Circuit and Traditional Resistance Training Acutely Modulate Circulating Sclerostin, OPN, and RANKL Levels in Young Adults

Physical activity is crucial for bone health, mediating its benefits through mechanical loading and intricate biochemical signaling between bone and muscle tissues. This bone-muscle crosstalk is largely facilitated by a class of signaling molecules known as exerkines. While exercise is known to regulate osteokines, the specific acute responses of various exerkines to different exercise modalities, such as circuit training versus traditional resistance exercise, remain largely unexplored. Understanding these acute responses is key to optimizing exercise prescriptions for bone health.

This randomized repeated-measures crossover pilot study investigated acute exerkine responses in n = 12 healthy young adults. Participants performed two distinct exercise protocols: circuit training (CT) (cycle ergometer, push-up, step-ups, medicine ball twist, and front squats with kettlebell for three rounds) and traditional resistance (TR) exercise (3 sets 10 repetitions at 50-60% 1 RM for leg press, seated cable row, barbell bench press, dumbbell deadlifts, and dumbbell seated shoulder press). Protocols were separated by a 2-week wash-out. Blood samples were collected before exercise (Pre), immediately post-exercise (IP), and 30 minutes post-exercise (30P) to analyze serum sclerostin (SCL), dickkopf-1 (DKK-1), receptor activator of nuclear factor kappa-B ligand (RANKL), osteopontin (OPN), brain-derived neurotrophic factor (BDNF), irisin, and interleukin 6 (IL-6) using ELISA.

A significant interaction between protocol, timepoint, and sex was observed for sclerostin (SCL) levels (p = 0.038). In males, SCL levels increased from Pre to IP under both training protocols: CT saw an increase from 0.10 ± 0.02 ng/mL to 0.14 ± 0.02 ng/mL, and TR from 0.20 ± 0.02 ng/mL to 0.21 ± 0.02 ng/mL. SCL levels subsequently decreased from IP to 30P in both protocols (CT: 0.14 ± 0.02 to 0.10 ± 0.01 ng/mL; TR: 0.22 ± 0.02 to 0.17 ± 0.02 ng/mL).

In females, SCL levels also increased from Pre to IP under both training protocols (CT: 0.03 ± 0.02 ng/mL to 0.06 ± 0.02 ng/mL; TR: 0.07 ± 0.02 ng/mL to 0.13 ± 0.02 ng/mL).

There was a significant time effect for osteopontin (OPN) and RANKL concentrations, with marginal means showing OPN was significantly higher at the Pre time point. The abstract did not provide specific numbers for the post-hoc analyses of OPN and RANKL beyond this.