Touba, M T (2008) The effect of dietary supplementation on fatigue and recovery after resistance exercise in females. Doctoral thesis, Liverpool John Moores University.

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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 < 0.001) across recovery time, but there was no significant difference for MVC at 48h for both legs and 24h, 48h for the dominant leg, and no significant difference for RFD between pre-exercise and 24h and 48h for the dominant leg. The fatigue protocol reduced measured force variables by 23.7% and 34.2%, and recovery from fatigue had been achieved after 48 hours. Study 3: The objective was to quantify the effect of carbohydrate supplementation on muscular strength after resistance exercise in females. Carbohydrate (CHO) supplementation and placebo trials were randomised and conducted at the same time of day (9: 00 am), on two separate occasions with one week between sessions. For the CHO trial, participants ingested a carbohydrate solution (0.5g CHO per kg/BM). The resistance exercise protocol described in study 2 was employed in this experiment. Instead of using 70% of the 1-RM, a work load in this study corresponding to 80% 1-RM was used. A significant (P<0.05) overall main effect for condition and time on MVC and RFD was found, but there was a non-significant interaction between condition and time. The data showed that there was a faster recovery in the CHO condition with a suggestion of supercompensation. The resistance exercise for the lower body resulted in a significant decrease (P<0.05) in MVC immediately after resistance exercise, and this occurred similarly in both CHO and placebo trials. Study 4: The objective was to quantity the effect of creatine (Cr) supplementation on muscular strength and biochemical responses to resistance exercise in female subjects. The methodological studies described in the pilot and main studies were use to create the protocols to reliably assess MVC and RFD. Subjects undertook a resistance exercise session at an intensity corresponding to 80% of 1-RM. They were required to consume 20g of creatine monohydrate or placebo in a double-blind experimental design for 5 days before being-tested. Blood samples were taken before each session of tests, and analyzed for blood biochemical variables which included: creatine kinase (CK), growth hormone (GH), Myoglobin (MYO). A significant effect of Cr was found on MVC and RFD recovery (P<0.01). Body mass was not significantly different between sessions (P= 0.14) but there was a slight increase (1.0 kg) following Cr supplementation compared to other conditions. The CK and MYO, data revealed no significant main effect on time and conditions (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.

Item Type:	Thesis (Doctoral)
Subjects:	R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions:	Sport & Exercise Sciences
Date Deposited:	14 Mar 2017 10:35
Last Modified:	03 Sep 2021 23:30
DOI or ID number:	10.24377/LJMU.t.00005918
URI:	https://researchonline.ljmu.ac.uk/id/eprint/5918

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