In high intensity interval training (HIIT), bouts of intense work are alternated with less intense periods. HIIT provides an effective stimulus to increase the volume of exercise at or above 90% heart rate maximum (HRmax). Magnesium (Mg) modulates energy metabolism and enzymatic processes. Studies suggest that Mg assists oxidative transport, improves glucose availability, delays lactate accumulation, and reduces inflammation. A gap exists in understanding how Mg affects HIIT. Moreover, the influence of a Vegan (VD) vs Omnivore (OD) diet on HIIT performance outcomes (e.g., heart rate [HR] and time-to-fatigue [TTF]), has yet to be investigated. PURPOSE: This study explored the relations between VD and OD Mg intake and HRmax and TTF during a HIIT treadmill (TM) protocol. It was hypothesized that a higher Mg intake would be associated with a lower HRmax and extended TTF. METHODS: Five healthy participants (1 female, 4 males; 27.2 ± 3.4 years) were enrolled and completed a TM HRmax test and HIIT protocol. The HIIT session comprised four repetitions of 4-minute higher intensity bouts at 85-95% HRmax followed by 3-minute recovery periods at 60-70% HRmax. Dietary Mg was assessed using the ASA24 recall. Values are reported as group mean difference ± SD. Hedges g effect sizes (ES) were calculated, and Pearson correlation coefficients were determined. RESULTS: As expected, Mg intake was higher in VD than OD subjects with a large effect size (558.6 ± 29.0 mg, ES = 19.2). Differences in measured HRmax and TTF between groups was also observed, with VD having a lower HRmax (14.3 ± 1.5 bpm, ES = 9.3) and extended TTF (2.0 ± 0.5 min, ES = 3.9). A strong negative correlation (r = -0.98) was identified between Mg intake and measured HRmax, as well as Mg and RHR (r = -0.73). A moderate positive correlation (r = 0.66) was found for Mg intake and TTF. CONCLUSION: These preliminary data suggest that the higher Mg intake found in persons with a VD is associated with a lower HRmax and extended TTF during HIIT, compared to persons with an OD.



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