Objectives: Assess the effect of water dousing on heat strain and performance during self- and fixed-paced exercise in the heat.
Design: Crossover, block-randomized controlled trial.
Methods: Thirteen trained runners completed a 10-km time trial (TT) and 60-minute fixed-pace run (60% velocity of
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The Effect of Water Dousing on Heat Strain and Performance During Endurance Running in the Heat
Mitchell Anderson, Clint Bellenger, Georgia K. Chaseling, and Samuel Chalmers
Standardization of the Dmax Method for Calculating the Second Lactate Threshold
Samuel Chalmers, Adrian Esterman, Roger Eston, and Kevin Norton
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 logbased 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
Samuel Chalmers, Adrian Esterman, Roger Eston, and Kevin Norton
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.
The Relationship Between Performance and Injury in Junior Australian Football Athletes
Hunter Bennett, Samuel Chalmers, John Arnold, Steve Milanese, Chloe Blacket, Andrei Niculescu, and Joel Fuller
Purpose: Determine the impact of preseason and between-seasons changes in individual physical performance on injury risk in elite junior Australian football players and if injuries sustained during a season impact subsequent-season performance improvement. Methods: This prospective cohort study assessed individual performance measures (sprint speed, jump, agility, and aerobic endurance) during preseason over 4 consecutive seasons. Injury status (injured/not injured) was tracked weekly to determine the relationship between individual performance and in-season injury occurrence. Mixed models were used to determine the relationship between physical performance and injury, and the effect of injury on physical performance improvement. Results: A total of 206 players played 2 consecutive seasons and were included (17.6 y, 181.9 cm, 75.7 kg). Faster players during preseason experienced higher injury incidence (injuries/season) during that playing season (incidence rate ratio = 0.127; P = .034). Injury incidence was not influenced by between-seasons change in any performance measure. Players injured during their first season maintained their aerobic fitness, which declined in noninjured players (d = 0.39; P = .013). Players who sustained a lower-limb injury during their first season saw smaller improvements in sprint speed than players who did not get injured (d = 0.39; P = .035). Conclusion: Faster players experience higher injury incidence than slower players and may require specific prevention interventions. Players who experience a lower-limb injury during the playing season do not improve sprint speed between seasons to the same extent as players who do not get injured, highlighting the need for targeted high-speed running ability development as part of rehabilitation.
