Muscle metabolic status and acid-base balance during 10-s work:5-s recovery intermittent and continuous exercise

Abstract

Gastrocnemius muscle phosphocreatine ([PCr]) and hydrogen ion ([H(+)]) were measured using (31)P-magnetic resonance spectroscopy during repeated bouts of 10-s heavy-intensity (HI) exercise and 5-s rest compared with continuous (CONT) HI exercise. Recreationally active male subjects (n = 7; 28 yr ± 9 yr) performed on separate occasions 12 min of isotonic plantar flexion (0.75 Hz) CONT and intermittent (INT; 10-s exercise, 5-s rest) exercise. The HI power output in both CONT and INT was set at 50% of the difference between the power output associated with the onset of intracellular acidosis and peak exercise determined from a prior incremental plantar flexion protocol. Intracellular concentrations of [PCr] and [H(+)] were calculated at 4 s and 9 s of the work period and at 4 s of the rest period in INT and during CONT exercise. [PCr] and [H(+)] (mean ± SE) were greater at 4 s of the rest periods vs. 9 s of exercise over the course of the INT exercise bout: [PCr] (20.7 mM ± 0.6 vs. 18.7 mM ± 0.5; P < 0.01); [H(+)] (370 nM ± 13.50 vs. 284 nM ± 13.6; P < 0.05). Average [H(+)] was similar for CONT vs. INT. We therefore suggest that there is a glycolytic contribution to ATP recovery during the very short rest period (<5 s) of INT and that the greater average power output of CONT did not manifest in greater [H(+)] and greater glycolytic contribution compared with INT exercise.

β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis

“…The only study that employed a chronic (7 days) sodium bicarbonate supplementation phase showed a significant effect of the additional sodium bicarbonate supplementation with β-alanine over β-alanine alone 48. This may be due to the multiple-bout nature of the test, which most likely resulted in a higher acidosis than the continuous exercise protocols employed in other studies;30 49 or due to the chronic supplementation protocol employed, which may have resulted in a more pronounced blood alkalosis,50 although the authors did not measure this directly. Nonetheless, the current meta-analytic data suggest that co-supplementation of β-alanine with sodium bicarbonate can lead to additional gains over those with β-alanine alone.…”

Additive effects of beta-alanine and sodium bicarbonate on upper-body intermittent performance

“…Evidence indicates that SB is particularly effective in exercise involving multiple high-intensity bouts, as this model seems to result in a more prominent acidosis, being more limited by pHi reductions (Belfry et al 2012). In the present study, SB ingestion over 7 days (i.e.…”

“…upper-body high-intensity intermittent exercise in the current study vs. continuous single-bout high-intensity leg-exercises in previous studies (Sale et al 2011; Bellinger et al 2012), which may have accounted for the discrepant results. In fact, evidence indicates that multiple bouts of supra-maximal exercise results in higher muscle acidosis than continuous supra-maximal exercises (Hermansen and Osnes 1972; Belfry et al 2012). Moreover, it was demonstrated that arm exercises were more sensitive to performance improvements induced by increased buffering capacity (via sodium bicarbonate ingestion) than leg exercises, possibly because the former leads to greater blood H + concentration (Robertson et al 1987).…”

“…Alternatively, one may argue that the characteristics of the physical tests might also explain the inability to clearly detect the beneficial effects of increased buffering capacity on performance. Knowingly, intermittent supra-maximal exercise promotes a considerably greater intramuscular acidosis than continuous high-intensity exercise (Hermansen and Osnes 1972; Belfry et al 2012), probably because the former is more reliant on glycolytic ATP resynthesis (Belfry et al 2012). Thus, it is reasonable to assume that intermittent exercise performance is more limited by muscle acidosis and, hence, more prone to be improved by increased buffering capacity.…”

Influence of training status on high-intensity intermittent performance in response to β-alanine supplementation

“…The differences in results might be due to the protocols employed; previous studies may not have used exercise tests of sufficient intensity or duration to be influenced by decreased intramuscular pH, or may have been susceptible to pacing strategies, masking any ergogenic effects of increased muscle buffering capacity. Intermittent supra-maximal exercise promotes a considerably greater intramuscular acidosis than continuous high-intensity exercise (Hermansen and Osnes 1972; Belfry et al 2012), probably because the former is more reliant on glycolytic ATP resynthesis (Belfry et al 2012). Thus, it is reasonable to assume that intermittent exercise performance is more likely to be limited by muscle acidosis and, hence, more susceptible to improvements with increased buffering capacity.…”