Background: Athletes with patellar tendinopathy (PT) have postural stability deficits; however, the underlying mechanisms and factors responsible remain unknown. The effect on postural stability in PT of decreased quadriceps strength, altered proprioception, lower-limb muscle tightness, and knee pain, which explain postural stability deficiency in other populations, is uninvestigated. Hypothesis: Proprioceptive acuity, muscle tightness, quadriceps strength, and pain predict postural stability in athletes with PT. Study Design: Cross-sectional comparative study. Level of Evidence: Level 2. Methods: A total of 43 athletes with PT and 43 healthy athletes were enrolled. Static and dynamic postural stability, proprioceptive acuity, muscle tightness, quadriceps strength, and pain were evaluated using a force platform, Y-balance test (YBT), a weight discrimination protocol, a goniometer, an isometric dynamometer, and a valid questionnaire, respectively. Results: Athletes with PT had significantly worse static and dynamic postural stability in the affected limb (AL) compared with the nonaffected limb (NAL) (P < 0.01) and the control group (P < 0.01). Athletes suffering from PT revealed lower quadriceps strength (P < 0.01), proprioceptive acuity (P = 0.02), and higher muscle tightness in the AL compared with the NAL and controls. Quadriceps weakness of the AL and pain in athletes with PT explained the variance of dynamic postural stability impairment. Conclusion: Athletes with PT have postural stability deficiency compared with healthy peers. Our results demonstrate that quadriceps muscle weakness and pain are the factors that explain postural stability impairment. Clinical Relevance: These results can assist clinicians in the design of therapeutic balance rehabilitation programs by acting not only on pain relief but also on quadriceps strengthening through resistance training to avoid subsequent injuries in athletes with PT.

Context: The aim of this study was to investigate the effects of 8-week ballistic-strength-training program using a validated specific throwing device (ie, Arm/Shoulder Specific Strength Device), on isokinetic shoulders' rotation muscle-torques and ratios as well as range of motion in team handball players. Design: A repeated-measures experimental design with a randomized controlled trial was used. Methods: Twenty-six high-level competitive male U-19 team handball players were randomly assigned into training (TG, n = 15) and control (n = 11) groups. The TG undertook a twice a week for 8-week periodized throws program with an individually predetermined optimal load. The program incorporated shackled eccentric and concentric exercises using the Arm/Shoulder Specific Strength Device. Peak torques, functional, and conventional ratios for both arms at different angular velocities (60 degrees center dot s(-1), 180 degrees center dot s(-1), and 300 degrees center dot s(-1)) were assessed over time and between groups, using an isokinetic dynamometer. Results: A significant improvement for TG (P < .01; d = 1.13 [moderate]; +20.2%) of the concentric peak torques for dominant arm in external rotation was observed at 300 degrees center dot s(-1). Significant (P < .05-.01) increases were also noted for nondominant arm at the 3 studied angular velocities. In addition, 300 degrees center dot s(-1) eccentric peak torques of the dominant arm and nondominant arm have significantly improved for both external and internal rotations (P < .05; d = .99 [moderate] and d = 1.21 [large]; +15.7% and + 17.9%, respectively) with small changes at the other angular assessed velocities. Posttraining, TG's dominant arm showed significant improvements (P < .05-.01) in functional and conventional ratios at all velocities. Notably, significant differences (P < .05-.01) were observed at 60 degrees center dot s(-1) and across all velocities when comparing the TG with the control group. TG showed significant increase for internal rotation and external rotation shoulder range of motions (P < .05; d = 1.22-1.27 [large]), +5.0% and +7.7%, respectively). Conclusions: The specific 8-week throwing training program on the Arm/Shoulder Specific Strength Device showed significant performance improvements in almost all assessed isokinetic concentric and eccentric peak torques as well as internal and external range of motion increase for both arms while ensuring rotator cuff torque ratios and shoulder mobility in team handball real sport-specific condition.

Abstract Background While there is ample evidence on the effects of single-mode aerobic and speed training on physical fitness in soccer players, less is known on the combined effects of these exercise regimens on physical and psychological factors. Aim This study aimed to compare the effects of aerobic and speed training with soccer-specific training versus soccer-specific training only on aerobic performance during the YOYO intermittent fitness test level 1 (final velocity, total distance [TD], maximal oxygen consumption [VO2max]), repeated sprint ability (best, total sprint time [RSABT, RSATT], sprint decrement [RSA dec]) performance and somatic anxiety (SA), cognitive anxiety (CA), and self-confidence (SC) adaptations in soccer players. Methods Thirty-eight highly trained male athletes aged 18.9 ± 0.5 years were randomly assigned to an aerobic and speed training group (COMB-G; n = 20) or an active control group (CON-G; n = 18). Aerobic training comprised intermittent exercises at 110–120% of the final velocity achieved at the end of the YOYO IL1 test. Speed training involved maximal sprints over 15–20-m with 5–6 sets per session. Aerobic or speed training lasted 20 min per session and replaced parts of the soccer-specific training. CON-G performed the soccer-specific training including technical, tactical drills and small-sided games. Training volume was similar between groups. Pre, post intervention, all participants performed a repeated-sprint ability (RSA) test, the YO-YO IL1 test and the players completed a Competitive Scale Anxiety Inventory (CSAI-2). Results A two (group: COMB-G, CON-G) by two (time: pre, post) mixed ANOVA (group-by-time) was computed. Significant group-by-time interactions were found for RSATT (F = 117.3; p < 0.001; Pη2 = 1.78), RSABT (F = 82.4; p < 0.001; Pη2 = 1.53), final velocity (F = 85.8; p < 0.001; Pη2 = 1.53), TD (F = 87.1; p < 0.001; Pη2 = 1.56), and VO2max (F = 18.0; p < 0.001; Pη2 = 0.72). In addition, significant group-by-time interactions were observed for SC (F = 90.2; p < 0.001; d = 1.60), SA (F = 60.5; p < 0.001; Pη2 = 1.70), and CA (F = 20.7; p < 0.001; Pη2 = 0.75). Post-hoc analyses indicated significant improvements for all dependent variables from pre- to post-training in favor of COMB-G. Conclusion Aerobic and speed training in combination with soccer-specific training is a safe and effective training method as it exerts positive effects not only for physical fitness but also for self-confidence and the coping of anxiety in male soccer players.

Abstract Background Previously, researchers reported performance enhancements following long-term plyometric training in athletes with anterior cruciate ligament reconstruction (LCA). However, the effects of combined eccentric and plyometric training on measures of isokinetic strength and psychological statues in male athletes have not been examined yet. Knowledge on the effects of combined eccentric and plyometric training help to better plan and program rehabilitations sessions and thus return-to-sports. Objective This study sought to compare the effects of three different rehabilitation training programs, eccentric training (ECC), plyometric training (PLYO), or combined eccentric and plyometric training (COMB), on psychological measures (kinesiophobia [TSK-CF], functional knee assessment, knee injury and osteoarthritis outcome score [KOOS], international knee documentation committee 2000 questionnaire [IKDC], and knee flexor and extensor isokinetic muscle performance (peak torque [PT], total work, ratio [R-HQ], and ratio of total work [R-TW]) at different angular velocities post ACL surgery in male elite athletes. Methods Forty elite male athletes from different sports (e.g., athletics, team sports) with ACL reconstruction participated in this study. The study started after a 14-weeks post-surgery rehabilitation program, which was identical for all subjects. After this initial rehabilitation period, athletes were randomly assigned to three experimental groups, ECC (n = 10), PLYO (n = 10), and COMB (n = 10), and a control group (CON: n = 10). Testing was conducted pre- and post-the 6-weeks intervention period and included the TSK-CF, KOOS, and IKDC. Peak torque of the knee extensors/flexors was tested at 90, 180, 240 °/s, after the 6-weeks training program only. Results Participants’ adherence rate was 100% across all groups and none reported any training or test-related injury. No significant between-group baseline differences (pre-6-weeks intervention) were observed for any of the reported psychological and muscle strength parameters. Significant group-by-time interactions were found for TSK-CF (p = 0.001, d = 2.85), KOOS (p = 0.001, d = 1.31), and IKDC (p = 0.001, d = 1.07). The post-hoc analyses indicated that COMB showed larger pre-post improvements for all psychological variables (p < 0.001, d = 2.95 to 13.15), compared with PLYO, ECC, and CON. Contrast analyses demonstrated that COMB yielded significantly greater improvements compared with CON, PLYO, ECC for all isokinetic parameters at all three angular velocities (all p < 0.001, d = 0.99 to 4.61). Conclusion The results showed that COMB induced greater gains for measures of psychological status and isokinetic muscle strength compared with single-mode PLYO and ECC in elite male athletes during a post-surgery ACL rehabilitation period. Accordingly, it is recommended to implement COMB as an effective rehabilitation means to improve knee function in male elite athletes. Trial registration This study does not report results related to health care interventions using human participants and therefore it was not prospectively registered.

This study aimed to compare the effects of an acute bout of small-sided soccer game (SSG) and sprint exercise on attention, mood, and enjoyment in untrained adolescent boys. Eighteen adolescent boys aged 13–15 years participated in a counterbalanced order intervention: 1—No-training control condition (CONTROL), 2—SSG (SOCCER), and 3—Repeated sprint (SPRINT) sessions. Before and after the sessions, all participants completed the revised d2-test of attention and a mood assessment (i.e., Brunel mood scale [BRUMS]). Rating of perceived exertion (RPE) and perceived enjoyment (i.e., physical activity enjoyment scale) were evaluated after each session. A 3 × 2 repeated measures analysis of variance with contrast-coded test was used to analyze the data. Attentional test performance increased from pre- to post-exercise intervention for both SOCCER and SPRINT (main effect of Phase, F = 40.81, p < .001, ηp 2 = 0.48), compared with the CONTROL. BRUMS scores did not change for any of the interventions. RPE was significantly lower after SOCCER compared with SPRINT ( t = 3.05 [3.20–7.18], p < .001, ηp 2 = 0.46). SOCCER was perceived to be significantly more enjoyable compared with SPRINT ( p = .03) and CONTROL ( p < .001). To conclude, an acute bout of exercise based on SOCCER or SPRINT exercise was beneficial for adolescent boys’ attention, with significantly better enjoyment reported after the SOCCER session, whereas we did not observe any mood effects.

In the first chapter of the community sport section, the impact of COVID-19 on physical activity and inactivity is investigated. Given that a lack of physical activity can have severe consequences for the general health of individuals, whether they are young or old, understanding the impact of lockdowns and government health policy interventions is a challenging but critical task. Here, Chapter 21 takes a holistic approach and explores the impact of COVID-19 regulations on the physical activity of both sedentary people as well as professional athletes. The chapter also highlight the importance of home-based training strategies to minimise the impact of lockdown restrictions.

Information about when to apply an appropriate eccentric hamstring strength training stimulus during long-term athlete development is essential for effective programming and improving balance performance. This study examined the effects of six-week eccentric hamstring training on dynamic balance performance in youth handball players of different maturity statuses (pre- or post-peak height velocity (PHV)). A randomized controlled design with 45 young male handball players (14.6 ± 0.3 years) from a local national handball club were randomly allocated to a 6 week, twice weekly eccentric hamstring training in two experimental groups: a pre-PHV (maturation offset: −2.13 ± 0.63, n = 10) and post-PHV (maturation offset: 0.79 ± 0.34, n = 12) group and two control groups: maturation offset: −2.09 ± 0.61, n = 10 and maturation offset: 0.55 ± 0.67, n = 13. Dynamic balance performance was evaluated by using the composite score during the lower quarter Y-balance test from pre- and post-intervention. A significant effect on balance scores was found from pre to post (F = 11.4; p = 0.002; η2p = 0.22), intervention (F = 5.4; p = 0.025; η2p = 0.12), and maturation (F = 369; p < 0.001; η2p = 0.9), but no significant interaction effects were found (F ≥ 3.3; p ≥ 0.077; η2p ≤ 0.07). Post hoc analysis revealed that the post-PHV group had a higher score than the pre-PHV group. Furthermore, that dynamic balance increased in the post-PHV group after intervention much more in the control post-PHV group. It was concluded that somatic maturation influences dynamic balance performance and that eccentric hamstring training results in greater improvement in balance performance in young male handball players for the post-pubertal group.

BackgroundThe standard method to treat physically active patients with anterior cruciate ligament (ACL) rupture is ligament reconstruction surgery. The rehabilitation training program is very important to improve functional performance in recreational athletes following ACL reconstruction.ObjectivesThe aims of this study were to compare the effects of three different training programs, eccentric training (ECC), plyometric training (PLYO), or combined eccentric and plyometric training (COMB), on dynamic balance (Y-BAL), the Lysholm Knee Scale (LKS), the return to sport index (RSI), and the leg symmetry index (LSI) for the single leg hop test for distance in elite female athletes after ACL surgery.Materials and MethodsFourteen weeks after rehabilitation from surgery, 40 elite female athletes (20.3 ± 3.2 years), who had undergone an ACL reconstruction, participated in a short-term (6 weeks; two times a week) training study. All participants received the same rehabilitation protocol prior to the training study. Athletes were randomly assigned to three experimental groups, ECC (n = 10), PLYO (n = 10), and COMB (n = 10), and to a control group (CON: n = 10). Testing was conducted before and after the 6-week training programs and included the Y-BAL, LKS, and RSI. LSI was assessed after the 6-week training programs only.ResultsAdherence rate was 100% across all groups and no training or test-related injuries were reported. No significant between-group baseline differences (pre-6-week training) were observed for any of the parameters. Significant group-by-time interactions were found for Y-BAL (p < 0.001, ES = 1.73), LKS (p < 0.001, ES = 0.76), and RSI (p < 0.001, ES = 1.39). Contrast analysis demonstrated that COMB yielded significantly greater improvements in Y-BAL, LKS, and RSI (all p < 0.001), in addition to significantly better performances in LSI (all p < 0.001), than CON, PLYO, and ECC, respectively.ConclusionIn conclusion, combined (eccentric/plyometric) training seems to represent the most effective training method as it exerts positive effects on both stability and functional performance in the post-ACL-surgical rehabilitation period of elite female athletes.

Research has proposed various ways to develop ballistic/explosive arm rotational movements for throwers but demonstrated inherent limitations for the lack of traditional resistance training respecting sport-specific tasks. A prototype device was conceived for ballistic multi-joint throwing exercises. Forty-three high-level competitive U19 male handball players participated in the study aged 18.42 ± 1.17 years; 82.36 ± 3.07 mass kg; and 184.91 ± 6.06 m height. Subjects underwent tests on the ASSSD, which operates into consecutive accelerative and decelerative actions, for throwing characteristics determination. Concentric (CON) and eccentric (ECC) variables during overhead throws as force, power, velocity, acceleration and angle when occurred peak force (PF), power (PP) and velocity (PV) were defined. The relative reliability was calculated using the intraclass correlation coefficients (ICCs) showing strong agreement between trials. The absolute reliability was analyzed using standard error of measurement SEM (0.03-2.75), and Coefficients of variation CVs (2.84-4.59%) for studied variables, reveals excellent interday reliability. Validity was assessed using linear regressions, r and p values showing good relationship between PF and PP gathered from ASSSD and isokinetic peak torques at different angular velocities of dominant arm (DA). The device sensitivity was verified when assessing CON-ECC PF, CON-ECC PP and CON PV with elite/non-elite players. The ASSSD has demonstrated its reliability, validity and sensitivity intended for testing, training monitoring and sport performance assessment.

BACKGROUND: Fascination with the moon has spanned millennia. It has recently been asserted that the moon cycle affects endurance performance in untrained individuals. The present study aimed at investigating the effects of the lunar cycle on intermittent endurance physical performance, balance and reaction-time capabilities, and selected physiological and psychological parameters in trained athletes. METHODS: Twelve male Taekwondo athletes (age, 22.3 +/- 0.8 years; height, 178.8 +/- 6.5 cm; body mass, 72.75 +/- 7.28 kg; %body fat, 13.9 +/- 3.6%) performed the Yo-Yo intermittent recovery test level-1 (YYIR T), the Y-balance test (YBT), and a reaction-time test (RT) during different lunar cycle phases (new moon (NM), full moon (FM), and half-moon). Participants' psychological profiles and well-being indices (i.e. a profile of mood state (PO MS) and Hooper Index) were also taken during each moon phase. The testing sessions during the different moon phases were performed in a counterbalanced order. The tests order remained the same (PO MS, then Hooper index, RT, YBT, YYIRT and rating of perceived exertion scale (RPE)), and all sessions were performed at noon (11:00 to 13:00 h) during the first day of each evaluated lunar phase. RESULTS: Analysis of variance tests showed that no significant differences were found between the three moon phases in all analyzed variables. CONCLUSIONS: This study showed that the different lunar cycle phases did not have significant effects on the selected physical performances and psychological indices in trained athletes

Purpose: The aims of this study were to (1) investigate the health-related physical fitness profile of untrained adolescent boys in comparison to adolescent soccer players, (2) determine the intensity and enjoyment of 6v6 and 4v4 small-sided games, and (3) evaluate the health-related effects of a short-period of soccer training in the untrained group. Methods: Forty-one adolescent boys (untrained, n = 24: age = 15.9 +/- 0.6 years; trained, n = 17: age = 15.7 +/- 0.7 years) were recruited. For Purpose 1, the players (n = 17) and the untrained (n = 24) boys were tested for speed, jumping power, balance, flexibility, and aerobic capacity. After baseline testing, Purposes 2 and 3 were addressed by randomly assigning the untrained boys to either a soccer-training group (small-sided games, 2 sessions per week for 8 weeks) or to a control group, followed by identical retesting. Results: At baseline, physical fitness was higher (p < 0.001) in trained players than in untrained for aerobic fitness, sprinting, jumping power, and balance. Small-sided games using 6v6 or 4v4 elicited similar heart rate (HR) (mean: similar to 85% peak heart rate, HRpeak), rate of perceived exertion, and enjoyment responses. Over 8 weeks, the between-group analysis revealed that soccer training had a large beneficial effect on balance (45%) when compared with control group with unclear effects on other fitness parameters. Conclusion: Adolescent soccer players had markedly higher physical fitness compared with untrained adolescents. Small-sided soccer games practiced by untrained adolescents elicited high exercise intensity. While 8 weeks of twice-weekly soccer training sessions induced significant improvement in balance, the short duration of the study was not sufficient to result in between-group differences in sprint and jump performance or aerobic fitness. (C) 2018 Published by Elsevier B.V. on behalf of Shanghai University of Sport.

BACKGROUND:It has been shown that recreational soccer was a highly motivating and social activity which produces large improvements in health-related indices in sedentary healthy and unhealthy subjects. The purpose of this study was to compare the acute parasympathetic reactivation after small-sided soccer games (SSG) and repeated sprints training (RST) sessions.METHODS:Eight post-pubertal untrained adolescents (age 15.8±0.6 years, body mass 59.1±3.7 kg, height 1.7±0.1 m) performed a RST, SSG and a control session in a counterbalanced order. Heart rate variability (HRV) indices in time and frequency domain, heart rate recovery and rating of perceived exertion (RPE) were evaluated.RESULTS:RPE was significantly lower after SSG compared with RST (P=0.02, ES=1.1). There was a significant decrease in mean R-R intervals after RST (difference: -19.6%, P<0.01, ES=1.7) and after SSG (-19.2%, P<0.01, ES=2.3). A significant decrease was also noted in SDNN after RST (-26.6%, P=0.02, ES=1.8) and SSG (-37.8%, P=0.01, ES=1.1). For RMSSD, a significant decrease was observed only after SSG (48%, P=0.01, ES=1.3). No significant change in all HRV indices after the control condition.CONCLUSIONS:SSG and RST elicited high and similar heart rates responses. A low parasympathetic reactivation during early recovery was noted after both RST and SSG. These results were important especially for clinician looking to prescribe repeated sprint or small-sided game for sedentary subjects.

The aim of this study was to evaluate the effects of soccer training on short-term heart-rate variability, blood pressure, and physical fitness in untrained healthy adolescents. Twenty-two adolescent boys took part in this study: 11 boys were randomly assigned to participate in an 8-week soccer training and 11 boys served as a control group. Soccer exhibited significant increases in high-frequency power (difference 52.9%, P = 0.03, effect size: ES = 1.2), root mean squared of the standard deviation rMSSD (10.8%, P = 0.02, ES = 1), and a significant decrease in sympathetic activity LF (26.3%, P = 0.004, ES = 1.4). The control group showed an increase in rMSSD (9.4%, P = 0.05, ES = 1). The soccer group showed increases in estimated aerobic fitness (30.9%, P = 0.001, ES = 1.50) and 20-m sprint performance (4.1%, P = 0.004, ES = 0.8) with a trend to an improvement in horizontal jumping (3.8%, P = 0.15, ES = 0.8). In conclusion, soccer-based training improved measures of both physical fitness and autonomic function making soccer an effective training strategy for improving health-related fitness measures in untrained adolescents.

The purpose of this study was to examine systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), rating of perceived exertion (RPE) and perceived enjoyment responses to a repeated-sprint training session (RST) compared to a small-sided soccer game session (SSG) in untrained adolescents. Twelve healthy post-pubertal adolescent males (age 15.8±0.6 years, body mass 59.1±3.7 kg, height 1.7±0.1m) performed RST and SSG sessions in a randomized and counterbalanced order. Blood pressure and HR were measured at rest and at 10, 20 and 30 minutes after interventions, and RPE and enjoyment were assessed. RST and SSG elicited similar exercise HR (74.0% vs. 73.7% of HR peak during RST and SSG respectively, P>0.05). There was no significant change in SBP or DBP after the 2 interventions (all P>0.05, ES<0.5) with a trend to a decrease in SBP after SSG at 30 min after intervention (moderate effect, ES=0.6). Pearson’s correlation analysis revealed a significant and large correlation between baseline BP values and magnitude of decline after both RST and SSG. Heart rate during recovery was higher compared with baseline at all times after both sessions (all P<0.05), with HR values significantly lower after SSG versus RST at 30 min after interventions (82.3±3.2 versus 92.4±3.2 beats/min, respectively, P=0.04). RPE was significantly lower (P=0.02, ES=1.1) after SSG than after RST, without significant differences in enjoyment. In conclusion, repeated sprint and small-sided games elicited similar exercise intensity without a significant difference in perceived enjoyment. Post-exercise hypotension after the two forms of training may depend on resting BP of subjects.

The aim of the present study was to examine the effects of the Nordic hamstring exercise (NHE) on pain threshold, flexibility and 2000m rowing performance in elite rowers with lower back pain (LBP). Ten elite rowers (age 17.6 ± 2.12 years) with LBP participated in this study. Participants completed 6-weeks of NHE in addition to their usual training program. Pre- and post-training tests included measures of pain threshold of the lower back, flexibility (sit and reach test) and 2000 m rowing performance. The results demonstrated that an organized HNE caused a significant decrease in pain threshold from 4.8±2 to 3±1.4 (P = 0.03, ES = 0.9) and a non-significant but moderate improvement in rowing performance from 6.9±0.7 min to 6.3±0.9 min (P = 0.1, ES = 0.8). The sit and reach test revealed a non-significant change from 14.9±8.2 cm to 15.2±6.5 cm (P = 0.9, ES = 0.04). We conclude that the NHE may represent an effective method for reducing pain in elite rowers with moderate improvement in rowing performance.

Evidence for nonlocal muscle fatigue (NLMF) has been inconsistent in adults, with no studies investigating youth. The objective was to examine NLMF in youth. Forty-two young males (age, 10-13 years) were tested for maximal voluntary isometric contraction (MVIC) force of the ipsilateral and contralateral knee extensors at 90° and 120° knee flexion, elbow flexors at 90°, handgrip, knee extensor isokinetic torque (300°·s-1 analyzed at 90° and 120° knee flexion), as well as a unilateral countermovement jump (CMJ) and Y Balance test (YBT). Isokinetic fatigue group (n = 15) had unilateral fatigue induced with 10 sets of 20 repetitions of maximal isokinetic knee extensor contractions at 300°·s-1. Isometric fatigue group (n = 15) used 10 repetitions of 6-s knee extensor MVIC whereas the control group (n = 12) were not fatigued. There was no significant difference in the response to the isometric- or isokinetic-fatigue intervention protocols. Main time effects indicated that NLMF was evident with the contralateral knee extensor MVIC at 90° (p = 0.008; 8.9%), knee extensor isokinetic torque at 90° (p < 0.001; 11.4%), and 120° (p = 0.05; 5.4%), CMJ (p = 0.02; 11.5%), handgrip (p = 0.06; 4.5%), elbow flexors (p < 0.001; 7.7%), and YBT (p = 0.001; 5.6%). Ipsilateral NLMF deficits occurred with handgrip (p < 0.001; 7.3%), elbow flexors MVICs (p < 0.001; 10.7%), CMJ (p = 0.02; 12.2%), and YBT (p = 0.002; 3.8%). NLMF with similar relative fatigue-induced deficits of fatigued and nonfatigued limbs suggest that youth fatigue is highly dependent upon the extent of activation or inhibition of the nervous system. Coaches of young athletes might consider developing technical motor skills before fatiguing exercise components, which might hinder the proficiency of their performance.

Static (SS) and dynamic stretching (DS) can lead to subsequent performance impairments or enhancement with the stretched limb. Crossover or non-local muscle fatigue (NLMF) refers to unilateral fatigue-induced impairments in a contralateral or non-exercised muscle. Whereas there are conflicting findings in the NLMF literature, there are few studies examining the effect of an acute bout of SS or DS on contralateral flexibility, torque or power. Fourteen highly trained subjects (means ± standard deviations: 18 ± 2 years; 179·4 ± 4·6 cm; 70·5 ± 6·3 kg; %body fat: 10·7 ± 2·5%) were tested before and following separate sessions of eight repetitions of 30 s of unilateral hip flexion SS or DS. Pre- and postintervention testing at 1 and 10 min included hip flexor range of motion (ROM), isokinetic leg flexion torque and power at 60°.s-1 and 300°.s-1 of the stretched and contralateral limbs. The stretched limb had a 6·3% (P = 0·01; ES: 0·91) ROM increase with DS at 10 min. The contralateral non-stretched hip flexors experienced ROM increases with SS of 5·7% (P = 0·02; ES: 0·68) from pretest to 1 min post-test, whereas DS showed 7·1% (P<0·0001; ES: 1·09) and 8·4% (P = 0·005; ES: 0·89) increases, respectively. There were no relative differences in ROM changes between conditions or limbs nor any stretch-induced changes in isokinetic torque or power. In conclusion, unilateral SS and DS augment contralateral limb ROM likely through an increased stretch tolerance.