Effects of sodium bicarbonate

The effects sodium bicarbonate ingestion has on performance and blood lactate concentration during a maximal 60 second sprint

Abstract

The purpose of this study was to examine the effect sodium bicarbonate ingestion (NaHCOз) has on performance and blood lactate concentration during a 60 second all out sprint. Nine recreationally active subjects (M=4, F=5) (add mean stdev) ingested either 300 mg·kgˉˡ of NaHCOз or 250g·kgˉˡ of Sodium chloride (PL) in a randomized, double blind design, 30 minutes before undertaking a maximal 60 cycling test. Subjects performed the test twice, ingesting either solution on two separate days, separated by a week. No significant differences were observed between PL vs NaHCOз ingestion for peak power (826.11 ± 300.50 vs 844.55 ± 192.82, P = 0.05), or for relative peak power (PL vs NaHCOз: 12.10 ± 1.65 vs 12.56 ± 1.92: P < 0.05). Despite this a significant difference was found between NaHCOз and PL ingestion for blood lactate concentrations (P = 0.016). When Subjects ingested the NaHCOз solution they were able to buffer 6% more lactate than when they ingested the PL solution. The results of this study suggest ingesting 300 mg·kgˉˡ, 30 minutes before a 60 second sprint does not significantly improve performance but does increase blood lactate, enhancing the removal of hydrogen and lactate ions from the working muscles.

Introduction

Over the past 50 years, the ergogenic effects of sodium bicarbonate (NaHCOз) have been extensively studied (Bronus, 2002). When undertaking high intensity, short duration activities that last between 1-7 minutes, athletes and amateurs alike could consume NaHCOз to potentially enhance performance in sports such as football, cycling and athletic sprint events (400m/800m of rowing, swimming and running) (Burk et al, 2006). It has been suggested ingesting NaHCOз can buffer the lactic acid produced by the working muscles during high intensity exercise, delaying the onset of fatigue (Bronus, 2002).

More specifically, during high intensity exercise lasting longer than 20-30 seconds, anaerobic glycolysis becomes the primary energy source (Burke et al, 2006). During the exercise, hydrogen and lactate ions accumulate causing a gradual decrease in pH. pH sensitive enzymes, in particular phosphofructokinase, can reduce the rate of glycolysis and the production of adenosine tri-phosphate (ATP) lowering energy production and increasing fatigue (Requena et al, 2005). Burke et al, (2006) explain how this accumulation can also impair the release of calcium from the sarcoplasmic recticulum, this inhibits muscle force production by impairing the interaction of myofilaments during the crossbridge cycle. Nevertheless research suggests, ingesting NaHCOз enhances the extracelluar buffering capacity (Street et al. 2005) increases the removal of lactate and hydrogen from the working muscles (Zabala et al. 2008) and increases the activities of pH sensitive enzymes (Hollidge-Horvat et al, 2000). Marx et al. (2002) suggest, in theory this should delay the onset of fatigue, prolong the progressive reduction in pH levels and allow the athlete to produce maximum force.

Numerous studies have demonstrated improvements in high intensity short duration performance following sodium bicarbonate ingestion, prior to the start of exercise (Goldfinch et al. 1988; McNaughton et al. 1997; McNaughton et al. 2001 & Montefoort et al. 2004). McNaughton et al. (1997) found 300 mg·kgˉˡ of NaHOC3 contributed to significant improvements in peak power during a 60 second all out sprint between subjects ingesting a NaHOC3 and placebo drink (779 ± 23.4, 706 ± 23.1), respectively. Subjects also had significantly higher blood lactate concentrations 1 minute after exercise. More recently, Montfoort et al. (2004) suggested sodium bicarbonate could improve sprint performance lasting between 60 – 120 seconds. They found time to exhaustion was longer for subjects ingesting a 300 mg·kgˉˡ of NaHCOз solution; 82.3 seconds, compared to subjects ingesting sodium lactate; 77.4 s, sodium citrate;78.2 s and sodium chloride; 77.4 s.

Nevertheless some studies have suggested NaHCOз has no influence on short, high intensity performance (Inbar et al. 1983; Tiryaki et al. 1995; Marx et al. 2002, Zabala et al. 2008). In one study, Marx et al. (2002) found no significant differences in peak power output between a placebo and NaHCOз solution during a 90 second maximal sprint on a cycle ergometer (535.7 ± 54.4 and 534.7 ± 61.6 watts), respectively. In another more recent study, Zabala et al, (2008) found NaHCOз had no influence on peak power output in 9 elite BMX riders. Nevertheless, the lack of significant results obtained could be attributed to the 30 second Wingate's performed. Research has suggested 30 seconds may not be long enough to produce significant results (Requena et al. 2005).

Therefore the aim of the current study is to assess the effect sodium bicarbonate has on peak/ power output and lactate accumulation during a maximal sprint. It is hypothesised that subjects ingesting the sodium bicarbonate solution will achieve higher peak power scores and have lower blood lactate accumulation due to induced alkalosis, enabling a higher force production, slower decrease in pH and increased removal of lactate and hydrogen from the working muscles.

Method

Subjects.

Nine participants (m=4, f =5) (mean, stdev) volunteered for the study. The study was approved by the University of Brighton's ethics committee. Prior to testing, each subject was made aware of the experimental procedures and possible side effects involved and completed a medical questionnaire and supplied written informed consent. The subjects were recruited from a Sport and Exercise Science course at the University of Brighton. All testing took place at the same time of day in the Welkin Laboratories, University of Brighton.

Experimental overview.

The subjects were tested on two different occasions. The first time the subjects reported to the laboratory they had their height (cm) and weight (Kg) recorded. The subjects then performed a 60 second maximal test after ingesting either a sodium bicarbonate (NaHCOз) or a placebo solution, sodium chloride (NaCL). At the same time a week later the subjects reported to the laboratory for the second time. This time the subjects performed the 60 second maximal sprint but ingested the opposite solution to the week before. Each 60 second sprint was preceded by a warm up of 5 minutes sub maximal cycling (Monark, 824 Ergodemic, Switzerland) against a resistance of 1 kg, steadily raising their heart rate to 130bpm. In an attempt to ensure the results were unaffected by external factors, subjects were asked to keep a similar diet and exercise routine leading up to the separate testing days.

Solution ingestion.

When the subjects arrived at the laboratory they were given one of two solutions, either 300 mg·kgˉˡ of NaHCOз or 250g·kgˉˡ of NaCL. McNaughton et al. (1992) suggested 300 mg·kgˉˡ is the ideal dosage for subjects performing 60 seconds of maximal exercise. The solutions were given using a double blind randomized design. In an attempt to mask the taste, each solution was mixed with 500ml of low calorie flavouring. The solutions were ingested 30 minutes prior to the start of the testing.

60 second sprint.

Once the warm up was completed subjects were transferred to an SRM (Julich, Germany) bike for the 60 second sprint test. The bike was adjusted for seat and handle bar height depending on the subject characteristics. The heights were noted and subjects used the same specifications for the following week. Additionally, the subjects were instructed to remain seated during both sprints to standardize results. Once comfortable, the subjects were given a 5 second warning and instructed to pedal as fast as possible for the full 60 seconds on the start signal. During every sprint subjects were given strong verbal encouragement and wore a heart rate monitor (Polar FS1, US). In addition to the subject's peak power, heart rate was recorded every 25 seconds throughout the sprint.

Lactate analysis.

Arterialised capillary blood samples were taken 2 minutes prior to the 60 second sprint and 5 minutes after the sprint was completed. A 20µl sample of blood was attained via a fingertip prick (Accu-Check Soft Clix Pro) and analysed for lactate concentrations (Hawksley Haemotospin 1300).

Statistical analysis.

Subject's collective scores were calculated as mean ± standard deviation (SD). A paired t-test

was used to establish significant differences between the two solutions, results were considered significant at P < 0.05. Statistical analysis was carried out on SPSS version 16.00 for Windows Vista.

Results

Peak power.

After analysing the data, a paired t-test showed found no significant differences (P < 0.05) between subjects ingesting the NaHCOз and placebo (PL) for peak power output. When subjects ingested the nahco3 solution they achieved slightly higher scores (mean ± SD), 844.55 ± 192.82 Watts (w), compared to PL ingestion: 826.11 ± 300.50 (w), P < 0.05.

Relative peak power.

A paired t-test revealed no significant differences for relative peak power between the two solutions (Figure. 1; P < 0.05). Compared with the PL solution, subjects ingesting the NaHCOз solution demonstrated a slightly higher relative power output (placebo vs. NaHCOз): 12.10 ± 1.65 vs. 12.56 ± 1.92: P < 0.05).

Blood lactate.

There was a significant difference between subjects blood lactate for the two different solutions (Figure 2. P = 0.016). Subjects ingesting the NaHCOз solution were able to buffer more lactate than subjects ingesting the PL solution: 11.51 ± 2.23 vs 9.00 ± 1.93mmol/l; P < 0.05, respectively.

Discussion

The aim of the present study was to investigate the effect sodium bicarbonate ingestion has on a maximal 60 second sprint. The study found no significant differences between peak and relative power for subjects ingesting either a placebo or NaHCOз solution. Nevertheless, a significant difference (P = 0.016) was observed in the subjects blood lactate levels. Subjects ingesting the NaHCOз solution had significantly higher blood lactate levels (see fig. 2) than when they ingested the placebo solution.

Significant increases in blood lactate after sodium bicarbonate ingestion has been observed before (Goldfinch et al, 1988; Stephens et al, 2002; Price et al, 2003).

The significant increase in blood lactate levels could be attributed to the enhancement of the extracellular buffering capacity (Street et al, 2005) which allowed a greater efflux of blood lactate from the working muscles, possibly assisted by a greater Ph gradient (Requena et al, 2005). Burke et al, (2006) explain how the increased efflux from the working muscles allows the athlete to tolerate higher amounts of lactate.

Despite this, there was still no significant improvement in performance. Although a lack of significant results for peak power has been observed before (Marx et al, 2002; Zabala et al, 2008) the results of the present study contradict the findings of McNaughton et al, (1997). Even though the subjects ingesting the NaHCOз as opposed to the PL solution, achieved slightly higher mean relative peak power scores: 12.56 ± 1.92, 12.10 ± 1.65 watts, respectively, they were insignificant improvements. McNaughton et al, (1997) found peak power to significantly increase for subjects using a similar protocol (ingesting 300 mg·kgˉˡ of NaHCOз during a 60 second sprint). The disparity in findings between the two studies could be attributed to the timing of NaHCOз ingestion. In the present study NaHCOз ingestion occurred 30 minutes prior to the start of the exercise protocol, where as the subjects from McNaughton et al, (1997) ingested NaHCOз 90 minutes before the start of their protocol. Pottegier et al, (1996) found optimum absorption time under these conditions was 120 minutes. Therefore, it is probable that 30 minutes may have been to shorter duration to allow subjects to reach peak pH, or enhance the contractile ability of the muscles involved (McNaughton et al, 1997) to improve subsequent performance.

In addition, the subject population could have also influenced the results of the study. Linderman et al, (1994) explain how trained athletes who undertake some form of high intensity sprint training have a better buffering capacity then untrained individuals. Whether or not some subjects were well trained or not was not recorded during the study. This could explain the disparity in the results as sedentary subjects are more likely to experience the benefits of induced alkalosis than trained subjects (McNaughton, 1992).

Lastly, whether or not subject's experienced gastrointestinal stress was not recorded. The ingestion of sodium bicarbonate has been linked to diarrhoea, cramping (Burke et al, 2006) and bloating (Linderman et al, 1994). Subjects experiencing these adverse effects could have endured gastrointestinal discomfort during the testing protocol, possibly influencing performance. Requena et al, (2005) explain that in order to minimise gastrointestinal stress it is important that subjects are individually and completely familiarised with the testing protocol and ingest NaHCOз with plenty of water. Future research should take these methodological concerns into account when designing investigations into the effects of sodium bicarbonate on performance.

In conclusion, the findings of the present study suggest ingesting 300 mg·kgˉˡ of NaHCOз causes a greater efflux of blood lactate from the working muscles, although it is still unclear on the proposed benefits of NaHCOз ingestion on performance.

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