Osteogenic index of step exercise depending on choreographic movements, session duration, and stepping rate.

BACKGROUND Step exercise has been promoted as a low impact physical activity recommended for the improvement of cardiorespiratory and muscular fitness. This recreational activity might also be recommended to improve bone health since mechanical load plays an important role in the normal development of the skeleton. METHODS Our main purpose was to characterised 100 step sessions and to calculated osteogenic index (OI) according to Turner and Robling: OI (one session) = peak ground reaction force(BW)*ln(number of loading cycles+1). RESULTS Main results (mean+/-SD) were as follows: OI was 12.0+/-0.8; peak ground reaction force (GRF) was 1.40+/-0.10 times body weight (BW); session duration was 38.6+/-8.3 min; stepping rate was 134.6+/-4.7 beats per minute (bpm); the movements performed most often were marching, knee hop, side leg, L step, and over the top; and the number of loading cycles was 4194.1+/-1055.2. OI and GRF increased significantly when stepping rate was higher than 135 bpm. This stepping rate might be used as a reference for higher intensity classes. A frequency of two to three sessions per week of step exercise is recommended. CONCLUSIONS Despite the benefits that have been stated when step classes are structured correctly and adapted to the participants, further research is needed concerning biomechanical load, exercise prescription, and injury prevention.