Vegan diet vs. omnivorous diet : impact on recovery of muscle function : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science Nutrition and Dietetics at Massey University, Auckland, New Zealand

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Purpose: The purpose of the study was to compare the recovery of skeletal muscle function post-strenuous exercise between healthy young males on a vegan diet with healthy young males on an omnivorous diet. Methods: Six vegan (33±6 years, 75±13 kg, 1.79±0.06 m, 23.13±2.82 kg/m²) and six omnivore (27±7 years, 84±12 kg, 1.77±0.07 m, 27.07±4.77 kg/m²) healthy males performed an established muscle-damaging exercise protocol, consisting of 5 sets of 20 drop jumps from a 0.6 m high platform. Skeletal muscle function was evaluated using double-legged countermovement jumps (CMJ). Generalized pain at rest and during CMJ was accessed with a visual analogue pain scale (VAS) and muscle-specific soreness at rest was assessed by asking participants to verbally rate the level of pain experienced in specific muscles of each leg. Pressure pain threshold (PPT) was used as a secondary measure of muscle-specific soreness, using a handheld algometer. These parameters were measured before drop jumps and at specific time points (0 h, 1 h, 3 h, 24 h, 48 h and 72 h following the drop jumps). 4-day food diaries were collected to access participants’ habitual diets. Results: There was no significant difference in CMJ height over time points (F=4.223, P=0.370) across the study, and diet type also had no significant effect on CMJ height (F=0.820, P=0.786). There was a significant increase for generalised pain at rest (F=10.868, P=0.002) and during CMJ (F=8.428, P=0.003), observed over time points, which was similar between diet types. Subjective pain at specific muscles at rest was also mostly similar between vegans and omnivores, except for glutes left leg (F=12.377, P=0.017) and inner thigh left leg (F=10.741, P=0.022), where vegans had less pain. PPT was not affected by the exercise protocol and was similar between vegans and omnivores, except for the calf lateral head left leg where omnivores had a slightly lower PPT (F=10.988, P=0.021). Conclusion: The study found no differences in recovery of skeletal muscle function between omnivores and vegans, despite sporadic differences in muscle soreness. Mechanisms linking habitual diet and delayed-onset muscle soreness (DOMS) are still unclear, and the results of our study should be confirmed by larger or more powerful studies, as well as studies directed to address this specific question.