Physiological Responses and Physical Performance during Football in the Heat

PURPOSE: To examine the impact of hot ambient conditions on physical performance and physiological responses during football match-play. METHODS: Two experimental games were completed in temperate (∼ 21°C; CON) and hot ambient conditions (∼ 43°C; HOT). Physical performance was assessed by match analysis in 17 male elite players during the games and a repeated sprint test was conducted after the two game trials. Core and muscle temperature were measured and blood samples were obtained, before and after the games. RESULTS: Muscle and core temperatures were ∼ 1°C higher (P<0.05) in HOT (40.3 ± 0.1 and 39.5 ± 0.1°C, respectively) compared to CON (39.2 ± 0.1 and 38.3 ± 0.1°C). Average heart rate, plasma lactate concentration, body weight loss as well as post-game sprint performance were similar between the two conditions. Total game distance declined (P<0.05) by 7% and high intensity running (>14 km ⋅ h(-1)) by 26% in HOT compared to CON), but peak sprint speed was 4% higher (P<0.05) in HOT than in CON, while there were no differences in the quantity or length of sprints (>24 km ⋅ h(-1)) between CON and HOT. In HOT, success rates for passes and crosses were 8 and 9% higher (P<0.05), respectively, compared to CON. Delta increase in core temperature and absolute core temperature in HOT were correlated to total game distance in the heat (r = 0.85 and r = 0.53, respectively; P<0.05), whereas, total and high intensity distance deficit between CON and HOT were not correlated to absolute or delta changes in muscle or core temperature. CONCLUSION: Total game distance and especially high intensity running were lower during a football game in the heat, but these changes were not directly related to the absolute or relative changes in core or muscle temperature. However, peak sprinting speed and execution of successful passes and crosses were improved in the HOT condition

Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing.

Prolonged unaccustomed exercise involving muscle lengthening (eccentric) actions can result in ultrastructural muscle disruption, impaired excitation-contraction coupling, inflammation and muscle protein degradation. This process is associated with delayed onset muscle soreness and is referred to as exercise-induced muscle damage. Although a certain amount of muscle damage may be necessary for adaptation to occur, excessive damage or inadequate recovery from exercise-induced muscle damage can increase injury risk, particularly in older individuals, who experience more damage and require longer to recover from muscle damaging exercise than younger adults. Furthermore, it is apparent that inter-individual variation exists in the response to exercise-induced muscle damage, and there is evidence that genetic variability may play a key role. Although this area of research is in its infancy, certain gene variations, or polymorphisms have been associated with exercise-induced muscle damage (i.e. individuals with certain genotypes experience greater muscle damage, and require longer recovery, following strenuous exercise). These polymorphisms include ACTN3 (R577X, rs1815739), TNF (-308 G>A, rs1800629), IL6 (-174 G>C, rs1800795), and IGF2 (ApaI, 17200 G>A, rs680). Knowing how someone is likely to respond to a particular type of exercise could help coaches/practitioners individualise the exercise training of their athletes/patients, thus maximising recovery and adaptation, while reducing overload-associated injury risk. The purpose of this review is to provide a critical analysis of the literature concerning gene polymorphisms associated with exercise-induced muscle damage, both in young and older individuals, and to highlight the potential mechanisms underpinning these associations, thus providing a better understanding of exercise-induced muscle damage

The thermal and nonthermal effects of high and low doses of pulsed short wave therapy (PSWT)

The definitive version is found at: www3.interscience.wiley.com Copyright Wiley [Full text of this article is not available in the UHRA]The study aimed to investigate the thermal and non-thermal effects of pulsed short wave therapy (PSWT) using high and low dose of PSWT together with placebo and control conditions in healthy subjects. Method. A single–blind, crossover design was employed with 31 subjects who all participated in three conditions: High PSWT (PD 200 μsec, PRR 800 Hz, MP 24 W, 10 minutes), Low PSWT (PD 100 μsec, PRR 200 Hz, MP 3 W, 10 minutes), and Placebo PSWT (PD 20 μsec, PRR 50 Hz, MP 0.05 W, 10 minutes). Fourteen subjects additionally participated in a Control condition (no treatment, 10 minutes). Measurements of skin temperature, blood flow, heart rate, and core temperature were taken before, during, and after the application of PSWT. Data were analyzed using a repeated measures analysis of variance (ANOVA) model with a Bonferroni post-hoc comparison. Results. A significant increase in blood volume and skin temperature with both the high- and low-dose applications during the treatment period was demonstrated. There were significant differences between time periods and between treated and untreated limbs compared with the control condition. The blood flow changes during the low-dose application were not significantly different from placebo. Some subjects were unable to detect significant changes in skin temperature. Conclusion. Significant physiological changes associated with the application of PSWT have been demonstrated, challenging the notion of a lack of effect of this therapy. The study also demonstrated a measurable increase in skin temperature, which was not associated with thermal sensory perception; thus, skin sensation may not be clinically reliable for detecting real changes in temperature. Subjects with a wide age range of ages were deliberately recruited; however, these results may not extrapolate to a patient population who could react differently to the same intervention. Further studies in the clinical environment are therefore needed.Peer reviewe