Performing successfully in the heat at the 2004 Olympic Games in Athens: Which active cooling strategies represent best practice for endurance athletes

Previous research using athletes has documented that precooling can improve endurance performance, especially in warm conditions. However, research comparing performance following different cooling techniques which are incorporated into a prerace routine is rare. Purpose: The purpose of this study was to compare the effects of two precooling techniques on cycling time trial performance in warm conditions. Methods: Six endurance trained, regionally competitive cyclists completed one maximal graded exercise test (V02peak 71.4 ±3.2 ml’kg-1min-1) and four ~40 min laboratory cycling time trials in a heat chamber (34.3 ± 1.1°C; 41.2 ± 3.0% relative humidity (rh)) using a fixed power-variable power format. After familiarisation, cyclists prepared for the time trial using two different precooling strategies and a control condition administered in a counterbalanced order. The three trials included: 1) no cooling (Control), 2) cooling jacket for 40 min (Jacket) or 3) 30 min water immersion (29°C to 24°C at a rate of 0.2°C\u27min-1 ) followed by cooling jacket for 40 min (Combination). Comparisons were made using a two-way ANOV A with repeated measures and Student\u27s paired t-tests where appropriate. Results: Rectal temperature (Tre) prior to the time trial was 37.8 ± 0.1°C in Control, similar in Jacket (37.8 ± 0.3°C) and significantly lower in Combination (37.1 ±0.2 C, p \u3c 0.01). Blood lactate during each treatment was similar except for the final readings (Control = 15.8 ± 4.4 mM, Jacket = 19.8 ± 4.3 mM and Combination = 17.5 ± 4.0 mM, p \u3c 0.005). Heart rate was similar throughout the time trial for each treatment. Compared to the Control trial, performance time was similar for Jacket (-16 ± 36s, -1.5%; p = 0.34) but faster for Combination (-42 ± 25s, -3.8%; p = 0.01). The pacing strategy for Control and Combination were similar (gradually reducing split times) but unique for Jacket (started with a fast split time followed by a temporary increase in split times). Conclusions: A combination precooling strategy incorporating immersion in cool water followed by the use of a cooling jacket can: 1) produce decreases in Tre that persist throughout a warm up and 2) improve laboratory cycling time trial performance. The effects of a cooling jacket alone on Tre are subtle and do not appear to persist throughout a warm up. Further research is required to understand the influence of cooling jackets on pacing strategy during time trials performed in the heat

Physiological demands of road sprinting in professional and U23 cycling. A pilot study

This pilot study described and compared the power output (absolute, relative to body weight and relative to frontal area) recorded during successful road sprints in professional and under 23 men’s cycling races. The study also described the exercise intensity and requirements of sprinters throughout final 10 min of the race. Nine successful (top 3) sprints performed by a professional (PRO: 23 y old, 1.76 m, 71.8 kg) and an under 23 (U23: 18 y old, 1.67 m, 63.2 kg) cyclist sprinter were analysed in this study. No statistical differences were found in absolute peak and average sprint power (PRO: 1370±51 W and 1120±33 W; U23: 1318±60 W and 1112±68 W). The average power output relative to body weight and to projected frontal area (Ap) was lower in PRO than U23 (15.6±0.4 and 17.4±1.1 W•kg-1; and 2533±76 and 2740±169 W•Ap-1, respectively) (P=0.016). The intensity of the last 10 min prior to the sprint was significantly higher in PRO than U23 (4.6±0.3 and 3.7±0.2 W•kg-1, respectively) (P2500 W•Ap-1 or \u3e15.5 W•kg-1 for approximately 14 s, with a peak power output \u3e3100 W•Ap-1 or \u3e19 W•kg-1) indicates that sprint characteristics may be somewhat similar between PRO or U23 races. Further research is warranted in order to better understand physiological and tactical aspects important to road sprint cycling

Effect of Maturation on Hemodynamic and Autonomic Control Recovery Following Maximal Running Exercise in Highly Trained Young Soccer Players

The purpose of this study was to examine the effect of maturation on post-exercise hemodynamic and autonomic responses. Fifty-five highly trained young male soccer players (12–18 years) classified as pre-, circum-, or post-peak height velocity (PHV) performed a graded running test to exhaustion on a treadmill. Before (Pre) and after (5th–10th min, Post) exercise, heart rate (HR), stroke volume (SV), cardiac output (CO), arterial pressure (AP), and total peripheral resistance (TPR) were monitored. Parasympathetic (high frequency [HFRR] of HR variability (HRV) and baroreflex sensitivity [Ln BRS]) and sympathetic activity (low frequency [LFSAP] of systolic AP variability) were estimated. Post-exercise blood lactate [La]b, the HR recovery (HRR) time constant, and parasympathetic reactivation (time-varying HRV analysis) were assessed. In all three groups, exercise resulted in increased HR, CO, AP, and LFSAP (P < 0.001), decreased SV, HFRR, and Ln BRS (all P < 0.001), and no change in TPR (P = 0.98). There was no “maturation × time” interaction for any of the hemodynamic or autonomic variables (all P > 0.22). After exercise, pre-PHV players displayed lower SV, CO, and [La]b, faster HRR and greater parasympathetic reactivation compared with circum- and post-PHV players. Multiple regression analysis showed that lean muscle mass, [La]b, and Pre parasympathetic activity were the strongest predictors of HRR (r2 = 0.62, P < 0.001). While pre-PHV players displayed a faster HRR and greater post-exercise parasympathetic reactivation, maturation had little influence on the hemodynamic and autonomic responses following maximal running exercise. HRR relates to lean muscle mass, blood acidosis, and intrinsic parasympathetic function, with less evident impact of post-exercise autonomic function

Physical Demands of Sprinting in Professional Road Cycling

The aim of this study was to quantify the demands of road competitions ending with sprints in male professional cycling. 17 races finished with top-5 results from 6 male road professional cyclists (age, 27.0±3.8 years; height, 1.76±0.03 m; weight, 71.7±1.1 kg) were analysed. SRM power meters were used to monitor power output, cadence and speed. Data were averaged over the entire race, different durations prior to the sprint (60, 10, 5 and 1 min) and during the actual sprint. Variations in power during the final 10 min of the race were quantified using exposure variation analysis. This observational study was conducted in the field to maximize the ecological validity of the results. Power, cadence and speed were statistically different between various phases of the race (p<0.001), increasing from 316±43 W, 95±4 rpm and 50.5±3.3 km·h−1 in the last 10 min, to 487±58 W, 102±6 rpm and 55.4±4.7 km·h−1 in the last min prior to the sprint. Peak power during the sprint was 17.4±1.7 W·kg−1. Exposure variation analysis revealed a significantly greater number of short-duration high-intensity efforts in the final 5 min of the race, compared with the penultimate 5 min (p=0.010). These findings quantify the power output requirements associated with high-level sprinting in men’s professional road cycling and highlight the need for both aerobic and anaerobic fitness

Alternate-day low energy availability during Spring Classics in professional cyclists

Purpose: To assess energy and carbohydrate (CHO) availability and changes in blood hormones in 6 professional male cyclists over multiple single-day races. Methods: The authors collected weighed-food records, power-meter data, and morning body mass measurements across 8 d. CHO intakes were compared with contemporary guidelines. Energy availability (EA) was calculated as energy intake minus exercise energy expenditure, relative to fat-free mass (FFM). Skinfold thickness and blood metabolic and reproductive hormones were measured prestudy and poststudy. Statistical significance was defined as P ≤ .05. Results: Body mass (P = .11) or skinfold thickness (P = .75) did not change across time, despite alternate-day low EA (14 [9] vs 57 [10] kcal·kg−1 FFM·d−1, race vs rest days, respectively; P 46 kcal·kg−1 FFM·d−1) on days between. CHO intakes were significantly higher on race versus rest days (10.7 [1.3] vs 6.4 [0.8] g·kg−1·d−1, respectively; P < .001). The cyclists reached contemporary prerace fueling targets (3.4 [0.7] g·kg−1·3 h−1 CHO; P = .24), while the execution of CHO guidelines during race (51 [9] g·h−1; P = .048) and within acute (1.6 [0.5] g·kg−1·3 h−1; P = .002) and prolonged (7.4 [1.0] g·kg−1·24 h−1; P = .002) postrace recovery was poor. Conclusions: The authors are the first to report the day-by-day periodization of energy and CHO in a small sample of professional cyclists. They also examined the logistics of conducting a field study under stressful conditions in which major cooperation from the subjects and team management is needed. Their commentary around these challenges and possible solutions is a major novelty of the article

Physiological responses to cold water immersion following cycling in the heat

Cold water immersion (CWI) has become a popular means of enhancing recovery from various forms of exercise. However, there is minimal scientific information on the physiological effects of CWI following cycling in the heat. Purpose:To examine the safety and acute thermoregulatory, cardiovascular, metabolic, endocrine, and inflammatory responses to CWI following cycling in the heat. Methods: Eleven male endurance trained cyclists completed two simulated ~40-min time trials at 34.3 ± 1.1°C. All subjects completed both a CWI trial (11.5°C for 60 s repeated three times) and a control condition (CONT; passive recovery in 24.2 ± 1.8°C) in a randomized cross-over design. Capillary blood samples were assayed for lactate, glucose, pH, and blood gases. Venous blood samples were assayed for catecholamines, cortisol, testosterone, creatine kinase, C-reactive protein, IL-6, and IGF-1 on 7 of the 11 subjects. Heart rate (HR), rectal (Tre), and skin temperatures (Tsk) were measured throughout recovery. Results: CWI elicited a significantly lower HR (CWI: Δ116 ± 9 bpm vs. CONT: Δ106 ± 4 bpm; P = .02), Tre (CWI: Δ1.99 ± 0.50°C vs. CONT: Δ1.49 ± 0.50°C; P = .01) and Tsk. However, all other measures were not significantly different between conditions. All participants subjectively reported enhanced sensations of recovery following CWI. Conclusion: CWI did not result in hypothermia and can be considered safe following high intensity cycling in the heat, using the above protocol. CWI significantly reduced heart rate and core temperature; however, all other metabolic and endocrine markers were not affected by CWI