Extreme environmental conditions present athletes with diverse challenges; however, not all sporting events are limited by thermoregulatory parameters. The purpose of this leading article is to identify specific instances where hot environmental conditions either compromise or augment performance and, where heat acclimation appears justified, evaluate the effectiveness of pre-event acclimation processes. To identify events likely to be receptive to pre-competition heat adaptation protocols, we clustered and quantified the magnitude of difference in performance of elite athletes competing in International Association of Athletics Federations (IAAF) World Championships (1999-2011) in hot environments (>25 °C) with those in cooler temperate conditions (<25 °C). Athletes in endurance events performed worse in hot conditions (~3 % reduction in performance, Cohen's d > 0.8; large impairment), while in contrast, performance in short-duration sprint events was augmented in the heat compared with temperate conditions (~1 % improvement, Cohen's d > 0.8; large performance gain). As endurance events were identified as compromised by the heat, we evaluated common short-term heat acclimation (≤7 days, STHA) and medium-term heat acclimation (8-14 days, MTHA) protocols. This process identified beneficial effects of heat acclimation on performance using both STHA (2.4 ± 3.5 %) and MTHA protocols (10.2 ± 14.0 %). These effects were differentially greater for MTHA, which also demonstrated larger reductions in both endpoint exercise heart rate (STHA: -3.5 ± 1.8 % vs MTHA: -7.0 ± 1.9 %) and endpoint core temperature (STHA: -0.7 ± 0.7 % vs -0.8 ± 0.3 %). It appears that worthwhile acclimation is achievable for endurance athletes via both short-and medium-length protocols but more is gained using MTHA. Conversely, it is also conceivable that heat acclimation may be counterproductive for sprinters. As high-performance athletes are often time-poor, shorter duration protocols may be of practical preference for endurance athletes where satisfactory outcomes can be achieved.

A single bout of resistance training induces residual fatigue, which may impair performance during subsequent endurance training if inadequate recovery is allowed. From a concurrent training standpoint, such carry-over effects of fatigue from a resistance training session may impair the quality of a subsequent endurance training session for several hours to days with inadequate recovery. The proposed mechanisms of this phenomenon include: (1) impaired neural recruitment patterns; (2) reduced movement efficiency due to alteration in kinematics during endurance exercise and increased energy expenditure; (3) increased muscle soreness; and (4) reduced muscle glycogen. If endurance training quality is consistently compromised during the course of a specific concurrent training program, optimal endurance development may be limited. Whilst the link between acute responses of training and subsequent training adaptation has not been fully established, there is some evidence suggesting that cumulative effects of fatigue may contribute to limiting optimal endurance development. Thus, the current review will (1) explore cross-sectional studies that have reported impaired endurance performance following a single, or multiple bouts, of resistance training; (2) identify the potential impact of fatigue on chronic endurance development; (3) describe the implications of fatigue on the quality of endurance training sessions during concurrent training, and (4) explain the mechanisms contributing to resistance training-induced attenuation on endurance performance from neurological, biomechanical and metabolic standpoints. Increasing the awareness of resistance training-induced fatigue may encourage coaches to consider modulating concurrent training variables (e.g., order of training mode, between-mode recovery period, training intensity, etc.) to limit the carry-over effects of fatigue from resistance to endurance training sessions.

This study examined the acute effect of strength and endurance training sequence on running economy (RE) at 70% and 90% ventilatory threshold (VT) and on running time to exhaustion (TTE) at 110% VT the following day. Fourteen trained and moderately trained male runners performed strength training prior to running sessions (SR) and running prior to strength training sessions (RS) with each mode of training session separated by 6 h. RE tests were conducted at baseline (Base-RE) and the day following each sequence to examine cost of running (CR), TTE, and lower extremity kinematics. Maximal isometric knee extensor torque was measured prior to and following each training session and the RE tests. Results showed that CR at 70% and 90% VT for SR-RE (0.76 ± 0.10 and 0.77 ± 0.07 mL·kg(-0.75)·m(-1)) was significantly greater than Base-RE (0.72 ± 0.10 and 0.70 ± 0.11 mL·kg(-0.75)·m(-1)) and RS-RE (0.73 ± 0.09 and 0.72 ± 0.09 mL·kg(-0.75)·m(-1)) (P < 0.05). TTE was significantly less for SR-RE (237.8 ± 67.4 s) and RS-RE (275.3 ± 68.0 s) compared with Base-RE (335.4 ± 92.1 s) (P < 0.01). The torque during the SR sequence was significantly reduced for every time point following the strength training session (P < 0.05). However, no significant differences were found in torque following the running session (P > 0.05), although it was significantly reduced following the strength training session (P < 0.05) during the RS sequence. These findings show that running performance is impaired to a greater degree the day following the SR sequence compared with the RS sequence.

This study investigated whether the addition of inspiratory muscle training (IMT) to an existing program of preseason soccer training would augment performance indices such as exercise tolerance and sports-specific performance beyond the use of preseason training alone. Thirty-one men were randomized across 3 groups: experimental (EXP: n = 12), placebo (PLA: n = 9), and control (CON: n = 10). The EXP and PLA completed a 6-week preseason program (2× weekly sessions) in addition to concurrent IMT with either an IMT load (EXP) or negligible (PLA) inspiratory resistance. Control group did not use an IMT device or undertake soccer training. All participants performed the following tests before and after the 6-week period: standard spirometry; maximal inspiratory mouth pressure (MIP); multistage fitness test (MSFT); and a soccer-specific fitness test (SSFT). After 6-weeks training, EXP significantly improved: MIP (p = 0.002); MSFT distance covered (p = 0.02); and post-SSFT blood lactate (BLa) (p = 0.04). No other outcomes from the SSFT were changed. Pre- to posttraining performance outcomes for PLA and CON were unchanged. These findings suggest the addition of IMT to preseason soccer training improved exercise tolerance (MSFT distance covered) but had little effect on soccer-specific fitness indices beyond a slightly reduced posttraining SSFT BLa. In conclusion, there may be benefit for soccer players to incorporate IMT to their preseason training but the effect is not conclusive. It is likely that a greater preseason training stimulus would be particularly meaningful for this population if fitness gains are a priority and evoke a stronger IMT response.

The initial bout appeared to provide protection against a number of muscle damage indicators suggesting a greater need for recovery following the initial session of typical lower body resistance exercises in resistance-untrained men although sub-maximal running should be avoided following the first two sessions.