Failure and non-failure resistance exercise in trained individuals

Abstract

The rate and magnitude of muscular strength and power improvements are reduced the longer an individual is engaged in consistent moderate to high intensity resistance exercise training. It is therefore thought that trained individuals need to 'work harder' by performing resistance exercise to failure to evoke a large increase in acute fatigue and optimise improvements in muscular strength and power following a period of training. Previous literature has demonstrated that performing resistance exercise to failure stimulates significant acute reductions and chronic improvements in muscular strength and power. However, it is not well understood whether a less stressful and potentially safer exercise modality, such as not completing exercise to the point of failure, can achieve similar or superior outcomes in trained individuals. Disagreement within the current literature that has compared failure and non-failure based resistance exercise prescription may stem from many factors, potentially related to differences in methodological design and a relatively poor understanding of the mechanisms that promote acute and chronic changes in muscular strength and power in trained individuals. Therefore, this thesis contains a series of investigations designed to address the disagreement within the present body of literature and examine gaps in the understanding of the need for trained individuals to perform resistance exercise to failure to improve muscular strength and power. Study 1 investigated changes in muscular strength and power following an acute bout of isometric failure and non-failure based exercise of the knee extensors. Failure exercise was observed to promote greater reductions in muscular strength than a similar bout of non-failure exercise. Peripheral, rather than central mechanisms were found to facilitate reductions in muscular strength with both exercise modalities and likely mediated the greater reduction in muscular strength following failure exercise prescription. As isotonic contractions are more commonly performed in many real world training and competitive environments, Study 2 examined a single session of dynamic failure and non-failure exercise. This investigation demonstrated that a single bout of failure exercise was no more effective at stimulating reductions in plantar flexor strength than a similar bout of non-failure exercise. The decline in strength likely resulted from significant impairment of central neural drive to the muscle. However, a potentiation of muscular excitation-contraction coupling processes seems to have produced an acute increase in muscular power output. The final investigation presented in this thesis (Study 3) examined changes in muscular strength and power following short term failure and non-failure training. Whilst plantar flexor power did not improve with training, failure and non-failure exercise modalities were equally effective at improving plantar flexor strength. The results demonstrated that improvements in muscular strength were likely produced from improved functionality of the muscular contractile apparatus and not from adaptations within spinal or supraspinal neural pathways. The body of work presented in this thesis has demonstrated that both failure and non-failure based exercise evoke an increase in muscular fatigue acutely, which for the most part, was observed to promote a similar acute reduction in muscular strength between modalities. The acute increase in muscular fatigue likely facilitated the similar improvements in muscular strength observed with failure and non-failure exercise following short term training in trained populations. However, the central and peripheral fatigue mechanisms that mediated acute reductions in muscular strength following failure and non-failure exercise did not appear to have any relevance for predicting the training outcome.

Date of Award	2016
Original language	English