in vivo sagittal and coronal plane knee kinematics and ACL strain during a single-leg jump. We hypothesized that ACL strain would be modulated primarily by motion in the sagittal plane and that limited coronal plane motion would be measured during this activity. Study Design: Descriptive laboratory study. Methods: Seventeen healthy participants (8 male/9 female) underwent magnetic resonance imaging (MRI) followed by high-speed biplanar radiography, obtained as participants performed a single-leg jump. Three-dimensional models of the femur, tibia, and associated ACL attachment site footprints were created from the MRIs and registered to the radiographs to reproduce the position of the knee during the jump. ACL strain, knee flexion/extension angles, and varus/valgus angles were measured throughout the jump. Spearman rank correlations were used to assess relationships between mean ACL strain and kinematic variables. Results: Mean ACL strain increased with decreasing knee flexion angle (ρ = −0.3; P =.002), and local maxima in ACL strain occurred with the knee in a straight position in both the sagittal and the coronal planes. In addition, limited coronal plane motion (varus/valgus angle) was measured during this activity (mean ± SD, −0.5°± 0.3°). Furthermore, we did not detect a statistically significant relationship between ACL strain and varus/valgus angle (ρ = −0.01; P =.9). Conclusion: ACL strain was maximized when the knee was in a straight position in both the sagittal and coronal planes. Participants remained in <1° of varus/valgus position on average throughout the jump. As a ligament under elevated strain is more vulnerable to injury, landing on a straight knee may be an important risk factor for ACL rupture. Clinical Relevance: These data may improve understanding of risk factors for noncontact ACL injury, which may be useful in designing ACL injury prevention programs. [ABSTRACT FROM AUTHOR]

The objective of this investigation was to compare isokinetic strength, countermovement jump and drop jump variables between high-contributors and low-contributors within NCAA Division I Men's and Women's lacrosse athletes. Men's (N=36) and Women's (N=30) NCAA Division I lacrosse athletes completed strength testing of the quadriceps and hamstring across three speeds (60°·s−1 , 180°·s−1 , 300°·s−1), countermovement and drop jumps. To determine the discriminative ability of select lower-limb strength and power characteristics participants were categorized as high-contributors (Males N=18, age=20.3±0.4 yrs, height=183.9±5.5 cm, mass=90.8±5.8 kg; Females N=15, age=20.8±0.8 yrs, height=169.3±6.7 cm, mass=64.1±7.2 kg) or low-contributors (Males N=18, age=19.5±0.2 yrs, height=184.1±5.6 cm; mass=87.9±8.1 kg; Females N=15, age=19.7±0.2 yrs, height=169.8±7.0 cm, mass=62.9±7.7 kg) based upon the number of games the participants competed in during the regular season. Within the male cohort, moderate significant (p<0.05) differences were observed between high-contributors and low-contributors in isokinetic hamstring strength of the left leg at 300°·s−1 (d=0.69) and peak power in countermovement jump (d= 0.68). Within the women's cohort a large (d= 0.87) significant difference (p<0.05) in isokinetic strength of the left hamstring was observed between high-contributors and low-contributors at 60°·s−1. Hamstring strength and lower-limb power are important strength measures for lacrosse performance and should be prioritized in training prescription for lacrosse athletes. [ABSTRACT FROM AUTHOR]

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Objective: Discrepancies in the definition of adductor canal block (ACB) lead to inconsistent results. To investigate the actual analgesic and motor-sparing effects of ACB by anatomically defining femoral triangle block (FTB), proximal ACB (p-ACB), and distal ACB (d-ACB), we re-classified the previously claimed ACB approaches according to the ultrasound findings or descriptions in the corresponding published articles. A meta-analysis with subsequent subgroup analyses based on these corrected results was performed to examine the true impact of ACB on its analgesic effect and motor function (quadriceps muscle strength or mobilization ability). An optimal ACB technique was also suggested based on an updated review of evidence and ultrasound anatomy. Materials and Methods: We systematically searched studies describing the use of ACB for knee surgery. Cochrane Library, PubMed, Web of Science, and Embase were searched with the exclusion of non-English articles from inception to 28 February 2022. The motor-sparing and analgesic aspects in true ACB were evaluated using meta-analyses with subsequent subgroup analyses according to the corrected classification system. Results: The meta-analysis includes 19 randomized controlled trials. Compared with the femoral nerve block group, the quadriceps muscle strength (standardized mean difference (SMD) = 0.33, 95%-CI [0.01; 0.65]) and mobilization ability (SMD = −22.44, 95%-CI [−35.37; −9.51]) are more preserved in the mixed ACB group at 24 h after knee surgery. Compared with the true ACB group, the FTB group (SMD = 5.59, 95%-CI [3.44; 8.46]) has a significantly decreased mobilization ability at 24 h after knee surgery. Conclusion: By using the corrected classification system, we proved the motor-sparing effect of true ACB compared to FTB. According to the updated ultrasound anatomy, we suggested proximal ACB to be the analgesic technique of choice for knee surgery. Although a single-shot ACB is limited in duration, it remains the candidate of the analgesic standard for knee surgery on postoperative day 1 or 2 because it induces analgesia with less motor involvement in the era of multimodal analgesia. Furthermore, data from the corrected classification system may provide the basis for future research. [ABSTRACT FROM AUTHOR]

Purpose: This study examined tissue oxygen saturation (StO2) of the vastus lateralis (VL) muscles of chronic stroke survivors during a graded exercise test (GXT). We hypothesized that the reduction in StO2 will be blunted in the paretic versus nonparetic VL during a maximum effort GXT. Methods: Chronic stroke survivors performed a GXT, and StO2 of the VL in each leg was measured using near-infrared spectroscopy. Twenty-six stroke survivors performed a GXT. Results: At rest, there was no difference in StO2 between the paretic and nonparetic VL (65 ± 9% vs 68 ± 7%, respectively, P =.32). The maximum change in StO2 from rest during the GXT was greater in the nonparetic versus the paretic VL (−16 ± 14% vs −9 ± 10%, respectively, P <.001). The magnitude of the oxygen resaturation response was also greater in the nonparetic versus the paretic VL (29 ± 23% vs 18 ± 15%, respectively, P <.001). VO2 peak was associated with the magnitude of the VL StO2 change during (r2 = 0.54, P <.0001) and after (r2 = 0.56, P <.001) the GXT. Conclusion: During a GXT, there is a blunted oxygen desaturation response in the paretic versus the nonparetic VL of chronic stroke survivors. In the paretic VL, there was a positive correlation between the oxygen desaturation response during the GXT and VO2 peak. [ABSTRACT FROM AUTHOR]

This was a transversal analytical study. Exercise capacity is usually decreased in cystic fibrosis, impacting the disease prognosis. As well, peripheral muscle strength and nutritional status seem to be related to exercise capacity (EC). To verify the relationship between peripheral muscle strength, pulmonary function and body composition with EC in children and adolescents with CF. The study included CF children/adolescents that were clinically stable. The disease's severity was classified according to the Schwachman-Doerschuk score. Initially the subjects underwent bioimpedance and spirometry tests. Quadriceps muscle strength (QMS) and handgrip strength (HG) were evaluated by dynamometry. The Modified Shuttle Walk Test (MSWT) was conducted along with gas analysis in order to measure EC. Twenty-five children/adolescents (10.30 ± 2.33 years old) participated in the survey. 72% were eutrophic, with a mean FEV1 of 68.55%, predicted percentage of the MSWT walked distance (%WD) was 70.91%, and QMS 65.80%. QMS presented significant correlations with absolute WD (r = 0.54), oxygen peak consumption (r = 0.72), lean body mass (LM) (r = 0.83), and body mass index (BMI) (r = 0.69). HG was related with BMI (r = 0.45) and LM (r = 0.65). There was a difference in the %WD between the groups with higher/lower strength (p =.02). There was no correlation between HG and EC in this studied sample. Early involvement of QMS was observed even in individuals with low disease severity. This finding reinforces the importance of including this QMS assessment in CF reference centers to monitor, prevent and prescribe adequate exercise training for these individuals. [ABSTRACT FROM AUTHOR]

Little is known about how chronic unilateral anterior knee pain (AKP) affects bilateral quadriceps function and lower quarter flexibility. To determine if patients with chronic unilateral AKP present bilateral deficits in quadriceps function and lower quarter flexibility. Twenty-two patients with chronic unilateral AKP (pain duration: 48.6 months) and 22 matched healthy controls were evaluated. Pain perception and functional outcomes were obtained. Knee joint and thigh circumferences, quadriceps subcutaneous tissue thickness and function (i.e. maximal and explosive strength, activation, and endurance), and lower quarter flexibility (i.e. hamstrings and iliopsoas/rectus femoris muscle) in both legs were compared across conditions. Knee joint and thigh circumferences, and quadriceps subcutaneous tissue thickness were not different between conditions (P ≥.39). Compared with matched healthy controls, patients with chronic unilateral AKP showed: 1) greater pain perception (0.0 versus 4.4 cm, P <.0001); 2) a lower score for functional outcomes (79.6 versus 53.9, P <.0001); 3) less bilateral quadriceps maximal (3.5 versus 2.8 Nm/kg, P <.0001) and explosive (10.8 versus 8.7 Nm/kg/s, P =.01) strength, activation (0.95 versus 0.83, P <.0001), and endurance (1.66 versus 1.52 Nm/kg, P =.02); and 4) less bilateral hamstrings (86.8 versus 72.6°, P =.002) and iliopsoas/rectus femoris (11.6 versus 7.8°, P <.05) flexibility. Patients with chronic unilateral AKP (without knee joint effusion or quadriceps muscle atrophy) appear to have bilateral deficits in quadriceps function and lower quarter flexibility, which should be addressed with pain reduction. [ABSTRACT FROM AUTHOR]

Purpose: Bone–patellar tendon–bone (BPTB) graft harvest for anterior cruciate ligament reconstruction alters patellar tendon properties, which inflict poor quadriceps neuromuscular function. BPTB autografts are associated with higher rates of posttraumatic osteoarthritis, which in turn is associated with pathological gait. The purpose of this study was to investigate the latency between the time of peak quadriceps activity and the peak knee flexion moment during gait, between those with BPTB grafts (n = 23) and other graft types (hamstring autograft or allografts, n = 54), 5 ± 2 months and 2 yr (25 ± 3 months) after anterior cruciate ligament reconstruction. We hypothesized that longer latencies would be observed in the BPTB graft group in the involved limb. We expected latencies to shorten over time. Methods: Knee moments and quadriceps EMG were collected during gait, and vastus medialis, vastus lateralis, rectus femoris (RF), and quadriceps latencies were calculated. Linear mixed-effects models were used to compare latencies between graft types and over the two time points. Results: The main effects of graft type were observed for vastus medialis (P = 0.005) and quadriceps (P = 0.033) latencies with the BPTB graft group demonstrating longer latencies. No main effects of graft type were observed for vastus lateralis (P = 0.051) and RF (P = 0.080) latencies. Main effects of time were observed for RF latency (P = 0.022). Conclusions: Our hypothesis that the BPTB graft group would demonstrate longer extensor latency was supported. Contrary to our second hypothesis, however, latency only improved in RF and regardless of graft type, indicating that neuromuscular deficits associated with BPTB grafts may persist 2 yr after surgery. Persistent deficits may be mediated by changes in the patellar tendon's mechanical properties. Graft-specific rehabilitation may be warranted to address the long-term neuromechanical deficits that are present after BPTB graft harvest. [ABSTRACT FROM AUTHOR]

It is believed that clinical management of osteoarthritis should address muscle weakness to improve physical function and prevent disability and frailty This sub-study investigated the effects of supervised progressive resistance training (RT), supervised Nordic Walking (NW), and unsupervised home-based exercise (HBE) on muscle and functional performance; and associations between these exercise-induced changes in persons with hip osteoarthritis. Forty-two patients with hip osteoarthritis were recruited from a larger RCT (NCT01387867). All the groups (RT, n = 15; NW, n = 12; HBE, n = 15) exercised 1 h 3 times/week for 4 months. Quadriceps cross-sectional area (QCSA, MRI-determined); quadriceps strength (QMVC); leg extensor power (LEP); functional performance (chair stands (30sCS); stair climbs (TSC); and 6-minute walk (6MWT)) were assessed at baseline and 4 months. Per protocol analyses (one-way ANOVA and Bonferroni test) showed significant between-group differences for improvements in QCSA in the most symptomatic leg favoring RT versus NW (2.3 cm2, 95% CI [0.6, 3.9]) and HBE (2.3 cm2 [0.8, 3.9]); and 30sCS (1.8 repetitions [0.2–3.3]), and 6MWT (35.1 m [3.5–66.7]) favoring NW versus HBE. Associations existed between exercise-induced changes in QCSA and QMVC (r = 0.366, p =.019) for the most symptomatic leg and between changes in 6MWT and QMVC (r = 0.320, p =.04) and LEP (r = 0.381, p =.01), respectively, for the least symptomatic leg. Resistance training appeared effective for improving muscle mass, but less effective for improving muscle strength, power, and functional performance. Only exercise-induced changes in muscle strength and power of the least symptomatic leg, not the most symptomatic leg, were related to changes in functional performance. [ABSTRACT FROM AUTHOR]

Foam rolling (FR) is a practice that has increased in popularity before and after resistance training. The purpose of this study was to compare the acute effects of different foam rolling periods for the lower body muscles on subsequent performance, myoelectric activity and rating of perceived exertion in trained men. Fourteen men (26.2 ± 3.2 years, 178 ± 0.04 cm, 82.2 ± 10 kg and body mass index 25.9 ± 3.3kg/m-2) volunteered for this study. Four repetition maximum (4-RM) loads were determined for hexagonal bardeadlift and 45°- angled leg press during test and retest sessions over two nonconsecutive days. The experimental conditions included a traditional protocol (TP) with no prior foam rolling, and four other conditions that involved FR applied to the quadriceps, hamstrings and triceps surae for one set of 30 sec (P1), two sets of 30 sec (P2), three sets of 30 sec (P3), or four sets of 30 sec (P4).The resistance training consisted of five sets with 4-RM loads. The number of repetitions completed, the myoelectric activity of lower limbs were recorded, as well as the rating of perceived exertion for each protocol. There were no differences between the protocols in the total repetitions for the hexagonal bar deadlift and 45° angled leg press exercises. Similar results between protocols were also noted for muscle activity and rated perceived exertion (RPE). Therefore, the results of the present study indicated that the FR didn't provide effects on performance, myoelectric activity and rating of perceived exertion responses during high intensity resistance performance for lower limb exercises. [ABSTRACT FROM AUTHOR]

Aims: To evaluate changes in the bioelectrical activity of thigh muscles in concentric and eccentric movements of a sit-to-stand test in women with knee osteoarthritis after a preoperative home exercise program (HEP). Secondly, to compare patients with healthy controls. Methods: Seventeen women with knee osteoarthritis and ten healthy controls participated. The bioelectrical activity of thigh muscles during sit-to-stand test and isometric maximal voluntary contraction force of leg extensor muscles were measured. Results: Post-HEP, the knee osteoarthritis group demonstrated lower bioelectrical activity of antagonist muscles in the concentric and eccentric movements, and reduced asymmetry in muscle activation between limbs. Poorer results were noted compared to controls pre-and post-HEP. Conclusions: In knee osteoarthritis patients, the bioelectrical activity of thigh muscles during the sit-to-stand test improves after eight weeks of preoperative HEP. Preoperative HEP reduces co-activation of thigh muscles and activation asymmetry between limbs in concentric and eccentric movements of a sit-to-stand task. [ABSTRACT FROM AUTHOR]

In this paper, a real-time knee extension monitoring and rehabilitation system for people, such as patients, the elderly, athletes, etc., is developed and tested. The proposed system has three major functions. The first function is two-channel surface electromyography (EMG) signal measurement and processing for the vastus lateralis (VL) and vastus medialis (VM) muscles using a developed EMG device set. The second function is the knee extension range of motion (ROM) measurement using an angle sensor device set (i.e., accelerometer sensor). Both functions are connected and parallelly processed by the NI-myRIO embedded device. Finally, the third function is the graphical user interface (GUI) using LabVIEW, where the knee rehabilitation program can be defined and flexibly set, as recommended by physical therapists and physicians. Experimental results obtained from six healthy subjects demonstrated that the proposed system can efficiently work with real-time response. It can support multiple rehabilitation users with data collection, where EMG signals with mean absolute value (MAV) and root mean square value (RMS) results and knee extension ROM data can be automatically measured and recorded based on the defined rehabilitation program. Furthermore, the proposed system is also employed in the hospital for validation and evaluation, where bio-feedback EMG and ROM data from six patients, including (a) knee osteoarthritis, (b) herniated disc, (c) knee ligament injury, (d) ischemic stroke, (e) hemorrhagic stroke, and (f) Parkinson are obtained. Such data are also collected for one month for tracking, evaluation, and treatment. With our proposed system, results indicate that the rehabilitation people can practice themselves and know their rehabilitation progress during the time of testing. The system can also evaluate (as a primary treatment) whether the therapy training is successful or not, while experts can simultaneously review the progress and set the optimal treatment program in response to the rehabilitation users. This technology can also be integrated as a part of the Internet of Things (IoT) and smart healthcare systems. [ABSTRACT FROM AUTHOR]

This study examined the effects of gaze fixation and different kinds of smooth-pursuit eye movements on the trunk and lower extremity muscle activities and center of pressure. Methods: Twenty-four subjects were selected for the study. The activity of trunk and lower limb muscles (tibialis anterior, lateral gastrocnemius, medial gastrocnemius, vastus midialis obliques, vastus lateralis, biceps femoris, rectus abdominis, and erector spinae) and the COP (center of pressure) (surface area ellipse, length, and average speed) were measured to observe the effects of gaze fixation and different kinds of smooth-pursuit eye movements on the center of pressure and muscle activities during one leg standing. Before the experiment, a Gaze point GP3 HD Eye Tracker (Gazept, Vancouver, BC, Canada) was used to train eye movement so that the subjects would be familiar with smooth eye movement. Repeated each exercise 3 times at random. In order to avoid the sequence deviation caused by fatigue, the movement sequence is randomly selected. Result: The center of pressure and muscle activities were increased significantly when the smooth-pursuit eye movement with one leg standing compared with gaze fixation with one leg standing. In smooth-pursuit eye movements, the changes in the center of pressure and muscle activities were increased significantly with eye and head movement. When the head and eyes moved in opposite directions, the center of pressure and muscle activities were increased more than with any other exercises. Conclusion: Smooth-pursuit eye movement with one leg movement affects balance. In particular, in the smooth-pursuit eye movement with one leg standing, there were higher requirements for balance when the eyes and head move in the opposite direction. Therefore, this movement can be recommended to people who need to enhance their balance ability. [ABSTRACT FROM AUTHOR]

Introduction: Anterior cruciate ligament (ACL) rupture is one of the most common sport injuries, particularly in women. Objectives: The aim of this study was investigating the interaction between gender and injured limb on the isokinetic ratio of H/Q on both healthy and affected sides in patients with ACL rupture. Study design: This original study was semi-experimental, retrospective, and single blind. Methods: In this study, eighteen athletes (7 women and 11 men) in the ages of 20 to 35 years participated voluntarily. All the participants had the experience of ACL partial tearing more than 6 months, which were symptom-free at the time of our study and they return to full activity by the help of conservative treatment. After warming up, they performed an isokinetic test for knee flexion and extension at a constant speed of 60o per second. Each movement was performed 10 times with three repetitions and the average ratio of hamstrings to quadriceps (H/Q) calculated by the device software was transferred to spss23 software and it was investigated through the statistical test of two-way analysis of variance (α=0.05). Results: In the results of the present study, the H/Q ratio was significantly higher in the affected leg of women and there was a significant difference between the healthy and affected sides in women (P=0.044). However, comparing the healthy and affected legs in men and also the comparison of the healthy leg of men and women and the affected leg of men and women were not significantly different (P>0.05). Conclusion: Perhaps this can be attributed to the feeling of greater instability in the affected knee of women after ACL injury and their greater dependence on ACL. So, women show greater hamstring/quadriceps activity in their affected side to support their injured knee, and also compensate dynamic instability due to ACL deficiency. [ABSTRACT FROM AUTHOR]

Context: The effect of acute static stretching (ASS) on the lower limb reaction time (RT) has been recently questioned to decrease the risk of falling and injuries in situations requiring a rapid reaction, as in the cases of balance disturbance. Objective: The main purpose of this study was to detect the effect of ASS on the lower limb RT using a virtual reality device. Design: Two-group control group design. Setting: Research laboratory. Participants: The control and experimental groups were formed randomly from 60 female university students. Intervention: Each participant in the experimental group was tested before and after ASS for the quadriceps, hamstrings, and planter flexor muscles, and compared with the control group with warming-up exercise alone. The stretching program involved warming up in the form of circular running inside the lab for 5 minutes followed by stretching of each muscle group three times, to the limit of discomfort of 45 seconds, with resting period of 15 seconds between stretches. Main Outcome Measures: The measurements included the RT of the dominant lower-extremity using the dynamic stability program STABL Virtual Reality System (model no. DIZ 2709; Motekforce Link). Results: There was a statistically significant reduction (F = 162, P <.05) in posttest RT between the 2 groups and significant decrease in RT after stretching in the experimental group (7.5%; P <.05). Conclusion: ASS of the lower limb muscles tends to decrease the lower limb RT and improve movement performance. [ABSTRACT FROM AUTHOR]

Context: Altered lower-extremity muscle activity has been associated with lower-extremity kinematics in individuals with patellofemoral pain (PFP). However, few studies have examined these relationships, and the results are inconsistent. Objective: To compare the lower-extremity muscle activity, kinematics, pain level, and reach distance during the anterior reach of the star excursion balance test (SEBT) between participants with PFP and healthy individuals (control [CON] group). Design: Case control. Setting: Research laboratory. Participants: Twenty-eight (PFP = 14 and CON = 14) participants volunteered. Intervention: Each participant performed 3 maximal voluntary isometric contractions of the gluteus maximus, gluteus medius (GMED), adductor longus (AL), and vastus medialis, and 5 anterior reaches of the SEBT. Main Outcome Measures: Three-dimensional joint kinematics of the hip and knee at the time of touchdown of the SEBT and integrated electromyography of each muscle were recorded during the descent phase of the SEBT. Coactivation ratios between the GMED and AL were calculated (GMED/AL). Pain level was assessed at the baseline and during performance of the SEBT, using a visual analog scale. Results: Participants with PFP demonstrated decreased GMED/AL coactivation ratio (P =.01) and shorter reach distance (P =.01) during anterior reach of the SEBT compared with the CON group. Participants with PFP demonstrated higher pain levels at baseline (P =.03) and during test performance (P <.001) compared with the CON group and increased pain level during the test performance compared with the baseline (P <.001). No other significant differences were observed. Conclusions: There were alterations in muscle activity during SEBT performance, suggesting that overactivity of AL relative to GMED is a unique neural recruitment pattern in those with PFP. However, hip and knee joint kinematics did not seem to contribute to deficits in the anterior reach distance, suggesting a need for continued assessment of these deficiencies. [ABSTRACT FROM AUTHOR]

Purpose: To characterize the relationships between muscle oxygenation and performance during on- and off-water tests in highly trained sprint canoe–kayak athletes. Methods: A total of 30 athletes (19 kayakers and 11 canoeists) performed a maximal incremental test on a canoe or kayak ergometer for determination of VO2max and examination of the relation between peak power output (PPO) and physiological parameters. A subset of 21 athletes also performed a 200- and a 500- (for women) or 1000-m (for men) on-water time trial (TT). Near-infrared spectroscopy monitors were placed on the latissimus dorsi, biceps brachii, and vastus lateralis during all tests to assess changes in muscle O2 saturation (SmO2) and deoxyhemoglobin concentration ([HHb]). The minimum O2 oxygenation (SmO2min) and maximal O2 (Δ[HHb] extraction) were calculated for all subjects. Results: PPO was most strongly correlated with VO2max (R =.9), but there was also a large correlation between PPO and both SmO2min and Δ[HHb] in latissimus dorsi (R = −.5, R =.6) and vastus lateralis (R = −.6, R =.6, all P <.05). Multiple regression showed that 90% of the variance in 200-m performance was explained by both Δ[HHb] and SmO2min in the 3 muscles combined (P <.01) and 71% of the variance in 500-/1000-m performance was explained by Δ[HHb] in the 3 muscles (P <.01). This suggests that O2 extraction is a better predictor of performance than VO2max in sprint canoe–kayak. Conclusions: These results highlight the importance of peripheral adaptations in both short and long events and stress the relevance of adding muscle oxygenation measurements during testing and racing in sprint canoe–kayak. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare the relative exercise intensity at which the onset of accelerated muscle deoxygenation occurs during the 20-m shuttle run test (20mSRT) between boys and men and to examine whether the timing of the onset of acceleration appearance is related to 20mSRT performance in boys. Methods: Twenty-four boys performed the 20mSRT, during which concentration changes in oxygenated and deoxygenated hemoglobin and myoglobin (ΔOxy-Hb and ΔDeoxy-Hb, respectively) in the m. vastus lateralis were monitored using a portable near-infrared spectroscopy device. The boys' data were compared with those of 29 men in a previous study. Results: An onset of accelerated decrease in Δ[Oxy-Hb − Deoxy-Hb] was found in 11 of the 24 boys (45.8%) and 20 of the 29 men (69.0%) and was found at a higher relative exercise intensity in the boys than in the men. The number of laps at which the onset of acceleration occurred correlated with total laps in the boys (r =.87). Conclusions: These findings demonstrate that the onset of accelerated muscle deoxygenation during the 20mSRT occurs at a higher relative exercise intensity in boys than in men. Our findings also show that the timing of the onset of acceleration appearance is associated with 20mSRT performance in boys. [ABSTRACT FROM AUTHOR]

The primary purpose of this study is to determine whether recreational runners with patellofemoral pain (PFP) exhibit greater peak patella cartilage stress compared with pain-free runners. A secondary purpose was to determine the kinematic and/or kinetic predictors of peak patella cartilage stress during running. A total of 22 female recreational runners (12 with PFP and 10 pain-free controls) participated in this study. Patella cartilage stress profiles were quantified using subject-specific finite element models simulating the maximum knee flexion angle during the stance phase of running. Input parameters to the finite element model included subject-specific patellofemoral joint geometry, quadriceps muscle forces, and lower-extremity kinematics in the frontal and transverse planes. Tibiofemoral joint kinematics and kinetics were quantified to determine the best predictor of stress using stepwise regression analysis. Compared with the pain-free runners, those with PFP exhibited greater peak hydrostatic pressure (PFP vs control: 21.2 [5.6] MPa vs 16.5 [4.6] MPa) and maximum shear stress (PFP vs control: 11.3 [4.6] MPa vs 8.7 [2.3] MPa). Knee external rotation was the best predictor of peak hydrostatic pressure and peak maximum shear stress (38% and 25% of variances, respectively), followed by the knee extensor moment (21% and 25% of variances, respectively). Runners with PFP exhibit greater peak patella cartilage stress during running compared with pain-free individuals. The combination of knee external rotation and a high knee extensor moment best predicted the elevated peak stress during running. [ABSTRACT FROM AUTHOR]

Estimation of muscle forces through musculoskeletal simulation is important in understanding human movement and injury. Unmatched filter frequencies used to low-pass filter marker and force platform data can create artifacts during inverse dynamics analysis, but their effects on muscle force calculations are unknown. The objective of this study was to determine the effects of filter cutoff frequency on simulation parameters and magnitudes of lower-extremity muscle and resultant joint contact forces during a high-impact maneuver. Eight participants performed a single-leg jump landing. Kinematics was captured with a 3D motion capture system, and ground reaction forces were recorded with a force platform. The marker and force platform data were filtered using 2 matched filter frequencies (10–10 Hz and 15–15 Hz) and 2 unmatched filter frequencies (10–50 Hz and 15–50 Hz). Musculoskeletal simulations using computed muscle control were performed in OpenSim. The results revealed significantly higher peak quadriceps (13%), hamstrings (48%), and gastrocnemius forces (69%) in the unmatched (10–50 Hz and 15–50 Hz) conditions than in the matched (10–10 Hz and 15–15 Hz) conditions (P <.05). Resultant joint contact forces and reserve (nonphysiologic) moments were similarly larger in the unmatched filter categories (P <.05). This study demonstrated that artifacts created from filtering with unmatched filter cutoffs result in altered muscle forces and dynamics that are not physiologic. [ABSTRACT FROM AUTHOR]

Purpose: Fatigue negatively alters dynamic knee control, and the functional hamstring/quadriceps ratio (H/QFUNC) plays an important role in stabilizing the joint. The aim of this study was to investigate the influence of soccer-specific exercise on H/QFUNC in under (U) 13-, U15-, and U17-year-old female soccer players. Methods: A total of 36 female players performed concentric and eccentric actions of the hamstrings at 60°, 120°, and 180°/s before and after an age group--specific field-based soccer protocol. H/QFUNC was determined in the first 30° of knee flexion. Results: Significant angle x velocity (P = .001) and time x angle (P = .033) interaction effects were found indicating a lower H/QFUNC with increased movement velocity at 0°--10° as opposed to greater knee flexion angles. Fatigue-related effects were only evident near full knee extension. Probabilistic inferences indicated that changes in H/QFUNC were generally unclear in U13s, likely detrimental in U15s, and very likely beneficial in U17s. Conclusions: Altered muscular control following soccer-specific exercise is age dependent with players' 1-year post-peak height velocity at greatest risk of injury. Injury prevention and screening need to be age and maturation appropriate, should consider the effects of fatigue, and include movements near full extension. [ABSTRACT FROM AUTHOR]

Objective: Evaluate the relationship between subjective knee function and lower-extremity strength in individuals with patellofemoral pain (PFP). Design: Cohort. Setting: Laboratory. Participants: Participants were 30 individuals with PFP (20 females and 10 males; 76.02 [17.88] kg, 173.04 [7.58] cm, and 24.9 [7] y). Main Outcome Measures: Subjects completed the Activities of Daily Living Scale (ADLS) and had lower-extremity hip and knee isometric strength assessed. Strength was compared between low and high subjective functioning ADLS groups. Correlations for strength and subjective function were assessed, with a linear regression utilized to determine if strength predicted subjective function. Results: Quadriceps strength was significantly greater in the high subjective function group (38.5 [13.9] percent body mass) than in the low subjective function group (27.88 [8.96] percent body mass, P =.02). Significant correlations were seen between the ADLS and all 5 lower-extremity strength measures (r =.376–.535). Quadriceps strength was a strong predictor of subjective function in those with PFP, explaining 28.6% of the total variance in the ADLS. Conclusions: Quadriceps strength was a strong predictor of subjective function when assessed by the ADLS in patients with PFP and significantly greater in those with higher subjective function. A strong relationship exists between self-reported function and lower-extremity strength, suggesting the need to evaluate and treat lower-extremity weakness. [ABSTRACT FROM AUTHOR]

Context: Study of muscle volumes in patients after anterior cruciate ligament (ACL) injury and reconstruction (ACL-R) is largely limited to cross-sectional assessment of the thigh musculature, which may inadequately describe posttraumatic and postsurgical muscle function. No studies have prospectively examined the influence of ACL injury and reconstruction on lower-extremity muscle volumes. Objective: Assess magnetic resonance imaging-derived lower-extremity muscle volumes, and quantify quadriceps strength and activation in patients following ACL injury and reconstruction. Design: Prospective case series. Setting: Research laboratory and magnetic resonance imaging facility. Patients (or Other Participants): Four patients (2 men and 2 women; age = 27.4 (7.4) y, height = 169.2 (8.1) cm, and mass = 74.3 (18.5) kg) scheduled for ACL-R. Intervention(s): Thirty-five muscle volumes were obtained from a bilateral lower-extremity magnetic resonance imaging before and after ACL-R. Main Outcome Measures: Muscle volumes expressed relative to (1) a normative database presurgery and postsurgery, (2) limb symmetry presurgery and postsurgery, and (3) percentage change presurgery to postsurgery. Quadriceps function was quantified by normalized knee extension maximal voluntary isometric contraction torque and central activation ratio. Results: Involved vastus lateralis and tibialis anterior were consistently smaller than healthy individuals (z < -1 SD) presurgery and postsurgery in all patients. Involved rectus femoris and vastus lateralis were more than 15% smaller than the contralateral limb presurgery, whereas the involved rectus femoris, gracilis, vastus medialis, vastus intermedius, and vastus lateralis muscle volumes exceeded 20% asymmetry postoperatively. Involved gracilis and semitendinosus atrophied more than 30% from presurgery to postsurgery. Involved maximal voluntary isometric contraction torque and central activation ratio increased by 12.7% and 12.5%, respectively, yet strength remained 33.2% asymmetric postsurgery. Conclusions: Adaptations in lower-extremity muscle volumes are present following ACL injury and reconstruction. Anterior thigh and shank muscles were smaller than healthy individuals, and large asymmetries in quadriceps volumes were observed presurgery and postsurgery. Selective atrophy of the semitendinosus and gracilis occurred following surgery. Volumetric deficits of the quadriceps musculature may exist despite improvements in muscle strength and activation. [ABSTRACT FROM AUTHOR]

Context: Foot and ankle injuries are common and often require a nonweight-bearing period of immobilization for the involved leg. This nonweight-bearing period usually results in muscle atrophy for the involved leg. There is a dearth of objective data describing muscle activation for different ambulatory aids that are used during the aforementioned nonweight-bearing period. Objective: To compare activation amplitudes for 4 leg muscles during (1) able-bodied gait and (2) ambulation involving 3 different ambulatory aids that can be used during the acute phase of foot and ankle injury care. Design: Within-subject, repeated measures. Setting: University biomechanics laboratory. Participants: Sixteen able-bodied individuals (7 females and 9 males). Intervention: Each participant performed able-bodied gait and ambulation using 3 different ambulatory aids (traditional axillary crutches, knee scooter, and a novel lower-leg prosthesis). Main Outcome Measure: Muscle activation amplitude quantified via mean surface electromyography amplitude throughout the stance phase of ambulation. Results: Numerous statistical differences (P < .05) existed for muscle activation amplitude between the 4 observed muscles, 3 ambulatory aids, and able-bodied gait. For the involved leg, comparing the 3 ambulatory aids: (1) knee scooter ambulation resulted in the greatest vastus lateralis activation, (2) ambulation using the novel prosthesis and traditional crutches resulted in greater biceps femoris activation than knee scooter ambulation, and (3) ambulation using the novel prosthesis resulted in the greatest gastrocnemius activation (P < .05). Generally speaking, muscle activation amplitudes were most similar to able-bodied gait when subjects were ambulating using the knee scooter or novel prosthesis. Conclusions: Type of ambulatory aid influences muscle activation amplitude. Traditional axillary crutches appear to be less likely to mitigate muscle atrophy during the nonweighting, immobilization period that often follows foot or ankle injuries. Researchers and clinicians should consider these results when recommending ambulatory aids for foot or ankle injuries. [ABSTRACT FROM AUTHOR]

Context: Foam rolling is a popular intervention used by allied health professionals and the general population. Current research suggests that foam rolling may have an effect on the ipsilateral antagonist muscle group and produce a cross-over effect in the muscles of the contralateral limb. The purpose of this study was to examine the acute effects of foam rolling to the left quadriceps on ipsilateral antagonist hamstrings and contralateral quadriceps muscle group pressure pain threshold (PPT). Through this research, we sought to gather data to further develop the methodology for future studies of this intervention. Design: A pretestposttest exploratory study. Setting: University kinesiology laboratory. Participants: 21 healthy adults (age = 27.52 ±8.9 y). Intervention: Video-guided foam roll intervention on the left quadriceps musculature. Main Outcome Measures: Ipsilateral hamstring (antagonist) and contralateral quadriceps muscle PPT. Results: A significant difference was found between pretest to posttest measures for the ipsilateral hamstrings (i[20] = -6.2, P < 0.001) and contralateral quadriceps (i[20] = -9.1, P < 0.001) suggesting an increase in PPT. Conclusions: These findings suggest that foam rolling of the quadriceps musculature may have an acute effect on the PPT of the ipsilateral hamstrings and contralateral quadriceps muscles. Clinicians should consider these results to be exploratory and future investigations examining this intervention on PPT is warranted. [ABSTRACT FROM AUTHOR]

Purpose: To elucidate the relationship between the muscularity of individual lower-limb muscles and 100-m-race time (t100) in young-adult male sprinters. Methods: Thirty-one young-adult male sprinters took part in this study (age 19.9 ± 1.4 y, height 173.5 ± 4.6 cm, body mass 67.0 ± 4.9 kg, t100 10.23-11.71 s). Cross-sectional images from the origin to insertion of 12 lowerlimb muscles were obtained with via magnetic resonance imaging (MRI). The absolute volume of each muscle, the ratio of total volume of measured muscles to body mass, the ratio of individual muscle volume to body mass, and the ratio between 2 individual muscle volumes were calculated as indices of muscularity using the images. A stepwise multiple-regression analysis was performed to examine the association between the indices and t100. Results: A stepwise multiple-regression analysis produced an equation (adjusted R² = .234) with the gluteus maximus-to-quadriceps femoris muscle-volume ratio (β = -0.509, P = .003) as the explanatory variable. Conclusions: Individual differences in 100-m-race performance cannot be explained by the muscularity of specificmuscles, and 23% of the variability in the performance can be explained by the relative difference between the muscularity of gluteus maximus and quadriceps femoris; faster runners have a greater gluteus maximus relative to quadriceps femoris. [ABSTRACT FROM AUTHOR]

Evidence indicates that low-level laser therapy (LLLT) minimizes fatigue effects on muscle performance. However, the ideal LLLT dosage to improve athletes' performance during sports activities such as cycling is still unclear. Therefore, the goal of this study was to investigate the effects of different LLLT dosages on cyclists' performance in time-to-exhaustion tests. In addition, the effects of LLLT on the frequency content of the EMG signals to assess fatigue mechanisms were examined. Twenty male competitive cyclists participated in a crossover, randomized, double-blind, placebo-controlled trial. They performed an incremental cycling test to exhaustion (on day 1) followed by 4 time-to-exhaustion tests (on days 2-5) at their individual maximal power output. Before each time-to-exhaustion test, different dosages of LLLT (135, 270, and 405 J/thigh, respectively) or placebo were applied at the quadriceps muscle bilaterally. Power output and muscle activation from both lower limbs were recorded throughout the tests. Increased performance in time-to-exhaustion tests was observed with the LLLT-135 J (-22 s; P < .01), LLLT-270 J (-13 s; P = .03), and LLLT-405 J (-13 s; P = .02) compared to placebo (149 ± 23 s). Although LLLT-270 J and LLLT-405 J did not show significant differences in muscle activation compared with placebo, LLLT-135 J led to an increased high-frequency content compared with placebo in both limbs at the end of the exhaustion test (P ≤ .03). In conclusion, LLLT increased time to exhaustion in competitive cyclists, suggesting this intervention as a possible nonpharmacological ergogenic agent in cycling. Among the different dosages, LLLT-135 J seems to promote the best effects. [ABSTRACT FROM AUTHOR]

The interplay between biarticular and monoarticular muscles of the knee and hip joints during bipedal squats (SQBP) requires adequate central‐nervous control mechanisms to enable smooth and dynamic movements. Here, we investigated motor control between M. vastus medialis (VM), M. vastus lateralis (VL), and M. rectus femoris (RF) in 12 healthy male recreational athletes during SQBP with three load levels (50%, 62.5%, and 75% of 3‐repetition maximum) following a standardized strength training protocol (3 sets of 10 repetitions). To quantify differences in motor control mechanisms in both time and frequency domains, we analyzed (1) muscle covariation via correlation analyses, as well as (2) common neural input via intermuscular coherence (IMC) between RF, VM, and VL. Our results revealed significantly higher gamma IMC between VM‐VL compared with RF‐VL and RF‐VM for both legs. Correlation analyses demonstrated significantly higher correlation coefficients during ascent periods compared with descent periods across all analyzed muscle pairs. However, no load‐dependent modulation of motor control could be observed. Our study provides novel evidence that motor control during SQBP is characterized by differences in common input between biarticular and monoarticular muscles. Additionally, muscle activation patterns show higher similarity during ascent compared with descent periods. Future research should aim to validate and extend our observations as insights into the underlying control mechanisms offer the possibility for practical implications to optimize training concepts in elite sports and rehabilitation. [ABSTRACT FROM AUTHOR]

Background: The skeletal muscle microbiopsy protocol was introduced to the Exercise and Sports Science (ESS) research field in 1999 and has been used as a protocol to directly examine muscular structural and biochemical changes. There is much variation in the reporting of the microbiopsy protocol and its related pre‐ and post‐procedure for participant care and sample collection. The purpose of this narrative and methodological review is to compare the microbiopsy to the traditional Bergström protocol used in the ESS field, identify and summarize all related microbiopsy protocols used in previous ESS studies and determine the most frequently used microbiopsy protocols aspects and associated pre‐ and post‐biopsy procedures. Methods: A review of literature up to January 2022 was used following the PRISMA and Cochrane Methodological Review Guide to determine frequently used methods that may facilitate optimal and potential recommendations for muscle microbiopsy needle gauge (G), concentration or dose (% or ml) and administration of local anesthetic, co‐axial/cannula introducer gauge (G), muscle depth (cm), muscle sample size collected (mg), passes to collect samples, time points of muscle sampling, and promotion of participant compliance and minimization of adverse events. Results: Eighty‐five articles were selected based on the inclusionary requirements related to the ESS field or methodological considerations. The most frequently reported aspects in previous research to suggest the location of the vastus lateralis is the midpoint between the patella and the greater trochanter of the femur or 1/3 or 2/3 the distance from the patella to anterior superior iliac spine, 14 G biopsy needle, subcutaneous injected lidocaine administration (2 ml, 1%), 13 G co‐axial/cannula, 1–2 cm muscle depth, 10–20 mg of muscle sample, ~3‐time points, and 2–3 passes. Discussion: There is much variation in the reporting of the microbiopsy protocol and its related pre‐ and post‐biopsy procedures. Standardization in reporting may promote recommendations to optimize data integrity, participant safety, participant adherence to the study design, and increase reproducibility. Recommendations are made for the microbiopsy procedure based on frequently reported characteristics. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to directly compare the effects of 30 min muscle (VIBmuscle) vs. tendon (VIBtendon) local vibration (LV) to the quadriceps on maximal voluntary isometric contraction (MVIC) and rate of torque development (RTD) as well as on central nervous system excitability (i.e. motoneuron and cortical excitability).Methods: Before (PRE) and immediately after (POST) LV applied to the quadriceps muscle or its tendon, we investigated MVIC and RTD (STUDY #1; n = 20) or vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) electromyography responses to thoracic electrical stimulation (TMEPs; motoneuron excitability) and transcranial magnetic stimulation (MEPs; corticospinal excitability) (STUDY #2; n = 17). MEP/TMEP ratios were further calculated to quantify changes in cortical excitability.Results: MVIC decreased at POST (P = 0.017) without any difference between VIBtendon and VIBmuscle, while RTD decreased for VIBtendon (P = 0.013) but not VIBmuscle. TMEP amplitudes were significantly decreased for all muscles (P = 0.014, P < 0.001 and P = 0.004 for VL, VM and RF, respectively) for both LV sites. While no changes were observed for MEP amplitude, MEP/TMEP ratios increased at POST for VM and RF muscles (P = 0.009 and P = 0.013, respectively) for both VIBtendon and VIBmuscle.Conclusion: The present results suggest that prolonged muscle and tendon LV are similarly effective in modulating central nervous system excitability and decreasing maximal force. Yet, altered explosive performance after tendon but not muscle LV suggests greater neural alterations when tendons are vibrated. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is Available in the Text. Objectives: To investigate whether the addition of whole-body vibration therapy to standard rehabilitation improves postural stability and lower limb strength following anterior cruciate ligament (ACL) reconstruction. Data sources: A computer-based literature search of MEDLINE, AMED, SPORTDiscus, Embase, CINAHL, CENTRAL, and Physiotherapy Evidence Database (PEDro) included studies up to October 2019. Main results: Seven randomised controlled trials of moderate-to-high methodological quality involving 244 participants were included. Meta-analysis found statistically significant improvements in medial–lateral stability [standardized mean difference (SMD) = 0.50; 95% confidence interval (CI), 0.12-0.88] and overall stability (SMD = 0.60; 95% CI, 0.14-1.06) favoring whole-body vibration therapy, but effects were not significant for quadriceps strength (SMD = 0.24; 95% CI, −0.65 to 1.13), hamstring strength (SMD = 0.84; 95% CI, −0.05 to 1.72), lower limb strength (SMD = 0.76; 95% CI, −0.16 to 1.67), or anterior-posterior stability (SMD = 0.19; 95% CI, −0.39 to 0.76). Conclusions: The addition of whole-body vibration therapy to standard postoperative rehabilitation following ACL reconstruction does not appear to significantly improve lower limb strength and anterior–posterior stability but may improve medial–lateral and overall postural stability. We found small sample sizes in all included trials, statistical heterogeneity, and methodological quality concerns, including publication bias, suggesting that larger high-quality trials are likely to be influential in this field. Registration: PROSPERO 155531. [ABSTRACT FROM AUTHOR]

Abián-Vicén, J, Martínez, F, Jiménez, F, and Abián, P. Effects of eccentric single-leg decline squat training performed with different execution times on maximal strength and muscle contraction properties of the knee extensor muscles. J Strength Cond Res 36(11): 3040–3047, 2022—The eccentric phase of the single-leg decline squat (SLDSe) has been described as a method to maximally load the knee extensor and has been used as an easy and effective rehabilitation exercise for patellar tendinopathy. The purpose of this study was to examine the impact of 6-week SLDSe training with 2 technical execution times on changes related to strength and muscle contractile properties. Thirty-six healthy volunteers were randomly divided into 3 groups: a control group (CG, n = 13, no training), a slow training group (n = 11, SLDSe in 6 seconds), and a fast training group (n = 12, SLDSe in 3 seconds). Subjects completed a 6-week SLDSe training program (80% of eccentric one repetation maximum [1RM]) 3 days a week. Pre, post, and 6-week follow-up of maximal dynamic and isometric strength and muscle contractile properties were assessed. After 6 weeks, training maximal loads showed a significant increase (p < 0.05) in 1RM of the SLDSe (∼92–95%), the concentric peak torque at 180°·s−1 (∼38%) and 60°·s−1 (∼25%), and the extension isometric peak torque (∼12%), with no differences between both experimental groups. Moreover, a decrease (p < 0.05) was found in the contraction time of the vastus medialis (VM) and the response time of the 3 analyzed quadriceps muscles. After the 6-week detraining period, there was a decrease in strength in all tests and in both experimental groups (1RM = 28–37%, isometric and isokinetic tests = 7–17%) and all contractile properties returned to baseline, except for the response time of the vastus lateralis in the fast training group and the contraction time of the VM in the STG. In conclusion, the SLDSe training protocol produced significant increases in muscle strength, showing important neuromuscular changes regardless of the technical execution time. It was also found that the training reduced the response and contraction time of the knee extensor musculature. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of whole-body vibration (WBV) exercises combined with traditional physiotherapy on the hamstrings-to-quadriceps (H:Q) ratio, walking ability, and control of posture in children with hemiparetic cerebral palsy (CP). A total of 34 children with spastic hemiparetic CP (boys and girls) participated in this 2-arm, parallel, randomized controlled trial. The inclusion criteria were spasticity ranging from 1 to 1+, gross level skills (I and II), at least 1 meter tall, standing alone, and walking forward and backward. They were randomly allocated to the control group (traditional physiotherapy) and study group and were treated by the same physiotherapy program combined with WBV training (3 times per week for 2 successive months). Quadriceps and hamstring muscle strength, walking performance, and postural control were evaluated before and after intervention by a blinded assessor. The post-intervention values of the hamstring and quadriceps muscle force, gross motor function, and stability indices of the 2 groups were higher than the pre-values (P <.05). In addition, the post-values of the study group were higher than those of the control group (P <.05). Regarding the H:Q ratio, there was no significant difference between pre-values or the post-values of both groups (P =.948 and P =.397, respectively). There were no significant differences between the pre- and post-values of each group (P =.500 and P =.195, respectively). Eight weeks of WBV training combined with traditional physiotherapy was more effective than traditional physiotherapy alone in improving walking ability and postural control. Furthermore, the combined intervention strengthened the quadriceps and hamstring muscles, with no change in the H:Q ratio in children with hemiparetic CP. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the acute and prolonged effects of dermal suction on joint range of motion (ROM) and passive muscle stiffness. Eight-minute dermal suction was prescribed for the quadriceps femoris in 15 participants. Hip extension ROM, knee flexion ROM, and passive muscle stiffness of the rectus femoris (RF) and vastus lateralis (VL) were measured before and immediately, 30 min, 60 min, 120 min, 24 h, and 48 h after dermal suction. Passive muscle stiffness was measured using shear wave elastography. Hip extension ROM significantly increased immediately (p = 0.032), 60 min (p = 0.029), and 120 min (p = 0.031) after dermal suction compared with before dermal suction; however, it was not significantly different at 30 min, 24 h, and 48 h after dermal suction (p > 0.05). Passive muscle stiffness of the RF and VL and knee flexion ROM did not significantly change at any measurement time compared with before dermal suction (p > 0.05). Our preliminary results suggest that dermal suction improves hip extension ROM immediately after dermal suction of the quadriceps femoris, followed by a return to the pre-prescription level 30 min after. However, the effect was prolonged for 120 min and disappeared before 24 h. [ABSTRACT FROM AUTHOR]

Background: Regaining preinjury levels of activity and progressing rehabilitation factors after anterior cruciate ligament (ACL) reconstruction have shown mixed results. Purpose: To evaluate the timing and rate of return for knee range of motion (ROM), stability, strength, and subjective scores after ACL reconstruction with contralateral patellar tendon graft (PTG). Study Design: Case series; Level of evidence, 4. Methods: Included were 2148 patients (1238 male patients, 910 female patients) who underwent primary ACL reconstruction with a contralateral PTG between 1995 and 2017 and had complete objective data through 3 months of follow-up. All patients participated in a rehabilitation program specific to goals for each knee. Patients were evaluated objectively with goniometric measurement of ROM, isokinetic quadriceps strength testing, and laxity with a KT-2000 arthrometer. Subjective data were collected at 2 and 5 years. Results: Normal extension on the reconstructed knee was attained for 95% of patients at 1 week postoperatively; normal flexion on the reconstructed knee was reached by 77% of patients by 3 months. At 3 months postoperatively, mean limb symmetry index strength was 104%, and the strength on the ACL-reconstructed and graft-donor knees was 87% and 86% of their respective preoperative strength. Mean manual maximum side-to-side difference in laxity was 2.0 mm at 1 month. Most patients (90%) returned to level 8 sports or higher and did so at an average of 5.7 months. Mean International Knee Documentation Committee scores for the ACL-reconstructed and graft-donor knees were 89 and 91 at 2 years (n = 1015 patients) and 84 and 90 at 5 years (n = 1275 patients), respectively. Mean Cincinnati Knee Rating Scale scores for the ACL-reconstructed and graft-donor knees were 92 and 96 at 2 years (n = 1184) and 88 and 94 at 5 years (n = 1236), respectively. Conclusion: For patients who underwent ACL reconstruction with a contralateral PTG, postoperative ROM and strength were restored quickly by splitting the rehabilitation into different goals between the two knees. Using a contralateral PTG, this structured rehabilitation plan can lead to a relatively quick return to sport and good subjective long-term outcomes. [ABSTRACT FROM AUTHOR]