ASCHENBACH, W., J. OCEL, L. CRAFT, C. WARD, E. SPANGENBURG, and J. WILLIAMS. Effect of oral sodium loading on high-intensity arm ergometry in college wrestlers. Med. Sci. Sports Exerc., Vol. 32, No. 3, pp. 669–675, 2000.
Purpose: The aim of this study was to examine the effect of 0.3 g·kg−1 of NaHCO3, 0.21 g·kg−1 of NaCl, and a low-calorie placebo control (PC) on high-intensity arm ergometry in eight college wrestlers (aged 20.6 ± 0.8 yr, body mass 70.4 ± 2.1 kg).
Methods: Subjects performed eight 15-s intervals of maximal effort arm ergometry separated by 20 s of recovery cranking. Treatments were administered in a randomized, double-blind manner in two equal doses at 90 and 60 min before testing. Venous blood samples were withdrawn at baseline, preexercise, and postexercise intervals.
Results: Preexercise pH (7.33 ± 0.01, 7.31 ± 0.01, and 7.40 ± 0.01) and base excess (2.41 ± 0.35, 0.93 ± 0.39, and 8.45 ± 0.51) after PC and NaCl ingestion, respectively, were similar, whereas ingestion of NaHCO3 resulted in significantly higher values (P ≤ 0.05). Postexercise pH (7.02 ± 0.01, 7.02 ± 0.03, and 7.09 ± 0.03) and base excess (−13.29 ± 0.96, −14.49 ± 1.01, and −8.83 ± 1.38) were significantly lower after both PC and NaCl ingestion compared with NaHCO3 ingestion. Postexercise plasma [lactate] was also greater in both PC and NaHCO3 trials (21.42 ± 1.52, 20.07 ± 1.39, and 22.65 ± 1.77 mmol·L−1). However, peak power (370.7 ± 26.0, 346.3 ± 13.6, and 354.3 ± 18.9 W) and total work accomplished in eight intervals (30.2 ± 1.5, 29.6 ± 1.1, and 29.9 ± 1.1 kJ), and percent fatigue (31.0 ± 2.7, 29.0 ± 3.2, and 29.2 ± 4.0%) were similar.
Conclusions: These data contradict previous reports of ergogenic benefits NaHCO3 and NaCl administration before exercise and further suggest that performance in this type of activity may not be enhanced by exogenously induced metabolic alkalosis or sodium ingestion.
Many competitive athletic events require a sustained maximal effort. It is widely accepted that rapid glycolysis is the principal means by which energy requirements are met during these types of activities. The compromise in using the glycolytic pathway is that, although it yields ATP rapidly, it also produces lactic acid, which is readily dissociated into a lactate anion (Lac−) and a proton (H+) within physiologic pH ranges (11). The accumulation of these two metabolites and concomitant reduction in myoplasmic pH is termed metabolic acidosis, which has been shown to be deleterious to sarcoplasmic reticulum function (2,8,9), glycolytic flux (42), myofilaments (2,7,8), and force production (1,4,8). Therefore, the ability to prevent extreme changes in myoplasmic [Lac−] and pH during high-intensity activity would theoretically delay the onset of fatigue (23) and enhance performance. Sodium bicarbonate (NaHCO3) has been examined as a potential means to improve high-intensity performance by augmenting the capacity of the bicarbonate buffer system in blood and interstitium. Increased extracellular [HCO3−] and pH have been shown to facilitate translocation of Lac− and H+ from the myoplasm and attenuate profound shifts in acid-base status and fatigue during intense exercise.
Theoretically, induced alkalosis would be most effective during activities that cause severe perturbations in acid-base balance. Repeated sprints and upper-body exercise have typically resulted in far more profound acid-base imbalances than single, exhaustive bouts or lower-body tasks (33,36). This has led several investigators (5,16,28,36) to postulate that these tasks may be most responsive to NaHCO3 administration. In fact, Robertson et al. (36) observed a differential ergogenic effect in time to exhaustion during upper and lower body ergometry at 80% V̇O2peak and attributed this to buffering of a greater acidotic shift that occurred during arm exercise. However, no attempt has been made to examine the effectiveness of NaHCO3 administration on a combination of these types of activities (repeated bouts and upper body exercise), which has been shown to elicit dramatic changes in acid-base status previously in this laboratory (44).
The majority of previous investigations of NaHCO3 administration have used untrained, healthy college-aged men as subjects and have yielded greatly varied results. This is unfortunate because 1) the practical benefit of induced alkalosis would best be realized by elite athletes during intense competition and 2) testing a homogenous group of elite athletes, especially in the manner in which they are trained, can be expected to result in far less variability during a series of performance tests, thus increasing the probability of achieving statistically significant results (26). Some studies using these types of trained subjects in “sport specific” protocols have observed improvements in sprint times (12,46), interval swimming (10), rowing (31), and cycling (30). However, even these results with trained athletes have been contradicted (3,35). This may be, in part, because elite athletes already possess a high level of intracellular carnosine and a greater total buffering capacity (34), which may minimize any added benefit of NaHCO3 ingestion. Although the efficacy of NaHCO3 has been studied in a number of “glycolytic” events, no attempt has been made to examine the sport of wrestling, which may be characterized as brief, repeated bouts of supramaximal and submaximal upper-body activity and has been shown to elicit blood lactate values greater than 10 mmol·L−1 after a simulated match (17).
Studies that have reported ergogenic properties of NaHCO3 directly attributed these effects to ingestion of [HCO3−]. Sodium chloride (NaCl) has been used in small amounts during some previous studies (5,18) to reference the effects of NaHCO3, although few have considered potential effects of Na+ by providing an alternate control. Mitchell et al. (32) observed that intravenous infusion of both NaHCO3 and NaCl improved cycling endurance at 80% V̇O2peak by 70%, despite the fact that only NaHCO3 prevented the development of acidosis during the exercise protocol. This effect may be attributed to an increased intravascular volume due to the infusion of sodium-containing fluids, which would result in better perfusion of exercising skeletal muscle and not simply to an enhanced capacity of the bicarbonate buffering system (32). However, Heigenhauser and Jones (13) and Stewart (41) describe the physicochemical effects of orally administered Na+ on the concentrations of strong ions in various fluid compartments in the body, which concomitantly influences [HCO3−] and [H+]. Hinchcliff et al. (15) reported that oral administration of both NaHCO3 and NaCl increased peak speed and performance time in equines during progressive treadmill running, despite the fact that blood pH was significantly more acidic both before and after exercise in the NaCl trial. Kozak-Collins et al. (22) found no difference between equal oral doses of NaHCO3 and NaCl with respect to the number of bouts completed during exhaustive leg ergometry, notwithstanding differences in acid-base status throughout the protocol. However, the lack of a control trial and inability to collect pertinent physiologic data makes interpretation of these results difficult. Taken together, these findings imply that 1) the dose of NaCl may not have been physiologically inert and 2) performance in these cases seemed to be independent of the development or degree of acidosis. Therefore, the objective of this investigation was to test our hypothesis that orally administered NaHCO3 and NaCl would elicit ergogenic benefits in a group of collegiate wrestlers performing a specifically designed repeated-bout arm ergometry protocol.
Virginia Polytechnic Institute and State University, Department of Human Nutrition, Foods, and Exercise Science, Blacksburg, VA
Submitted for publication June 1998.
Accepted for publication June 1999.
Address for correspondence: William Aschenbach, Research Division, Joslin Diabetes Center, 1 Joslin Place, Boston, MA 02215.