Determinants of exercise-induced muscle damage and the repeated bout effect in men and women

Marshall, Steven James (2020) Determinants of exercise-induced muscle damage and the repeated bout effect in men and women. Doctoral thesis, Northumbria University.

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Abstract

Exercise induced muscle damage (EIMD) is a consequence of lengthening muscle actions, with the amount of strain placed on the muscle a key determinant of the magnitude of damage experienced. When exposed to lengthening muscle actions, skeletal muscle rapidly adapts so that when the same exercise is repeated, these markers of EIMD are attenuated, with this adaptation termed the repeated bout effect (RBE). Changes in muscle lengthening and increases in tendon compliance between exercise sessions have been hypothesised to be a mechanism underpinning the RBE, but this currently remains unclear. Moreover, muscle and tendon behaviour between two bouts of muscle damaging exercise has yet to be investigated in a female population. Therefore, the aim of this was to use US to further understand the properties and behaviour of the patella tendon (PT) and vastus lateralis (VL) in males and females and how these properties contribute to the EIMD response to ECC exercise and the magnitude of the repeated bout effect. In chapter 3, measures of PT cross sectional area (CSA) using ultrasonography were validated against magnetic resonance imaging. Additionally, the test-retest reliability of these measures were tested between two independent US operators. Measures of PT CSA were found to be valid and reliable and could be used interchangeably. Moreover, inter- and intra rater reliability was deemed excellent. In chapter 4, procedures for using ultrasonography to assess VL and PT behaviour at rest and during maximal exercise was shown to have excellent test-retest reliability, which did not differ between males and females. Finally, in chapter 5, it was found that VL muscle fascicle lengthening was approximately 7.6% lower following a repeated bout of lengthening exercise, and this was coupled with an attenuated EIMD response following the second bout. Additionally, this response did not differ between males, females using an oral contraceptive pill and eumenorrheic females. This work extends the understanding of muscle and tendon behaviour during repeated bouts of damaging lengthening contractions and that this behaviour is similar between males and females.

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