Grant: DRA : Canada Graduate Research Scholarship - Doctoral Program (CGRS D)

Exclusive breastfeeding is recommended for the first six months of life for parental and infant health. However, many athletes are concerned that physical activity will negatively impact their breastmilk and overall health. This research project aims to assess the impact of a high intensity interval training program on lactation and bone health. We will recruit 66 individuals who are at least 18 years of age,12-16 weeks postpartum and exclusively breastfeeding their infants. They will be randomly assigned to one of two 16-week exercise interventions or a control group. The exercise interventions will meet current guidelines for postpartum physical activity (equivalent to 120 minutes of physical activity each week). One group will perform high intensity interval training (HIIT), and the other group will perform moderate intensity continuous training (i.e., a standard exercise prescription). Pre- and post-intervention, participants will visit our laboratory for a fitness assessment (graded exercise test on a cycle ergometer) with blood and breastmilk samples taken prior to exercise and 5- and 30-minutes post exercise to assess markers of bone formation and resorption and breastmilk composition (protein, lipids, lactate). Participant body composition (bone mineral density, fat and muscle mass) will also be measured using dual-energy x-ray absorptiometry. For seven days following each laboratory visit, participants physical activity and food intake will be monitored using a physical activity monitor and by taking photos of their food. Breastmilk volume will be measured in a 24-hour period during this time by weighing the infant pre-and-post feeding. The results of this study will be the first to address athletes concerns about the compatibility of high intensity aerobic training and lactation.