Samuel Chalmers

High prevalence of dysfunctional, asymmetrical, and painful movement in elite junior Australian Football players assessed using the Functional Movement Screen.

OBJECTIVES The purpose of this study was to describe the prevalence of dysfunctional, asymmetrical, and painful movement in junior Australian Football players using the Functional Movement Screen (FMS). DESIGN Cross-sectional study. METHODS Elite junior male Australian Football players (n=301) aged 15-18 years completed pre-season FMS testing. The FMS consists of 7 sub-tests: deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, trunk stability push-up (TSPU) and rotary stability. The shoulder mobility, TSPU, and rotary stability tests were combined with an accompanying clearing test to assess pain. Each sub-test was scored on an ordinal scale from 0 to 3 and summed to give a composite score out of 21. Composite scores ≤14 were operationally defined as indicating dysfunctional movement. Players scoring differently on left and right sides were considered asymmetrical. Players reported whether they missed any games due to injury in the preceding 22 game season. RESULTS Sixty percent of players (n=182) had composite scores ≤14, 65% of players (n=196) had at least one asymmetrical sub-test, and 38% of players (n=113) had at least one painful sub-test. Forty-two percent of players (n=126) missed at least one game in the previous season due to injury. Previous injury did not influence composite score (p=0.951) or asymmetry (p=0.629). Players reporting an injury during the previous season were more likely to experience pain during FMS testing (odds ratio 1.97, 95% confidence interval 1.23-3.18; p=0.005). CONCLUSIONS Junior Australian Football players demonstrate a high prevalence of dysfunctional, asymmetrical, and painful movement during FMS testing.

Standardization of the Dmax Method for Calculating the Second Lactate Threshold

PURPOSE The purpose of this study was to test the reliability and validity of 2 standardized methods for calculating speed at the second lactate-threshold point (LT2) based on the preexisting Dmax (LTD) and modified Dmax (LTMOD) procedures. METHODS 13 trained male road runners and triathletes completed 2 incremental laboratory running tests to determine LT2, followed by separate time trials (5, 10, 15 km) on an outdoor running track. Two new methods were proposed for calculating the speed at LT2: (1) the single standardized lactate threshold (LTSDs) and (2) the paired standardized lactate threshold (LTSDp) for quantifying changes over time. RESULTS The LTSDs and LTSDp methods had high relative (ICC ≥ .98) and absolute (CV ≤ 1.9%) reliability in identifying the speed at LT2. The speed at LT2 according to the LTSDs and LTSDp methods had a strong correlation and was not different to the performance speed during the 10- and 15-km time trials (≤2.3%; ρc > 0.8; P > .05). The following natural log-based formula was created to estimate the percentage of LT2 speed (using the LTSDs method) that could be sustained for events ~15-75 min: y = -7.256(ln x) + 157.64, where y = %LT2 speed, x = time-trial performance (s), and ln = natural log. CONCLUSIONS The standardized methods are reliable for determining LT2. The LTSDs and LTSDp methods for calculating the speed at LT2 from a near-maximal incremental test calculated speeds similar to those exhibited in 10- and 15-km running time trials. A prediction equation for estimating the percentage of LT2 that can be sustained for events of ~15-75 min was generated.

Brief Heat Training: No Improvement of the Lactate Threshold in Mild Conditions

PURPOSE Athletes often seek the minimum required time that might elicit a physiological or performance change. It is reasonable to suggest that heat training may improve aerobic-based performance in mild conditions. Therefore, rather than providing a traditional heat-exposure stimulus (ie, 7-10 × 60-100 min sessions), the current article details 2 studies that aimed to determine the effect of brief (≤240 min exposure) heat training on the second lactate threshold (LT2) in mild conditions. METHODS Forty-one participants completed 5 (study 1, n = 18) or 4 (study 2, n = 23) perceptually regulated treadmill exercise training sessions in 35°C and 30% relative humidity (RH) (experimental group) or 19°C and 30% RH (control group). Preincremental and postincremental exercise testing occurred in mild conditions (19°C and 30% RH). Linear mixed-effects models analyzed the change in LT2. Results Heat training did not substantially change LT2 in either study 1 (+1.2%, d = 0.38, P = .248) or study 2 (+1.9%, d = 0.42, P = .163). LT2 was not substantially changed in the control group in study 1 (+1.3%, d = 0.43, P = .193), but a within-group change was evident in study 2 (+2.3%, d = 1.04, P = .001). CONCLUSIONS Brief heat training was inadequate to improve the speed at LT2 in mild conditions more than comparable training in mild conditions. The brief nature of the heattraining protocol did not allow adaptations to develop to the extent required to potentially confer a performance advantage in an environment that is less thermally stressful than the training conditions.

Asymmetry during Functional Movement Screening and injury risk in junior football players: a replication study

An indicator of movement quality and potential injury risk during Functional Movement Screen (FMS) testing is the presence of asymmetry when comparing the left and right sides of the body. The aim of the study was to investigate the reproducibility of the injury risk model proposed in our previous research (Chalmers et al. 2017; derivation study) that showed an increased injury risk for elite junior Australian football players demonstrating ≥2 asymmetrical FMS subtests. We used a direct replication design. Players underwent pre‐season FMS testing, and an injury surveillance system monitored 277 male participants during the subsequent regular season competition. Designated club officials monitored the weekly competition participation of players. The definition of an injury was “a trauma or medical condition which caused a player to miss a competitive game”. Cox proportional hazards regression models were used to investigate the relationship between asymmetry and number of games played before first injury (ie, survival time). The level of reproducibility was determined according to statistical significance, effect size, and subjective assessment. Demonstrating asymmetry during FMS testing was not associated with a significant increase in prospective injury risk in the replication study (P > .05). Moreover, effect sizes (hazard ratios) from the derivation dataset were not within the 95% confidence intervals of the respective asymmetry predictor in the replication dataset. Subjectively, researchers were in agreement that the findings from the derivation data were not successfully reproduced. Clinicians and researchers should be cautious about using FMS asymmetry findings to derive injury risk for junior football players.

The effect of ice slurry ingestion on body temperature and cycling performance in competitive athletes

The effects of pre cooling on endurance performance are widely known. In contrast, the approach of cooling during endurance exercise in combination with pre-exercise cooling has been poorly understood. The purpose of the present study was to determine whether the effects of precooling and cooling during exercise enhance exercise performance compared to the ingestion of a thermo-neutral beverage (20 °C) or precooling alone in cycling performance. This was an experimental study using a randomised crossover design in which 7 cyclists underwent three trials comprising of 45 min steady state cycling (SS) at 70% VO2 max and a subsequent 10 km time trial (TT) in hot conditions (32 °C, 50% relative humidity). Rectal temperature (Tre), heat storage (HS), heart rate (HR), blood lactate concentration (BLA) and thermal sensation (TS) were measured. The intervention consisted of: (1) ingestion of thermo-neutral beverage before and during SS cycling (TN), (2) ingestion of ice slurry beverage and application of iced towels (precooling) prior to exercise, and then ingestion of thermo-neutral beverage during SS (PRE) and (3) precooling strategy as above plus ice slurry ingestion during SS cycling (PRE + MID). The intake of thermo-neutral or ice slurry beverage (14 g/kg) occurred over 30 min before and every 15 min during SS cycling. There was no significant difference in TT performance between all the conditions (P =0.72). However, PRE and PRE + MID caused a significant decrease in Tre (P < 0.05) from TN during exercise. Accordingly, both precooling and a combination of precooling and mid-cooling during exercise in hot conditions may be a practical and effective way of reducing core temperature. Future studies should investigate longer distance events and timing of ice slurry ingestion.

In-play cooling strategies for sport in hot and humid conditions*

Over 40%, and rising, of the global human population currently reside in the climatically ‘torrid’ geographical zone (hot and humid environmental conditions). High ambient temperatures and humidity during sporting events place an added burden onto the physical stress. This load inherently increases the risk of heat-related illness, which remains one of the leading causes of sudden death in exercising individuals. For example, heat illness was the third most common specific cause of death (1.9 annual incidences) between 1990 and 2010 in high school and college American football players. Tennis is a popular global summer sport that features 4 pinnacle Grand Slam tournaments per year at the professional level. The United States and Australian tournaments often coincide with hot environmental conditions that have resulted in athletes aborting play due to heat-related health issues. This Discovery article highlights the study by Schranner et al. who examined the effectiveness of in-play cooling interventions during simulated tennis match-play performed in the most extreme environmental conditions observed during the United States Open in recent years (36 C and 50% relative humidity). The study first sought to examine the effectiveness of the currently recommended in-play cooling strategy for professional tennis: ice wrapped in a wet towel around the neck, and cold towels simultaneously placed on the head and thighs during each mandatory rest period (following every ‘odd’ game and completion of set). Ice towels facilitate cooling through the transfer of heat from skin in direct contact with a cold towel (conductive heat loss). Due to the limited utility of conductive heat loss via covering a small surface area, the authors secondly sought to test the efficacy of a cooling strategy that promotes powerful evaporative heat loss. The strategy involved wetting uncovered skin on the neck, face, arms, and thighs with a damp sponge of cool/tepid water while being exposed to air flow generated by a fan at 6.4 m/s (FANwet) during each mandatory rest period. 4 The authors hypothesized that the FANwet trial would best mitigate thermal strain. Both the ice towel and FANwet interventions led to similar reductions in the rise of rectal temperature (»0.5 C) over the course of the match in comparison to a control match (no cooling intervention) (Fig. 1). The cooling effect was evident from the seventh game of the first set during the FANwet intervention, and onwards from the first game of the second set during the ice towel intervention. Both cooling interventions positively influenced perceptual (rating of thermal sensation and perceived effort) and cardiovascular (heart rate) strain measures. Although the FANwet intervention did not further enhance rectal temperature reductions versus the existing policy of applying ice and cold towels, the practical utility of the FANwet trial remains attractive to lower levels of competition where the preparation and replenishment of ice might be difficult for players and officials. However, the effectiveness of the skin wetting component of the FANwet intervention for reducing the rise in core temperature may be somewhat stunted in humid conditions since maximal skin wettedness may already be elicited physiologically due to the associated reductions in sweating efficiency. Therefore in conditions similar to the United States Open (warm/humid), it could be hypothesized that additional airflow alone may elicit a similarly beneficial cooling response by improving sweating efficiency in the face of negligible dry heat gain. A follow-up study by the same research group using a similar methodology illustrated the importance of environmental conditions for the effectiveness of different cooling strategies during the mandatory rest periods in tennis. Simulating the very hot, but conversely to the United States Open, very dry conditions of the Australian Open Grand Slam tennis tournament (45 C, <10% relative humidity), the FANwet trial was more effective

Supplemental intermittent-day heat training and the lactate threshold

Heat acclimation over consecutive days has been shown to improve aerobic-based performance. Recently, it has been suggested that heat training can improve performance in a temperate environment. However, due to the multifactorial training demands of athletes, consecutive-day heat training may not be suitable. The current study aimed to investigate the effect of brief (8×30min) intermittent (every 3-4 days) supplemental heat training on the second lactate threshold point (LT2) in temperate and hot conditions. 21 participants undertook eight intermittent-day mixed-intensity treadmill exercise training sessions in hot (30°C; 50% relative humidity [RH]) or temperate (18°C; 30% RH) conditions. A pre- and post-incremental exercise test occurred in temperate (18°C; 30% RH) and hot conditions (30°C; 50% RH) to determine the change in LT2. The heat training protocol did not improve LT2 in temperate (Effect Size [ES]±90 confidence interval=0.10±0.16) or hot (ES=0.26±0.26) conditions. The primary finding was that although the intervention group had a change greater than the SWC, no statistically significant improvements were observed following an intermittent eight day supplemental heat training protocol comparable to a control group training only in temperate conditions. This is likely due to the brief length of each heat training session and/or the long duration between each heat exposure.