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Abstract: Choice, EE, Tufano, JJ, Jagger, KL, and Cochrane-Snyman, KC. Match-play external load and internal load in NCAA Division II women's soccer. J Strength Cond Res 37(12): e633-e639, 2023-The purpose of this study was to describe average match-play demands for NCAA DII women's soccer, including positional and time-specific differences, and relationships between variables. External load was assessed using total distance, relative distance, sprint distance, number of power plays, peak speed, and Player Load. Internal load was assessed using session rating of perceived exertion (sRPE). Mixed factor analysis of variance was used to assess time by position (midfielder, forward, or defender) for dependent measures. Correlations were assessed between separate pair groups. Average match-play demands included 9,463 ± 2,591 m total distance, 172 ± 48 m·min -1 relative distance, 531 ± 301 m sprint distance, peak speeds of 26 ± 1.6 kph, 46.71 ± 21.75 power plays, and 457.84 ± 121.78 AU Player Load. Significant ( p < 0.05) positional differences were found for total distance, Player Load, match load, and peak speed. Significant, moderate correlations were found between relative distance and match load, and sRPE and total distance, Player Load, and power plays (all p < 0.001). Results indicate there are positional differences within a women's DII soccer team, with midfielders accumulating the longest distances (10,509 ± 2,913 m) and greatest Player Load (527.79 ± 130.5 AU) and match load (576 ± 343 AU), forwards running the fastest peak speeds (26.8 ± 1.5 kph), and defenders maintaining most consistent performance. Match-play external and internal load data should be monitored by player position and half for DII women's soccer., (Copyright © 2023 National Strength and Conditioning Association.)

Purpose: This study aimed to assess the V̇O 2 uptake obtained during a GXT and subsequent verification phase in untrained participants in a hot environment., Methods: Twelve sedentary males completed a GXT followed by a biphasic supramaximal-load verification phase in a hot environment (39°C, 32% relative humidity). Rest between tests occurred in a temperate chamber and lasted until gastrointestinal temperature returned to baseline., Results: Mean verification phase V̇O 2max (37.8 ± 4.3 mL·kg -1 ·min -1 ) was lower than GXT (39.8 ± 4.1 mL·kg -1 ·min -1 ; P = 0.03) and not statistically equivalent. Using an individualized analysis approach, only 17% (2/12) of participants achieved a V̇O 2 plateau during the GXT. Verification phase confirmed GXT V̇O 2max in 100% of participants, whereas the traditional and the new age-dependent secondary V̇O 2max criteria indicated GXT V̇O 2max achievement at much lower rates (8/12 [67%] vs 7/12 [58%], respectively). Correlational indices between GXT and verification phase V̇O 2max were strong (intraclass correlation coefficient = 0.95, r = 0.86), and Bland-Altman analysis revealed a low mean bias of -2.1 ± 1.9 mL·kg -1 ·min -1 and 95% limits of agreement (-5.8 to 1.7 mL·kg -1 ·min -1 )., Conclusions: Very few untrained males achieved a V̇O 2 plateau during GXT in the heat. When conducting GXT in a hot condition, the verification phase remains a valuable addition to confirm V̇O 2max in untrained males., (Copyright © 2023 Written work prepared by employees of the Federal Government as part of their official duties is, under the U.S. Copyright Act, a “work of the United States Government” for which copyright protection under Title 17 of the United States Code is not available. As such, copyright does not extend to the contributions of employees of the Federal Government.)

Purpose: The purpose of this study was to explore whether offset loading in the barbell squat altered ground-reaction force (GRF) and muscle activation in the dominant (D) and nondominant (ND) lower limb compared to traditional squats., Methods: Twelve well-trained men (age 26.4 [3.2] y; 10.3 [1.9] y experience) performed 3 sets of 10 repetitions at 60% of their previously measured 1-repetition maximum. Sets were quasi-randomized between traditional loading (TDL), dominant-side offset loading (OS-D), and nondominant-side offset loading (OS-ND). All repetitions were performed on a dual force plate with electromyography sensors on the prime mover muscles of the squat. GRF symmetry was assessed using the symmetry index (SI) to determine the direction (D [+] or ND [-]) and magnitude (%) of the asymmetry. Finally, the first 3 and final 3 repetitions of each set were compared for compensatory changes in symmetry., Results: OS-D induced a significant change in limb SI relative to TDL (5.21% vs 1.44%; P = .011); however, no significant difference in limb SI was seen between TDL and OS-ND (-0.66% vs 1.44%; P = .278). No asymmetries between D and ND muscle activation were present in any condition. TDL and OS-D squats exhibited significant improvements in limb SI between the first 3 and final 3 repetitions (P = .035 and .011, respectively); however, no such improvement was seen in OS-ND., Conclusions: OS-D is capable of significantly altering GRF limb SI in a bilateral squat; however, OS-ND appears to exhibit no GRF or electromyography effects relative to TDL. Thus, the results of this study do not support the use of OS-ND in the pursuit of strengthening a weaker limb, suggesting that unilateral training may be a preferred mode of exercise for this desired outcome.

Advancements in sport technology have made quantifying match-play external load (e.g., total distance, sprint distance, number of sprints) a popular option for athletics personnel. These variables of volume and intensity are useful for both objectively monitoring training in field-based sports and for designing training programs. As physical abilities differ across playing levels, match-play demands likely also differ. This narrative review compiles and compares the match-play external load data for women's soccer at the professional and collegiate levels. Databases were searched through July 2022, yielding 13 primary articles that assessed the match-play demands of women's soccer (3 professional, 8 Division I, 1 Division II, and 1 Division III). The results indicate that the average total distance covered were similar between the professional, Division I and Division III levels, but the variability was greater among Division III compared to professional and Division I players. Data for Division II are scarce, but the total distance covered appears to be less than for professional, Division I and Division III. There was also large variability for sprint distance and number of sprints across data at all playing levels. Considering the lack of studies of Division II and Division III players, more research is necessary to determine how playing level may affect external load profiles, as isolated studies likely only reflect data from isolated teams.

Abstract: Jenkins, NDM, Miramonti, AA, Hill, EC, Smith, CM, Cochrane-Snyman, KC, Housh, TJ, and Cramer, JT. Mechanomyographic amplitude is sensitive to load-dependent neuromuscular adaptations in response to resistance training. J Strength Cond Res 35(11): 3265-3269, 2021-We examined the sensitivity of the mechanomyographic amplitude (MMGRMS) and frequency (MMGMPF) vs. torque relationships to load-dependent neuromuscular adaptations in response to 6 weeks of higher- vs. lower-load resistance training. Twenty-five men (age = 22.8 ± 4.6 years) were randomly assigned to either a high- (n = 13) or low-load (n = 12) training group and completed 6 weeks of leg extension resistance training at 80 or 30% 1RM. Before and after 3 and 6 weeks of training, mechanomyography signals were recorded during isometric contractions at target torques equal to 10-100% of the subjects' baseline maximal strength to quantify MMGRMS and MMGMPF vs. torque relationships. MMGRMS decreased from Baseline to weeks 3 and 6 in the high-load, but not low-load group, and was dependent on the muscle and intensity of contraction examined. Consequently, MMGRMS was generally lower in the high- than low-load group at weeks 3 and 6, and these differences were most apparent in the vastus lateralis (VL) and rectus femoris muscles at higher contraction intensities. MMGMPF was greater in the high- than low-load training group independent of time or muscle. The MMGRMS vs. torque relationship was sensitive to load-dependent, muscle-specific neuromuscular adaptations and suggest reductions in neuromuscular activation to produce the same absolute submaximal torques after training with high, but not low loads., (Copyright © 2019 National Strength and Conditioning Association.)

Purpose: This study aimed to investigate the effect of CBD oil on perceived muscle soreness, inflammation, and strength performance after eccentric exercise (ECC) of the elbow flexors., Methods: Thirteen untrained men (mean ± SD age, 21.85 ± 2.73 yr) performed 6 sets of 10 maximal ECC isokinetic muscle actions of the elbow flexors as part of a double-blind crossover design. Noninvasive (perceived soreness, arm circumference, hanging joint angle (JA), and peak torque (PT)) measures were taken before and after ECC, and 24, 48, and 72 h after ECC. All subjects completed both the supplement (CBD: 150 mg POST, 24 h, 48 h) and placebo (PLC: POST, 24 h, 48 h) condition separated by 2 wk. Four separate two-way repeated-measures ANOVA (condition [CBD vs PLC] × time [PRE vs POST vs 24 h vs 48 h vs 72 h]) were used to analyze perceived soreness, arm circumference, JA, and PT. One-way repeated-measures ANOVA were used to decompose significant interactions and main effects., Results: There was no condition-time interaction or main effect of condition (P > 0.05) for perceived soreness, arm circumference, JA, or PT. There were main effects for time for perceived soreness (P = 0.000, ηp2 = 0.71) and JA (P = 0.006, ηp2 = 0.35)., Conclusions: The current dose of 150 mg CBD oil at POST, 24 h, and 48 h had no effect on noninvasive markers of muscle damage in the upper extremity. At the current dose and schedule, CBD oil may not be beneficial for untrained men as a recovery aid after exercise-induced muscle damage., (Copyright © 2021 by the American College of Sports Medicine.)

Purpose: This study aimed to evaluate the validity and reliability of a verification test to confirm GXT V˙O2max in a hot environment., Methods: Twelve recreationally trained cyclists completed a two-test protocol that included a GXT progressing 20 W·min-1 followed by a biphasic supramaximal-load verification test (1 min at 60% increasing to 110% maximal GXT wattage until failure) in a hot environment (39°C, 32% relative humidity). Rest between tests occurred in a thermoneutral room and was anchored to the duration required for gastrointestinal temperature to return to baseline., Results: Mean verification test V˙O2max (51.3 ± 8.8 mL·kg-1·min-1) was lower than GXT (55.9 ± 7.6 mL·kg-1·min-1, P = 0.02). Verification tests confirmed GXT V˙O2max in 92% of participants using individual analysis thresholds. Bland-Altman analysis revealed a sizable mean bias (-4.6 ± 4.9 mL·kg-1·min-1) with wide 95% limits of agreement (-14.0 to 5.0 mL·kg-1·min-1) across a range of V˙O2max values. The high coefficient of variation (9.6%) and typical error (±3.48 mL·kg-1·min-1) indicate potential issues of test-retest reliability in the heat., Conclusions: Verification testing in a hot condition confirmed GXT V˙O2max in virtually all participants, indicating robust utility. To enhance test-retest reliability in this environment, protocol recommendations for work rate and recovery between tests are provided., (Copyright © 2020 by the American College of Sports Medicine.)

Objectives: This study examined the time course of changes and patterns of responses in electromyographic amplitude (EMG AMP) and EMG mean power frequency (MPF) for the superficial quadriceps muscles during exhaustive treadmill runs within the severe exercise intensity zones (SIZ 1 and SIZ 2 )., Methods: The EMG signals for the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) as well as times to exhaustion (T lim ) were recorded in ten runners during two exhaustive treadmill runs (SIZ 1 and SIZ 2 ). The composite and individual responses were compared among muscles and between intensities., Results: The composite patterns of responses in EMG AMP (linear, quadratic, and cubic increases; r 2 /R 2 =0.684-0.848) and EMG MPF (linear, quadratic, and cubic decreases; r 2 /R 2 =0.648 - 0.852) for the VL and RF were consistent with neuromuscular fatigue in both zones, but those for the VM were not (quadratic, cubic, and non-significant relationships with responses near baseline). The RF tended to demonstrate greater fatigue (EMG MPF decreased from 80-100% T lim ). There was large inter-individual variability (only 10-60% of responses consistent with composite) in response to fatiguing treadmill running., Conclusions: The current findings support the examination and characterization of neuromuscular fatigue on an intensity, muscle, and subject-by-subject basis., Competing Interests: Dr. Nathaniel Jenkins reports grants from the American Heart Association, National Strength and Conditioning Association Foundation, and from the Center for Integrative Research on Childhood Adversity under NIGMS Award Number P20GM109097, personal fees from serving as a book reviewer for Human Kinetics, and honorarium from the National Strength and Conditioning Association as a speaker at the 2019 Annual Meeting; all outside of the submitted work. The remaining authors have nothing to disclose.

Purpose: The mediators of the perception of effort during exercise are still unclear. The aim of the present study was to examine physiological responses during runs using a rating of perceived exertion (RPE)-clamp model at the RPE corresponding to the gas exchange threshold (RPE GET ) and 15% above GET (RPE GET+15% ) to identify potential mediators and performance applications for RPE during treadmill running., Methods: Twenty-one runners ([Formula: see text] max  = 51.7 ± 8.3 ml kg -1 min -1 ) performed a graded exercise test to determine maximal oxygen consumption and the RPE associated with GET and GET + 15% followed by randomized 60 min RPE-clamp runs at RPE GET and RPE GET+15% . Mean differences for [Formula: see text], heart rate (HR), minute ventilation ([Formula: see text]), respiratory frequency ([Formula: see text], respiratory exchange ratio (RER), and velocity were compared across each run., Results: After minute 14, [Formula: see text], RER and velocity did not differ across conditions, but decreased across time (p < 0.05). There was a significant (p < 0.05) condition × time interaction for [Formula: see text], where values were significantly higher during RPE-clamp runs at RPE GET+15% and decreased across time in both conditions. There were no differences across condition or time for HR, and only small difference between conditions for [Formula: see text]., Conclusions: HR and [Formula: see text] may play a role in mediating the perception of effort, while [Formula: see text], RER, and [Formula: see text] may not. Although HR and [Formula: see text] may mediate the maintenance of a perceptual intensity, they may not be sensitive to differentiate perceptual intensities at GET and GET + 15%. Thus, prescribing exercise using an RPE-clamp model may only reflect a sustainable [Formula: see text] within the moderate intensity domain.

Objectives: To examine the time course of changes in electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) responses during cycle ergometry to exhaustion performed above (CP +10% ) and below (CP -10% ) critical power (CP) to infer motor unit activation strategies used to maintain power output., Methods: Participants performed a 3-min all out test to determine CP, and 2 randomly ordered, continuous rides to exhaustion at CP +10% and CP -10% ·V̇O 2 , EMG AMP, EMG MPF, MMG AMP, MMG MPF, and time to exhaustion (T lim ) were recorded. Responses at CP -10% and CP +10% were analyzed separately., Results: At CP -10% , EMG and MMG AMP were significantly greater than the initial 5% timepoint at 100% T lim . EMG MPF and MMG MPF reflected a downward trend that resulted in no significant difference between timepoints. At CP +10% , EMG AMP was significantly greater than the initial 5% timepoint from 60% to 100% T lim . MMG AMP was less than the initial 5% timepoint at only 50% T lim . EMG and MMG MPF were significantly less than the initial 5% timepoint at 20% T lim and 100% T lim , respectively., Conclusions: The timecourse of changes in EMG and MMG signals were different at CP -10% and CP +10% , but responses observed indicated cycle ergometry to exhaustion relies on similar motor unit activation strategies.

Bergstrom, HC, Housh, TJ, Cochrane-Snyman, KC, Jenkins, NDM, Byrd, MT, Switalla, JR, Schmidt, RJ, and Johnson, GO. A model for identifying intensity zones above critical velocity. J Strength Cond Res 31(12): 3260-3265, 2017-The purpose of this study was to describe the V[Combining Dot Above]O2 responses relative to V[Combining Dot Above]O2peak at 4 different intensities within the severe domain and, based on the V[Combining Dot Above]O2 responses, identify intensity zones above critical velocity (CV). Twelve runners (mean ± SD age = 23.2 ± 3.0 years) performed an incremental treadmill test (ITT) to exhaustion to determine the V[Combining Dot Above]O2peak and velocity associated with V[Combining Dot Above]O2peak (vV[Combining Dot Above]O2peak). Critical velocity was determined from 4 exhaustive, constant velocity, randomly ordered treadmill runs (V1, V2, V3, and V4; V1 = highest, V4 = lowest). The V[Combining Dot Above]O2 responses were recorded during each of the constant velocity runs. Mean differences among V[Combining Dot Above]O2peak values from the ITT and the highest value recorded during the constant velocity runs were examined. The V[Combining Dot Above]O2 values at exhaustion for V1 (3.32 ± 0.10 L·min, p = 0.15) and V2 (3.27 ± 0.91 L·min, p = 0.13) were not significantly different from V[Combining Dot Above]O2peak (3.39 ± 0.96 L·min) from the ITT. The V[Combining Dot Above]O2 values at exhaustion for V3 (3.18 ± 0.88 L·min; p = 0.007) and V4 (3.09 ± 0.86 L·min; p = 0.003), however, were significantly less than the V[Combining Dot Above]O2peak from the ITT. There were intensity-dependent V[Combining Dot Above]O2 responses above CV. Based on these findings, we have hypothesized 3 intensity zones (first severe intensity zone [SIZ1], second severe intensity zone [SIZ2], and extreme intensity zone [EIZ]) within the severe and extreme domains, which are characterized by specific V[Combining Dot Above]O2 responses and may be used to design programs that maximize aerobic performance adaptations.

We examined the neuromuscular adaptations following 3 and 6 weeks of 80 vs. 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. Twenty-six men (age = 23.1 ± 4.7 years) were randomly assigned to a high- (80% 1RM; n = 13) or low-load (30% 1RM; n = 13) resistance training group and completed leg extension resistance training to failure 3 times per week for 6 weeks. Testing was completed at baseline, 3, and 6 weeks of training. During each testing session, ultrasound muscle thickness and echo intensity, 1RM strength, maximal voluntary isometric contraction (MVIC) strength, and contractile properties of the quadriceps femoris were measured. Percent voluntary activation (VA) and electromyographic (EMG) amplitude were measured during MVIC, and during randomly ordered isometric step muscle actions at 10-100% of baseline MVIC. There were similar increases in muscle thickness from Baseline to Week 3 and 6 in the 80 and 30% 1RM groups. However, both 1RM and MVIC strength increased from Baseline to Week 3 and 6 to a greater degree in the 80% than 30% 1RM group. VA during MVIC was also greater in the 80 vs. 30% 1RM group at Week 6, and only training at 80% 1RM elicited a significant increase in EMG amplitude during MVIC. The peak twitch torque to MVIC ratio was also significantly reduced in the 80%, but not 30% 1RM group, at Week 3 and 6. Finally, VA and EMG amplitude were reduced during submaximal torque production as a result of training at 80% 1RM, but not 30% 1RM. Despite eliciting similar hypertrophy, 80% 1RM improved muscle strength more than 30% 1RM, and was accompanied by increases in VA and EMG amplitude during maximal force production. Furthermore, training at 80% 1RM resulted in a decreased neural cost to produce the same relative submaximal torques after training, whereas training at 30% 1RM did not. Therefore, our data suggest that high-load training results in greater neural adaptations that may explain the disparate increases in muscle strength despite similar hypertrophy following high- and low-load training programs.

Purpose: To examine inter-individual variability versus composite models for the patterns of responses for electromyography (EMG) and mechanomyography (MMG) versus time relationships during moderate and heavy cycle ergometry using a rating of perceived exertion (RPE) clamp model., Methods: EMG amplitude (amplitude root-mean-square, RMS), EMG mean power frequency (MPF), MMG-RMS, and MMG-MPF were collected during two, 60-min rides at a moderate (RPE at the gas exchange threshold; RPEGET) and heavy (RPE at 15 % above the GET; RPEGET+15 %) intensity when RPE was held constant (clamped). Composite (mean) and individual responses for EMG and MMG parameters were compared during each 60-min ride., Results: There was great inter-individual variability for each EMG and MMG parameters at RPEGET and RPEGET+15 %. Composite models showed decreases in EMG-RMS (r (2) = -0.92 and R (2) = 0.96), increases in EMG-MPF (R (2) = 0.90), increases in MMG-RMS (r (2) = 0.81 and 0.55), and either no change or a decrease (r (2) = 0.34) in MMG-MPF at RPEGET and RPEGET+15 %, respectively., Conclusions: The results of the present study indicated that there were differences between composite and individual patterns of responses for EMG and MMG parameters during moderate and heavy cycle ergometry at a constant RPE. Thus, composite models did not represent the unique muscle activation strategies exhibited by individual responses when cycling in the moderate and heavy intensity domains when using an RPE-clamp model.