THE EFFECTS OF CAFFEINE ON BLOOD LACTATE LEVELS DURING SUBMAXIMAL EXERCISE

Abstract

INTRODUCTION: Blood lactate concentration reflects the balance between lactate production and clearance. It is considered a marker of exercise intensity and muscle glycolysis. It is expressed in mmol/L of lactate found in the plasma of blood. Research shows that caffeine, a stimulant with ergogenic properties, increases blood lactate levels. It is also shown to improve aerobic performance and increase time to exhaustion during exercise. The physiological underpinnings of caffeine-provoked endurance performance gains are not yet fully understood but may be related to enhanced calcium availability, adenosine receptor antagonism and consequential reductions in pain and perceived exertion, and augmented lipolysis and subsequent glycogen sparing, among other hypothesized mechanisms. PURPOSE: The purpose of this study was to look at the effects of caffeine gum on blood lactate levels during submaximal exercise. METHODS: Six men (age 23.3 ± 1.97 yrs) of the UTA Kinesiology department, volunteered to participate in this study. Each subject filled out a caffeine questionnaire prior to testing. Each subject was given either two pieces of caffeine gum or sugar-free mint gum prior to testing. Each subject then performed a 30 minute submaximal exercise test to 70% age-predicted max heart rate on a cycle ergometer. Prior to gum consumption and again before starting the test, heart rate (HR), blood pressure (BP), and rate of perceived exertion (RPE) were recorded, along with blood lactate levels measured by the Accutrend Lactate Analyzer. During each test heart rate, blood pressure, rate of perceived exertion, and blood lactate levels were recorded every 10 minutes. RESULTS: The blood lactate levels measured during rest after chewing caffeine gum was 3.40 ± 1.34 mmol/L, which approached a significant difference (p=0.036, p<0.05) from blood lactate levels after chewing mint gum (2.08 ± 0.61 mmol/L). Average values: La1 (C: 2.15 ± 0.67 mmol/L; M: 1.87 ± 0.37 mmol/L); La10 (C:5.95 ± 1.45 mmol/L; M: 9.33 ± 5.91 mmol/L); La20 (C:5.67 ± 2.06 mmol/L; M: 6.83 ± 2.85 mmol/L); La30 (C:5.42 ± 0.87 mmol/L; M:5.75 ± 1.87 mmol/L); and La5 (C:4.40 ± 1.82 mmol/L; M: 4.38 ± 1.77 mmol/L) were not significantly different between gum types (p>0.05). However there was a significant difference (p<0.05) between gum types for systolic blood pressure at 10 (BP10) (C:127.5 ± 9.35 mmHg; M: 149.17 ± 9.17 mmHg) and 20 (BP20)(C:135.83 ± 11.14 mmHg; M: 155.83 ± 9.17 mmHg) minutes of cycling. CONCLUSION: The results of this study examined the effects of caffeine gum on blood lactate levels, heart rate, blood pressure, and rate of perceived exertion during submaximal cycling. However, the data indicates that caffeine gum does not have a significant effect on submaximal exercise.