Colin Robertson

Background and Purpose: Fixture congestion, game-intensities and limited recovery negatively influence physical/physiological responses during a competitive soccer season. Therefore, the aim of the investigation was to examine weekly alterations in neuromuscular performance markers, creatine kinase and hydration in elite soccer players throughout a season. Study Design: Longitudinal Observational Study. Methods: Sixteen male professional soccer players competing in the English Football League Championship were assessed over the course of a season. All players provided a urine sample, a blood sample to assess creatine-kinase concentration and performed a countermovement jump test at the start of the season, in-season, pre-and post-match over 38 weeks. Results: Jump height was the most common marker of performance to be significantly reduced in-season compared to baseline (-5.4 to -11.3%, P<0.05) with 45.2% of the time-points affected. Measures of FT:CT (-7.5 to -12.4%) and AP (-9.4 to -11.5%), also showed significant deteriorations throughout the season compared to baseline (P<0.05) at several time-points. Max force (MF) significantly increased in-season (+5.1 to 7.0%) in 20% of the observed time-points compared to baseline. CK concentration significantly increased during 19% of the time-points (P<0.05; 62 to 159%). Urine osmolality demonstrated significant differences in season compared to baseline, but none to levels of dehydration. Conclusion: Monitoring elite soccer players over the course of a competitive season shows alterations in neuromuscular performance and hydration status. These data suggest that assessing counter-movement jump performance may be a useful marker for monitoring responses to training/competition, while creatine-kinase and hydration status may be limited.

Elite athletes are particularly susceptible to sleep inadequacies, characterised by habitual short sleep (<7 hours/night) and poor sleep quality (eg, sleep fragmentation). Athletic performance is reduced by a night or more without sleep, but the influence on performance of partial sleep restriction over 1–3 nights, a more real-world scenario, remains unclear. Studies investigating sleep in athletes often suffer from inadequate experimental control, a lack of females and questions concerning the validity of the chosen sleep assessment tools. Research only scratches the surface on how sleep influences athlete health. Studies in the wider population show that habitually sleeping <7 hours/night increases susceptibility to respiratory infection. Fortunately, much is known about the salient risk factors for sleep inadequacy in athletes, enabling targeted interventions. For example, athlete sleep is influenced by sport-specific factors (relating to training, travel and competition) and non-sport factors (eg, female gender, stress and anxiety). This expert consensus culminates with a sleep toolbox for practitioners (eg, covering sleep education and screening) to mitigate these risk factors and optimise athlete sleep. A one-size-fits-all approach to athlete sleep recommendations (eg, 7–9 hours/night) is unlikely ideal for health and performance. We recommend an individualised approach that should consider the athlete’s perceived sleep needs. Research is needed into the benefits of napping and sleep extension (eg, banking sleep).

Purpose: Examine changes from 90-minutes of competitive match-play in countermovement jump (CMJ), creatine kinase (CK) and urine osmolality (Uosm) in elite football players over a season and their association to match external load.
Methods: Eighteen football players participated. CMJ, CK and Uosm were collected 24-h pre-match and 48-h post-match. Match-performance data was examined using Prozone®.
Results: Post-match CK concentrations increased 49 % (ES: 0.66), while CMJ flight-time (FT), flight time: contraction time ratio (FT:CT), take-off velocity (TV) and average power (AP) decreased 2.4-7.4 % post-match (ES: 0.39-0.63). CMJ height post-match reduced 4.2 % (ES: 0.35). CMJ FT and AP showed associations with high intensity distance covered (HID), high intensity number (HIN), explosive sprints (EXS) and medium intensity accelerations (r = -0.395 to -0.496). Changes in CMJ FT also displayed associations to total sprint distance (TSD), total sprint number (TSN) and medium intensity decelerations (r = -0.395 to -0.446, P < 0.05). Increases in CMJ CT were associated with HIN (r = 0.39), and CMJ AF with HIN, EXS and medium accelations/decelerations (r = -0.397 to 0.459) completed during the match.
Conclusion: CMJ outputs from the push-off phase and countermovement phase were sensitive to change in neuromuscular fatigue. CK concentrations were sensitive to match-play demands. This helps practitioners determine player readiness and has implications for individual recovery strategies.

The lack of standardization of methods and procedures have hindered agreement in the literature related to time-of-day effects on repeated sprint performance and needs clarification. Therefore, the aim of the present study was to investigate and systematically review the evidence relating to time-of-day based on performance measures in repeated-sprints. The entire content of PubMed (MEDLINE), Scopus, SPORTDiscus® (via EBSCOhost) and Web of Science was searched. Only experimental research studies conducted in male adult participants aged ≥18yrs, published in English before June 2019 were included. Studies assessing repeated-sprints between a minimum of two time-points during the day (morning versus evening) were deemed eligible. The primary search revealed that a total of 10 out of 112 articles were considered eligible and subsequently included. Seven articles were deemed strong and three moderate quality. Eight studies found repeated-sprint performance across the first, first few, or all sprints, to increase in favor of the evening. The magnitude of difference is dependent on the modality and the exercise protocol used. The non-motorized treadmill established an average 3.5-8.5% difference in distance covered, average and peak velocity, and average power, across all sprints in three studies and in peak power in two studies. In cycling, power output differed across all sprints by 6.0% in one study and 8.0% for the first sprint only in five studies. All four studies measuring power decrement values (i.e. rate of fatigue) established differences up to 4.0% and two out of five studies established total work to be significantly higher by 8.0%. Repeated-sprint performance is affected by time-of-day with greater performance in the late/early afternoon. The magnitude is dependent on the variable assessed and the mode of exercise. There is a clear demand for more rigorous investigations which control factors that specifically relate to investigations of time-of-day and are specific to the sport of individuals.

Purpose:Investigate football-induced fatigue during hypoxia on RS and perceptual-cognitive skills.
Methods: Ten semi-professional footballers underwent a control session (0-m) to quantify RS in a non-fatigued state; and three hypoxia sessions (0-m;1500-m;3000-m) examining RS and perceptual-cognitive skills for a given physical workload. The mean number of correct responses (%) for anticipation and decision-making accuracy were obtained at the 30-min mark of each half. HR, TC, RPE and %O2sat were measured during warm-up, football-induced fatigue and RS test.
Results: HR, RPE and %O2sat were different between conditions (ES=0.44-6.13). RS were affected by football-induced fatigue for DC (4.8%;ES=0.68) and AV (5.5%;ES=0.79). In hypoxia, a 6.5% was found for DC, 6.3% for AV and 3.1% for PV at 1500-m compared to 0-m (P<0.05). Further significant changes of 12.8% DC, 12.8% AV and 6.2% PV (P<0.0005) were found at 3000-m compared to 0-m. More pronounced declines in perceptual-cognitive skills were found as altitude increased (5.0-12.5%;ES=1.17-2.41) and between halves (5.3-6.7%).
Conclusion: The data demonstrates the RS test was sensitive to fatigue/hypoxia for a given physical load. Simulated matches in hypoxia revealed larger decreases, in RS and perceptual-cognitive skills, highlighting the need for optimal acclimatisation strategies, including physical and technical preparation, prior to playing at altitude.

We have investigated the effects that sleep restriction (3-h sleep during two consecutive nights) have on an evening (17:00 h) submaximal weightlifting session; and whether this performance improves following a 1-h post-lunch powernap. Fifteen resistance-trained males participated in this study. Before the experimental protocol commenced, 1RM bench press and inclined leg press and normative habitual sleep were recorded. Participants were familiarised with the testing protocol, then completed three experimental conditions with two nights of prescribed sleep: (i) Normal (N): retire at 23:00 h and wake at 06:30 h, (ii) partial sleep-deprivation (SD): retire at 03:30 h and wake at 06:30 h and (iii) partial sleep-deprivation with nap (SDN): retire at 03:30 h and wake at 06:30 h with a 1-h nap at 13:00 h. Each condition was separated by at least 7 days and the order of administration was randomised and counterbalanced. Rectal (Trec) and mean skin (Ts) temperatures, Profile of Mood Scores, subjective tiredness, alertness and sleepiness values were measured at 08:00, 11:00, 14:00 and 17:00 h on the day of the weightlifting session. Following the final temperature measurements at 17:00 h, participants completed a 5-min active warm-up before a ‘strength’ protocol. Participants performed three repetitions of right-hand grip strength, then three repetitions at each incremental load (40%, 60% and 80% of 1RM) for bench press and inclined leg press, with a 5-min recovery in between each repetition. A linear encoder was attached perpendicular to the movement, to the bar used for the exercises. Average power (AP), average force (AF), peak velocity (PV), distance (D) and time-to-peak velocity (tPV) were measured (MuscleLab software) during the concentric phase of the movements for each lift. Data were analysed using general linear models with repeated measures. The main findings were that SD reduced maximal grip (2.7%), bench press (11.2% AP, 3.3% AF and 9.4% PV) and leg press submaximal values (5.7% AP) with a trend for a reduction in AF (3.3% P = 0.06). Furthermore, RPE increased for measures of grip strength, leg and bench press during SD. Following a 1-h powernap (SDN), values of grip and bench press improved to values similar in N, as did tiredness, alertness and sleepiness. There was a main effect for “load” on the bar for both bench and leg press where AP, AF, tPV values increased with load (P < 0.05) and PV decreased from the lightest to the heaviest load for both bench and leg press. An interaction of “load and condition” was present in leg press only, where the rate of change of AP is greater in the N than SD and SDN conditions. In addition, for PV and tPV the rate of change was greater for SDN than N or SD condition values. In summary, SD had a negative effect on grip strength and some components of bench and inclined leg press. The use of a 1-h power nap that ended 3 h before the “strength” assessment had a positive effect on weightlifting performance, subjective mood and ratings of tiredness.

The present study investigated the magnitude of diurnal variation in back squat and bench press using the MuscleLab linear encoder over three different loads and assessed the benefit of an active warm-up to establish whether diurnal variation could be negated. Ten resistance-trained males underwent (mean ± SD: age 21.0 ± 1.3 years, height 1.77 ± 0.06 m, and body mass 82.8 ± 14.9 kg) three sessions. These included control morning (M, 07:30 h) and evening (E, 17:30 h) sessions (5-min standardized warm-up at 150 W, on a cycle ergometer), and one further session consisting of an extended active warm-up morning trial (ME, 07:30 h) until rectal temperature (Trec) reached previously recorded resting evening levels (at 150 W, on a cycle ergometer). All sessions included handgrip, followed by a defined program of bench press (at 20, 40, and 60 kg) and back squat (at 30, 50, and 70 kg) exercises. A linear encoder was attached to an Olympic bar used for the exercises and average force (AF), peak velocity (PV), and time to peak velocity (tPV) were measured (MuscleLab software; MuscleLab Technology, Langesund, Norway) during the concentric phase of the movements. Values for Trec were higher in the E session compared to values in the M session (Δ0.53 °C, P < 0.0005). Following the extended active warm-up in the morning (ME), Trec and Tm values were no different to the E values (P < 0.05). Values for Tm were lower in the M compared to the E condition throughout (P < 0.05). There were time-of-day effects for hand grip with higher values of 6.49% for left (P = 0.05) and 4.61% for right hand (P = 0.002) in the E compared to the M. Daily variations were apparent for both bench press and back squat performance for AF (3.28% and 2.63%), PV (13.64% and 11.50%), and tPV (−16.97% and −14.12%, where a negative number indicates a decrease in the variable from morning to evening). There was a main effect for load (P < 0.0005) such that AF and PV values were larger at higher masses on the bar than lower ones and tPV was smaller at lower masses on the bar than at higher masses for both bench press and back squat. We established that increasing Trec in the M–E values did not result in an increase of any measures related to bench press and back squat performance (P > 0.05) to increase from M to E levels. Therefore, MuscleLab linear encoder could detect meaningful differences between the morning and evening for all variables. However, the diurnal variation in bench press and back squat (measures of lower and upper body force and power output) is not explained by time-of-day oscillations in Trec.

We have investigated the magnitude of diurnal variation in back squat and bench press performance using the MuscleLab force velocity transducer. Thirty resistance-trained males (mean ± SD: age 21.7 ± 1.4 years; body mass 80.5 ± 4.5 kg; height 1.79 ± 0.06 m) underwent two sessions at different times of day: morning (M, 07:30 h) and evening (E, 17:30 h). Each session included a period when rectal temperature (Trec) was measured at rest, a 5-min standardized 150 W warm-up on a cycle ergometer, then defined programme of bench press (at 20, 40 and 60 kg) and back squat (at 30, 50 and 70 kg) exercises. A linear encoder was attached to an Olympic bar used for the exercises and average force (AF), peak velocity (PV) and time-to-peak velocity (tPV) were measured (MuscleLab software; MuscleLab Technology, Langesund, Norway) during the concentric phase of the movements. Values for Trec at rest were higher in the evening compared to morning values (0.48°C, P < 0.0005). Daily variations were apparent for both bench press and back squat performance for AF (1.9 and 2.5%), PV (8.3 and 12.7%) and tPV (−16.6 and −9.8%; where a negative number indicates a decrease in the variable from morning to evening). There was a main effect for load where AF and tPV increased and PV decreased from the lightest load to the heaviest for both bench press and back squat (47.1 and 80.2%; 31.7 and 57.7%; −42.1 and −73.9%; P < 0.0005 where a negative number indicates a decrease in the variable with increasing load). An interaction was found only for tPV, such that the tPV occurs earlier in the evening than the morning at the highest loads (60 and 70 kg) for both bench press and back squat, respectively (mean difference of 0.32 and 0.62 s). In summary, diurnal variation in back squat and bench press was shown; and the tPV in complex multi-joint movements occurs earlier during the concentric phase of exercise when back squat or bench press is performed in the evening compared to the morning. This difference can be detected using a low cost, portable and widely available commercial instrument and enables translation of past laboratory/tightly controlled experimental research in to main-stream coaching practice.

Objectives:
Conduct a comprehensive epidemiological study of match injury characteristics (incidence, severity, causes, diagnostics, and temporal trends) in professional rugby league.
Design:
Prospective cohort design.
Methods:
Data was captured over the 2013, '14, and '15 seasons, collected via an online-reporting survey tool, and underpinned by nominal group technique-agreed definitions. Injury details were provided by club medical staff in accordance to the survey fields from all European Super League teams (e.g. injury occurrence/return dates, diagnosis, mechanism, recurrence). All time-loss injuries have been reported.
Results:
Injury incidence of 57 injuries/1000h has been observed over the three-year period, with an average of 34days missed per injury. The final 20-min period was the most significant period for injury occurrence, and higher incidence of injury/1000h played was during the start of the season in February, although an absolute injury risk for injury frequency was shown in April due to the greatest playing time. Forward positions reported the highest injury incidence whilst tackle activities were the most frequent mechanism of injury. Concussions and hamstring strains (5 injuries/1000h) were the most commonly diagnosed injuries, although the knee joint region (10 injuries/1000h) was the most frequently injured area.
Conclusions:
In light of the most common injury diagnoses, mechanisms, identified seasonal risk, and time of match, the data should look to inform player preparation in terms of physical conditioning and tackle technique in order to optimise player welfare and availability for participation.