Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Medical and Health Science

Abstract

Mixed Martial Arts (MMA) athletes are weighed 24 h prior to competition. In order to compete in a lower weight class MMA athletes will often rapidly lose weight via dehydration. Despite the prevalence, there is currently no known published data examining the effects of acute dehydration on physiology and performance in mixed martial arts athletes. The present study aimed to examine: i) the effects of 5% acute dehydration on performance (vertical jump, medicine ball throw, grip strength and repeated sled push) and physiology (body weight, haematocrit, urine specific gravity, serum osmolality and urine osmolality) of MMA athletes. A total of 14 MMA athletes between the ages of 18 and 40 y with at least 2 y of competitive experience were recruited. Participants performed a familiarisation session, followed by two experimental sessions including a control protocol (CONT) or a dehydration protocol (DHY) in a randomised order. During the DHY athletes cycled for 3 h in a heated chamber (40˚C and 30% relative humidity) wearing a sweat suit in order to lose 5% of their bodyweight (BW). Athletes then underwent a 3 h recovery period, during which they consumed fluids/food ad libitum. Athletes then performed a series of performance tests, including vertical jump, medicine ball throw, wrist grip and repeated sled push. A further 21 h recovery period was allowed before athletes performed the same tests. Prior to weight loss, immediately post weight loss, pre performance testing (3 h post weight loss) and 24 h post weight loss, urine and blood samples were collected and body weight was measured. A lower average speed during the repeat sled push (5.65 ± 1.3 km.h-1) was observed 3 h post DHY compared with 3 h post CONT (6.99 ± 0.85 km.h-1; P-1) when compared with 24 h post CONT (7.12 ± 0.95 km.h-1; P-1 and 9.14 ± 1.1 km.h-1 were observed 3 h post DHY/CONT and 8.82 ± 1.41 km.h-1 and 9.35 ± 1.06 km.h-1 24 h post DHY/CONT. A decreased time to fatigue and increased perceived exertion was also observed. The decrements in performance were observed at both 3 h and 24 h post DHY with the decrements still being present but not as large 24 h. When comparing measures of hydration in the DHY with CONT, significantly lower measures of hydration were observed 30 min post DHY and 3 h post DHY. None of the measured markers of hydration indicated athletes were dehydrated 24 h post DHY. The observations of this present study indicate that current weight loss practices in MMA and other combat sports may not be conducive to the best physical performance possible. Current practices should be reconsidered since performance was compromised even following 24 h of recovery. Future research should investigate possible physiological mechanisms behind the observed decrement in performance.

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