To characterize side-to-side differences in the lower leg muscle–bone unit between the nondominant leg (NL) and the dominant leg (DL) using maximum voluntary forefoot ground reaction force (F m1LH) during multiple one-legged hopping (m1LH) and tibial bone mass and geometry measured by peripheral quantitative computed tomography (pQCT).
Sixty-six male high-level soccer players (age range = 12–18 yr) performed m1LH to determine F m1LH acting on the forefoot during landing for the NL and DL separately. pQCT scans were obtained to assess bone structural variables at 4%, 14%, 38%, and 66% tibia length and calf muscle cross-sectional area at the 66% site.
First, participants displayed significant (P < 0.05) side-to-side differences in bone mass and geometry at 4%, 14%, and 38% (but not at the 66% site) of tibia length, with higher values in NL relative to DL (+0.7% to +5.6%), most evident at the 14% site. Second, no asymmetries were found for F m1LH between the two legs (P = 0.442). Third, the relationship between F m1LH and vBMC14% was strong for both NL and DL (R 2 = 0.48 and R 2 = 0.54, respectively), but side-to-side differences in F m1LH (ΔF m1LH) and side-to-side differences in vBMC14% (ΔvBMC14%) were not related (R 2 = 0.04).
Contrary to expectations from the mechanostat theory, ΔF m1LH and ΔvBMC14% did not differ in proportion to each other. It seems that playing soccer is a well-balanced activity with respect to F m1LH. However, the NL contributes to the supporting of the action of the DL, meaning that the loading experienced by the tibia might be more pronounced for the NL relative to the DL, leading to the observed higher bone strength values for the NL.
1Exercise Physiology, Institute of Human Movement Sciences, ETH Zurich, SWITZERLAND; and 2Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, SWITZERLAND
Address for correspondence: Marco Toigo, Ph.D., Exercise Physiology, ETH Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; E-mail: email@example.com.
Submitted for publication September 2012.
Accepted for publication February 2013.