Five Weeks of Sprint Interval Training Improve Muscle Glycolytic Content and Activity But Not Time to Task Failure in Severe Intensity Exercise.

PURPOSE: This study examined the impact of a 5 weeks sprint interval training (SIT) intervention on time to task failure (TTF) during severe intensity constant work rate (CWR) exercise, as well as in glycolytic enzymatic content and activity, and glycogen content. METHODS: Fourteen active males were randomized into either a SIT group (n = 8) composed of 15 SIT-sessions over 5 weeks, or a control group (n = 6). At pre-training period, participants performed: i) ramp incremental test to measure the cardiorespiratory function; ii) CWR cycling TTF at 150% of the power output (PO) at the respiratory compensation point (RCP-PO) with muscle biopsies at rest and immediately following task failure. After 5 weeks, the same evaluations were repeated (i.e., exercise intensities matched to current training status), and an additional cycling CWR matched to pre-training 150% RCP-PO was performed only for TTF evaluation. The content and enzymatic activity of glycogen phosphorylase (GPhos), hexokinase (HK), phosphofructokinase (PFK), and lactate dehydrogenase (LDH), as well as the glycogen content, were analyzed. Content of monocarboxylate transporter isoform 4 (MCT4) and muscle buffering capacity were also measured. RESULTS: Despite improvements in total work performed at CWR post-training, no differences were observed for TTF. The GPhos, HK, PFK, and LDH content and activity, and glycogen content also improved post-training only in the SIT group. Further, the MCT4 concentrations and muscle buffering capacity was also improved only for SIT group. However, no difference in glycogen depletion was observed between groups and time. CONCLUSIONS: Five weeks of SIT improved the glycolytic pathway parameters and total work performed, however, glycogen depletion was not altered during CWR severe intensity exercise, and TTF remained similar.

Beta-Alanine Supplementation Improves Throwing Velocities in Repeated Sprint Ability and 200-m Swimming Performance in Young Water Polo Players.

The purpose of this study was to investigate the effects of beta-alanine supplementation on specific tests for water polo. Fifteen young water polo players (16 ± 2 years) underwent a 200-m swimming performance, repeated-sprint ability test (RSA) with free throw (shooting), and 30-s maximal tethered eggbeater kicks. Participants were randomly allocated into two groups (placebo × beta-alanine) and supplemented with 6.4g∙day-1of beta-alanine or a placebo for six weeks. The mean and total RSA times, the magnitude based inference analysis showed a likely beneficial effect for beta-alanine supplementation (both). The ball velocity measured in the throwing performance after each sprint in the RSA presented a very like beneficial inference in the beta-alanine group for mean (96.4%) and percentage decrement of ball velocity (92.5%, likely beneficial). Furthermore, the percentage change for mean ball velocity was different between groups (beta-alanine=+2.5% and placebo=-3.5%; p = .034). In the 30-s maximal tethered eggbeater kicks the placebo group presented decreased peak force, mean force, and fatigue index, while the beta-alanine group maintained performance in mean force (44.1%, possibly beneficial), only presenting decreases in peak force. The 200-m swimming performance showed a possibly beneficial effect (68.7%). Six weeks of beta-alanine supplementation was effective for improving ball velocity shooting in the RSA, maintaining performance in the 30-s test, and providing possibly beneficial effects in the 200-m swimming performance.