HIIT human skeletal muscle

Eleven men performed nine sessions of HIIT consisting of 10x4 minutes of cycling at 91 % of HRmax (~ 83 % of VO2peak intensity), with two minutes of rest between intervals, over the course of three weeks. The VO2peak increased by 8.7 % following training (P < 0.05). Before and 3 h after the 1st and 9th exercise bout, skeletal muscle biopsies were obtained from the middle portion of the vastus lateralis muscle. Samples were visually inspected, and blood, fat and connective tissue were removed. Samples were then immediately frozen in liquid nitrogen and stored at -80°C until analysis. Participant information, testing and exercise protocol, as well as biopsy procedure have been in Ydfors et al., 2016.
We hypothesized that the blunting of transcription after three weeks of HIIT is specific to certain pathways, including metabolic regulation and that these genes have communal transcriptional regulation.