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Objectives To explore the practicality of using functional principal components analysis (fPCA) and intra-athlete z-score changes for individual athlete monitoring post-ACL injury and surgery. Design A single athlete case study using within-athlete repeated measures in the context of applied athlete monitoring. Methods Using single leg (left) drop landing (3 landings per session) onto a force plate, the athlete completed 6 sessions prior (healthy) and 3 sessions post-ACL injury/surgery. Maximum vertical ground reaction force (vGRF), time to stabilisation (TTS) and outputs from fPCA (fPC scores) for the healthy sessions were used to develop intra-athlete means and standard deviations for each variable. Post-surgery measures were given z-scores relative to the healthy mean and standard deviation for each variable. The standard normal deviate (z = 1.96) was used as a threshold to flag landings that could be indicative of changes in movement behaviour. Results Maximum vGRF revealed no post-surgery trials that exceeded the standard normal deviate threshold based on the healthy data. TTS identified one landing post-surgery that exceeded the threshold. Scores for fPC2, fPC3 and fPC4 revealed landings that exceeded the threshold, with fPC4 demonstrating landings greater than the threshold for every trial (except two) post-surgery. Conclusions Including fPCA identified significant and stable changes to the landing strategy (particularly within fPC4). When used in conjunction with other measures such as maximum vGRF and TTS, fPCA has the potential to provide meaningful insights into athlete monitoring models regarding changes to movement characteristics after injury.

This study examined the influence of body composition on temperature and blood flow responses to post-exercise cold water immersion (CWI), hot water immersion (HWI) and control (CON). Twenty-seven male participants were stratified into three groups: 1) low mass and low fat (LM-LF); 2) high mass and low fat (HM-LF); or 3) high mass and high fat (HM-HF). Experimental trials involved a standardised bout of cycling, maintained until core temperature reached 38.5°C. Participants subsequently completed one of three 15-min recovery interventions (CWI, HWI, or CON). Core, skin and muscle temperatures, and limb blood flow were recorded at baseline, post-exercise, and every 30 min following recovery for 240 min. During CON and HWI there were no differences in core or muscle temperature between body composition groups. The rate of fall in core temperature following CWI was greater in the LM-LF (0.03 ± 0.01°C/min) group compared to the HM-HF (0.01 ± 0.001°C/min) group (P = 0.002). Muscle temperature decreased to a greater extent during CWI in the LM-LF and HM-LF groups (8.6 ± 3.0°C) compared with HM-HF (5.1 ± 2.0°C, P < 0.05). Blood flow responses did not differ between groups. Differences in body composition alter the thermal response to post-exercise CWI, which may explain some of the variance in the responses to CWI recovery.

AB Purpose: Cold water immersion (CWI) may be beneficial for acute recovery from exercise, but it may impair long-term performance by attenuating the stimuli responsible for adaptation to training. We compared effects of CWI and passive rest on cycling performance during a simulated cycling grand tour. Methods: Thirty-four male endurance-trained competitive cyclists were randomized to CWI for four times per week for 15 min at 15[degrees]C or control (passive recovery) groups for 7 d of baseline training, 21 d of intensified training, and an 11-d taper. Criteria for completion of training and testing were satisfied by 10 cyclists in the CWI group (maximal aerobic power, 5.13 +/- 0.21 W[middle dot]kg-1; mean +/- SD) and 11 in the control group (5.01 +/- 0.41 W[middle dot]kg-1). Each week, cyclists completed a high-intensity interval cycling test and two 4-min bouts separated by 30 min. CWI was performed four times per week for 15 min at 15[degrees]C. Results: Between baseline and taper, cyclists in the CWI group had an unclear change in overall 4-min power relative to control (2.7% +/- 5.7%), although mean power in the second effort relative to the first was likely higher for the CWI group relative to control (3.0% +/- 3.8%). The change in 1-s maximum mean sprint power in the CWI group was likely beneficial compared with control (4.4% +/- 4.2%). Differences between groups for the 10-min time trial were unclear (-0.4% +/- 4.3%). Conclusion: Although some effects of CWI on performance were unclear, data from this study do not support recent speculation that CWI is detrimental to performance after increased training load in competitive cyclists

The use of cold-water immersion (CWI) for postexercise recovery has become increasingly prevalent in recent years, but there is a dearth of strong scientific evidence to support the optimization of protocols for performance benefits. While the increase in practice and popularity of CWI has led to multiple studies and reviews in the area of water immersion, the research has predominantly focused on performance outcomes associated with postexercise CWI. Studies to date have generally shown positive results with enhanced recovery of performance. However, there are a small number of studies that have shown CWI to have either no effect or a detrimental effect on the recovery of performance. The rationale for such contradictory responses has received little attention but may be related to nuances associated with individuals that may need to be accounted for in optimizing prescription of protocols. To recommend optimal protocols to enhance athletic recovery, research must provide a greater understanding of the physiology underpinning performance change and the factors that may contribute to the varied responses currently observed. This review focuses specifically on why some of the current literature may show variability and disparity in the effectiveness of CWI for recovery of athletic performance by examining the body temperature and cardiovascular responses underpinning CWI and how they are related to performance benefits. This review also examines how individual characteristics (such as physique traits), differences in water-immersion protocol (depth, duration, temperature), and exercise type (endurance vs maximal) interact with these mechanisms.

The current study aimed to examine the influence of body fat percentage on thermal responses to water immersion at the two temperature extremes used in athletic recovery, by comparing the thermal responses of low- and high-fat individuals to immersion in hot water (HWI) or cold water (CWI). Thirty-nine subjects completed a body composition assessment (to determine low-fat and high-fat groups), and 15 minutes of either CWI (n = 20) or HWI (n = 19), followed by 30 minutes of passive rest. Core temperature (Tc), skin temperature (Tsk), and thermal sensation (TSS) were recorded at various time points during immersion and throughout the rest period. There were no significant differences between the low- and high-fat groups during CWI; however, the low-fat group had a significantly lower Tc compared to the high-fat group at 10, 20, and 30 minutes post-CWI (p less than 0.05). During HWI, the low-fat group had a significantly higher Tc at 5 minutes (p less than 0.05). In the low-fat group, TSS was significantly lower at 15 minutes of CWI (p = 0.03) and significantly higher at 15 minutes of HWI (p = 0.03), relative to the high-fat group. There were no significant differences between groups for Tsk measurements. Percentage body fat affects physiological and perceptual responses to immersion in both hot and cold water. Current hydrotherapy practices may need to be individualized to ensure optimal recovery.