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Background Ulnar collateral ligament injuries are rampant in the sport of baseball where kinetic chain impacts, stemming from misappropriation of stride length or changes that occur in competition due to fatigue, have not been evaluated for dynamic elbow stability effects. Hypothesis/Purpose To examine the relationship between clinical measures of grip strength and altered stride length in baseball pitchers. It is believed that shorter stride lengths would reduce grip strength in baseball pitchers. Study Design Crossover Study Design Methods A total of 19 uninjured pitchers (15 collegiate and 4 high school) (age 18.63 ± 1.67 years, height 1.84 ± 0.054 m, mass 82.14 ± 0.054 kg) threw two simulated 80-pitch games at ±25% of their desired stride length recorded by motion capture with two force plates and a radar gun to track each throw. A handheld grip dynamometer was used to record the mean change in grip strength after games from baseline measures. Pairwise comparisons at baseline and post-game denoted grip strength changes and dominant grip strength offsets for stride length conditions. Results Subjects with shorter stride lengths revealed a significant decline in grip strength in the dominant arm from baseline (pre-game; 45.1 kg vs. post-game; 43.2 kg, p=0.017, ES=0.28), however all other tests involving dominant grip strength changes and offset analyses were not statistically different for under-stride and over-stride length conditions. Conclusions Clinical evaluation of grip strength has the potential to identify altered lower body mechanics and may be considered as a safe and effective monitoring strategy to integrate with motion capture in determining optimal stride lengths for baseball pitchers. Level of Evidence Level 3

Propulsion and bracing ground reaction force (GRF) in overhand throwing are integral in propagating joint reaction kinetics and ball velocity, yet how stride length effects drive (hind) and stride (lead) leg GRF profiles remain unknown. Using a randomised crossover design, 19 pitchers (15 collegiate and 4 high school) were assigned to throw 2 simulated 80-pitch games at ±25% of their desired stride length. An integrated motion capture system with two force plates and radar gun tracked each throw. Vertical and anterior-posterior GRF was normalised then impulse was derived. Paired t-tests identified whether differences between conditions were significant. Late in single leg support, peak propulsion GRF was statistically greater for the drive leg with increased stride. Stride leg peak vertical GRF in braking occurred before acceleration with longer strides, but near ball release with shorter strides. Greater posterior shear GRF involving both legs demonstrated increased braking with longer strides. Conversely, decreased drive leg propulsion reduced both legs' braking effects with shorter strides. Results suggest an interconnection between normalised stride length and GRF application in propulsion and bracing. This work has shown stride length to be an important kinematic factor affecting the magnitude and timing of external forces acting upon the body.

This is the second component of a two-part series investigating 3D momentum profiles specific to overhand throwing, where altering stride reportedly influences throwing mechanics resulting in significantly different physiologic outcomes and linear momentum profiles. Using a randomized cross-over design, nineteen pitchers (15 collegiate and 4 high school) were assigned to pitch two simulated 80-pitch games at ±25% of their desired stride length. An 8-camera motion capture system (240Hz) integrated with two force plates (960Hz) and radar gun tracked each overhand throw. Segmental angular momentums were summed yielding throwing arm and total body momentums, from which compensation ratio's (relative contribution between the two) were derived. Pairwise comparisons at hallmark events and phases identified significantly different angular momentum profiles, in particular total body, throwing arm, and momentum compensation ratios (P⩽0.05) as a result of manipulating stride length. Sagittal, frontal, and transverse angular momentums were affected by stride length changes. Transverse magnitudes showed greatest effects for total body, throwing arm, and momentum compensation ratios. Since the trunk is the main contributor to linear and angular momentum, longer strides appear to better regulate transverse trunk momentum in double support, whereas shorter strides show increased momentum prior to throwing arm acceleration.

This study assessed pitching performance by examining variability in ball velocities among skilled pitchers over two simulated games, where stride lengths were altered while monitoring the effect o...

The purpose of this study was to examine the infuence of trunk lean and contralateral hip abductor strength on the peak knee adduction moment (KAM) and rate of loading in persons with moderate medial knee osteoarthritis. Tirty-one males (17 with osteoarthritis, 14 controls) underwent 3-dimensional motion analysis, strength testing of hip abductors, and knee range of motion (ROM) measures, as well as completing the knee osteoarthritis outcome score (KOOS). No diferences were found between groups or limbs for gait cycle duration, but the osteoarthritis group had longer double-limb support during weight acceptance (p < 0.001) and delayed frontal plane trunk motion towards the stance limb (p < 0.01). Tis was refected by a lower rate of loading for the osteoarthritis group compared to controls (p < 0.001), whereas no diferences were found for peak KAM. Trunk angle, contralateral hip abductor strength, and BMI explained the rate of loading at the involved knee (p < 0.001), an association not found for the contralateral knee or control knees. Prolonged trunk lean over the stance limb may help lower peak KAM values. Rate of frontal plane knee joint loading may partly be mediated by the contralateral limb’s abductor strength, accentuating the importance of bilateral lower limb strength for persons with knee osteoarthritis., Financial support was received from the Icelandic Physiotherapy Association.

The principle of lower limb support, and the contribution of hip, knee and ankle moments to an overall limb support strategy for an impact-like, rapid deceleration movement may help explain individual moment magnitude changes, thereby providing insight into how injury might occur or be avoided. Twenty subjects performed single limb, impact-like, deceleration landings at three different knee flexion angles in the range of 0–25, 25–50 and 50–75°. Kinematic and kinetic measures identified hip, knee and ankle moment contribution to limb support moments (LSMs) in three planes. Repeated measures ANOVA compared LSMs and the contribution of individual joint moments at initial contact (IC) and 50 ms after. There were no significant differences in the overall LSMs at IC in any plane when the deeper knee flexion landings (25–50° and 50–75°) were compared to the 0–25° landing position but there were significant changes in the 50 ms period after IC. There were greater overall extensor LSMs, less resistance to medial opening of the knee and decreased support against internal tibia rotation when landing in greater knee flexion. The role of individual joint moments changed rapidly in the 50 ms period after initial landing; and, the relative contribution of the hip and ankle moments depended on the degree of limb flexion at landing. Analyses of individual joint moments emphasized the critical role that the hip joint moments have in balancing potentially injurious knee moments in all three planes for all three landing conditions.

Changing stride length during overhand throwing delivery is thought to alter total body and throwing arm linear momentums, thereby altering the proportion of throwing arm momentum relative to the total body. Using a randomized cross-over design, nineteen pitchers (15 collegiate and 4 high school) were assigned to pitch two simulated 80-pitch games at ±25% of their desired stride length. An 8-camera motion capture system (240Hz) integrated with two force plates (960Hz) and radar gun tracked each throw. Segmental linear momentums in each plane of motion were summed yielding throwing arm and total body momentums, from which compensation ratio's (relative contribution between the two) were derived. Pairwise comparisons at hallmark events and phases identified significantly different linear momentum profiles, in particular, anteriorly directed total body, throwing arm, and momentum compensation ratios (P⩽.05) as a result of manipulating stride length. Pitchers with shorter strides generated lower forward (anterior) momentum before stride foot contact, whereas greater upward and lateral momentum (toward third base) were evident during the acceleration phase. The evidence suggests insufficient total body momentum in the intended throwing direction may potentially influence performance (velocity and accuracy) and perhaps precipitate throwing arm injuries.

Diminishing baseball velocities are objective measures to delineate pitching fatigue. Yet, velocity changes over the course of a competitive season vs. a single game remain unknown. This study examined fastball velocity (FBV) trends of minor league pitchers over an 8-game span. We assumed that accumulation of pitches would cause similar velocity decreases within games to produce velocity decreases between games pitched. Retrospective analysis of major league-affiliated pitching charts indicated mean FBVs, game pitches thrown, game innings pitched, rest days, and pitching work to rest ratios (PWRRs) for 12 pitchers over 8 games. Regression analyses (p0.05) were performed using the ordinary least squares method. The FBV was the dependent variable, where the explanatory variable was the game number (representing cumulative workload). Further analyses were performed on ball velocity differences predicted by days rest and PWRRs. The FBV increased linearly for the first 8 games of the season (R = 0.91, F(1,7) = 64.67, p0.001). Over the 8 - game period, mean FBVs increased 0.25 m/s (0.56 mph) with the greatest velocity increase occurring between the first and eighth game at 1.97 m/s (4.4 mph). Days rest and PWRRs did not impact FBV differences. When compared with previous research, minor league pitchers at the Class A Short Season level did not show similar exertion responses to cumulative workloads (pitches and innings pitched). Recovery factors (rest days, PWRRs, and training) also did not impact FBVs. Velocity increases may be attributable to biomechanical compensations, skill development, strength and conditioning regimens, multistarter rotations, and other performance-related factors. Strength and conditioning professionals should be aware of ball velocity trends, as apparent changes may infer neuromuscular fatigue and increased injury susceptibility, which require in-season training modifications.

We investigated the effects of including kinematic constraints in the analysis of knee kinematics from skin markers and compared the result to simultaneously recorded trajectories of bone pin markers during gait of six healthy subjects. The constraint equations that were considered for the knee were spherical and revolute joints, which have been frequently used in musculoskeletal modelling. In the models, the joint centres and joint axes of rotations were optimised from the skin marker trajectories over the trial. It was found that the introduction of kinematic constraints did not reduce the error associated with soft tissue artefacts. The inclusion of a revolute joint constraint showed a statistically significant increase in the mean flexion/extension joint angle error and no statistically significant change for the two other mean joint angle errors. The inclusion of a spherical joint showed a statistically significant increase in the mean flexion/extension and abduction/adduction errors. In addition, when a spherical joint was included, a statistically significant increase in the sum of squared differences between measured marker trajectories and the trajectories of the pin markers in the models was seen. From this, it was concluded that both more advanced knee models as well as models of soft tissue artefacts should be developed before accurate knee kinematics can be calculated from skin markers.

Background Temporal-spatial gait parameters improve following total knee arthroplasty (TKA) but lower limb kinematics and moments fail to match those of age-matched healthy individuals. The aim of this study was to determine whether quadriceps strength, clinical measures of knee function, lower limb kinematics, and joint moments improve following arthroplasty and normalize over time. Methods Twelve patients underwent total knee arthroplasty were tested at 3 and 12 months following surgery. Twelve matched controls were also tested. All underwent quadriceps strength testing and gait analysis to calculate knee joint kinematics and kinetics. Function was assessed using clinical tests and self-report. Findings All clinical measures except for quadriceps strength significantly improved from 3 to 12 months. Gait asymmetry was observed at 3 months (lower stance times, peak knee flexion angle, range of motion and vertical ground reaction force), but ankle, knee and hip moments contributing to the total limb support moment were equivalent between legs. At 12 months, gait speed remained significantly slower than controls. Inter-limb differences in peak knee flexion angle and range of motion persisted. Greater hip and lower knee moments were evident in the operated limb, compared to the non-operated limb and controls. Quadriceps strength was positively correlated with faster times on the Time Up and Go and Stair Climbing Test and greater distances during the 6 Minute Walk test. Interpretation Patients who have undergone TKA demonstrate improvements in function as measured by self-report and functional performance measures. Gait becomes more symmetric and quadriceps strength becomes stronger. Some approached the values of healthy control subjects. Important differences still remain however. The larger hip extensor contribution to the total support moment may be to compensate for the diminished knee extensor contribution during level walking. Since instrumented gait analysis and functional performance measures appear to reflect different aspects of recovery following total knee replacement, both should be considered when evaluating gait and function.

Background: Evidence that knee braces used for the treatment of osteoarthritis mediate pain relief and improve function by unloading the joint (increasing the joint separation) remains inconclusive. Alternatively, valgus-producing braces may mediate pain relief by mechanically stabilizing the joint and reducing muscle cocontractions and joint compression. In this study, therefore, we sought to examine the degree to which so-called unloader braces control knee instability and influence muscle cocontractions during gait. Methods: Sixteen subjects with radiographic evidence of knee malalignment and medial compartment osteoarthritis were recruited and fitted with a custom Generation II Unloader brace. Gait analysis was performed without use of the brace and with the brace in neutral alignment and in 4° of valgus alignment. A two-week washout period separated the brace conditions. Muscle cocontraction indices were derived for agonist and antagonist muscle pairings. Pain, instability, and functional status were obtained with use of self-reported questionnaires, and the results were compared. Results: The scores for pain, function, and stability were worst when the knee was unsupported (the baseline and washout conditions). At baseline, nine of the sixteen patients reported knee instability and five of the nine complained that it affected their activities of daily living. Poor knee stability was found to be correlated with low ratings for the activities of daily living, quality of life, and global knee function and with increased pain and symptoms. Knee function and stability scored best with the brace in the neutral setting compared with the brace in the valgus setting. The cocontraction of the vastus lateralis-lateral hamstrings was significantly reduced from baseline in both the neutral (p = 0.014) and valgus conditions (p = 0.023), and the cocontraction of the vastus medialis-medial hamstrings was significantly reduced with the valgus setting (p = 0.068), as a result of bracing. Patients with greater varus alignment had greater decreases in vastus lateralis-lateral hamstring muscle cocontraction. Conclusions: When knees with medial compartment osteoarthritis are braced, neutral alignment performs as well as or better than valgus alignment in reducing pain, disability, muscle cocontraction, and knee adduction excursions. Pain relief may result from diminished muscle cocontractions rather than from so-called medial compartment unloading.

The goal of opening wedge high tibial osteotomy (HTO) is to reduce excessive loading on the medial compartment of the knee by correcting varus deformity, thereby reducing pain and improving function. Although surgical outcome is reportedly poor in cases of under- or over-correction, the recommended alignment varies. The aim of this study was to investigate the effect of the degree of frontal plane knee alignment following open wedge HTO surgery on muscle co-contraction, joint moments, and self-reported functional outcome. Sixteen patients with medial compartment osteoarthritis (OA), who were scheduled for an opening wedge osteotomy, were recruited for participation in the study. Data were collected using an optoeletric motion analysis system and varus and valgus angulations of the knee were measured, using standing, long cassette, radiographs of the lower extremities. Results showed that physical function improved significantly overall (p < 0.001). However, those subjects whose knee alignment was further away from the group’s postoperative mean tended to improve less in their Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS) scores than those closer to the mean (p = 0.07). They also had higher medial and lateral co-contractions and higher adduction moments one year after surgery (p ≤ 0.009 and p = 0.048, respectively) and were more likely to show a change towards increased medial muscle co-contraction following surgery, when compared to presurgical values. This outcome may contribute to accelerated degeneration of the knee for this group of people. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 2007

Eight healthy male subjects had intra-cortical bone-pins inserted into the proximal tibia and distal femur. Three reflective markers were attached to each bone-pin and four reflective markers were mounted on the skin of the tibia and thigh, respectively. Roentgen-stereophotogrammetric analysis (RSA) was used to determine the anatomical reference frame of the tibia and femur. Knee joint motion was recorded during walking and cutting using infrared cameras sampling at 120Hz. The kinematics derived from the bone-pin markers were compared with that of the skin-markers. Average rotational errors of up to 4.4 degrees and 13.1 degrees and translational errors of up to 13.0 and 16.1mm were noted for the walk and cut, respectively. Although skin-marker derived kinematics could provide repeatable results this was not representative of the motion of the underlying bones. A standard error of measurement is proposed for the reporting of 3D knee joint kinematics.

Posterior impingement syndromes of the ankle have been well described in the literature. It is most commonly associated with a prominent or fractured posterior talar process, an os trigonum or fibrotic scar tissue [Foot Ankle Int 15 (1994) 2; J Bone Joint Surg Am 78 (1996) 1491; Foot Ankle 11 (1991) 404]. There have been few reports of isolated posteromedial impingement lesions and those reported discuss findings of mechanical impingement resulting from disorganised scar tissue or ligament damage [Arthroscopy 9 (1993) 709; Am J Sports Med 29 (2001) 550]. We present two cases of posteromedial impingement of the ankle resulting from an isolated accessory bony lesion, causing symptoms distinct from fibrotic scar tissue impingement or the os trigonum syndrome.

The complexity of human tibiofemoral joint motion is now better understood with the advancement of new methodologies to measure tibiofemoral kinematics in vivo. Marker clusters anchored to stainless steel bone pins inserted directly into the femur and tibia provide the most sensitive and accurate means for directly measuring skeletal tibiofemoral joint motion. Despite its invasiveness, this technique has been successful, although complications have been reported with the femoral pin and its insertion site. The purpose of this technical report is twofold: to review the difficulties with the femoral pin and its insertion site from a historical perspective, and to identify the load force required from biological tissue to permanently deform the pin. In addition, proposals in the advancement of this method are discussed in the context of reducing impingement with the femoral pin and the Iliotibial band. Because stainless steel exhibits plastic behaviour with no sharp yield point, Apex self-drilling/self-tapping bone pins underwent incremental loading on an Instron materials testing machine. Loads were transmitted perpendicular to the pin with the threads partially exposed and fully secured in vice. Since the accuracy of our combined stereophotogrammetry and Optoelectric motion analysis was less than 0.4 mm, it was decided that plastic deformation occurred after deflections of 0.4 mm. With exposed threads, deflections larger than 0.4 mm were observed at 150 N and 100 N when loads were applied at 15 mm and 20 mm from the vice (representative of where the tissue came in contact with the pin). Loads greater than 200 N produced deflections less than 0.2 mm when threads were fully inserted. The 90 Hz resonant frequency for the marker cluster-bone pin complex is beyond the spectrum of human movement and can be lowpass filtered. To reduce impingement and pin bending, one solution may be to implant pins with a shorter threaded section. By completely penetrating the bone, only the smooth surface of the pin is exposed which is more resistant to bending. Otherwise pins with larger diameters and longer longitudinal incisions about the femoral insertion site are an alternative. Lengthening the longitudinal incisions about the insertion site, and correctly aligning and inserting the femoral pin between the Iliotibial band and quadriceps tendon may diminish impingement. Performing dynamic open chain flexion and extension movements while on the operating table may aid in aligning the pin at the incision site. This may stretch the IT band and quadriceps tendon and may guide the femoral pin into a more optimal position prior to it being inserted into the cortex of the bone.

Motion analyses of lower body mechanics offer new schemas to address injury prevention strategies among baseball pitchers, where the influence of stride length remains unknown. This study examined the temporal effect of stride length at constituent pitching events and phases. Nineteen competitive pitchers (15 collegiate, 4 high school) were randomly assigned to pitch two simulated, 80-pitch games at ±25% of their desired stride length. An integrated, three-dimensional motion capture system recorded each pitch. Paired t-tests were used to determine whether differences between stride conditions at respective events and within phases were significantly different. The results demonstrate the shorter strides mediated earlier onset of stride foot contact, reduced time in single support whereas double support intervals increased (p

CROTIN, R. L., K. KOZLOWSKI, P. HORVATH, and D. K. RAMSEY. Altered Stride Length in Response to Increasing Exertion among Baseball Pitchers. Med. Sci. Sports Exerc., Vol. 46, No. 3, pp. 565–571, 2014. Background: Overexertion caused by increased pitch counts can evoke protective biomechanical responses signified by decreased ball velocity, such as reduced throwing arm kinematics and kinetics. Among skilled pitchers, overexertion may not always present ball velocity decrements, because compensatory throwing biomechanics aid in maintaining peak ball velocity although lowering physiologic stress. Methods: Nineteen pitchers (collegiate and elite high school), randomly crossed over to pitch two simulated games at T25% of their desired stride length, were recorded by an eightcamera motion capture system (240 Hz) integrated with two piezoelectric force plates (960 Hz) and a professional model radar gun. HR, self-reported exertion scores, blood glucose and lactate, salivary biomarkers, peak linear hand and fastball velocities were examined. Repeated-measures ANOVA as well as independent and pairwise t-tests examined significant differences (P e 0.05). Results: Shortened strides reduced mean pitching HR by 11.1 bpm (P G 0.001), improved recovery capacity by 5.76% (P = 0.012), and lowered salivary cortisol from baseline (P = 0.001). Physiologic stress elevated with greater strides, because salivary alpha amylase was significantly elevated from baseline (P = 0.011) with no improvements evidenced in pitching HR or recovery capacity. Linear hand and ball velocities remained equivalent between stride conditions. Conclusion: Stride length can affect physical exertion without disrupting ball velocity, where shortening strides can plausibly respond to competitive exertion in baseball pitchers. Current pitch count standards and radar velocity accounts have not been proven efficacious in predicting exertion in professional and collegiate baseball, where biomechanical compensations arise to maintain ball velocity. In some instances, compensatory adaptations may be pathomechanic where future research

Regular exercise and weight reduction are not only important for maintaining general health, they are also strongly recommended conservative modalities for managing knee osteoarthritis (OA). The objective of this paper is to discuss the mechanics of knee joint loading and to review the most recent literature with respect to the functionality and efficacy of unloader braces for managing knee OA, specifically from the perspective of the middle-aged athlete. Evidence suggests valgus braces for medial compartment knee OA significantly reduce knee adduction angle measures and improve measures relating to medial knee joint loading, as well as gait symmetry and speed. Benefits were demonstrated during walking and during more demanding functional measures such as running and negotiating stairs. No studies have investigated the efficacy of bracing for relatively young athletic OA patients and, thus, the role of bracing for this population during sports remains unclear.

Background:For persons with unicompartment knee osteoarthritis (OA), off-unloader braces are a mechanical intervention designed to reduce pain, improve physical function, and possibly slow disease progression. Pain relief is thought to be mediated by distracting the involved compartment via external varus or valgus forces applied to the knee. In so doing, tibiofemoral alignment is improved, and load is shifted off the degenerative compartment, where exposure to potentially damaging and provocative mechanical stresses are reduced.Objectives:To provide a synopsis of the evidence documented in the scientific literature concerning the efficacy of offloader knee braces for improving symptomatology associated with painful disabling medial compartment knee OA.Search Strategy:Relevant peer-reviewed publications were retrieved from a MEDLINE search using the terms with the reference terms osteoarthritis, knee, and braces (per Medical Subject Headings), plus a manual search of bibliographies from original and review articles and appropriate Internet resources.Results:For persons with combined unicompartment knee OA and mild to moderate instability, the strength of recommendation reported by the Osteoarthritis Research Society International in the ability of off-loader knee braces to reduce pain, improve stability, and diminish the risk of falling was 76% (95% confidence interval, 69%–83%). The more evidence the treatment is effective, the higher the percentage.Conclusions:Given the encouraging evidence that off-loader braces are effective in mediating pain relief in conjunction with knee OA and malalignment, bracing should be fully used before joint realignment or replacement surgery is considered. With the number of patients with varus deformities and knee pain predicted to increase as the population ages, a reduction of patient morbidity for this widespread chronic condition in combination with this treatment modality could have a positive impact on health care costs and the economic productivity and quality of life of the affected individuals.

We investigated the accuracy of a linear soft tissue artefact (STA) model in human movement analysis. Simultaneously recorded bone-mounted pin and skin marker data for the thigh and shank during walking, cutting and hopping were used to measure and model the motion of the skin marker clusters within anatomical reference frames (ARFs). This linear model allows skin marker movements relative to the underlying bone contrary to a rigid-body assumption. The linear model parameters were computed through a principal component analysis, which revealed that 95% of the variance of the STA motion for the thigh was contained in the first four principal components for all three tasks and all subjects. For the shank, 95% of the variance was contained in the first four principal components during walking and cutting and first five during hopping. For the thigh, the maximum residual artefact was reduced from 27.0 mm to 5.1 mm (walking), 22.7 mm to 3.0 mm (cutting) and 16.2 mm to 3.5 mm (hopping) compared to a rigid-body assumption. Similar reductions were observed for the shank: 24.2 mm to 1.9 mm (walking), 20.3 mm to 1.9 mm (cutting) and 14.7 mm to 1.8 mm (hopping). A geometric analysis of the first four principal components revealed that, within the ARFs, marker cluster STA is governed by rigid-body translations and rotations rather than deformations. The challenge remains, however, in finding the linear model parameters without bone pin data, but this investigation shows that relatively few parameters in a linear model are required to model the vast majority of the STA movements.

In order to identify abnormal or pathological motions associated with clinically relevant questions such as injury mechanisms or factors leading to joint degeneration, it is essential to determine the range of normal tibiofemoral motion of the healthy knee. In this study we measured in vivo 3D tibiofemoral motion of the knee during gait and characterized the nonsagittal plane rotations and translations in a group of six healthy young adults. The subjects were instrumented with markers placed on intracortical pins inserted into the tibia and femur as well as marker clusters placed on the skin of the thigh and shank. The secondary rotations and translation excursions of the knee were much smaller than those derived from skin markers and previously described in the literature. Also, for a given knee flexion angle, multiple combinations of transverse and frontal plane knee translation or rotation positions were found. This represents normal knee joint motions and ensemble averaging of gait data may mask this important subject-specific information.

Functional outcomes in anterior cruciate ligament-deficient "potential copers" and "non-copers" may be related to their knee stabilization strategies. Therefore, the purpose of this study was to differentiate dynamic knee stabilization strategies of potential copers and non-copers through analysis of sagittal plane knee angle and tibia position during disturbed and undisturbed unilateral standing. Ten uninjured potential coper and non-coper subjects stood in unilateral stance on a platform that translated anteriorly, posteriorly and laterally. Knee angle and tibia position with reference to the femur were calculated before and after platform movement. During perturbation trials, potential copers maintained kinematics that were similar to uninjured subjects across conditions. Conversely, non-copers stood with greater knee flexion than uninjured subjects and a tibia position that was more posterior than the other groups. Both non-copers and potential copers demonstrated small changes in tibia position following platform movement, but direction of movement was not similar. The similarities between the knee kinematics of potential copers and uninjured subjects suggest that potential copers compensated well from their injury by utilizing analogous dynamic knee stabilization strategies. In comparison to the other groups, by keeping the knee in greater flexion and the tibia in a more posterior position, non-copers appear to constrain the tibia in response to a challenging task, which is consistent with a "stiffening strategy". Based on the poor functional outcomes of non-copers, a stiffening strategy does not lead to dynamic knee stability, and the strategy may increase compressive forces which could contribute to or exacerbate articular cartilage degeneration.

The purpose of this study was to develop a regression equation capable of accurately predicting a 1 repetition maximum bench press in collegiate women athletes. The findings of this study could benefit future women athletes by providing coaches and trainers with an easy method of determining maximum upper body strength in women athletes. Sixty-five University of Georgia NCAA Division 1 women athletes from 9 different sports were measured prior to the start of their season utilizing 2 repetition tests to fatigue (25 kg: REPS55; 31.8 kg: REPS70) and a 1 repetition maximum (1RM) bench press test in random order. Other independent variables that were used with a submaximal weight to predict 1RM were total body weight, lean body mass (LBM), height, and percent body fat. The variables of REPS70 and LBM were the best predictors of 1RM utilizing Pearson product correlations (r = 0.909, p = 0.000; r = 0.445, p = 0.000) and multiple regression results (R(2) = 0.834, p = 0.000) for this population. The results from this study indicate muscular endurance repetitions using an absolute weight of 31.8 kg in conjunction with LBM can be used to accurately predict 1RM bench press strength in collegiate women athletes.

Examine the neuromuscular response to functional knee bracing relative to anterior tibial translations in vivo.During randomised brace conditions, electromyographic data with simultaneous skeletal tibiofemoral kinematics were recorded from four anterior cruciate ligament deficient subjects to investigate the effect of the DonJoy Legend functional brace during activity.Knee braces do not increase knee stability but may influence afferent inputs from proprioception and therefore one might expect changes in muscle firing patterns, amplitude and timing.Hoffman bone pins affixed with markers were implanted into the tibia and femur for kinematic measurement. The EMG data from the rectus femoris, semitendinosus, biceps femoris, and lateral head of the gastrocnemius were integrated for each subject in three separate time periods: 250 ms preceding footstrike and two consecutive 125 ms time intervals following footstrike.With brace, semitendinosus activity significantly decreased 17% prior to footstrike whereas bicep femoris significantly decreased 44% during A2, (P0.05). Rectus femoris activity significantly increased 21% in A2 (P0.05). No consistent reductions in anterior translations were evident.Our preliminary findings, based on a limited number of subjects, indicate joint stability may result from proprioceptive feedback rather than the mechanical stabilising effect of the brace. Despite a significant increase in rectus femoris activity upon landing, only one subject demonstrated an increase in anterior tibial drawer.Studies have shown functional braces do not mechanically stabilise the anterior cruciate ligament deficient knee. Perhaps bracing alters proprioceptive feedback. It has been shown that bracing the anterior cruciate ligament deficient knee may affect hamstring and quadriceps activity. Our findings stresses the importance of functional knee bracing combined with proprioceptive and muscular coordination training in order to increase joint stability.

Objective . The purpose of this study was to compare the kinematics, muscle activation, and force production between Parkinson's patients and healthy, age-matched participants during sit-to-stand transfers. Design . This cross-sectional study employed a 2 × 2 × 3 multivariate analysis of variance to test for significant differences between and within groups. Background . The underlying mechanisms that predispose an individual to lose strength during the clinical progression of Parkinson's disease have proved to be elusive, especially during performance of functional tasks such as the sit to stand transfer. Methods . Twenty-four men (mean age: 71.5 years) categorized as Parkinson's patients ( n =13) and healthy adults ( n =11) participated in this study. Two force platforms measured antero-posterior and vertical force components as well as peak torque. Muscle activation was measured by a six channel, bilateral electromyography system. A lower-body kinematic assessment was conducted utilizing a highspeed motion analysis system. Results . No statistically significant differences were found between groups for the outcome variables measured. However, Parkinson's patients did exhibit significant within -group bilateral differences for the variables of knee angle at seat-off, peak vertical force and peak torque. Conclusion . Data from this study reveal that persons with mild to moderate Parkinson's disease exhibit moderately altered bilateral mechanics when performing a sit to stand transfer compared to their healthy peers. Relevance The inability to produce constant equilateral force when performing functional tasks could be an indicator for the increased propensity of falls or other instabilities in this population.

To determine whether knee flexion influenced bony contact movements during flexion.Accurate three-dimensional (3D) measurements of tibiofemoral bony contact points in vivo was performed using magnetic resonance imaging technology at 0 degrees, 30 degrees and 60 degrees of flexion.Magnetic resonance imaging is an accurate non-invasive tool for visualizing muscles, tendons, and bone, and provides precise 3D co-ordinates.Magnetic resonance imaging recordings were made from the right knee of 16 subjects with no history of knee dysfunction at 0 degrees, 30 degrees and 60 degrees of flexion. Joint contact movements were reported as changes of the contact point's position on the medial and lateral tibial condyle with respect to a fixed reference point for each flexion angle.The dominant motion of the centroid of the contact area was posterior with a concomitant inferior and lateral displacement when flexing from 0-30 degrees. Increased flexion to 60 degrees the contact points moved slightly anterior, superior and continued laterally. Comparing movements between the medial and lateral compartments, larger displacement magnitudes were observed laterally. Additionally, tibial rotations of 3-5 degrees were noted relative to the femur.Based on magnetic resonance imaging co-ordinates and the rotated anatomical reference frame, the geometric equations to derive the contact point between the tibiofemoral articulating surfaces is a viable means to investigate tibiofemoral bony contact movement.Contact areas and pressure distributions have been reported using cadaveric specimens but interpretation of the results is limited. Other investigations have been restricted to sagittal plane movement. Using kinematic magnetic resonance imaging, accurate non-invasive 3D recordings of the normal knee at increments of flexion are possible. The normative baseline date can be compared against that of the pathological knee, such as cruciate ligament injury or the status of post-operative meniscectomy in order to examine skeletal joint motion and stability.

Objective. To describe three-dimensional tibial and femoral movements in vivo and examine the effect of a brace on knee kinematics during moderate to intense activity. Design. Skeletal kinematics of anterior cruciate ligament deficient knees was measured with and without braces during moderate to intense activity. Background. Invasive markers implanted into the tibia and femur are the most accurate means to directly measure skeletal motion and may provide a more sensitive measure of the differences between brace conditions. Methods. Steinmann traction pins were implanted into the femur and tibia of four subjects having a partial or complete anterior cruciate ligament rupture. Non-braced and braced conditions were randomly assigned and subjects jumped for maximal horizontal distance to sufficiently stress the anterior cruciate ligament. Results. Intra-subject peak vertical force and posterior shear force were generally consistent between conditions. Intra-subject kinematics was repeatable but linear displacements between brace conditions were small. Differences in angular and linear skeletal motion were observed across subjects. Bracing the anterior cruciate ligament deficient knee resulted in only minor kinematic changes in tibiofemoral joint motion. Conclusion. In this study, no consistent reductions in anterior tibial translations were observed as a function of the knee brace tested. Relevance Investigations have reported that knee braces fail when high loads are encountered or when load is applied in an unpredictable manner. Questions remain regarding tibiofemoral joint motion, in particular linear displacements. The pin technique is a means for direct skeletal measurement and may provide a more sensitive measure of the differences between brace conditions.

The purpose of this review article is twofold: to report on the use of intracortical pins to measure three-dimensional tibiofemoral and patellofemoral joint kinematics and highlight methodological concerns associated with this procedure. Tibiofemoral and patellofemoral kinematics has been extensively investigated using reflective markers attached to the surrounding soft tissue of the calf and thigh. However, surface markers may not adequately represent true anatomical locations and skin movement artefacts present the most critical source of measurement error. Consequently, knowledge about skeletal tibiofemoral kinematics is limited, in particular abduction-adduction and internal-external rotations. Considerable questions remain regarding what constitutes normal motion of the knee. A way to avoid the problem of surface markers is use invasive markers to directly measure skeletal motion. To date, many co-ordinate systems have been used to describe three-dimensional skeletal kinematics of the lower limb in vivo. They include helical axes, finite helical axes, instantaneous helical axes, and the joint co-ordinate system based on local anatomic landmarks. Although each method accurately describes the relative motion in 6 d. of f., the differences in how the motion is partitioned may account for the differences across investigations. Additionally, the problem of defining the anatomical co-ordinate system makes comparisons across subjects and studies difficult since subtle differences may be caused by small deviations in the anatomical reference alignment. Cross talk is also a primarily a concern. For joints that articulate principally about one axis, the primary flexion/extension that is registered will be cross-talked into ab/adduction and internal/external rotations.