The effect of dietary supplementation on fatigue and recovery after resistance exercise in females

Abstract

Resistance exercise has been a popular form of muscle strength development for sport participants. This type of exercise activates a wide variety of physiological mechanisms involved with the exercising of muscle. The aim of this thesis was to investigate responses to dietary supplementation on muscular strength and biochemical indices to resistance exercise in female subjects. Firstly, to determine the reliability of the isometric test designed, and the number of trials required to-obtain reproducible measurements of maximum voluntary isometric force and rate of force development. Secondly, to establish heavy resistance exercise volume and intensity to produce a fatigue effect of a 40% reduction in measured force variables. Thirdly, to determine the optimal recovery period required to overcome the effect of fatigue responses to heavy resistance exercise after ingesting carbohydrate supplement (CHO). Finally, to determine the effect of creatine supplementation (Cr) on fatigue and recovery responses after resistance exercise in female subjects. Study one (1. A): The objective of study one was to quantify for female subjects, maximum voluntary isometric contractions (MVC) and rate of force development (RFD) and to evaluate the repeatability (between-days) of measurements. The data showed a small systemic bias between days for both, right and left leg and showed good reliability between days for MVC (range 5.4% to 11.5%), (9.55% to 36.3%) and (5.8% to 11.4%) for both legs, right leg and left leg, respectively. The LOA for RFD showed good reliability between days for all conditions (range 0.1% to 7.4%). It was concluded that the average of 3 trials between days is satisfactory for the repeatability of MVC and RFD. Study one (1. B) This second part of study one was to determine if there was a fatiguing effect of the testing protocol and also to establish the fatigue effect of the heavy resistance exercise. The same subjects were used as in study IA, but with the fatigue effects of an exercise trial between sessions 2 and 3. Subjects performed three sets of six different resistance exercises involving the lower body at an intensity corresponding to 60% of 1- RM (8-10 repetitions). The LOA for MVC was 0.6%, 13.7%, and 6.7%, for both legs, right leg and left leg respectively, and for RFD was 0.3%, 4.4%, and 5.3% for both legs. It was concluded that using both legs for studying the MVC was more reliable than using one leg for within-day and between-days force measurements. Study 2: The objective of study two was to establish the heavy resistance exercise volume and intensity to produce a fatigue effect of a 40% reduction in measured force variables and to establish the fatigue and recovery responses over a 48 hour period. Subjects were familiarised with the same testing procedures as in the pilot study 1B. All subjects performed three sets of six different exercises (lying leg curls, dumbbell lunges, barbell squats, leg extensions, straight leg deadlift, leg presses) at an intensity corresponding to 70% of 1-RM (8-10 repetitions). Measurements were obtained after 2h, 24h and 48h recovery for MVC and RFD. A significant main effect was found for time on MVC and RFD for both legs and the dominant leg (P 0.05). Indicating that the fatigue protocol did not induce muscle damage the GH data showed a significant mean effect of time and conditions (P<0.05), conforming an hormonal response to exercise. It was concluded that oral creatine supplementation enhances recovery following a resistance exercise challenge with a suggestion of a super-compensation at 48 hours. In summary, the procedure of resistance exercise was used in the four experimental studies and nutritional supplementation (CHO and Cr) significantly reduced the decline in maximal peak force and enhanced recovery following resistance exercise. It was concluded that the recovery from heavy resistance exercise in female appears to be aided by dietary supplementation producing an increase in the recovery of both maximal voluntary contraction force and rate of force development.