Bone Marker Responses to Resistance Exercise with Vascular Restriction in Young and Older Men

Abstract

Acute bouts of low intensity resistance exercise with blood flow restriction (BFR) have been shown to decrease bone resorption markers in young men. It is important to examine the influence of age on these bone marker responses. PURPOSE: To compare bone marker responses of young (n=10; 18-25 yrs) and older men (n=10; 50-64 yrs) during an acute bout of lower body resistance exercise with either a traditional (NoBFR) heavy training load (80% 1RM, 3 sets, 8 reps) or a low intensity (20% 1RM, 4 sets, 20, 15, 15, and 15 reps) session with vascular restriction (BFR). METHODS: Subjects were assigned to the two exercise sessions in a randomized, cross-over design, separated by 4 days: NoBFR or BRF for knee extension and leg press exercises. Blood samples were obtained via an indwelling venous catheter at the following time points: pre-exercise; immediate post-exercise; 15, 30, 60 min post; and 24 hours post to assess Bone-specific Alkaline Phosphatase (BAP) and C-terminal Telopeptides of Type I Collagen (CTX) using commercial ELISA kits. RESULTS: Young men had higher serum levels of both BAP (p < 0.01) and CTX (p < 0.01) at all time points compared to the older men. BAP significantly increased (p < 0.05) in response to the NoBFR protocol for both young (12% immediate post, 6% 30 min post) and older men (7% immediate post, 7% 15 min post, 4% 30 min post). The only BAP trend for the BFR protocol occurred in young men (increase from pre to immediate post, p = 0.064). There was a significant time (p < 0.05) main effect for CTX. Both resistance exercise protocols resulted in significant decreases (p < 0.01) in CTX from pre-exercise to 60 min post-exercise; however, there was a trend (p = 0.059) for the % CTX change to be greater for BFR (-20.8% ± 4.1) than NoBFR (-13.6% ± 3.7). CONCLUSION: The patterns of bone marker responses to the NoBFR and BFR protocols were similar for the young and older men. Both exercise protocols were associated with a decrease in the bone resorption marker; however, the NoBFR protocol was more effective in stimulating an increase in the bone formation marker. Our findings are consistent with previous reports that BFR decreases bone resorption markers. BAP seems to be more responsive to high intensity resistance exercise