Influence of training intensity on adaptations in acid/base transport proteins, muscle buffer capacity, and repeated-sprint ability in active men.
Level 3 - non-randomized controlled study
Controlled comparative training trial without explicit statement of randomization in abstract
PubMed 27742804 · doi:10.1152/japplphysiol.00630.2016
What was done
Sixteen active men completed 4 weeks of work-matched high-intensity interval training (HIIT) performed either just above the lactate threshold (HIITΔ20; n = 8) or close to peak aerobic power (HIITΔ90; n = 8). The study measured adaptations in muscle acid-base transport protein abundance (MCT1, MCT4, basigin, NHE1, NBCe1, CAII, CAIII, CAIV, CAXIV), in vitro nonbicarbonate muscle buffer capacity, repeated-sprint ability (5 × 6-s sprints; 24 s passive rest), power at lactate threshold, peak oxygen uptake, and the effects of 6 weeks of subsequent detraining.
What was found
Training intensity did not discriminate between adaptations for most outcomes: both groups increased abundance of MCT1, NHE1, NBCe1, CAII, and CAXIV, with little change in CAIII, CAIV, or in vitro muscle buffer capacity. Divergent responses occurred for MCT4, which increased only in HIITΔ20 (effect size [ES]: 1.06, 90% confidence limits × / ÷ 0.77), and basigin, which increased only in HIITΔ90 (ES: 1.49, × / ÷ 1.42). Repeated-sprint ability improved similarly in both groups. Power at lactate threshold improved only in HIITΔ20 (ES: 0.49, 90% confidence limits ± 0.38), while peak oxygen uptake did not change in either group. All protein adaptations and repeated-sprint improvements returned to baseline after 6 weeks of detraining.
Why it matters
The findings demonstrate that many muscle acid-base transport protein adaptations and sprint capacity improvements occur with work-matched HIIT across a wide range of intensities, but these muscular gains are rapidly lost once training ceases.
Limits
The sample size is very small (n = 8 per group, total n = 16) and restricted entirely to active men, limiting generalizability to females and other fitness populations. The abstract does not indicate whether group assignment was randomized, and the intervention was short (4 weeks).
Cited by
- supports High-intensity exercise training leads to an upregulation of monocarboxylate transporters (MCTs) in skeletal muscle to facilitate lactate transport.