Concurrent training : neuroendocrine and molecular mechanisms of strength and endurance training incompatibility

Combining strength and endurance training within the same regimen is aptly referred to as “concurrent training”. Research conducted over the previous 3 decades has indicated concurrent training can result in attenuated development of strength, power and hypertrophy when compared to strength training in isolation. Despite extensive research the mechanisms contributing to this so called “interference effect” are yet to be fully \nelucidated, as is the influence of manipulating acute training programme variables within a concurrent regimen. As such, the purposes of this thesis were to investigate and draw conclusions regarding underlying physiological mechanisms relating to the interference effect. Additionally, this thesis sought to examine the effects of manipulating programme variables, including frequency and sequencing of exercise within concurrent training regimens on strength related adaptation. The findings of this thesis indicate overall training volume and frequency of endurance training within a concurrent intervention influences the presence and magnitude of the inhibition of strength development. Concurrent training volumes of 3 d·wk-1 elicited muted strength development, whereas lower frequencies did not. Whilst interference was not attributable to neuromuscular factors, it was reported that cortisol was only elevated following higher training frequencies, indicating training stress and catabolism may \ncontribute to interference. Additionally, the sequencing of strength and endurance training can influence endocrine and signalling responses associated with strength adaptation, and it appears strength prior to endurance elicits greater increases in growth associated signalling. \nThe findings of this thesis indicate that overall training stress influences the presence and magnitude of interference experienced, and is reflected in catabolic endocrine responses. Additionally, strength prior to endurance training promotes more favourable anabolic signalling than vice versa, which over time may contribute to greater strength type adaptations.