Journal of Dietary Supplements, 11(2):166–174, 2014 C 2014 by Informa Healthcare USA, Inc. Available online at www.informahealthcare.com/jds DOI: 10.3109/19390211.2013.859215
ARTICLE
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Timing Influence of Carbohydrate-Protein Ingestion on Muscle Soreness and Next-Day Running Performance Beau Kjerulf Greer, PhD1 , Anna Price, PhD2 , & Brett Jones, BS3 1
Sacred Heart University, Physical Therapy and Human Movement Science, Fairfield, Connecticut, USA, 2 Sacred Heart University, Fairfield, Connecticut, USA, 3 Sherpa, LLC, Westport, Connecticut, USA
ABSTRACT. The present study investigates timing effects of a carbohydrate-protein (CHO-PROT) beverage on indicators of muscle damage and next day running performance. Nine trained subjects completed three trials of a 30 min downhill run, followed by a 1.5 mile treadmill running time trial 24 hr later in a blinded, crossover design. Either a CHO-PROT or noncaloric placebo beverage was given 30 and 5 min prior to, at the 15 min mark during, immediately after, and 30 min after the downhill running protocol. In the first treatment (T1), a total of 360 kilocalories were given 30 and 5 min prior to downhill running, as well as at the 15 min mark, with placebos used at other time points. In the second treatment (T2), an isocaloric amount was given but only immediately after and 30 min after downhill running, with placebos used at other time points. In the placebo treatment, a placebo was given at all time points. There were no significant differences in the 1.5 mile time trial or soreness between trials (p > .05). Regardless of timing, the ingestion of a CHO-PROT beverage had no effect on next day running performance or muscular soreness versus a placebo. KEYWORDS.
ergogenic aids, muscle damage, sports drink
INTRODUCTION The efficacy of adding protein (PROT) to carbohydrate (CHO) beverages for use before, during, or after endurance exercise remains controversial (Betts & Stevenson, 2011). Evidence suggests that the addition of PROT to a CHO-containing beverage does not provide an immediate performance benefit as long as exogenous CHO is fed near the maximal oxidative rate (Betts & Stevenson, 2011), and to date there are no demonstrated mechanisms as to why PROT would act as an ergogenic aid in this capacity (Betts & Stevenson, 2011; Cermak, Solheim, Gardner, Tarnopolsky, & Gibala, 2009). However, there is evidence that the ingestion of PROT and Address correspondence to: Beau Kjerulf Greer, PhD, Sacred Heart University, Physical Therapy and Human Movement Science, Fairfield, Connecticut, USA (E-mail: [email protected]). This study was supported by a Sacred Heart University Research and Creativity Grant. (Received 10 April 2013; accepted 10 September 2013)
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its consequential replenishing of the free amino acid pool reduces indirect indicators of muscle damage during endurance exercise (Saunders, Kane, & Todd, 2004; Saunders, Moore, Kies, Luden, & Pratt, 2009), perhaps via anabolic (Tischler, Desautels, & Goldberg, 1982) or anticatabolic (Tipton & Wolfe, 1998) mechanisms. This potential attenuation of damage could lead to a performance benefit during subsequent, or “next day” exercise trials. Studies have shown both positive effects (Berardi, Noreen, & Lemon, 2008; Saunders et al., 2004) and no effect (Cermak et al., 2009; Green, Corona, Doyle, & Ingalls, 2008; Romano-Ely, Todd, Saunders, & Laurent, 2006) of CHO-PROT beverages on subsequent exercise performance as compared to CHO alone. Similar inconsistencies exist in regard to indirect indicators of muscle damage (Green et al., 2008; Saunders et al., 2004; Valentine, Saunders, Todd, & St Laurent, 2008). To this point, the influence of PROT or amino acids on aerobic performance and indirect indictors of muscle damage has been the sole focus of research. The purpose of the present study was to determine if the timing of a carbohydrate-protein (CHO-PROT) beverage affects muscle soreness and next-day aerobic exercise performance. Previous studies have presented rationale for examining timing effects of CHO-PROT beverages (Cockburn, Hayes, French, Stevenson, & St Clair Gibson, 2008; Cockburn, Stevenson, Hayes, Robson-Ansley, & Howatson, 2010), however these studies used muscle-damaging protocols and performance outcome variables that were not aerobic in nature; therefore, the results of these studies have little application to the endurance athlete. MATERIALS AND METHODS Nine (n = 6 male; n = 3 female) individuals were recruited for the present study. Subject characteristics were as follows (mean ± S.D.): age 21.4 ± 1.0 yr; body mass 75.3 ± 3.7 kg (male), 53.8 ± .7 kg (female); body fat 10.3 ± 1.7% (male), 19.4 ± 0.7% (female). Participants were required to have exercised aerobically at least three times per week for the previous year, as well as be in the top 50th percentile for aerobic fitness as determined by a 1.5 miles time trial run for males, and the top 80th percentile for females (ACSM, 2000). The higher relative standard for females was to ensure a more consistent finishing time, reducing the standard deviation and, therefore, decreasing the odds of a type II error. The absolute difference between these standards is 2 s for the subject age pool. Participants were weighed using a physician’s scale and had their body fat tested by a 3 site-skinfold measurement (Lange calipers, Ann Arbor MI) by an experienced tester. All participants signed an informed consent document, and all study procedures were approved by the Sacred Heart University Institutional Review Board. The time trial used for aerobic fitness stratification served as the first of two familiarization trials; these trials served to attenuate a potential learning curve during the study. A 1.5 miles time trial was chosen as the performance outcome measure due to criticism that other studies in this research area have not used outcome performance tests with established reliability (Cooper, 1977). No fewer than 7 days after the second familiarization trial, participants returned to the laboratory for the first of three trials (see Figure 1). The study maintained a
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FIGURE 1. Study Design. The order of conditions was randomly assigned.
crossover design with 7 days between each trial. A stratified, randomized treatment approach was employed as to eliminate the influence of a repeated bout effect on muscle damage or a performance learning curve. Even though a significant gender influence is unlikely in the present study (Clarkson & Hubal, 2001), the three female participants were randomized separately from the males so that each subject would have a different trial order. Menstrual cycle was not controlled for as estrogen is unrelated to markers of muscular damage (Clarkson & Hubal, 2001). Participants were discouraged from performing lower body resistance exercise for 72 hr prior to each trial, as well as exercising aerobically for 48 hr prior, in order to reduce the change of preexisting muscle damage (Clarkson & Hubal, 2002).
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For all trials, participants performed 30 min of downhill (–9.5% grade) treadmill running at 8.0 mph. This was achieved by six 5-min intervals, with 2 min of standing rest between intervals. This protocol was designed to induce skeletal muscle damage and is similar to one previously published (Green et al., 2008). Muscle soreness (0–10) of the quadriceps was assessed with a step down motion prior to and 24-hr after the downhill run (Warren, Lowe, & Armstrong, 1999). A 1.5 mile time trial treadmill run was also performed 24-hr after the downhill run. No verbal encouragement or physiological feedback was given during the time trial. For each trial, all environmental conditions were standardized and the treadmill belt was checked for proper calibration. Order effects were examined for both the time trial and for changes in muscle soreness. Participants received verbal instruction in regards to the dietary requirements of the study. They recorded their diet for three days prior to each trial, as well as all food/caloric beverages consumed between the downhill run and the time trial. Participants were required to fast for 4 hr prior to both the downhill run and time trial. Fasting, with the exception of beverages supplied by the investigators, was also required for 2 hr postdownhill run. Participants were given back copies of their dietary records and asked to repeat the diet as closely as possible for subsequent trials. Dietary data was computed using commercially available dietary software (NutritionCalc Plus 2.0, Salem). Mean energy, macronutrient, Vitamin C, and Vitamin E intake were analyzed as they potentially have influence over muscle damage indicators (Goldfarb, 1999). The three experimental trials differed only in the timing and content of beverage consumed before, during, and after the downhill treadmill run. Either a CHOR , PacificHealth Laboratories, Matawan NJ) or noncaloric PROT (Accelerade placebo beverage was given 30 and 5 min prior to, at the 15 min mark during, immediately after, and 30 min after the downhill running protocol. In the first treatment (T1), a total of 360 kilocalories (72 g CHO, 18 grams PROT) was given 30 and 5 min prior to downhill running, as well as at the 15 min mark, with placebos used at other time points. In the second treatment (T2), the same caloric amount was given but only immediately after and 30 min after downhill running, with placebos used at other time points. In the placebo treatment (PL), a placebo was given at all time points. The total fluid volume consumed during all trials was similar (approximately 92 fluid ounces). Artificial flavors and noncaloric sweeteners along with containers that hide appearance were utilized to help blind participants. This study follows a 3 × 2, trial x time, within-subjects design with repeated measures in regards to muscle soreness; a similar design was employed for time trial performance save only a single measure was taken for each trial. ANOVA with repeated measures was used to analyze within-subjects differences for continuous data, with statistical significance set at p < .05. Although it has become commonplace to treat 0–10 soreness data with ANOVA or t tests (Greer, Woodard, White, Arguello, & Haymes, 2007; White et al., 2008), it is improper to treat ordinal data with parametric statistics. Therefore, the difference in muscle soreness before and after the downhill run was calculated (i.e., soreness before downhill run – soreness after downhill run) to develop a “change in muscle soreness” score. A Friedman test was used to examine if there was a significant difference in the soreness score between participants in the three trials (i.e., T1, T2, or PL). A Friedman test was
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also used to examine if there was an order effect present in regards to change in muscle soreness. A Wilcoxon test with Bonferonni correction for multiple comparisons was used to examine the differences in the change in soreness score between the first and second, first and third, and second and third testing periods. The p value for the Wilcoxon test with Bonferonni correction was p < .017 (0.05/3). All calculations were performed using commercially available statistical software (PASW Inc., Chicago).
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RESULTS All participants completed the testing procedures. ANOVA revealed no differences in dietary intake (p > .05) across trials and, therefore, no dietary element was used as a covariate. There were no significant differences in the 1.5 mile time trial between the T1 trial (648.11 ± 64.79 s), the T2 trial (660.00 ± 52.91 s), and the PL trial (654.00 ± 56.48 s) (p > .05; Figure 2). There was no order effect present between testing periods (p > .05); the largest, albeit nonsignificant, difference was between the first run (658.22 ± 69.91 s across all conditions) and the third run (651.56 ± 46.0 s across all conditions) (Figure 3). The median change in soreness scores were 2, 3, and 3 for the T1, PL, and T2 trials, respectively. There was no significant difference in the change in soreness score between conditions (X2 = 1.667, df = 2, p = .435). In regards to an order effect for muscle soreness, a significant difference was found between the median change
FIGURE 2. Mean (± standard deviation) time trial performance. T1 indicates CHO-PROT beverage prior to and during downhill running 24 hr prior; T2, CHO-PROT beverage received postexercise; PL, placebo trial. No significant differences (p > .05).
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FIGURE 3. Mean (± standard deviation) time trial performance by testing period across all conditions (i.e., order effect). No significant differences (p > .05).
in soreness score for the first testing period across all conditions (median = 5), and the second (median = 2) and third (median = 2) testing period (X2 = 11.667, df = 2, p = .003). However, the Wilcoxon tests with Bonferonni correction for multiple comparisons shows that change in soreness score differed significantly only between the first and third testing periods (p = .011). The difference in median change in soreness scores between the first and second testing periods was significant (p = .023) only before the Bonferonni correction.
DISCUSSION The primary finding from the present study was that a PROT-containing, CHOelectrolyte beverage had no influence over muscle soreness or next-day running performance, regardless of beverage timing. The study is unique in that the influence of beverage timing was examined, a performance test with established reliability was used, two familiarization trials were given, and that soreness data was properly treated via nonparametric statistics. The hypothesis of the present study was that a CHO-PROT beverage would be more effective in attenuating the markers of damage and aiding next-day performance if consumed prior to and during exercise as opposed to postexercise. This was hypothesized because muscle damage during most endurance-related activity is most likely due more to the metabolic need for oxidizeable substrates as opposed to mechanically induced damage (Greer et al., 2007; Tipton & Wolfe, 1998; White et al., 2008), although both contribute.
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Therefore, prevention of initial damage, as opposed to secondary damage mediated by the immune response, would require the exogenous amino acids to be present during the exercise bout when ATP need may surpass production via nonprotein sources of energy. PROT consumption postexercise aids in recovery and may affect next-day performance via the enhancement of muscle protein synthesis (Biolo, Tipton, Klein, & Wolfe, 1997), the attenuation of protein degradation (Tischler et al., 1982), or by aiding glycogen storage when carbohydrate intake is lower than optimal (Betts & Williams, 2010), but obviously cannot have influence over the extent of initial damage that occurs during the exercise bout. Since this assumes a metabolic origin for the majority of muscle damage created during endurance work, it is suggested by the authors that downhill running, although a common method for inducing muscle damage, may be an inappropriate methodology to examine the potential efficacy of such products as nutritional supplementation will most likely be ineffective at preventing high rates of mechanically induced muscle damage. As these rates are unlikely to occur during normal aerobic competition, the external validity of these studies is reduced as well. To this effect, PROT supplementation during cycling performance may be more effective at preventing damage than during running as the damage cycling produces is less mechanically induced since there is less of an eccentric component. The design of the present study was similar to Green et al. with the exception of beverage composition and timing (Green et al., 2008). They report that a CHO-PROT or CHOalone beverage fed postexercise had no effect as compared to a placebo on recovery from a downhill run as determined by various indirect indicators of muscle damage and maximal isometric quadriceps strength. Likewise, no effect on prevention or recovery from a downhill run was observed in the present study. Taking into account documented efficacy of CHO-PROT supplementation versus CHO alone or placebos (Saunders et al., 2004; Saunders, Luden, & Herrick, 2007; Saunders et al., 2009; Valentine et al., 2008), it appears that CHO-PROT beverages will provide the greatest benefit for subsequent or next-day exercise performance when used for noneccentrically biased aerobic exercise, such as cycling. As there was a significant order effect present for muscle soreness, 7 days between trials was inadequate to prevent the repeated bout effect in aerobically trained individuals. Although other studies in this research area often do not report examining whether an order effect was present for indirect indicators of muscle soreness, future studies using eccentrically biased exercise may want to consider longer rest periods between trials to minimize this effect, or use an initial exposure to highly eccentrically biased exercise prior to data collection in order to reduce the chance of a type II error. However, given the means of the present study, it is quite likely that no such error occurred. CONCLUSION Although the addition of PROT to CHO beverages is anecdotally becoming more popular, there remains conflicting opinions as to whether they will aid performance when consumed before or during endurance exercise (Betts & Stevenson, 2011). The present study does not support the use of CHO-PROT beverages before or after eccentrically biased aerobic exercise for the purposes of reducing symptoms
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of muscular damage or improving next-day performance. The study is unique in that several criticisms of methodologies in this research area were accounted for such as using performance tests with established reliability, the use of multiple familiarization trials, and the proper treatment of ordinal data. The influence of exercise mode should be investigated further in regards to the efficacy of CHO-PROT supplementation for muscle damage prevention and the improvement of next-day exercise performance.
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Declaration of interest: No author has a direct financial relation with the trademark, corporation, or software utilized in this study. No materials or software were provided by the companies/corporations.
REFERENCES ACSM. Guidelines for exercise testing & prescription (6th ed.). Baltimore, MD: Lippincott Williams & Wilkins, 2000. Berardi JM, Noreen EE, Lemon PW. Recovery from a cycling time trial is enhanced with carbohydrate-protein supplementation vs. isoenergetic carbohydrate supplementation. J Int Soc Sports Nutr. 2008;5:24. doi: 10.1186/1550-2783-5-24 Betts JA, Stevenson E. Should protein be included in CHO-based sports supplements? Med Sci Sports Exerc. 2011;43(7):1244–1250. doi: 10.1249/MSS.0b013e31821b0dcc Betts JA, Williams C. Short-term recovery from prolonged exercise: exploring the potential for protein ingestion to accentuate the benefits of carbohydrate supplements. Sports Med. 2010;40(11):941–959. doi: 10.2165/11536900-000000000-00000 Biolo G, Tipton KD, Klein S, Wolfe RR. An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. Am J Physiol. 1997;273(1 Pt 1):E122–E129. Cermak NM, Solheim AS, Gardner MS, Tarnopolsky MA, Gibala MJ. Muscle metabolism during exercise with carbohydrate or protein-carbohydrate ingestion. Med Sci Sports Exerc. 2009;41(12):2158–2164. doi: 10.1249/MSS.0b013e3181ac10bf Clarkson PM, Hubal MJ. Are women less susceptible to exercise-induced muscle damage? Curr Opin Clin Nutr Metab Care. 2001;4(6):527–531. Clarkson PM, Hubal MJ. Exercise-induced muscle damage in humans. Am J Phys Med Rehabil. 2002;81(11 suppl):S52–S69. doi: 10.1097/01.PHM.0000029772.45258.43 Cockburn E, Hayes PR, French DN, Stevenson E, St Clair Gibson A. Acute milk-based protein-CHO supplementation attenuates exercise-induced muscle damage. Appl Physiol Nutr Metab. 2008;33(4):775–783. doi: 10.1139/H08-057 Cockburn E, Stevenson E, Hayes PR, Robson-Ansley P, Howatson G. Effect of milk-based carbohydrate-protein supplement timing on the attenuation of exercise-induced muscle damage. Appl Physiol Nutr Metab. 2010;35(3):270–277. doi: 10.1139/H10-017 Cooper K. The aerobics way. New York: Bantam Books, 1977. Goldfarb AH. Nutritional antioxidants as therapeutic and preventive modalities in exerciseinduced muscle damage. Can J Appl Physiol. 1999;24(3):249–266. Green MS, Corona BT, Doyle JA, Ingalls CP. Carbohydrate-protein drinks do not enhance recovery from exercise-induced muscle injury. Int J Sport Nutr Exerc Metab. 2008;18(1):1–18. Greer BK, Woodard JL, White JP, Arguello EM, Haymes EM. Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise. Int J Sport Nutr Exerc Metab. 2007;17(6):595–607. Romano-Ely BC, Todd MK, Saunders MJ, Laurent TS. Effect of an isocaloric carbohydrate-protein-antioxidant drink on cycling performance. Med Sci Sports Exerc. 2006;38(9):1608–1616. doi: 10.1249/01.mss.0000229458.11452.e9 Saunders MJ, Kane MD, Todd MK. Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage. Med Sci Sports Exerc. 2004;36(7):1233–1238.
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Saunders MJ, Luden ND, Herrick JE. Consumption of an oral carbohydrate-protein gel improves cycling endurance and prevents postexercise muscle damage. J Strength Cond Res. 2007;21(3):678–684. doi: 10.1519/R-20506.1 Saunders MJ, Moore RW, Kies AK, Luden ND, Pratt CA. Carbohydrate and protein hydrolysate coingestions improvement of late-exercise time-trial performance. Int J Sport Nutr Exerc Metab. 2009;19(2):136–149. Tipton KD, Wolfe RR. Exercise-induced changes in protein metabolism. Acta Physiol Scand. 1998;162(3):377–387. Tischler ME, Desautels M, Goldberg AL. Does leucine, leucyl-tRNA, or some metabolite of leucine regulate protein synthesis and degradation in skeletal and cardiac muscle? J Biol Chem. 1982;257(4):1613–1621. Valentine RJ, Saunders MJ, Todd MK, St Laurent TG. Influence of carbohydrate-protein beverage on cycling endurance and indices of muscle disruption. Int J Sport Nutr Exerc Metab. 2008;18(4):363–378. Warren GL, Lowe DA, Armstrong RB. Measurement tools used in the study of eccentric contraction-induced injury. Sports Med. 1999;27(1):43–59. White JP, Wilson JM, Austin KG, Greer BK, St John N, Panton LB. Effect of carbohydrateprotein supplement timing on acute exercise-induced muscle damage. J Int Soc Sports Nutr. 2008;5:5. doi: 10.1186/1550-2783-5-5
ARTICLE
J Dietary Suppl Downloaded from informahealthcare.com by Queen's University on 12/30/14 For personal use only.
Timing Influence of Carbohydrate-Protein Ingestion on Muscle Soreness and Next-Day Running Performance Beau Kjerulf Greer, PhD1 , Anna Price, PhD2 , & Brett Jones, BS3 1
Sacred Heart University, Physical Therapy and Human Movement Science, Fairfield, Connecticut, USA, 2 Sacred Heart University, Fairfield, Connecticut, USA, 3 Sherpa, LLC, Westport, Connecticut, USA
ABSTRACT. The present study investigates timing effects of a carbohydrate-protein (CHO-PROT) beverage on indicators of muscle damage and next day running performance. Nine trained subjects completed three trials of a 30 min downhill run, followed by a 1.5 mile treadmill running time trial 24 hr later in a blinded, crossover design. Either a CHO-PROT or noncaloric placebo beverage was given 30 and 5 min prior to, at the 15 min mark during, immediately after, and 30 min after the downhill running protocol. In the first treatment (T1), a total of 360 kilocalories were given 30 and 5 min prior to downhill running, as well as at the 15 min mark, with placebos used at other time points. In the second treatment (T2), an isocaloric amount was given but only immediately after and 30 min after downhill running, with placebos used at other time points. In the placebo treatment, a placebo was given at all time points. There were no significant differences in the 1.5 mile time trial or soreness between trials (p > .05). Regardless of timing, the ingestion of a CHO-PROT beverage had no effect on next day running performance or muscular soreness versus a placebo. KEYWORDS.
ergogenic aids, muscle damage, sports drink
INTRODUCTION The efficacy of adding protein (PROT) to carbohydrate (CHO) beverages for use before, during, or after endurance exercise remains controversial (Betts & Stevenson, 2011). Evidence suggests that the addition of PROT to a CHO-containing beverage does not provide an immediate performance benefit as long as exogenous CHO is fed near the maximal oxidative rate (Betts & Stevenson, 2011), and to date there are no demonstrated mechanisms as to why PROT would act as an ergogenic aid in this capacity (Betts & Stevenson, 2011; Cermak, Solheim, Gardner, Tarnopolsky, & Gibala, 2009). However, there is evidence that the ingestion of PROT and Address correspondence to: Beau Kjerulf Greer, PhD, Sacred Heart University, Physical Therapy and Human Movement Science, Fairfield, Connecticut, USA (E-mail: [email protected]). This study was supported by a Sacred Heart University Research and Creativity Grant. (Received 10 April 2013; accepted 10 September 2013)
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its consequential replenishing of the free amino acid pool reduces indirect indicators of muscle damage during endurance exercise (Saunders, Kane, & Todd, 2004; Saunders, Moore, Kies, Luden, & Pratt, 2009), perhaps via anabolic (Tischler, Desautels, & Goldberg, 1982) or anticatabolic (Tipton & Wolfe, 1998) mechanisms. This potential attenuation of damage could lead to a performance benefit during subsequent, or “next day” exercise trials. Studies have shown both positive effects (Berardi, Noreen, & Lemon, 2008; Saunders et al., 2004) and no effect (Cermak et al., 2009; Green, Corona, Doyle, & Ingalls, 2008; Romano-Ely, Todd, Saunders, & Laurent, 2006) of CHO-PROT beverages on subsequent exercise performance as compared to CHO alone. Similar inconsistencies exist in regard to indirect indicators of muscle damage (Green et al., 2008; Saunders et al., 2004; Valentine, Saunders, Todd, & St Laurent, 2008). To this point, the influence of PROT or amino acids on aerobic performance and indirect indictors of muscle damage has been the sole focus of research. The purpose of the present study was to determine if the timing of a carbohydrate-protein (CHO-PROT) beverage affects muscle soreness and next-day aerobic exercise performance. Previous studies have presented rationale for examining timing effects of CHO-PROT beverages (Cockburn, Hayes, French, Stevenson, & St Clair Gibson, 2008; Cockburn, Stevenson, Hayes, Robson-Ansley, & Howatson, 2010), however these studies used muscle-damaging protocols and performance outcome variables that were not aerobic in nature; therefore, the results of these studies have little application to the endurance athlete. MATERIALS AND METHODS Nine (n = 6 male; n = 3 female) individuals were recruited for the present study. Subject characteristics were as follows (mean ± S.D.): age 21.4 ± 1.0 yr; body mass 75.3 ± 3.7 kg (male), 53.8 ± .7 kg (female); body fat 10.3 ± 1.7% (male), 19.4 ± 0.7% (female). Participants were required to have exercised aerobically at least three times per week for the previous year, as well as be in the top 50th percentile for aerobic fitness as determined by a 1.5 miles time trial run for males, and the top 80th percentile for females (ACSM, 2000). The higher relative standard for females was to ensure a more consistent finishing time, reducing the standard deviation and, therefore, decreasing the odds of a type II error. The absolute difference between these standards is 2 s for the subject age pool. Participants were weighed using a physician’s scale and had their body fat tested by a 3 site-skinfold measurement (Lange calipers, Ann Arbor MI) by an experienced tester. All participants signed an informed consent document, and all study procedures were approved by the Sacred Heart University Institutional Review Board. The time trial used for aerobic fitness stratification served as the first of two familiarization trials; these trials served to attenuate a potential learning curve during the study. A 1.5 miles time trial was chosen as the performance outcome measure due to criticism that other studies in this research area have not used outcome performance tests with established reliability (Cooper, 1977). No fewer than 7 days after the second familiarization trial, participants returned to the laboratory for the first of three trials (see Figure 1). The study maintained a
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FIGURE 1. Study Design. The order of conditions was randomly assigned.
crossover design with 7 days between each trial. A stratified, randomized treatment approach was employed as to eliminate the influence of a repeated bout effect on muscle damage or a performance learning curve. Even though a significant gender influence is unlikely in the present study (Clarkson & Hubal, 2001), the three female participants were randomized separately from the males so that each subject would have a different trial order. Menstrual cycle was not controlled for as estrogen is unrelated to markers of muscular damage (Clarkson & Hubal, 2001). Participants were discouraged from performing lower body resistance exercise for 72 hr prior to each trial, as well as exercising aerobically for 48 hr prior, in order to reduce the change of preexisting muscle damage (Clarkson & Hubal, 2002).
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For all trials, participants performed 30 min of downhill (–9.5% grade) treadmill running at 8.0 mph. This was achieved by six 5-min intervals, with 2 min of standing rest between intervals. This protocol was designed to induce skeletal muscle damage and is similar to one previously published (Green et al., 2008). Muscle soreness (0–10) of the quadriceps was assessed with a step down motion prior to and 24-hr after the downhill run (Warren, Lowe, & Armstrong, 1999). A 1.5 mile time trial treadmill run was also performed 24-hr after the downhill run. No verbal encouragement or physiological feedback was given during the time trial. For each trial, all environmental conditions were standardized and the treadmill belt was checked for proper calibration. Order effects were examined for both the time trial and for changes in muscle soreness. Participants received verbal instruction in regards to the dietary requirements of the study. They recorded their diet for three days prior to each trial, as well as all food/caloric beverages consumed between the downhill run and the time trial. Participants were required to fast for 4 hr prior to both the downhill run and time trial. Fasting, with the exception of beverages supplied by the investigators, was also required for 2 hr postdownhill run. Participants were given back copies of their dietary records and asked to repeat the diet as closely as possible for subsequent trials. Dietary data was computed using commercially available dietary software (NutritionCalc Plus 2.0, Salem). Mean energy, macronutrient, Vitamin C, and Vitamin E intake were analyzed as they potentially have influence over muscle damage indicators (Goldfarb, 1999). The three experimental trials differed only in the timing and content of beverage consumed before, during, and after the downhill treadmill run. Either a CHOR , PacificHealth Laboratories, Matawan NJ) or noncaloric PROT (Accelerade placebo beverage was given 30 and 5 min prior to, at the 15 min mark during, immediately after, and 30 min after the downhill running protocol. In the first treatment (T1), a total of 360 kilocalories (72 g CHO, 18 grams PROT) was given 30 and 5 min prior to downhill running, as well as at the 15 min mark, with placebos used at other time points. In the second treatment (T2), the same caloric amount was given but only immediately after and 30 min after downhill running, with placebos used at other time points. In the placebo treatment (PL), a placebo was given at all time points. The total fluid volume consumed during all trials was similar (approximately 92 fluid ounces). Artificial flavors and noncaloric sweeteners along with containers that hide appearance were utilized to help blind participants. This study follows a 3 × 2, trial x time, within-subjects design with repeated measures in regards to muscle soreness; a similar design was employed for time trial performance save only a single measure was taken for each trial. ANOVA with repeated measures was used to analyze within-subjects differences for continuous data, with statistical significance set at p < .05. Although it has become commonplace to treat 0–10 soreness data with ANOVA or t tests (Greer, Woodard, White, Arguello, & Haymes, 2007; White et al., 2008), it is improper to treat ordinal data with parametric statistics. Therefore, the difference in muscle soreness before and after the downhill run was calculated (i.e., soreness before downhill run – soreness after downhill run) to develop a “change in muscle soreness” score. A Friedman test was used to examine if there was a significant difference in the soreness score between participants in the three trials (i.e., T1, T2, or PL). A Friedman test was
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also used to examine if there was an order effect present in regards to change in muscle soreness. A Wilcoxon test with Bonferonni correction for multiple comparisons was used to examine the differences in the change in soreness score between the first and second, first and third, and second and third testing periods. The p value for the Wilcoxon test with Bonferonni correction was p < .017 (0.05/3). All calculations were performed using commercially available statistical software (PASW Inc., Chicago).
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RESULTS All participants completed the testing procedures. ANOVA revealed no differences in dietary intake (p > .05) across trials and, therefore, no dietary element was used as a covariate. There were no significant differences in the 1.5 mile time trial between the T1 trial (648.11 ± 64.79 s), the T2 trial (660.00 ± 52.91 s), and the PL trial (654.00 ± 56.48 s) (p > .05; Figure 2). There was no order effect present between testing periods (p > .05); the largest, albeit nonsignificant, difference was between the first run (658.22 ± 69.91 s across all conditions) and the third run (651.56 ± 46.0 s across all conditions) (Figure 3). The median change in soreness scores were 2, 3, and 3 for the T1, PL, and T2 trials, respectively. There was no significant difference in the change in soreness score between conditions (X2 = 1.667, df = 2, p = .435). In regards to an order effect for muscle soreness, a significant difference was found between the median change
FIGURE 2. Mean (± standard deviation) time trial performance. T1 indicates CHO-PROT beverage prior to and during downhill running 24 hr prior; T2, CHO-PROT beverage received postexercise; PL, placebo trial. No significant differences (p > .05).
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FIGURE 3. Mean (± standard deviation) time trial performance by testing period across all conditions (i.e., order effect). No significant differences (p > .05).
in soreness score for the first testing period across all conditions (median = 5), and the second (median = 2) and third (median = 2) testing period (X2 = 11.667, df = 2, p = .003). However, the Wilcoxon tests with Bonferonni correction for multiple comparisons shows that change in soreness score differed significantly only between the first and third testing periods (p = .011). The difference in median change in soreness scores between the first and second testing periods was significant (p = .023) only before the Bonferonni correction.
DISCUSSION The primary finding from the present study was that a PROT-containing, CHOelectrolyte beverage had no influence over muscle soreness or next-day running performance, regardless of beverage timing. The study is unique in that the influence of beverage timing was examined, a performance test with established reliability was used, two familiarization trials were given, and that soreness data was properly treated via nonparametric statistics. The hypothesis of the present study was that a CHO-PROT beverage would be more effective in attenuating the markers of damage and aiding next-day performance if consumed prior to and during exercise as opposed to postexercise. This was hypothesized because muscle damage during most endurance-related activity is most likely due more to the metabolic need for oxidizeable substrates as opposed to mechanically induced damage (Greer et al., 2007; Tipton & Wolfe, 1998; White et al., 2008), although both contribute.
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Therefore, prevention of initial damage, as opposed to secondary damage mediated by the immune response, would require the exogenous amino acids to be present during the exercise bout when ATP need may surpass production via nonprotein sources of energy. PROT consumption postexercise aids in recovery and may affect next-day performance via the enhancement of muscle protein synthesis (Biolo, Tipton, Klein, & Wolfe, 1997), the attenuation of protein degradation (Tischler et al., 1982), or by aiding glycogen storage when carbohydrate intake is lower than optimal (Betts & Williams, 2010), but obviously cannot have influence over the extent of initial damage that occurs during the exercise bout. Since this assumes a metabolic origin for the majority of muscle damage created during endurance work, it is suggested by the authors that downhill running, although a common method for inducing muscle damage, may be an inappropriate methodology to examine the potential efficacy of such products as nutritional supplementation will most likely be ineffective at preventing high rates of mechanically induced muscle damage. As these rates are unlikely to occur during normal aerobic competition, the external validity of these studies is reduced as well. To this effect, PROT supplementation during cycling performance may be more effective at preventing damage than during running as the damage cycling produces is less mechanically induced since there is less of an eccentric component. The design of the present study was similar to Green et al. with the exception of beverage composition and timing (Green et al., 2008). They report that a CHO-PROT or CHOalone beverage fed postexercise had no effect as compared to a placebo on recovery from a downhill run as determined by various indirect indicators of muscle damage and maximal isometric quadriceps strength. Likewise, no effect on prevention or recovery from a downhill run was observed in the present study. Taking into account documented efficacy of CHO-PROT supplementation versus CHO alone or placebos (Saunders et al., 2004; Saunders, Luden, & Herrick, 2007; Saunders et al., 2009; Valentine et al., 2008), it appears that CHO-PROT beverages will provide the greatest benefit for subsequent or next-day exercise performance when used for noneccentrically biased aerobic exercise, such as cycling. As there was a significant order effect present for muscle soreness, 7 days between trials was inadequate to prevent the repeated bout effect in aerobically trained individuals. Although other studies in this research area often do not report examining whether an order effect was present for indirect indicators of muscle soreness, future studies using eccentrically biased exercise may want to consider longer rest periods between trials to minimize this effect, or use an initial exposure to highly eccentrically biased exercise prior to data collection in order to reduce the chance of a type II error. However, given the means of the present study, it is quite likely that no such error occurred. CONCLUSION Although the addition of PROT to CHO beverages is anecdotally becoming more popular, there remains conflicting opinions as to whether they will aid performance when consumed before or during endurance exercise (Betts & Stevenson, 2011). The present study does not support the use of CHO-PROT beverages before or after eccentrically biased aerobic exercise for the purposes of reducing symptoms
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of muscular damage or improving next-day performance. The study is unique in that several criticisms of methodologies in this research area were accounted for such as using performance tests with established reliability, the use of multiple familiarization trials, and the proper treatment of ordinal data. The influence of exercise mode should be investigated further in regards to the efficacy of CHO-PROT supplementation for muscle damage prevention and the improvement of next-day exercise performance.
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Declaration of interest: No author has a direct financial relation with the trademark, corporation, or software utilized in this study. No materials or software were provided by the companies/corporations.
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