High Intensity High Volume Interval Training Improves Endurance Performance and Induces a Nearly Complete Slow-to-Fast Fiber Transformation on the mRNA Level

Abstract

We present here a longitudinal study determining the effects of two 3 week-periods of high intensity high volume interval training (HIHVT) (90 intervals of 6 s cycling at 250% maximum power, P_max/24 s) on a cycle ergometer. HIHVT was evaluated by comparing performance tests before and after the entire training (baseline, BSL, and endpoint, END) and between the two training sets (intermediate, INT). The mRNA expression levels of myosin heavy chain (MHC) isoforms and markers of energy metabolism were analyzed in M. vastus lateralis biopsies by quantitative real-time PCR. In incremental tests peak power (P_peak) was increased, whereas $\dot{V}$ O_2peak was unaltered. Prolonged time-to-exhaustion was found in endurance tests with 65 and 80% P_max at INT and END. No changes in blood levels of lipid metabolites were detected. Training-induced decreases of hematocrit indicate hypervolemia. A shift from slow MHCI/β to fast MHCIIa mRNA expression occurred after the first and second training set. The mRNA expression of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), a master regulator of oxidative energy metabolism, decreased after the second training set. In agreement, a significant decrease was also found for citrate synthase mRNA after the second training set, indicating reduced oxidative capacity. However, mRNA expression levels of glycolytic marker enzyme glyceraldehyde-3-phosphate dehydrogenase did not change after the first and second training set. HIHVT induced a nearly complete slow-to-fast fiber type transformation on the mRNA level, which, however, cannot account for the improvements of performance parameters. The latter might be explained by the well-known effects of hypervolemia on exercise performance.

Keywords: energy metabolism; interval training; muscular aerobic capacity; myosin heavy chain; performance parameter; systemic aerobic capacity.

Figure 1

Schematic representation of training and testing sessions. Training phase I: first set of 9 training sessions in 3 weeks; training phase II: second set of 9 training sessions in 3 weeks. Testing sessions: baseline, BSL, before begin of training; intermediate, INT, week between the two training phases; endpoint, END, after end of training. 1: Incremental test (IT); 2: Wingate test (WT); 3: Endurance test 80% (ET80); 4: Endurance test 65% (ET65).

Figure 2

Schematic representation of a doubled Wingate-Test. Power output during the two Wingate-tests is set to 100%. One minute pause between warm-up and the two 30 s all-out sprints.

Figure 3

Analysis of (A) ventilation and (B) respiratory exchange ratio during the second (2nd), eighth (8th), and seventeenth (17th) training session of the high intensity high volume interval training (HIHVT). Data are presented as means ± SE. Minutes 0–5: rest (r) on the cycle ergometer; min 6–17: 2 min running-in at 10 Watt (W) followed by 10 min warm-up (wu) at 50% maximum power (P_max); min 18–62: training session with 90 intervals of 6 s at 250% P_max, each followed by a 24 s-pause at 10 W (exercise); min 63–67: cool-down (cd) at 50% P_max. ^*Significantly different (8th and 17th training session, respectively) from the 2nd training session, p < 0.05, at indicated period of time (min 18–62).

Figure 4

Analysis of blood lactate concentrations during the second (2nd), eighth (8th), and seventeenth (17th) training session of the HIHVT. Data are presented as means ± SE. Minutes 0–5: rest on the cycle ergometer; min 6–17: 2 min running-in at 10 Watt (W) followed by 10 min warm-up at 50% maximum power (P_max); min 18–62: training session with 90 intervals of 6 s at 250% P_max, each followed by a 24 sec-pause at 10 W; min 63–67: cool-down at 50% P_max. ^*Significantly different (8th and 17th training session, respectively) from the second training session, p < 0.01, at indicated points in time (min 18–62).

Figure 5

Analysis of (A) free fatty acid and (B) glycerol concentrations during the second (2nd), eighth (8th), and seventeenth (17th) training session of the HIHVT. Data are presented as means ± SE. Minutes 0–5: rest on the cycle ergometer; min 6–17: 2 min running-in at 10 Watt (W) followed by 10 min warm-up at 50% maximum power (P_max); min 18–62: training session with 90 intervals of 6 s at 250% P_max, each followed by a 24 s-pause at 10 W; min 63–67: cool-down at 50% P_max.

Figure 6

Analysis of (A) time-to-exhaustion in endurance tests at 65% P_max (ET65) and 80% P_max (ET80) at baseline (BSL) testing before the start of the HIHVT and at endpoint (END) testing after the entire HIHVT. Data are presented as means ± SE. ET65 and ET80 improvement: % improvement in time-to-exhaustion at END compared to BSL testing. ^*Significantly different from BSL testing, p < 0.05. Analysis of (B) respiratory exchange ratio in endurance tests ET65 at BSL and END testing. Data are presented as means ± SE. Minutes 0–5: rest (r) on the cycle ergometer; min 6–13: 2 min running-in at 10 Watt (W) followed by 6 min warm-up (wu) at 30% maximum power (P_max); endurance test to exhaustion at 80% P_max (exercise); recovery (rec); end: end of the test.

Figure 7

Analysis of (A,B) free fatty acid and (C,D) glycerol concentrations during (A,C) endurance tests (ET) 65, and (B,D) ET80 at baseline (BSL) testing, at endpoint (END) testing, and (B,D) as indicated, intermediate (INT) testing between the two sets of HIHVT training. Minutes 0–5: rest on the cycle ergometer; min 6–13: 2 min running-in at 10 Watt (W) followed by 6 min warm-up at 30% maximum power (P_max); endurance test to exhaustion at (A,C) 65% and (B,D) 80% P_max; recovery; end: end of the test.

Figure 8

Analysis of hematocrit before start of the HIHVT at baseline (BSL) testing, at endpoint (END) testing, and at intermediate (INT) testing. Data are presented as means ± SE. ^*Significantly different from BSL testing, p < 0.01; ⁺Significantly different from INT testing, p < 0.01.

Figure 9

Quantitative real-time PCR (qPCR) analysis of mRNA expression of (A) myosin heavy chain (MHC) isoforms I/β, IIa, and IId/x, (B) peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), citrate synthase (CS) and hydroxyacyl-CoA dehydrogenase (HADH) as markers of oxidative energy metabolism, (C) glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a marker of glycolytic energy metabolism, and (D) mitochondrial superoxide dismutase 2 (SOD2) as a marker of radical metabolism. Muscle biopsies were taken before the start of the HIHVT at baseline (BSL) testing, after the first (1st), ninth (9th), and eighteenth (18th) training session. MHC isoform expression is shown as percentage of total MHC isoform mRNA copies (set to 100%). The mRNA expression of other marker genes is shown in arbitrary units. Data are presented as means ± SE. ^*Significantly different from BSL testing, p < 0.05; ⁺Significantly different from the first training session, p < 0.05.