Change in work rate, burst mean power, burst area, and median power frequency across the first interval at each intensity level.

<p>Note: * Sig from 73%, † sign from 73% and 100%.</p

Exemplar raw EMG data as well as Morlet continuous wavelet transforms across one entire 60 second interval.

<p>Exemplar raw EMG data as well as Morlet continuous wavelet transforms across one entire 60 second interval.</p

Improvements in VO₂peak and exercise performance are greater following HI than LO.

<p>The mean VO₂peak (A) and time to 500 kcal (B) for the LO and HI groups are shown. The individual change in VO₂peak for all participants are also shown (C). *Significant (p<0.05) difference from Pre. † Significant (p<0.05) effect of training. ‡ Significant (p<0.05) interaction. ††Non-significant (p = 0.07) interaction.</p

Peak O₂ pulse increases to a greater extent following HI than LO.

<p>*Significant (p<0.05) difference from Pre. † Significant (p<0.05) effect of training. ‡ Significant (p<0.05) interaction.</p

Effect of HI and LO on markers of skeletal muscle oxidative capacity.

<p>Changes in protein content of COX I and COX IV (A) and the maximal enzyme activities of citrate synthase (CS) and β-hydroxyacyl-CoA dehydrogenase (βHAD) (C). Representative western blots, including loading controls, are also shown (B). † Significant (p<0.05) effect of training. ‡ Non-significant (p = 0.07) effect of training.</p

Participant Characteristics.

<p>Values are mean ± SD. yrs, years; cm, centimetres; kg, kilograms; BMI, body mass index; m, metres; mmol/L, millimoles per litre; µIU, micro international units; HOMA-IR, homeostatic model assessment of insulin resistance; W, watts; s, seconds; HRpeak, maximal heart rate from VO₂peak test; bpm, beats per minute; Training HR, average heart rate from first training session. Interval WR, average power produced during intervals from first training session.</p>†<p>Significant (p<0.05) effect of training.</p>‡<p>Significantly different (p<0.05) from LO.</p>§<p>Significant (p<0.05) interaction between groups.</p

Effects of HI and LO on PGC-1α, AMPK, and SIRT1 protein content.

<p>Changes in the protein content of PGC-1α, AMPK and SIRT1 (A). Representative western blots, including loading controls, are also shown (B). * Significant (p<0.05) effect of training. † Significant (p<0.05) interaction.</p

Overview of experimental protocol.

<p>Overview of experimental protocol.</p

Inter-Individual Variability in the Adaptive Responses to Endurance and Sprint Interval Training: A Randomized Crossover Study

<div><p>The current study examined the adaptive response to both endurance (END) and sprint interval training (SIT) in a group of twenty-one recreationally active adults. All participants completed three weeks (four days/ week) of both END (30 minutes at ~65% VO₂peak work rate (WR) and SIT (eight, 20-second intervals at ~170% VO₂peak WR separated by 10 seconds of active rest) following a randomized crossover study design with a three-month washout period between training interventions. While a main effect of training was observed for VO₂peak, lactate threshold, and submaximal heart rate (HR), considerable variability was observed in the individual responses to both END and SIT. No significant positive relationships were observed between END and SIT for individual changes in any variable. Non-responses were determined using two times the typical error (TE) of measurement for VO₂peak (0.107 L/min), lactate threshold (15.7 W), and submaximal HR (10.7bpm). Non-responders in VO₂peak, lactate threshold, and submaximal HR were observed following both END and SIT, however, the individual patterns of response differed following END and SIT. Interestingly, all individuals responded in at least one variable when exposed to both END and SIT. These results suggest that the individual response to exercise training is highly variable following different training protocols and that the incidence of non-response to exercise training may be reduced by changing the training stimulus for non-responders to three weeks of END or SIT.</p></div

Participant characteristics and group responses to END and SIT.

<p>Participant characteristics and group responses to END and SIT.</p