The purpose of this study was to measure the recovery kinetics of pH and lactate for the conditions of pre-exercise acidosis, alkalosis, and placebo states. Twelve trained male cyclists completed 3 exercise trials (110% workload at VO2max), ingesting either 0.3 g/kg of NH4Cl (ACD), 0.2 g/kg of Na+HCO3 - and 0.2 g/kg of sodium citrate (ALK), or a placebo (calcium carbonate) (PLAC). Blood samples (heated dorsal hand vein) were drawn before, during, and after exercise. Exercise-induced acidosis was more severe in the ACD and PLAC trials (7.15 ± 0.06, 7.21 ± 0.07, 7.16 ± 0.06, P < 0.05, for ACD, ALK, PLAC, respectively). Recovery kinetics for blood pH and lactate, as assessed by the monoexponential slope constant, were not different between trials (0.057 ± 0.01, 0.050 ± 0.01, 0.080 ± 0.02, for ACD, ALK, PLAC, respectively). Complete recovery of blood pH from metabolic acidosis can take longer than 45 min. Such a recovery profile is nonlinear, with 50% recovery occurring in approximately 12 min. Complete recovery of blood lactate can take longer than 60 min, with 50% recovery occurring in approximately 30 min. Induced alkalosis decreases metabolic acidosis and improves pH recovery compared to acidodic and placebo conditions. Although blood pH and lactate are highly correlated during recovery from acidosis, they recover at significantly different rates.
Robert Robergs, Keith Hutchinson, Shonn Hendee, Sean Madden and Jason Siegler
Anthony Couderc, Claire Thomas, Mathieu Lacome, Julien Piscione, Julien Robineau, Rémi Delfour-Peyrethon, Rachel Borne and Christine Hanon
To investigate the running demands and associated metabolic perturbations during an official rugby sevens tournament.
Twelve elite players participated in 7 matches wearing GPS units. Maximal sprinting speed (MSS) and maximal aerobic speed (MAS) were measured. High-intensity threshold was individualized relative to MAS (>100% of MAS), and very-high-intensity distance was reported relative to both MAS and MSS. Blood samples were taken at rest and after each match.
Comparison of prematch and postmatch samples revealed significant (P < .01) changes in pH (7.41–7.25), bicarbonate concentration ([HCO3–]) (24.8–13.6 mmol/L), and lactate concentration ([La]) (2.4–11.9 mmol/L). Mean relative total distance covered was 91 ± 13 m/min with ~17 m/min at high-intensity. Player status (whole-match or interchanged players), match time, and total distance covered had no significant impact on metabolic indices. Relative distance covered at high intensity was negatively correlated with pH and [HCO3–] (r = .44 and r = .42, respectively; P < .01) and positively correlated with [La] (r = .36; P < .01). Total distance covered and distance covered at very high intensity during the 1-min peak activity in the last 3 min of play were correlated with [La] (r = .39 and r = .39, respectively; P < .01).
Significant alterations in blood-metabolite indices from prematch to postmatch sampling suggest that players were required to tolerate a substantial level of acidosis related to metabolite accumulation. In addition, the ability to produce energy via the glycolytic energy pathway seems to be a major determinant in match-related running performance.
David M. Morris, Rebecca S. Shafer, Kimberly R. Fairbrother and Mark W. Woodall
The authors sought to determine the effects of oral lactate consumption on blood bicarbonate (HCO3−) levels, pH levels, and performance during high-intensity exercise on a cycle ergometer. Subjects (N = 11) were trained male and female cyclists. Time to exhaustion (TTE) and total work were measured during high-intensity exercise bouts 80 min after the consumption of 120 mg/kg body mass of lactate (L), an equal volume of placebo (PL), or no treatment (NT). Blood HCO3− increased significantly after ingestion of lactate (p < .05) but was not affected in PL or NT (p > .05). No changes in pH were observed as a result of treatment. TTE and total work during the performance test increased significantly by 17% in L compared with PL and NT (p = .02). No significant differences in TTE and total work were seen between the PL and NT protocols (p = .85). The authors conclude that consuming 120 mg/kg body mass of lactate increases HCO3− levels and increases exercise performance during high-intensity cycling ergometry to exhaustion.
David Michael Morris and Rebecca Susan Shafer
The authors sought to compare power output at blood lactate threshold, maximal lactate steady state, and pH threshold with the average power output during a simulated 20-km time trial assessed during cycle ergometry. Participants (N = 13) were trained male and female cyclists and triathletes, all permanent residents at moderate altitude (1,525–2,225 m). Testing was performed at 1,525 or 1,860 m altitude. Power outputs were determined during a simulated 20-km time trial (PTT), at blood pH threshold (PpHT), at maximal lactate steady state (PMLSS), and at blood lactate threshold determined by 2 methods: the highest power output that did not result in consecutive and continued increases in blood lactate concentrations from exercising baseline (PLT) and the highest power output that did not result in consecutive and continued increases of ≥1 mmol/L in blood lactate concentrations from exercising baseline (PLT1). PLT, PLT1, and PMLSS were all significantly lower than PpHT (p < .05) and PTT (p < .05). No significant difference was observed between PpHT and PTT (p > .05). Significant correlations were observed between each of the metabolic variables, PLT, PLT1, PMLSS, and PpHT, compared with PTT (p < .05). The authors conclude that, of the 4 metabolic variables, only PpHT offered an accurate reflection of PTT.
Vitor de Salles Painelli, Rafael Pires da Silva, Odilon Marques de Oliveira Junior, Luana Farias de Oliveira, Fabiana Braga Benatti, Tobias Rabelo, João Paulo Limongi França Guilherme, Antonio Herbert Lancha Junior and Guilherme Giannini Artioli
We investigated the effects of low- and high-dose calcium lactate supplementation on blood pH and bicarbonate (Study A) and on repeated high-intensity performance (Study B). In Study A, 10 young, physically active men (age: 24 ± 2.5 years; weight: 79.2 ± 9.45 kg; height: 1.79 ± 0.06 m) were assigned to acutely receive three different treatments, in a crossover fashion: high-dose calcium lactate (HD: 300 mg·kg−1 body mass), low-dose calcium lactate (LD: 150 mg·kg−1 body mass) and placebo (PL). During each visit, participants received one of these treatments and were assessed for blood pH and bicarbonate 0, 60, 90, 120, 150, 180, and 240 min following ingestion. In Study B, 12 young male participants (age: 26 ± 4.5 years; weight: 82.0 ± 11.0 kg; height: 1.81 ± 0.07 m) received the same treatments of Study A. Ninety minutes after ingestion, participants underwent 3 bouts of the upper-body Wingate test and were assessed for blood pH and bicarbonate 0 and 90 min following ingestion and immediately after exercise. In Study A, both HD and LD promoted slight but significant increases in blood bicarbonate (31.47 ± 1.57 and 31.69 ± 1.04 mmol·L−1, respectively) and pH levels (7.36 ± 0.02 and 7.36 ± 0.01, respectively), with no effect of PL. In Study B, total work done, peak power, mean power output were not affected by treatments. In conclusion, low- and high-dose calcium lactate supplementation induced similar, yet very discrete, increases in blood pH and bicarbonate, which were not sufficiently large to improve repeated high-intensity performance.
Peter D. Kupcis, Gary J. Slater, Cathryn L. Pruscino and Justin G. Kemp
The effect of sodium bicarbonate (NaHCO3) ingestion on prerace hydration status and on 2000 m ergometer performance in elite lightweight rowers was examined using a randomized, cross-over, double-blinded design.
To simulate body mass (BM) management strategies common to lightweight rowing, oarsmen reduced BM by approx. 4% in the 24 h preceding the trials, and, in the 2 h before performance, undertook nutritional recovery consisting of mean 43.2 kJ/kg, 2.2 g of CHO per kilogram, 31.8 mg of Na+ per kilogram, 24.3 mL of H2O per kilogram, and NaHCO3 (0.3 g of NaHCO3 per kilogram BM) or placebo (PL; 0.15 g of corn flour per kilogram BM) at 70 to 90 min before racing.
At 25 min before performance, NaHCO3 had increased blood pH (7.48 ± 0.02 vs PL: 7.41 ± 0.03, P = .005) and bicarbonate concentrations (29.1 ± 1.8 vs PL: 23.9 ± 1.6 mmol/L, P < .001), whereas BM, urine specific gravity, and plasma volume changes were similar between trials. Rowing ergometer times were similar between trials (NaHCO3: 397.8 ± 12.6; PL: 398.6 ± 13.8 s, P = .417), whereas posttest bicarbonate (11.6 ± 2.3 vs 9.4 ± 1.8 mmol/L, P = .003) and lactate concentration increases (13.4 ± 1.7 vs 11.9 ± 1.9 mmol/L, P = .001) were greater with NaHCO3.
Sodium bicarbonate did not further enhance rehydration or performance in lightweight rowers when undertaking recommended post-weigh-in nutritional recovery strategies.
Leandro C. Felippe, João P. Lopes-Silva, Rômulo Bertuzzi, Cian McGinley and Adriano E. Lima-Silva
The combined supplementation of caffeine (CAF) and sodium bicarbonate (NaHCO3) may have a potential ergogenic effect during intermittent-exercise tasks such as judo; however, its effect in this sport has not been tested.
To investigate the isolated and combined effects of CAF and NaHCO3 on judo performance.
Ten judokas performed 4 supplementation protocols—NaHCO3, CAF, NaHCO3 + CAF, and placebo (PLA) (cellulose)—followed by 3 Special Judo Fitness Tests (SJFTs) interspaced with 5 min rest.
In the first SJFT, the combined supplement (NaHCO3 + CAF) resulted in a higher number of throws than with PLA (24.4 ± 0.9 and 23.2 ± 1.5 throws, respectively, P = .02). There was no significant difference between conditions for the 2nd SJFT (P = .11). In the 3rd SJFT, NaHCO3 and NaHCO3 + CAF resulted in more throws than with PLA (23.7 ± 1.6, 24.4 ± 1.0, and 22.0 ± 1.6 throws, P = .001 and P = .03, respectively). When the total throws performed in the 3 SJFTs were summed, they were higher than PLA only for NaHCO3 + CAF (68.8 ± 4.4 and 72.7 ± 3.1 throws, respectively, P = .003). Postexercise plasma lactate after each SJFT was higher in all experimental conditions than with PLA (P = .001). There was no significant difference in rating of perceived exertion across the conditions (P = .18).
The results of the current study show that the combined supplementation of NaHCO3 + CAF increases judo performance compared with PLA.
Weiliang Chung, Audrey Baguet, Tine Bex, David J. Bishop and Wim Derave
Muscle carnosine loading through chronic oral beta-alanine supplementation has been shown to be effective for short-duration, high-intensity exercise. This randomized, placebo-controlled study explored whether the ergogenic effect of beta-alanine supplementation is also present for longer duration exercise. Subjects (27 well-trained cyclists/triathletes) were supplemented with either beta-alanine or placebo (6.4 g/day) for 6 weeks. Time to completion and physiological variables for a 1-hr cycling time-trial were compared between preand postsupplementation. Muscle carnosine concentration was also assessed via proton magnetic resonance spectroscopy before and after supplementation. Following beta-alanine supplementation, muscle carnosine concentration was increased by 143 ± 151% (mean ± SD; p < .001) in the gastrocnemius and 161 ± 56% (p < .001) in the soleus. Postsupplementation time trial performance was significantly slower in the placebo group (60.6 ± 4.4–63.0 ± 5.4 min; p < .01) and trended toward a slower performance following beta-alanine supplementation (59.8 ± 2.8–61.7 ± 3.0 min; p = .069). We found an increase in lactate/proton concentration ratio following beta-alanine supplementation during the time-trial (209.0 ± 44.0 (beta-alanine) vs. 161.9 ± 54.4 (placebo); p < .05), indicating that a similar lactate concentration was accompanied by a lower degree of systemic acidosis, even though this acidosis was quite moderate (pH ranging from 7.30 to 7.40). In conclusion, chronic beta-alanine supplementation in well-trained cyclists had a very pronounced effect on muscle carnosine concentration and a moderate attenuating effect on the acidosis associated with lactate accumulation, yet without affecting 1-h time-trial performance under laboratory conditions.
J.C. Siegler, J. Bell-Wilson, C. Mermier, E. Faria and R.A. Robergs
The purpose of this study was to profile the effect of active versus passive recovery on acid-base kinetics during multiple bouts of intense exercise. Ten males completed two exercise trials. The trials consisted of three exercise bouts to exhaustion with either a 12 min active (20% workload max) or passive recovery between bouts. Blood pH was lower in the passive (p) recovery compared to active (a) throughout the second and third recovery periods [second recovery: 7.18 ± 0.08 to 7.24 ± 0.09 (p), 7.23 ± 0.07 to 7.32 ± 0.07 (a), P < 0.05; third recovery: 7.17 ± 0.08 to 7.22 ± 0.09 (p), 7.23 ± 0.08 to 7.32 ± 0.08 (a), P < 0.05]. Exercise performance times did not differ between recovery conditions (P = 0.28). No difference was found between conditions for recovery kinetics (slope and half-time to recovery). Subsequent performance during multiple bouts of intense exercise to exhaustion may not be influenced by blood acidosis or mode of recovery.
Catherine Applegate, Mackenzie Mueller and Krystle E. Zuniga
Diet composition can affect systemic pH and acid-base regulation, which may in turn influence exercise performance. An acidic environment in the muscle impairs performance and contributes to fatigue; therefore, current trends in sports nutrition place importance on maximizing the alkalinity of the body with ergogenic aids and dietary strategies. This review examines the evidence on the effects of dietary manipulations on acid load and exercise performance. Ten studies that investigated the effect of high versus low dietary acid loads on athletic performance generally identified that low dietary acid loads increased plasma pH, but did not consistently improve exercise performance at maximal or submaximal exercise intensities. In addition, the few studies conducted have several limitations including lack of female subjects and use of exercise tests exclusive to cycling or treadmill running. Although the research does not strongly support a performance benefit from low dietary acid loads, a more alkaline dietary pattern may be beneficial for overall health, as dietary induced acidosis has been associated with greater risk of cardiovascular disease and bone disease. The review includes dietary recommendations for athletes to reduce dietary acid load while still meeting sports nutrition recommendations.