• Effects of Post Exercise Protein Supplementation on Bone Turnover in Adolescent Swimmers

      Theocharidis, Alexandros; Applied Health Sciences Program
      Objective: To compare the effects of whey protein supplementation to an isocaloric carbohydrate beverage consumed immediately after an intense swimming trial on the promotion of bone turnover in adolescent swimmers, with water provided as a placebo to the control group. Methods: Fifty-eight male (n=27, 14.04±1.5 years) and female (n=31, 13.75±1.8 years) swimmers were stratified into three groups matched for age, body mass and male/female split. The protein group consumed two post-exercise beverages of 0.3 g/kg of whey protein each, the isocaloric carbohydrate group consumed two post-exercise beverages of 0.3g/kg of maltodextrin and the control group had flavoured water. Participants provided one morning, fasted, blood sample, performed an exercise trial consisting of multiple bouts of intense swimming and then consumed their respective post-exercise beverages 2h apart. Participants provided a second blood sample ~8h from baseline, and returned 24h later for a follow-up, morning, fasted blood sample. Markers of bone formation (procollagen type 1 intact N-terminal propeptide [PINP]) and resorption (carboxy-terminal collagen crosslinks [CTXI]) were measured in serum. Bone turnover rate and balance were estimated using the Multiple of Medians of CTXI and PINP. Results: A three-way repeated measures ANOVA (time-by-group-by-sex) showed a significant time-by-group interaction for CTXI (p=0.021), with no effect of, or interaction with sex, reflecting a significant increase from baseline to 8h in the protein group only, which subsequently decreased significantly to lower values than baseline at 24h. For PINP, there was a time-by-group-by-sex interaction (p=0.04); however, despite the 3-way interaction, none of the post-hoc comparisons were statistically significant. The bone turnover rate showed a time-by-group interaction (p<0.001), with no effect of, or interaction with sex. Specifically, the bone turnover rate significantly increased at 8h in the protein group only, with the bone turnover balance favouring formation at 8h and 24h. Conclusion: These results shed light on the potential importance of protein supplied shortly after intense exercise in promoting bone turnover up to 24h following the exercise in adolescent athletes.