Background and Objective: Chondrocytes in the growth plate are a major player in the process of endochondral ossification through from proliferation to hypertrophy, leading to the longitudinal growth of the skeleton. Exercise promotes the longitudinal growth, whereas excessive exercise inhibits bone growth. The exercise condition is defined as a combination of intensity, frequency, and duration; and what these combinations leading to the best for the bone growth remain unclear. Our objective was to determine what combination of different exercise conditions lead to the best for a favorable response in the growth plate.
Methods: A total of 27 male young mice were divided into control group and 8 treadmill exercise groups; high-intensity (running), high-frequency (every day), and long-duration (60 min); high-intensity, high-frequency, and short-duration (15 min); high-intensity, low-frequency (Once in 3 d), and longduration; high-intensity, low-frequency, and short-duration; low-intensity (walking), high-frequency, and long-duration; low-intensity, high-frequency, and short-duration; low-intensity, low-frequency, and long-duration; low-intensity, low-frequency, and short-duration. We quantified histologic characteristics in the growth plate after exercise.
Results: The thickness of the growth plate, cell proliferation, and the number of hypertrophic chondrocytes in the growth plate increased in the high-intensity exercise compared with the lowintensity; further, osteoclasts in the primary spongiosa increased by high-intensity and low-frequency and long-duration exercise.
Conclusion: Our results suggest that chondrocyte activity and bone metabolism promote in highintensity and low-frequency and long-duration in young mice. These findings may shed light on the underlying of the promotion of the longitudinal bone growth by exercise.Author(s): Eriko Mizuno, Yoshio Wakimoto, Masato Nomura, Yuta Kohara, Shunsuke Shimaya, Ryota Suzuki, Hideki Moriyama