Bradford Factor and seasonal injury risk in Division I-A collegiate American footballers

© 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group. Purpose: To investigate if participation in a higher percentage of preseason sessions affects the injury profile within Division I-A American Collegiate and whether the Bradford Factor (BF) is viable for practitioner use. Methods: A retrospective research design was used. Training load and injury data were collected and analysed for two collegiate American football seasons for 70 players. Results: A total of 184 injuries were sustained across two seasons with 106 resulting in time loss (15.6 ± 5.4 time loss injuries per 1000 h). On average, athletes completed 93 ± 17% of preseason sessions. For injury likelihood in the following week, an increase in accumulated minutes in 7d increased the injury risk by 35%. For non-contact time-loss injuries, preseason completion showed a reduction in injury likelihood of 2% for additional 3 sessions completed. A high BF in preseason (>7) increases the risk compared to a low BF through the in-season period. Conclusion: Preseason completion was not associated with a substantial reduction in injury risk in-season. A clear difference in BF between groups was evident and may provide a practical “flagging” variable. The BF may provide a simple but practically meaningful measure to monitor adaptation

The effects of menstrual cycle phase on physical performance in female soccer players

© 2017 Julian et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: Female soccer has grown extensively in recent years, however differences in gender-specific physiology have rarely been considered. The female reproductive hormones which rise and fall throughout the menstrual cycle, are known to affect numerous cardiovascular, respiratory, thermoregulatory and metabolic parameters, which in turn, may have implications on exercise physiology and soccer performance. Therefore, the main aim of the present study was to investigate potential effects of menstrual cycle phase on performance in soccer specific tests. Methods: Nine sub elite female soccer players, all of whom have menstrual cycles of physiological length; performed a series of physical performance tests (Yo-Yo Intermittent endurance test (Yo-Yo IET), counter movement jump (CMJ) and 3×30 m sprints). These were conducted at distinct time points during two main phases of the menstrual cycle (early follicular phase (FP) and mid luteal phase (LP)) where hormones contrasted at their greatest magnitude. Results: Yo-Yo IET performance was considerably lower during the mid LP (2833±896 m) as compared to the early FP (3288±800 m). A trend towards significance was observed (p = 0.07) and the magnitude based inferences suggested probabilities of 0/61/39 for superiority/equality/inferiority of performance during the mid LP, leading to the inference of a possibly harmful effect. For CMJ (early FP, 20.0±3.9 cm; mid LP 29.6±3.0 cm, p = 0.33) and sprint (early FP, 4.7±0.1 s; mid LP, 4.7±0.1 s, p = 0.96) performances the results were unclear (8/24/68, 48/0/52, respectively). Conclusion: The results of this study are in support of a reduction in maximal endurance performance during the mid LP of the menstrual cycle. However, the same effect was not observed for jumping and sprint performance. Therefore, consideration of cycle phase when monitoring a player's endurance capacity may be worthwhile

The Effects of Sleep Loss on Military Physical Performance

© 2019, Springer Nature Switzerland AG. As part of both training and active service, military members can be exposed to prolonged periods of sleep loss. Given the extent of physical and cognitive performances viewed as critical to successful military performance, such sleep disruption may present risk to health and performance. The primary aim of this narrative review was to investigate evidence on the effect of inadequate sleep on measures of aerobic capacity, anaerobic capacity, muscular strength and muscular endurance in military personnel. Sleep loss appears to have the greatest negative impact on aerobic capacity, muscular endurance and military-specific performance in military populations. The findings showed varied results for handgrip strength and anaerobic capacity, with sleep loss inducing a decrease in mean power of the upper body. In comparison to other measures of performance, lower-body muscular strength appeared to be resilient to sleep restriction. However, due to the limited evidence and inter-individual variability in results there is no clear consensus on the specific volume of sleep loss that induces significant or meaningful performance decrements. The difficulties of conducting well-designed and -controlled interventions in military populations are appreciated. However, due to the low quality of reporting and lack of control for confounders (i.e. physical activity, load carriage, prior sleep debt, motivation and energy intake) in the majority of studies, it is difficult to establish the relationship between sleep loss and physical performance in military populations

Subjective wellness, acute: Chronic workloads, and injury risk in college football

© 2019 National Strength and Conditioning Association Sampson, JA, Murray, A, Williams, S, Sullivan, A, and Fullagar, HHK. Subjective wellness, acute: chronic workloads and injury risk in college football. J Strength Cond Res 33(12): 3367-3373, 2019-Acute:chronic workload ratios (ACWRs) are associated with injury risk across team sports. In this study, one season of workload and wellness data from 42 collegiate football players were retrospectively analyzed. Daily 7:21 day exponentially weighted moving average (EWMA) ACWRs were calculated, and z-score fluctuations (“normal,” “better,” and “worse”) in sleep, soreness, energy, and overall wellness were assessed relative to the previous day ACWRs and considered as an interactive effect on the risk of noncontact injury within 0-3 days. Fifty-five noncontact injuries were observed, and injury risks were very likely higher when ACWRs were 2 SDs above (relative risk [RR]: 3.05, 90% confidence interval [CI]: 1.14-8.16) and below (RR: 2.49, 90% CI: 1.11-5.58) the mean. A high ACWR was trivially associated (p, 0.05) with “worse” wellness (r = 20.06, CI: 20.10 to 20.02), muscle soreness (r = 20.07, CI: 20.11 to 20.03), and energy (r = 20.05, CI: 20.09 to 20.01). Feelings of “better” overall wellness and muscle soreness with collectively high EWMA ACWRs displayed likely higher injury risks compared with “normal” (RR: 1.52, 90% CI: 0.91 to 2.54; RR: 1.64, 90% CI: 1.10-2.47) and likely or very likely (RR: 2.36, 90% CI: 0.83 to 674; RR: 2.78, 90% CI: 1.21-6.38) compared with “worse” wellness and soreness, respectively. High EWMA ACWRs increased injury risk and negatively impacted wellness. However, athletes reporting “better” wellness, driven by “better” muscle soreness presented with the highest injury risk when high EWMA ACWRs were observed. This suggests that practitioners are responsive to, and/or athletes are able to self-modulate workload activities

A Combined Sleep Hygiene and Mindfulness Intervention to Improve Sleep and Well-Being During High-Performance Youth Tennis Tournaments

Purpose: To investigate the effects of combined sleep hygiene recommendations and mindfulness on actigraphy-based sleep parameters, perceptual well-being, anxiety, and match outcomes during high-performance junior tennis tournaments. Methods: In a randomized crossover design, 17 high-performance junior tennis players completed the baseline, control, and intervention (INT) conditions across 3 separate weeks. The baseline consisted of unassisted, habitual sleep during a regular training week, and the control was unassisted sleep during a tournament week. The players attended a sleep education workshop and completed a nightly sleep hygiene protocol during a tournament week for the INT. Analysis was performed on the weekly means and on the night prior to the first match of the tournament (T-1). Results: Significant differences were observed for increased time in bed, total sleep time, and an earlier bedtime (P P > .05, d > 1.00) was evident for decreased worry on T-1 of the INT. Small effect sizes were also evident for improved mood, cognitive anxiety, and sleep rating across the INT week. The match performance outcomes remained unchanged (P > .05). Conclusions: Sleep hygiene INTs increase the sleep duration of high-performance junior tennis players in tournament settings, including the night prior to the tournament’s first match. The effects on perceptual well-being and anxiety are unclear, although small trends suggest improved mood, despite no effect on generic match performance outcomes.</jats:p

Impaired sleep and recovery after night matches in elite football players

© 2016 Informa UK Limited, trading as Taylor & Francis Group. ABSTRACT: Despite the perceived importance of sleep for elite footballers, descriptions of the duration and quality of sleep, especially following match play, are limited. Moreover, recovery responses following sleep loss remain unclear. Accordingly, the present study examined the subjective sleep and recovery responses of elite footballers across training days (TD) and both day and night matches (DM and NM). Sixteen top division European players from three clubs completed a subjective online questionnaire twice a day for 21 days during the season. Subjective recall of sleep variables (duration, onset latency, time of wake/sleep, wake episode duration), a range of perceptual variables related to recovery, mood, performance and internal training loads and non-exercise stressors were collected. Players reported significantly reduced sleep durations for NM compared to DM (−157 min) and TD (−181 min). In addition, sleep restfulness (SR; arbitrary scale 1 = very restful, 5 = not at all restful) and perceived recovery (PR; acute recovery and stress scale 0 = not recovered at all, 6 = fully recovered) were significantly poorer following NM than both TD (SR: +2.0, PR: −2.6), and DM (SR: +1.5; PR: −1.5). These results suggest that reduced sleep quantity and quality and reduced PR are mainly evident following NM in elite players

Sleep and recovery in team sport: Current sleep-related issues facing professional team-sport athletes

© 2015 Human Kinetics, Inc. While the effects of sleep loss on performance have previously been reviewed, the effects of disturbed sleep on recovery after exercise are less reported. Specifically, the interaction between sleep and physiological and psychological recovery in team-sport athletes is not well understood. Accordingly, the aim of the current review was to examine the current evidence on the potential role sleep may play in postexercise recovery, with a tailored focus on professional team-sport athletes. Recent studies show that team-sport athletes are at high risk of poor sleep during and after competition. Although limited published data are available, these athletes also appear particularly susceptible to reductions in both sleep quality and sleep duration after night competition and periods of heavy training. However, studies examining the relationship between sleep and recovery in such situations are lacking. Indeed, further observational sleep studies in team-sport athletes are required to confirm these concerns. Naps, sleep extension, and sleep-hygiene practices appear advantageous to performance; however, future proof-of-concept studies are now required to determine the efficacy of these interventions on postexercise recovery. Moreover, more research is required to understand how sleep interacts with numerous recovery responses in team-sport environments. This is pertinent given the regularity with which these teams encounter challenging scenarios during the course of a season. Therefore, this review examines the factors that compromise sleep during a season and after competition and discusses strategies that may help improve sleep in team-sport athletes

Individual Patterns in Blood-Borne Indicators of Fatigue - Trait or Chance

© 2016 National Strength and Conditioning Association. Julian, R, Meyer, T, Fullagar, HHK, Skorski, S, Pfeiffer, M, Kellmann, M, Ferrauti, A, and Hecksteden, A. Individual patterns in blood-borne indicators of fatigue - trait or chance. J Strength Cond Res 31(3): 608-619, 2017 - Blood-borne markers of fatigue such as creatine kinase (CK) and urea (U) are widely used to fine-tune training recommendations. However, predictive accuracy is low. A possible explanation for this dissatisfactory characteristic is the propensity of athletes to react to different patterns of fatigue indicators (e.g., predominantly muscular [CK] or metabolic [U]). The aim of the present trial was to explore this hypothesis by using repetitive fatigue-recovery cycles. A total of 22 elite junior swimmers and triathletes (18 ± 3 years) were monitored for 9 weeks throughout 2 training phases (low-intensity, high-volume [LIHV] and high-intensity, low-volume [HILV] phases). Blood samples were collected each Monday (recovered) and Friday (fatigued) morning. From measured values of CK, U, free-testosterone (FT), and cortisol (C) as determined in the rested and fatigued state, respectively, Monday-Friday differences (Δ) were calculated and classified by magnitude before calculation of ratios (ΔCK/ΔU and ΔFT/ΔC). Coefficient of variation (CV) was calculated as group-based estimates of reproducibility. Linear mixed modeling was used to differentiate inter- and intraindividual variability. Consistency of patterns was analyzed by comparing with threshold values (1.1 for all weeks). Reproducibility was very low for fatigue-induced changes (CV ≥ 100%) with interindividual variation accounting for 45-60% of overall variability. Case-wise analysis indicated consistent ΔCK/ΔU patterns for 7 individuals in LIHV and 7 in HILV; 5 responded consistently throughout. For ΔFT/ΔC the number of consistent patterns was 2 in LIHV and 3 in HILV. These findings highlight the potential value of an individualized and multivariate approach in the assessment of fatigue

Hot, Tired and Hungry: The Snacking Behaviour and Food Cravings of Firefighters During Multi-Day Simulated Wildfire Suppression

Firefighters are exposed to numerous stressors during wildfire suppression, including working in hot temperatures and sleep restricted conditions. Research has shown that when sleep restricted, individuals choose foods higher in carbohydrates, fat, and sugar, and have increased cravings for calorie dense foods. However, there is currently no research on the combined effect of heat and sleep restriction on snacking behaviour. Conducting secondary analyses from a larger study, the current study aimed to investigate the impact of heat and sleep restriction on snacking behaviour and food cravings. Sixty-six firefighters completed three days of simulated physically demanding firefighting work and were randomly allocated to either the control (n = 18, CON; 19 °C, 8h sleep opportunity), sleep restricted (n = 16, SR; 19 °C, 4-h sleep opportunity), hot (n = 18, HOT; 33 °C, 8h sleep opportunity), or hot and sleep restricted (n = 14 HOT + SR; 33 °C, 4-h sleep opportunity) condition. During rest periods firefighters were able to self-select sweet, savoury, or healthy snacks from a ration pack and were asked to rate their hunger, fullness, and cravings every two hours (eating block). Mixed model analyses revealed no difference in total energy intake between conditions, however there was a significant interaction between eating block and condition, with those in the CON, HOT, and HOT + SR condition consuming significantly more energy between 1230 and 1430 compared to the SR condition (p = 0.002). Sleep restriction and heat did not impact feelings of hunger and fullness across the day, and did not lead to greater cravings for snacks, with no differences between conditions. These findings suggest that under various simulated firefighting conditions, it is not the amount of food that differs but the timing of food intake, with those that are required to work in hot conditions while sleep restricted more likely to consume food between 1230 and 1430. This has potential implications for the time of day in which a greater amount of food should be available for firefighters.</jats:p

Time to wake up: Individualising the approach to sleep promotion interventions

Sleep is fundamental to normal physiological and cognitive function. Sleep promotion strategies have been used extensively in clinical settings, as a treatment for various ailments (ie, insomnia). However, sleep problems are prevalent outside these realms, with 56% of American, 31% of Western European and 29% of Japanese people suffering from sleep problems the previous year. The global public health concern over sleep has increased the demand for sleep promotion interventions, but the efficacy of these strategies is unclear in otherwise healthy and athletic populations. One possibility is due to the presentation and analysis of grouped data, despite sleep naturally being a highly variable and inherent trait. We argue the case for (1) presenting sleep data at the individual level and (2) individualising sleep promotion interventions