Bone Turnover Markers Responses To Resistance Exercise Performed At Submaximal And Maximal Movement Velocity

Direct mechanical overloading as well as muscle contraction forces are applied to the bones during resistance exercise, which are strong stimuli for eliciting possible acute changes in bone turnover markers potentially involved in bone adaptational responses to exercise. PURPOSE: This study investigated potential exercise-induced changes in procollagen type I amino-terminal propeptide (PINP) and bone-specific alkaline phosphatase (BALP) in young volunteers after a bout of resistance exercise performed at either 70% (70%Max) or the maximal velocity of movement (Max). METHODS:Nine healthy males (age: 22.5 ± 3.3 years, height: 181 ± 5 cm, body mass: 81.6 ± 5.6 kg) underwent a protocol of resistance exercise of the knee extensors of both legs (4 sets squat and 4 sets leg press, 8 repetitions/set, with a load corresponding to that of 10-repetition maximum). A recovery period of 3 minutes was allowed between sets. Blood samples were collected before, immediately after and at 20- and 40-min post-exercise. Plasma levels of PINP and BALP were measured by enzyme-linked immunosorbent assay (ELISA). Two-way ANOVA was used for statistics and data are presented as mean ± SE. RESULTS: No difference was observed in PINP responses between the exercise conditions of different movement velocities, although a tendency (p = 0.07) for higher concentrations were found at 70%Max (20.1 ± 4.6 ng.ml-1) compared to Max (13.3 ± 2.2 ng.ml-1) 40 min post-exercise. Regarding the BALP responses, a higher relative to baseline increase at 40 min post-exercise (34.4 ± 5.9%) was found compared to immediately post-exercise increase (8.2 ± 5.7%) (main effect for time; p = 0.028). Furthermore, in the 70%Max condition there was also a higher (p = 0.007) relative to baseline increase at 40 min post-exercise (52.6 ± 8.4%) compared to immediately post-exercise (-0.3 ± 9.2%). CONCLUSIONS: Our findings suggest that resistance exercise at a submaximal velocity of concentric movements induces higher acute BALP responses compared to those caused by maximal velocity movements. Further studies are needed to characterize the mechanisms via which these bone turnover markers responses are differentially triggered and regulated during recovery after resistance exercise.