Figure 6

Effects of HIIT performed in single versus three shorter daily sessions on quantification of normal (A) and altered (B) mitochondria density in gastrocnemius muscle fibers. Transmission electron micrographs of transverse sections of the gastrocnemius muscle (C). White arrows show normal mitochondria, and black arrows show altered mitochondria. Representative mitochondria of the gastrocnemius muscle for Untrained, 1xHIIT, and 3xHIIT groups (D). Data are presented as mean ± SD. One-way ANOVA followed by the Tukey test. *p < 0.05, HIIT groups versus Untrained Group. 1xHIIT: High-Intensity Interval Training performed in single daily sessions; 3xHIIT: High-Intensity Interval Training performed in three shorter daily sessions.