Countermovement Jump is Not Affected During Final Competition Preparation Periods in Elite Rugby Sevens Players.

The changes in daily countermovement jump (CMJ) and activity profile of male rugby 7 players during the 3-week period immediately before international competition were examined. Velocity and distance data were measured via a 10-Hz global positioning system from 12 international-level athletes on 11 ± 1 occasions. Work rate (m∣min), total distance (TD), high-intensity distance (HID, >5.00 m·s(-1)), high-intensity work rate (meter per minute, >5.00 m·s(-1)), tackle number, and repeated high-intensity efforts (RHIEs) defined the activity profile along with session duration (minutes). CMJ performance was measured via percentage change from an individual best using a 5-jump protocol. A one-way repeated-measures ANOVA was selected to determine any change in CMJ performance across the training mesocycle. Effect sizes (ESs) were calculated to determine the magnitude of effects. No significant differences were noted in CMJ percentage change (p = 0.27). Significant differences were noted in work rate (p = 0.001, ES [range across the 3-week mesocycle]: 0.13-0.68), HID work rate (p = 0.001, ES: 0.35-0.75), RHIEs count (p = 0.002, ES: 0.03-0.61), tackle count (p < 0.001, ES: 0.13-0.90), HID (p < 0.003, ES: -0.32 to 0.32), and training duration (p < 0.001, ES: 0.37-1.36). No significant differences were noted in HI accelerations, player load, or TD. Rugby sevens players maintain CMJ performance throughout the final preparation period when the training load is managed.

Practices & attitudes towards recovery in elite Asian & UK adolescent athletes.

OBJECTIVES: Assess current practice and attitudes towards recovery in adolescent athletes. DESIGN: Questionnaires were administered either via print or online questionnaire. PARTICIPANTS: Athletes and coaches from within Asia were surveyed (n = 112 & 53), with a comparative sample in the UK (n = 53 & 8). MAIN OUTCOME MEASURES: The approaches and attitudes to recovery in both training and competition. RESULTS: Adolescent athletes perceive a variety of recovery modalities as important, though prioritise active recovery, nutrition and sleep. Attitudes towards recovery differed between athletes in Asia and the UK with respect to the perceived benefits of: sleep (96% believe in it in the UK v 69% in Asia, p < 0.01); nutrition (92 v 58%, p < 0.01); and active recovery (70 v 52%, p = 0.03). The number of recovery techniques used with Asian athletes was higher after training (p = 0.009) and competition (p < 0.01). Asian athletes rely more on 'feel' to justify interventions. CONCLUSIONS: There was a major disconnect amongst athletes' belief in particular strategies and their behaviours. The results of this study show the need for educating coaches and athletes.

A Pilot Study Using Entropy as a Noninvasive Assessment of Running.

PURPOSE: Running performance is influenced by the interaction of biomechanical and physiological factors. Miniaturized accelerometers worn by athletes can be used to quantify mechanical aspects of running and as a noninvasive tool to assess training status and progression. The aim of this study was to define and validate a method to assess running regularity and allow the estimation of an individual's oxygen uptake (V̇O2) and/or blood lactate-[La]b-based on data collected with accelerometers and heart rate. METHODS: Male adolescent endurance athletes completed an incremental submaximal aerobic stage test where V̇O2 and [La]b were measured. The test was terminated when [La]b concentration at the end of the stage exceeded 4 mmol/L. Two wireless triaxial accelerometers were placed on participants' right shank and lower back throughout the test. The root mean square (RMS) and sample entropy (SampEn) were calculated for the vertical, mediolateral, and anteroposterior components of acceleration. RESULTS: There were significant positive correlations of acceleration and entropy variables with [La]b and V̇O2, with moderate to high coefficients (r = .43-.87). RMS of the shank acceleration was the most highly related with both physiological variables. When the accelerometer was attached on the trunk, SampEn of the vertical acceleration had the strongest relationship with V̇O2 (r = .76, P < .01). CONCLUSIONS: The described method analyzing running complexity may allow an assessment of gait variability, which noninvasively tracks V̇O2 and/or [La]b, allowing monitoring of fatigue or training readiness for trained adolescent individuals.

SIXTY SECONDS OF FOAM ROLLING DOES NOT AFFECT FUNCTIONAL FLEXIBILITY OR CHANGE MUSCLE TEMPERATURE IN ADOLESCENT ATHLETES.

BACKGROUND: Physiotherapists and other practitioners commonly prescribe foam rolling as an intervention, but the mechanistic effects of this intervention are not known. PURPOSE: The aim of this investigation was to establish if a single bout of foam rolling affects flexibility, skeletal muscle contractility and reflected temperature. METHODS: Twelve adolescent male squash players were evaluated on two separate occasions (treatment and control visits) and were tested on both legs for flexibility of the hip flexors and quadriceps, muscle contractility (as measured by tensiomyography) and temperature of the quadriceps (assessed via thermography) at repeated time points pre- and post a 60s rolling intervention (pre-, immediately post, 5, 10, 15, and 30 minutes post). They rolled one leg on the treatment visit and did not perform rolling on the control visit. RESULTS: The main outcome measure was the flexibility of hip flexor and quadriceps at repeated time points up to 30 minutes post intervention. The average foam rolling force was 68% of subject's body weight. This force affected the combination of hip and quadriceps flexibility (p = 0.03; 2.4 degrees total increase with foam rolling) but not each muscle independently (p = 0.05 - 0.98) following a single 60s bout. Muscle contractility is not affected (p = 0.09 - 0.93) and temperature is not increased by foam rolling across time points (p = 0.19). CONCLUSIONS: A single sixty-second bout of rolling applied to the quadriceps induces a small significant change in flexibility that is of little practical relevance, while muscle contractility and temperature remain unchanged. Investigation of larger doses of rolling is merited in athletic populations to justify current practice. LEVEL OF EVIDENCE: 2c.

Activity Profile of International Rugby Sevens: Effect of Score Line, Opponent, and Substitutes.

PURPOSE: To investigate the influence of score line, level of opposition, and timing of substitutes on the activity profile of rugby sevens players and describe peak periods of activity. METHODS: Velocity and distance data were measured via 10-Hz GPS from 17 international-level male rugby sevens players on 2-20 occasions over 4 tournaments (24 matches). Movement data were reported as total distance (TD), high-speed-running distance (HSR, 4.17-10.0 m/s), and the occurrence of maximal accelerations (Accel, ≥2.78 m/s2). A rolling 1-min sample period was used. RESULTS: Regardless of score line or opponent ranking there was a moderate to large reduction in average and peak TD and HSR between match halves. A close halftime score line was associated with a greater HSR distance in the 1st minute of the 1st and 2nd halves compared with when winning. When playing against higher- compared with lower-ranked opposition, players covered moderately greater TD in the 1st minute of the 1st half (difference = 26%; 90% confidence limits = 6, 49). Compared with players who played a full match, substitutes who came on late in the 2nd half had a higher average HSR and Accel by a small magnitude (31%; 5, 65 vs 34%; 6, 69) and a higher average TD by a moderate magnitude (16%; 5, 28). CONCLUSIONS: Match score line, opposition, and substitute timing can influence the activity profile of rugby sevens players. Players are likely to perform more running against higher opponents and when the score line is close. This information may influence team selection.