Does Caffeine Consumption Influence Postcompetition Sleep in Professional Rugby League Athletes? A Case Study.

PURPOSE: To examine the sleep of rugby league athletes the night before and following an evening match and to investigate the association between caffeine intake and sleep on the night of competition. METHODS: On the night prior to, night of, and night after a professional rugby league match, 15 athletes had their sleep monitored using wrist activity monitors. Additionally, saliva samples were collected 60 minutes before and 30 minutes after the competition to assess salivary caffeine concentration. Differences in sleep across the 3 nights were examined using linear mixed models, and changes were assessed using effect size (ES). Pearson correlation (r) assessed the relationship between salivary caffeine levels and sleep indices. RESULTS: On the night of competition, athletes went to bed later than the night before (P = .00002, ES = 1.84) and night after (P = .0003, ES = 1.49) competition. Consequently, their sleep duration was reduced on the night of competition compared with the previous night (P < .0000003, ES = 2.36) and night after competition (P = .001, ES = 1.53). Postcompetition salivary caffeine concentration was substantially elevated in athletes when compared with precompetition measures (P < .00000001, ES = 4.44), and moderate, nonsignificant correlations were observed between changes in salivary caffeine concentration and delayed bedtime (r = .48, P = .07), increased sleep latency (r = .45, P = .09), decreased sleep duration (r = -.30, P = .28), and reduced sleep efficiency (r = -.34, P = .22). CONCLUSIONS: These results demonstrate that evening competition results in sleep disturbance in rugby league athletes, and caffeine supplementation prior to and during competition leads to substantial increases in postcompetition salivary caffeine concentration.

Women's Rugby League: Positional Groups and Peak Locomotor Demands.

The aims of this study were to (a) use a data-based approach to identify positional groups within National Rugby League Women's (NRLW) match-play and (b) quantify the peak locomotor demands of NRLW match-play by positional groups. Microtechnology (Global Navigational Satellite System [GNSS] and integrated inertial sensors; n = 142 files; n = 76 players) and match statistics (n = 238 files; n = 80 players) were collected from all NRLW teams across the 2019 season. Data-based clustering of match statistics was utilized to identify positional clusters through classifying individual playing positions into distinct positional groups. Moving averages (0.5, 1, 2, 3, 5, and 10 min) of peak running and average acceleration/deceleration demands were calculated via microtechnology data for each player per match. All analysis was undertaken in R (R Foundation for Statistical Computing) with positional differences determined via a linear mixed model and effect sizes (ES). Data-based clustering suggested that, when informed by match statistics, individual playing positions can be clustered into one of three positional groups. Based on the clustering of the individual positions, these groups could be broadly defined as backs (fullback, wing, and center), adjustables (halfback, five-eighth, and hooker), and forwards (prop, second-row, and lock). Backs and adjustables demonstrated greater running (backs: ES 0.51-1.00; p < 0.05; adjustables: ES 0.51-0.74, p < 0.05) and average acceleration/deceleration (backs: ES 0.48-0.87; p < 0.05; adjustables: ES 0.60-0.85, p < 0.05) demands than forwards across all durations. Smaller differences (small to trivial) were noted between backs and adjustables across peak running and average acceleration/deceleration demands. Such findings suggest an emerging need to delineate training programs in situations in which individual playing positions train in positional group based settings. Collectively, this work informs the positional groupings that could be applied when examining NRLW data and supports the development of a framework for specifically training female rugby league players for the demands of the NRLW competition.

Obstructive sleep apnea in professional rugby league athletes: An exploratory study.

OBJECTIVES: To explore the prevalence of obstructive sleep apnea (OSA) within a professional rugby league team and determine associations of OSA with ethnicity, positional group, and physical characteristics. DESIGN: Observational prospective cohort study. METHODS: Twenty-two professional rugby league athletes underwent one night of home-based polysomnography with apnea-hypopnea index (AHI), rapid eye movement (REM)AHI, non-REMAHI and supineAHI determined to indicate OSA. Linear models were used to assess if playing position (back or forward) or ethnicity (European-Australian or Polynesian) influenced AHI, REMAHI, non-REMAHI and supineAHI. Models were also built to determine differences according to body composition. RESULTS: Seven athletes were classified with mild OSA (6 forwards and 1 back, 3 European-Australians, and 4 Polynesians) and three with moderate OSA (2 forwards and 1 back, 3 Polynesians). When considering ethnicity, differences were observed between Polynesians and European-Australians for REMAHI (ES=0.90, p=0.02). Increased body mass index (BMI) was associated with a moderate increase in AHI (r=0.38, p=0.04) and non-REMAHI (r=0.36, p=0.05), while higher skinfold thickness moderately related to a higher AHI (r=0.40, p=0.05) non-REMAHI (r=0.47, p=0.02), and supineAHI (r=0.41, p=0.04). CONCLUSIONS: This exploratory study found 10 cases of OSA. Polynesian athletes and athletes classified as forwards constituted the majority of reported cases, suggesting their susceptibility to OSA. Furthermore, the data suggests that athletes with greater BMI and skinfold thickness may be predisposed to OSA.

Effects of External Counterpulsation on Postexercise Recovery in Elite Rugby League Players.

PURPOSE: External counterpulsation (ECP) has previously been used to treat cardiac patients via compression of the lower extremities during diastole to increase venous return and coronary perfusion. However, the effects of ECP on exercise performance and markers of recovery in elite athletes are largely unknown. METHODS: On 2 separate occasions, 48 h apart, 7 elite National Rugby League players performed an identical 60-min field-based conditioning session followed by a 30-min period of either regular ECP treatment or placebo. Power measures during repeated cycle bouts and countermovement jump height and contraction time derivatives were measured at rest and 5 h postexercise. Saliva samples and venous blood samples were taken at rest, postexercise, and 5 h postexercise to assess stress, inflammation, and muscle damage. RESULTS: After ECP treatment, cycling peak power output (P = .028; 11%) and accumulated peak power (P = .027; 14%) increased compared with the placebo condition. Postexercise plasma interleukin 1 receptor antagonist only increased after ECP (P = .024; 84%), and concentrations of plasma interleukin 1 receptor antagonist tended to be higher (P = .093; 76%) 5 h postexercise. Furthermore, testosterone-to-cortisol ratio was increased above baseline and placebo 5 h postexercise (P = .017-.029; 24-77%). The ratio of postexercise salivary α-amylase to immunoglobulin A decreased after treatment (P = .013; 50%) compared with the placebo control. CONCLUSIONS: Exercise performance and hormonal indicators of stress were improved and inflammation markers were reduced following acute ECP.

The influence of sleep hygiene education on sleep in professional rugby league athletes.

OBJECTIVE: To examine the usefulness of sleep hygiene education on the sleep of professional rugby league athletes during a 10-week period of the competitive season. DESIGN: Case study. PARTICIPANTS: Twenty-four professional rugby league athletes. MEASUREMENTS: Initially, participants were monitored for a 2-week period using wrist activity monitors allowing baseline estimation of sleep. Following this, 12 athletes attended two 30-minute sleep hygiene education seminars delivered over successive weeks, whereas the remaining 12 athletes received no education. Sleep was monitored in all athletes across the 2-week education period and for a 2-week period 1 month following the end of education. Split-plot analysis of variance and paired t tests were used to examine differences in sleep across the duration of the investigation. RESULTS: An initial sleep hygiene education seminar resulted in an earlier bedtime (effect size [ES] = 0.53 ±â€¯0.48), more time in bed (ES = 0.53 ±â€¯0.49), and increased sleep duration (ES = 0.47 ±â€¯0.44). A second sleep hygiene education seminar resulted in more time in bed (ES = 0.84 ±â€¯0.50) but a reduction in sleep efficiency (ES = 1.15 ±â€¯0.48). One month following sleep hygiene education, sleep behavior was comparable to that observed at baseline. CONCLUSION: This study shows that sleep hygiene education can lead to positive changes in sleep behavior. However, changes in sleep from education may not be sustained following the initial intervention.

Does self-perceived sleep reflect sleep estimated via activity monitors in professional rugby league athletes?

This study examined agreement between self-perceived sleep and sleep estimated via activity monitors in professional rugby league athletes. 63 athletes, from three separate teams wore actigraphy monitors for 10.3 ± 3.9 days. During the monitoring period, ratings of perceived sleep quality (on a 1-5 and 1-10 Likert scale), and an estimate of sleep duration were recorded daily. Agreement between sleep estimated via activity monitors and self-perceived sleep was examined using mean bias, Pearson correlation (r) and typical error of the estimate (TEE). 641 nights of sleep were recorded, with a very large, positive correlation observed between sleep duration estimated via activity monitors and subjective sleep duration (r = 0.85), and a TEE of 48 minutes. Mean bias revealed subjective sleep duration overestimated sleep by an average of 19.8 minutes. The relationship between sleep efficiency estimated via activity monitors and self-perceived sleep quality on a 1-5 (r = 0.22) and 1-10 Likert scale (r = 0.28) was limited. The outcomes of this investigation support the use of subjective measures to monitor sleep duration in rugby league athletes when objective means are unavailable. However, practitioners should be aware of the tendency of athletes to overestimate sleep duration.

Intra-individual variability in the sleep of senior and junior rugby league athletes during the competitive season.

This study examined the sleep intra-individual variability (IIV) of rugby league athletes across senior and junior levels during one week of the competitive season. Forty-five rugby league athletes across elite senior, sub-elite senior and elite junior levels each wore actigraphy monitors for seven days during the competitive season, and completed a subjective sleep diary each morning upon waking. Linear mixed models were used to assess differences in sleep measures between playing levels. Intra-individual standard deviations for each sleep measure were calculated for each athlete to determine their respective IIV, allowing differences in IIV between groups to be assessed. Elite junior athletes went to bed later (ES = 0.94 ± 0.50, p < 0.05) and woke later than elite senior athletes (ES = 0.94 ± 0.40, p < 0.05), while also displaying greater IIV when considering time in bed (ES = 1.14 ± 0.60, p < 0.05) and sleep duration (ES = 1.53 ± 0.64, p < 0.05) compared with elite senior athletes. Similarly, IIV was more pronounced in elite junior players for time in bed (ES = 0.88 ± 0.60, p < 0.05) and sleep duration (ES = 1.03 ± 0.64, p < 0.05) compared with sub-elite senior athletes. Despite this, elite junior athletes still obtained sufficient sleep duration, efficiency and quality. The outcomes of this investigation show a distinct difference in the habitual sleep-wake patterns of senior and junior rugby league athletes, and show how sleep IIV differs between playing levels in rugby league.

Do players and staff sleep more during the pre- or competitive season of elite rugby league?

This study establishes the sleep behaviour of players and staff during the pre- and competitive seasons of elite rugby league. For seven days during both the pre- and competitive seasons, seven rugby league players and nine full-time staff from one professional Australian rugby league club had their sleep monitored via wrist actigraphy and self-report sleep diaries. Two-way repeated measures analysis of variance determined differences between the pre- and competitive season in players and staff, with effect sizes (ES) used to interpret the practical magnitude of differences. Findings show an earlier bed time and wake time for players (-34 min, ES = 1.5; ±0.5 and -39 min, 2.1; ±0.5 respectively) and staff (-29 min, ES = 0.8; ±0.3 and -35 min, ES = 1.7; ±0.4 respectively) during pre-season when compared to the competitive season. Despite this, no differences were seen when considering the amount of time in bed, sleep duration or sleep efficiency obtained between the pre- and competitive seasons. Our results suggest that early morning training sessions scheduled during pre-season advances wake time in elite rugby league. However, both players and staff can aim to avoid reductions in sleep duration and sleep efficiency with subsequent adjustment of night time sleep patterns. This may be particularly pertinent for staff, who wake earlier than players during both the pre- and competitive seasons.

Do Lower-Body Dimensions and Body Composition Explain Vertical Jump Ability?

Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, Paquette, MR, and Relyea, GE. Do lower-body dimensions and body composition explain vertical jump ability? J Strength Cond Res 30(11): 3073-3083, 2016-Vertical jump (VJ) capability is integral to the level of success attained by individuals participating in numerous sport and physical activities. Knowledge of factors related to jump performance may help with talent identification and/or optimizing training prescription. Although myriad variables are likely related to VJ, this study focused on determining if various lower-body dimensions and/or body composition would explain some of the variability in performance. Selected anthropometric dimensions were obtained from 50 university students (25 men and 25 women) on 2 occasions separated by 48 or 72 hours. Estimated body fat percentage (BF%), height, body weight, hip width, pelvic width, bilateral quadriceps angle (Q-angle), and bilateral longitudinal dimensions of the feet, leg, thigh, and lower limb were obtained. Additionally, participants completed countermovement VJs. Analysis showed BF% to have the highest correlation with countermovement VJ displacement (r = -0.76, p < 0.001). When examining lower-body dimensions, right-side Q-angle displayed the strongest association with countermovement VJ displacement (r = -0.58, p < 0.001). Regression analysis revealed that 2 different pairs of variables accounted for the greatest variation (66%) in VJ: (a) BF% and sex and (b) BF% and body weight. Regression models involving BF% and lower-body dimensions explained up to 61% of the variance observed in VJ. Although the variance explained by BF% may be increased by using several lower-body dimensions, either sex identification or body weight explains comparatively more. Therefore, these data suggest that the lower-body dimensions measured herein have limited utility in explaining VJ performance.

Consistency of Lower-Body Dimensions Using Surface Landmarks and Simple Measurement Tools.

Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, and Paquette, MR. Consistency of lower-body dimensions using surface landmarks and simple measurement tools. J Strength Cond Res 30(9): 2600-2608, 2016-Body dimensions may influence various types of physical performance. This study was designed to establish the reliability and precision of bilateral lower-body dimensions using surface anatomic landmarks and either sliding calipers or goniometry. Fifty university students (25 men and 25 women) were measured on 2 separate occasions separated by 48 or 72 hours. A small digital caliper was used to acquire longitudinal dimensions of the feet, whereas a larger broad-blade caliper was used to measure lower-limb, hip, and pelvic dimensions. Quadriceps angle (Q-angle) was determined through surface goniometry. Data for all foot and lower-limb dimensions were both reliable and precise (intraclass correlation coefficient (ICC) ≥0.72, SEM 0.1-0.5 cm). Measures of Q-angle were also reliable and precise (ICC ≥0.85, SEM 0.2-0.4°). Findings from this investigation demonstrate that lower-body dimensions may be reliably and precisely measured through simple practical tests, when surface anatomic landmarks and standardized procedures are used. Although intertester reliability remains to be established, meticulous adherence to specific measurement protocols is likely to yield viable output for lower-body dimensions when more sophisticated methods are unavailable or inappropriate.

Effects of footwear condition on maximal jumping performance.

The purpose of this investigation was to examine the effects of footwear on kinetics and lower extremity electromyographic (EMG) activity during the vertical jump (VJ) and standing long jump. Fifteen men performed the 2 jump types in 3 footwear conditions: barefoot, minimal shoes, and cross-training shoes. Jump displacement and kinetic data were collected, along with EMG activity of the biceps femoris, medial gastrocnemius, peroneus longus, semitendinosus/semimembranosus, soleus (SOL), tibialis anterior, vastus lateralis, and vastus medialis. Subjective footwear performance and comfort were also assessed with a custom survey. No differences were found in jump displacement, peak ground reaction forces (GRF), countermovement and propulsive phase durations, vertical impulse, peak countermovement, or average propulsive EMG activity. Significant differences in peak propulsive root mean square EMG were found between barefoot and minimal shoes (p = 0.030) and minimal shoes and shod (p = 0.031) conditions for the SOL during the VJ, and for average countermovement EMG of the semitendinosus/semimembranosus during the VJ between barefoot and shod (p = 0.039). Moderate-to-large effect sizes (>0.59) were found between conditions for horizontal GRF, propulsive phase duration, average EMG amplitude, and duration of EMG activity during the countermovement. Participants reported higher comfort ratings when shod compared with barefoot and minimal shoes for both jumps. Participants also perceived better performance when shod compared with barefoot and minimal shoes for the VJ only. No acute differences in displacement were observed between barefoot, minimal shoes, and cross-trainer shoes during vertical and horizontal jumps. Some differences in muscle activation and timing seem to be present, and thus, training effects between footwear conditions should be examined. Footwear familiarization may prove beneficial, as acute increases in comfort seem unrelated to performance improvements.

A cross-sectional lower-body power profile of elite and subelite Australian football players.

Australian football (AF) is a sport which requires a vast array of physiological qualities, including high levels of strength and power. However, the power characteristics of AF players, particularly at the subelite level have not been extensively studied with further investigation warranted to understand the power capabilities and training requirements of elite and subelite AF groups. Therefore, the aim of this investigation was to develop a lower-body power profile of elite and subelite AF players. Eighteen elite and 12 subelite AF players completed a 1 repetition maximum (1RM) squat test to determine maximal lower-body strength, and countermovement jump (CMJ) and squat jump (SJ) testing to assess lower-body muscular power performance. Maximal lower-body strength was not statistically different between groups (p > 0.05). Elite players produced greater levels of peak power for CMJ at loads of 0, 30 (p < 0.05), and 40% (p < 0.01) of 1RM in comparison to subelite players. Squat jump peak power was statistically different between groups at 0, 20, 30, and 40% (p < 0.01) of 1RM; with elite players producing greater power than their subelite counterparts at all measured loads for SJ. Findings from this investigation demonstrate that elite AF players are able to generate greater levels of lower-body power than subelite AF players, despite no significant differences existing in maximal lower-body strength or body mass. As lower-body power levels clearly differentiate elite and subelite AF players, emphasis may be placed on improving the power levels of subelite players, particularly those aspiring to reach the elite level.