Table 2.

mtDNA, Tfam and NRF2 responses during 2 weeks of high-intensity interval training in human skeletal muscle

	Pre	1st-4 h	1st-24 h	3rd-4 h	3rd-24 h	5th-4 h	5th-24 h	7th-4 h	7th-24 h
mtDNA	1	1.2 ± 0.15	1.3 ± 0.1	1.1 ± 0.1	1.7 ± 0.1*	1.8 ± 0.2*	2.2 ± 0.4*§	1.1 ± 0.1‡a,c	1.7 ± 0.4*
Tfam mRNA	1	1.5 ± 0.2*†	1.2 ± 0.1*b	1.6 ± 0.2*†	1.4 ± 0.2*	1.6 ± 0.2*†	1.4 ± 0.2*	1.6 ± 0.3*†c	1.5 ± 0.3*†
Tfam protein	1	0.7 ± 0.1*†‡c	1.0 ± 0.1	ND	1.1 ± 0.1	ND	1.1 ± 0.1	ND	0.7 ± 0.1*†‡c
NRF-2 protein	1	1.0 ± 0.3	1.2 ± 0.1	ND	1.5 ± 0.3*#c	ND	1.0 ± 0.2	ND	1.7 ± 0.3*#†c

Values are relative to pre-training contents which were set to 1 and are presented as means ±s.e.m. mtDNA, mitochondrial DNA; Tfam, mitochondrial transcription factor A; NRF-2, nuclear respiratory factor 2, n= 8–9.

^*Significantly different from Pre (P < 0.05)

^#significantly different from 1st-4 h

^†significantly different from 1st-24 h

^‡significantly different from 3rd-24 h

^asignificantly different from 7th-24 h

^bsignificantly different from all 4 h time points

^csignificantly different from 5th-24 h

^§significantly different from all 24 h time points (P < 0.05).

ND, no data.