Author(s): YAMASHITA, Y., UMEMURA, Y., Institution: CHUKYO UNIVERSITY, Country: JAPAN, Abstract-ID: 531

INTRODUCTION:
Half-time (HT) strategies are important for preventing a decrease in high-intensity exercise performance in the early 2nd half during intermittent team sports [1]. Decreased body temperature during HT is reported to be associated with a decrease in high-intensity exercise performance in the early 2nd half [2]. Methods of passive heat maintenance such as wearing heated jackets and hot water immersion are considered to be effective for attenuating the reduction in body temperature and exercise performance [3]. The hands have a high surface area-to-mass ratio and arteriovenous anastomoses, which, together with superficial veins up to the elbow, constitute a specialized heat exchange organ [4], that which may be the large potential area for heat transfer. Therefore, the aim of current study was to investigate the effects of hot water immersion of the hand and forearm during HT on physiological response and exercise performance in a cold environment.
METHODS:
Ten healthy men (age 22 ± 2 years, height 170.6 ± 2.1 cm, body mass 63.1 ± 4.5 kg) participated in this study. Participants performed experimental sessions that consisted of 40 min of intermittent cycling in the 1st half, a 15-min HT, and an intermittent cycling sprint test as the 2nd half. During the 15-min HT, participants underwent two different interventions: seated rest (CON), and immersion of the hand and forearm in hot water (43℃) up to the elbow (HEAT). The intermittent cycling sprint test comprised 10 sets of 5 s maximal pedaling (weight × 0.075 kp) and 25 s recovery to evaluate their cycling sprint performance. Additionally, participants performed maximal voluntary isometric contraction (MVC) in knee extension at HT pre and post. The experimental sessions were conducted in a climate chamber set at a temperature of 5℃ and 50% relative humidity.
RESULTS:
Although the cycling sprint performance in the simulated 2nd half was not significantly different between the CON condition and the HEAT condition (CON: 682 ± 72 W, HEAT: 696 ± 64 W, p >0.05), rectal temperature (Tre) at post HT, pre, and post sprint test in the HEAT condition were significantly higher than that in the CON condition. Moreover, the change of Tre during HT in the HEAT condition was significantly lower than that in the CON condition (CON: –0.50 ± 0.08℃, HEAT: –0.27 ± 0.14℃, p < 0.05). The MVC force at HT post was significantly increased compared with HT pre in the HEAT condition (105.0 ± 6.1 %, p < 0.05) and was significantly higher than that in the CON condition (CON: 96.2 ± 6.9 %, HEAT: 105.0 ± 6.1 %, p < 0.05).
CONCLUSION:
Our results suggested that the hot water immersion of the hand and forearm during HT may provide a new HT strategy to prevent the reduction of Tre during HT and improve lower muscle strength in a cold environment.
References:
[1] Russell et al. (2015) Sports Med.
[2] Mohr et al. (2004) Scand J Med Sci Sports.
[3] Bishop. (2003) Sports Med.
[4] Vanggaard. (2012) Clin. Physiol. Funct. Image.