The removal of protons (H+) produced during intense exercise is important for skeletal muscle function, yet it remains unclear how best to structure exercise training to improve muscle pH regulation. We investigated whether 4 weeks of work-matched, sprint-interval training (SIT), performed 3 days per week, with either 1 min (Rest-1; n = 7) or 5 min (Rest-5; n = 7) of rest between sprints, influenced adaptations in acid/base transport protein content, non-bicarbonate muscle buffer capacity (βmin vitro), and exercise capacity in active women. Following one week of post-testing, comprising a biopsy, a repeated-sprint ability (RSA) test, and a graded-exercise test, maintenance of adaptations was then studied by reducing SIT volume to one day per week for a further 5 weeks. After 4 weeks of SIT, there was increased protein abundance of monocarboxylate transporter (MCT)1, sodium/hydrogen exchanger (NHE)1, and carbonic anhydrase (CA)XIV for both groups, but rest interval duration did not influence the adaptive response. In contrast, greater improvements in total work performed during the RSA test after 4 weeks of SIT was evident for Rest-5 compared to Rest-1 [effect size (ES): 0.51; 90% confidence limits ±0.37), whereas both groups had similarly modest improvements in VO2peak. When training volume was reduced to one day per week, enhanced acid/base transport protein abundance was maintained, although NHE1 content increased further for Rest-5 only. Finally, our data support intracellular lactate as a signaling molecule for inducing MCT1 expression, but neither lactate nor H+ accumulation appear to be important signaling factors in MCT4 regulation.
- pH regulation
- lactate transport
- intracellular buffering
- repeated-sprint ability
- Copyright © 2017, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology