Wallace Abel ChocMilk

8/2/2019 Wallace Abel ChocMilk

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I.J. Fitness (2010)6, Issue"\,pp. 25-32

Effects of chocolate milk on perceived exertion andmuscular strength following resistance training: Apilot study

Brian J. Wallace' and Mark G. Abel 2

'^Department of Kinesiology andHealth Promotion, University of Kentucky,USA.Email: [email protected]

Abstract The purpose of this study was to assess the effects of chocolate milk (suppement)ingestion on rating of perceived exertion (RPE), muscular peak strength, and fatigue following a boutof lower body resistance training. Seven male subjects (age = 24.13.1 years, mass = 85.711.2 kg,height = 179.3*4.6 cm) performed a baseline testing session on an isokinetic dynamometer todetermine peak knee concentric flexion and extension torque at 60 and 120 deg-s" 1, and fatigue during30 repetitions of knee flexions and extensions at 180 deg-s'. On separate days, a standardized owerbody resistance training protocol was performed. Fve minutes after, subjects ingested thesuppement or an artificially sweetened non-caloric pacebo of equal volume (such that suppementcarbohydrate (CHO) content equaled 0.5 g CHOkg '' of body mass), and again performed theisokinetic testing 60 minutes following the resistance training bout. RPE of the training session wasrecorded prior to isokinetic testing. The suppement significantly reduced RPE compared to thepacebo (5.851.46 vs-. 7.141.57). The resistance training protocol generally did not inducedecrements in peak torque output, or an increased level of muscular fatigue compared to baseline.Peak knee flexion torque was increased significantly at 120 deg-s 1 compared to baseline in the

suppement condition. The suppement significantly reduced knee flexion fatigue compared topacebo. Ingestion of chocolate milk reduces acute RPE, and may reduce muscular fatigue, from aresistance training bout. These findings may lead to enhanced acute recovery for individuas whoperform multiple bouts of anaerobic activity throughout a day.

Keywords; Isokinetic, Nutrition, Physcal performance, Strength

Introduction

Many individuals engaged in athletics (e.g., wrestlers, track athletes) or emergency rescueoccupations (e.g., firefighters) are required to perform multiple bouts of intense activity withlimited recovery periods. Both of these groups of individuals use glycogen as aprimary sourceof energy, and need to be able to recover between several fatiguing bouts of activity, allperformed within a period of a few hours.

Endurance activities and resistance training have both been shown to deplete muscle glycogenstores (Ivy et al., 2002a; Roy et al., 1997; Saunders et al., 2004). Consuming a combined protein(PRO) and carbohydrate (CHO) beverage increases glycogen stores more than CHO or PROalone following cycling and resistance exercise intended to deplete glycogen (Ivy et al., 2002a;Zawadzki et al, 1992; Miller et al., 2003). Levenhagen and colleagues (2001) also reported thatingesting nutrients immediately following exercise resulted in enhanced acute whole bodyprotein synthesis compared to ingesting them three hours post-exercise. Using resistancetraining, Esmarck et al., (2001) reported significant increases in body composition and strengthafter a twelve week training intervention when a PRO plus CHO beverage was consumed

r 2010 Ftness Society of India


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26 Brian J. Wallace and Mark G. Abel

immediately after exercise, versus two hours after. These studies demonstrate the efficacy ofconsuming a PRO plus CHO supplement shortly after training on physiological and chronicperformance measures, however, no published studies have investigated CHO plus PROsupplementation followingresistance training on acute performancemeasures.

In light of these studies, it hasbeen recommended that persons who participate in activities that

deplete glycogen stores consume a PRO plus CHO beverage immediately following theiractivity session (Ivy and Portman, 2004). Specifically, an approximate CHO to PRO ratio of4:1 taken during or after exercise has been shown to be effective hi prolonging the ability toperform multiple bouts of glycogen depleting exercise (Ivy et al., 2003; Karp et al., 2006).Additionally, Burke et al. (1993) reported that high glycemic-index foods increased insulin andmuscle glycogen content faster than low glycemic-index foods after glycogen depletingexercise. Recently chocolate milk has been suggested as a post-exercise beverage because ofits approximate 4:1 CHOrPROratio, high glycemic index, cost-effectiveness, and availability(Karp etal., 2006).

An individual's perception of their fatigue may influence effort and performance duringsequential exercise bouts. If one has the perception that they are less fatigued than they arephysiologically, they may put forth more effort, which could result in a better physical

performance. Recently, the use of RPE has been applied to resistance training in an effort tocreate a valid non-invasive way to monitor training intensity (Sweet et al., 2004). However,there is no literature evaluating the effects of chocolate milk supplementation on RPE or acuteperformancefollowing about of resistance training. Therefore, the purpose of this study was toexaminethe effectiveness of chocolate milk as a post resistance exercise recovery beverage byinvestigating its impact on acute RPE, peak torque, and fatigue following lower-extremityresistance training.

Material and Methods

Subjects: Seven (n=7) recreationally strength trained men (Table 1) participated in thisinvestigation. Subjects were required to be able to perform a one repetition maximum (1RM)squat of at least 1.5 times their body mass. All subjects were engaged in a whole body resistance

training program of three or more days per week for at least three consecutive months prior toparticipating. All subjects had experience in performing the exercises included in the trainingprotocol. Subjects read and signed an institution approved informed consent form prior toparticipating in thestudy. All procedures were approved by the university's InstitutionalReview Board prior to anytesting being conducted.

Table 1. Subjects( n = 7 Sdemographicsand maximumstrength

Agefyrs.j

Mean 24.1

SD 3.1

Height (cm)

179.3

4.6

Mass (kg)

85.7

11.2

10RM Squat ( k g )

105.0

26.9

in the tested free-weightexercises.

10 RM DL(kg)

107.2

30.6

lORMLC(kg)

58.613.1

DL=deadlift, LC=leg carlDesign:A randomized experimental cross-over design was used inthis investigation. Each subject completed four days of testing, and sessions were separated byat least forty-eight hours. Subjects were asked to refrain from strenuous physical activity duringthis time, andfor tw o days prior to theinitial testing session, in aneffort to prevent soreness and

gBefromiafl]session.!

half hoescribed caloriiaght squattingcii session.

fen tasted forth

at SO1

aniies obetween

Three


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Effects of Chocolate Milk and Resistance Training 27

S Bfe e efficacy of"ficat and chronicCHO plus PRO

: in activities that;'following tbek to PRO ratio ofing the ability toup et al, 2006).sased insulin and

cogen depletingerage because of;,and availability

femance duringled than they ant better physiag in an effort5004). Howevogi on RPE or acuteFfhis study was tovery beverage fay

lower-extremity

[ticipated in thisnaximum (IRM^S ebody resistancte months prior to'led in thetraining~Hit form prior toit s Institutional*

igtH exercises.

iORMLCfkg)

58.6

13.1

Ifeignwas used inlere separated bycal activity during

ait soreness and

&figuefrom influencing RPE, torque, or fatigue. Subjects were tested at the same time of daym each session. They were also asked to not eat or consume caloric beverages for at least oneand one-half hours prior to each testing session so that the effects of recent non-studyprescribed calories would be reduced. A similar dynamic warm-up consisting of various bodyweight squatting and lunging movements was performed by each subject at the beginning ofeach session.

Procedures:On the first day (Day 1) subjects' age, height, and mass were recorded. They wereAen tested for their 10RM on thebarbell back squat, deadlift,and machine leg curl exercisesasing a previously described protocol (Earle, 1999). For each exercise, this protocol requiredsubjects to perform ten repetitions at 50% oftheir estimated 1RM, five repetitions at 70%, three

repetitions at 80%, and one repetition at 90%, before performing up to three 1RM attempts.Three minutes of passive rest were allotted between warm-up sets, and five minutes wereallotted between maximum attempts. The exercise order was conducted at random for themaximum testing.On a subsequent day (Day 2) subjects performed a familiarization and testing session using anisokinetic dynamometer (Biodex Medical, Shirley, NY, USA). Subjects were positioned on theisokinetic machine using established procedures (Pincivero et al., 2003). Following severalsib-maximal familiarization repetitions, subjects completed five concentric knee flexion andextension trials on the dynamometer at both 60 and 120 deg-s"1. The trials were consecutivewithin each angular velocity condition, and three minutes of rest were allotted betweenconditions. The peak flexion andpeak extension values from each condition were recorded.Theorder of the peak torque trials were performedrandomly. Following thepeak torque trials, ameasure of fatigue was conducted over thirty consecutive knee flexion and extensionrepetitions at 180 deg-s"'using previously described methods (Pincivero et al., 2003). One kneeextension performance followed immediately by one knee flexion performance equaled onerepetition. Three minutes of passive rest were provided between all isokinetic testingconditions.

Session 1 :Performed 1RM tests

Session 2:Baseline isokinetic testing

Session 3 :Cpmpleted strength trainingsession, consumed placebo

OR supplement, &performed isokinetic testing

Session 4:Cpmpleted strength trainingsession, consumed placebo

OR supplement, &performed isokinetic testing

Figure 1 : Temporal outline of testing sessions

The procedures each subject performedon Day 3and Day 4were identical, with the exception ofwhichbeverage (placebo or supplement) was ingested followingthe resistance training protocol.On these days three sets often repetitions were performed on thebarbell back squat,deadlift,and


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28 Brian J . Wallace an d Mark G. Abel

machine leg curl exercises, at 100% of each subject's 10RM as tested on Day 1. Two minutes ofpassive rest were given between sets of the same exercise, and five minutes were given betweenexercises. If ten repetitions were not completed at the 10RM weight during a set, the prescribedweight for subsequent sets was reduced accordingly. Five minutes following the completion ofthe training bout, subjects drank either a non-caloric artificially sweetened placebo or skimchocolate milk (supplement: 32 g carbohydrate and 8 g protein per 237 ml) in random order. Eachsubject was provided with a beverage volume equivalent such mat the supplement contained 0.5 gCHO-kg"1 of body mass. The placebo and supplement beverages were provided to each subjectinequivalent volumes, and were consumed as quickly as tolerable. Subjects rested passively for onehour following the completion of the training protocol. At that time subjects were asked to ratetheir perceived exertion (Table 2) of the workout they had completed, as this time frame has beensuggested to be a better gauge of RPE following a resistance exercise bout than RPE fromimmediately after the session (Sweet et al., 2004). They were men tested on the isokineu'cdynamometer using the same procedures described for testing on Day 2 . A temporal outlineof thetestingprocedures is shown inFigure 1 .

StatisticalAnalysis:The raw data from the isokinetic tests were exported into a spreadsheet(Excel, Microsoft Corporation, Redmond, WA, USA), where the peak flexion and extensiontorques were calculated in absolute (Nm), normalized (Nm-kg"1), and scaled (Nm-kg"67) formats

to account for the effect of body mass on torque. At the 60 and 120 deg-s"1

conditions the peakconcentric flexion and extension value from each set were analyzed. Fatigue indexes werecalculated at the 1 80 deg-s"1 trials from each of the testing sessions as:

Percent fatigue = 100 [{last 5 repetitions/first 5 repetitions} x 100] (Pincivero etal., 2003).

Descriptive statistics were calculated for subject demographics, RPE, torque values, andfatigue. Two repeated measures analysis of variance (RMANOVA) (SigmaStat, Version 3.10.San Jose, CA) were used to determine the effect of supplement (baseline vs. placebo vs.supplement conditions) and angular velocity (60 deg-s"1 and 120 deg-s"1) on peak flexion andextension torque values. Two additional RMANOVAwere used to determine the effect of thesupplement (baseline vs. placebo vs. supplement conditions) on the knee flexion and extensionfatigue indexes (180 deg-s" 1). The Holm-Sidak procedure was used for post-hoc comparisons.A Wilcoxon test was performed to determine if RPE varied between the placebo and

supplement conditions. Significance was set atp


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30 Brian J. Wallace and Mark G. Abel

person has the psychological perception that they are less fatigued than they physiologicallyare, they may put forth more effort during exercise than they would if their own perception oftheir physiological fatigue was greater. This increased effort may result in better physicalperformance (Sayers, 2007). In addition to the perception of the workout being easier,subjects performedbetter on some performancemeasures, as shownby the knee flexion fatigueindexdata.

Figure 2. Extension and flexion percent fatigure at ISO deg.s

*Signif icant lyless than placebo. p


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Effects of Chocolate Milkan d Resistance Training 31

sey physiologiesrwra perception^I m better

f f c o u tbeingfeaee f lexion1

acesisnotaffeW7). Additionen a placeboand sof chocolate:tation resulted in s iredtoaCHOoalylmt and colleaguesih chocolate milk;ause of the calorie /canee between ourexercise and RPEcycling,and haveaining and used a

aed in theplacebo :ies, regardless oflost active duringlisted of moderatewjuld require fasta when depleted,were not reducedear as a result ofscause peak forceId be expected toable effect on the

:seasured torques, likely becausethe measurements were taken onlyone hour after thecompletion o f the exercise protocol. This short time period may not have been long enoug h foraftammatory and decretory responses to occur and have aneffect on the measuredpeak torques(Nikolaou etal., 1987). It is also possible thatthe training status o fthe subjects ledlo reduced z-line streaming than what wouldbe seen in lesser trained individuals, whichwouldlead toreduced cross-bridge disruptionand greater peak force retention (Proske andMorgan,2001).

It has been shown in cycling that aCHO plus PRO beverage can increase performance inactivities that rely primarily on glycolysis for energy(Karp et al., 2006; S aunders etal., 2004).Our results show that, after resistancetraining, the ability to maintain torque output over thirtyrelatively high velocity repetitions was maintained betterafter consuming the supplementcomparedto the placebo.Withknee flexion , the supplement led to sign ificantly reducedfatiguethan the placebo at 120 deg-s"'.In knee extension there w ere differencesin the same direction,but the results wereno t significant. These finding smay have occurreddue to thenutritionalcontent provided in the supplement. Specifically, due to the relatively high CHO content ofchocolate milk, glucose was readily availableto provide energyfor muscle contraction.Theadditional glucose available m ay have reduced fatigueby increasingAT P availability.Previous investigations have foundpositive benefits of CHO plus PRO supplementation onanaerobicperformance. However, these studieshaveused 2-3 times thevolumeof supplementcompared to the volume used in this study (Karp etal., 2006; S aunders etal., 2004). In aneffort:o keep the volume consumed at a level that would be com fortable for most people to con sumefollowing resistance training, w e controlled the volume such that total carbohydrate content

was equal to 0.5 g-kg'. Forexample, an 82 kgperson consumed 296 ml offluid for bothconditions. Other studies have used1.0-1.4 g-kg"' ,which would result in at least double thefluid consumption (Karpet al., 2006; Saunders et al., 2004). If a larger volumeof chocolatemilk w as consumed, larger im provements may hav e been shown in the fatigue index betweenthe placeboand supplement c onditions.In conclusion, although we found that the chocolate milk condition reduced fatigue,wecompared it to a non-caloric placeboand not anon-dairy beverage equalin calories withasimilar m acronutrient makeup. F uture investigations should compare such beverages, sincethescopeof ourstudywas to investigateif chocolate milk couldbe an adequate recovery beveragefrom resistance exercise,no thow it com pares to other caloric drinks. Based on the resultsfoundin cycling, we w ould expect that if we had d one this our resultswouldbe of similar direction,but lower magnitude than were shown (Karp etal., 2006). Consuming a greater volume ofsupplement islikely necessaryin order to achieve maximum benefits. However,our resultssuggest that consuminga volumeof chocolate milk witha CH Ocontent equalto only 0.5g-kg 'results in some positive benefits over consuminga beverage of no caloric value. Athletesandemergency rescue personnel may experience a reduced RPE and ac utely improve measures ofsarengthby consuming chocolate m ilk between boutsof high intensity activity.

ReferencesBora G. (1970). Perceived exertion as an indicatorof som atic stress.Scandinavian Journal of Rehabilitative

Medicine,2,92-98.Burke L., Collier G., and Hargreaves, M. (1993). Muscleglycogenstorageafter prolongedexercise:e ffec tof the

glycemicindexof carbohydratefeedings.Journalof Applied Physiology,75(2), 1019-1023.


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32 BrianJ. Wallace an d Mark G. Abel

Cheuvront S., Moffatt R., Biggerstaff K., Bearden S. and McDonough P. (1999). E f f e c t ofEndurox on metabol icresponsesto submaximal exercise. International Journal of Sports Nutrition, 9(4),434-442.

Connolly D. Sayers S. and and McHugh M. (2003). Treatmentand preventionof delayed onset muscle soreness.Journal of Strength and ConditioningResearch, 17(1), 197-208.

de Soua M., Simoes H., Oshiiwa M. and Rogero M. and TirapeguiJ. (2007). E f f e c t sof acutecarbohydrate supplementationduring sessionsofhigh-intensityintermittentexercise.European Journal of Applied Physiology, 99(1),57-63.

Earle R. (1999). Weight TrainingExercisePrescription,in Essentialsof Personal Tra in ing Sym posium Workbook .Lincoln, ME :NSCA Certification Commission.

Esmarck B., Andersen J., OlsenS., Richter E., Mizuno M., and Kjaer M. (2001). Timingof postexercise protein intakeis importantfor musclehypertrophywith resistance train ingin elderfy h u m a n s .Journal of Physiology, 535(1),301-311.

Ivy J., Goforth H., Damon B., McCauley T., Parsons E. and Price T. (2002). Early postexercise m uscle glycogenrecoveryis enhancedvfith a carbohydrate-proteinsupplement.Journal of Applied Physiology, 93,1337-1344.

Ivy J. and Portman R. (2004). Nutrient Timing.North Bergen, NJ: Basic HealthPublications, Inc.

Ivy J., Res P., Sprague R., and Widzer M. (2003). E f f e c t of a carbohydrate-proteinsupplementon enduranceperformance during exerciseof varying intensify. International Journal of Sports Nutrition and ExerciseMetabolism, 13(3), 382-395.

Karp J., Johnston J., Tecklenburg S., Mickleborough T, , Fly A. and Stager J. (2006). Chocola te mi lkas a post-exerciserecoverya id .International Journal of Sports Nutrition and Exercise Metabolism, 16( 1), 78-91.

Levenhagen D., Gresham J., Carlson M., Maron D., Borel M. and Flakoll P. (2001). Postexercise nutrient intaketiming in h u m a n sis crit icalto recoveryof leg glucoseand protein syn thesis.American Journal of PhysiologyEncocrinology and Metabolism, 280, E982-E993.

Miller S., Tipton K., Chinkes D., Wolf S. and Wolfe R. (2003). Independentand combinede f f e c t sofaminoac idsandglucoseafter resistance exercise.Medicine and Science in Sports and Exercise, 35(3), 449-455.

Nikolaou P., MacDonald B., Glisson R., SeaberA., & Garrett W. (1987). Biomechanical andhistological evaluationof muscleafter controlled straininjury.American Journal of Sports Medicine, 15( 1), 9-14.

PinciveroD., GandaioC. and YoshihikoI. (2003). Gender-specific k n e eextensortorque,flexor torque,and musclefa t igue responses dur ing ma ximale ffo r tcontractions.European Journal of Applied Physiology, 89,134-141.

ProskeU. and Morgan D. (2001). M u s c le d a m a g efw m eccentric exercise:mechanism, mechanical signs, adaptationand clinicalapplications.Journal of Physiology, 537(2), 333-345.

Roy B., Tamopolsky M., MacDougall J., Fowles J., and Yarasheski K. (1997). E f f e c tof glucose supplement t imingonprotein metabolismafter resistance training .Journal of Applied Physiology, 82(6), 1882-1888.

SaundersM., Kane M. and Todd M. (2004). E f f e c t sof a carbohydrate-protein beverageon cycling enduranceandmuscle damage.Medicine and Science in Sports and Exercise, 36(7), 1233-1238.

Sayers S. (2007). High-speedpower t ra in ing:A novel approachto resistance train ingin older men and w o m e n .Abrief reviewand pilot study.Journalof Strength and Conditioning Research, 21(2), 518-526.

Schisler J. and lanuzzo C. (2007). Running to m ainta in card iovascularfitness is not l imitedby short-term fasting orenhancedcarbohydra tesupplementation.Journal of Physical Activity and Health, 4(1), 101-112.

Sweet T., Foster C., McGuiganM. and Brice G. (2004). Quantification ofresistance training usingthe session ra tingofperceived exertion method.Journal of Strength and Conditioning Research, 18(4), 796-802.

Zawadzki K., Yaspelkis B. and Ivy J. (1992). Carbohydrate-protein complex increasesthe rate of muscle glycogenstorage after exercise.Journal of Applied Physiology, 72(5), 1854-1859.

AcknowledgementsThe authors report no conflicts of interest with the placebo or supplement used in thisinvestigation. No source of financial support was used fo r this study.

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