Titin is not the weak link in the Z‐disk streaming induced by plyometric exercise

Abstract

The purpose was to analyze the skeletal muscle changes induced by an acute bout of plyometric exercise (PlyEx) before and after a PlyEx training.Healthy untrained individuals (N=13) completed an acute bout of PlyEx (10×10 squat‐jumps, 1 min rest). Thereafter, 8 subjects completed 8 weeks of PlyEx, while 5 subjects were instructed to refrain from doing any jumping activity for 8 weeks. Seven days after the last training session all subjects repeated a second acute bout of PlyEx.The first acute bout of PlyEx induced a rise of creatine kinase activity (CK = 2421 ± 4978 U/l), Z‐line streaming mainly in fast twitch fibers, a stretch of the c‐terminus of titin (observed by immunogold) not limited to fast twitch fibers, and an increase in calpain‐3 autolysis. The second acute bout of PlyEx in the trained group did not induce: a rise of CK (110 ± 58 U/l), Z‐line streaming, or calpain‐3 activation; while in the control group only two subjects exhibited Z‐line streaming, although all subjects presented a stretch of titin.Eccentric explosive exercise induced a stretch of titin, which is not responsible for the weakness of the sarcomere and of the calpain‐3 activation involved in sarcomeric remodelling.Grant Funding Source: Claude Leon Foundation, National Research Foundation (NRF)