issues_2001_the aerobic mechanism in the 400 metres

15New Studies in Athletics • no. 2/2008

Introduction

n the past, the 400 metres has gen-erally been considered to be a high-ly anaerobic race. LACOUR et al.

(1990), for example, estimate the aerobiccomponent at just 28%, NEWSHOLME et al.(1992), state that only 25% of the energy

comes from the aerobic mechanism andFOSS & KETEYAN (1998) even go so far as totalk of an 18% aerobic contribution. However,some authors have shown higher values forthe aerobic quota. NUMMELA & RUSKO(1995) and HILL (1999), for example, bothcalculate minimum values for the aerobic fac-tor at 37%, for DUFFIELD et al. (2005) it is 41-45% and for WEYAND et al. (1994) the inter-vention of the aerobic mechanism is actuallymore important in terms of percentage (equiv-alent to 64-70%) than the anaerobic mecha-nisms (see Table 1).

In this article we make an in-depth exam-ination of the current knowledge of theenergetic characteristics of the 400m andtry to understand why the differentresearchers who have been concerned withthe subject furnish very different data on thecontribution of the aerobic mechanism.

© by IAAF

23:2; 15-23, 2008The aerobic mechanismin the 400 metres

By Enrico Arcelli, Marina Mambretti, Giuseppe Cimadoro, GiampieroAlberti

I

The 400m is generally considered to be ahighly anaerobic race, but the findings ofvarious researchers on the percentagecontributions of anaerobic and aerobicenergy mechanisms are not consistent.Drawing on a selection of publications,this article looks at how the energeticcharacteristics of the event are studiedand explains the reasons behind the vari-ation in findings. It considers 1) differ-ences between men and women athletes,2) differences between sprinter andendurance type athletes, 3) the influenceof different methodologies and 4) differ-ences caused by the performance level ofthe athletes studied. The authors findthat performance capacity represents themost important quantitative factor forexplaining the different percentages ofintervention of the energy mechanisms.They also look at oxygen consumptionand suggest an increase in pH level in thefirst 150-200m inhibits Type II musclefibres from using the aerobic mechanismin the later stages of the race.

ABSTRACTEnrico Arcelli is a Professor in the Facultyof Exercise Sciences at the University ofMilan. He is a former Head Coach formiddle- and long-distance events for theItalian Athletic Federation (FIDAL). Marina Mambretti is a 400m runner.Giuseppe Cimadoro is a coach of sprintevents. Giampiero Alberti is a Professor in theFaculty of Exercise Sciences at the Uni-versity of Milan. He is a coach of sprintevents.

AUTHORS

LITERATURE REVIEW

Specifically, we look at 1) how the variousresearchers have studied energetic charac-teristics in the event; 2) the reasons why thepercentages of aerobic and anaerobic con-tributions are considered different by thevarious authors; 3) oxygen consumptionduring the 400m and, in particular, whyafter the initial phase of 400m race con-sumption of oxygen has a slight tendencyto come near to maximum while it tends toreduce in the final phase of the test, assome authors maintain.

How various researchers have studiedenergetic characteristics in the 400m

Researchers have employed various meth-ods to determine energetic characteristics inthe 400m. LACOUR et al. (1990), for exam-ple, have calculated the total energeticexpenditure by measuring 400m runners’peak blood lactate after the race and by esti-mating both the amount of oxygen used andthe amount of alactacid mechanism used onthe basis of data in the literature.

WEYLAND et al. (1993), NUMMELA &RUSKO (1995) and SPENCER & GASTIN(2001) simulated a 400m race on the tread-mill using the method suggested by MEDBOet al. (1988) to calculate the “accumulatedoxygen deficit”. Thus, in each athlete, the

energetic cost of the race was measured atvarious sub-maximal speeds, and by extrap-olation, the “estimated cost” at the speed atwhich the test was run. At this speed, theeffective oxygen consumption of the athleterepresents the aerobic component while thedifference between the “estimated cost” andeffective oxygen consumption, in fact, consti-tute what is defined as “accumulated oxygendeficit”, which corresponds to the anaerobiccomponent.

HILL (1999), in turn, made athletes run onthe treadmill to evaluate oxygen consump-tion. At the end of a 400m race run by thesame athletes, he obtained blood lactate val-ues in order to calculate the intervention of theglycolitic anaerobic mechanism.

Finally, DUFFIELD et al. (2005) made 11men and 5 women do a test run on a 400mtrack, during which they measured effectiveoxygen consumption with the Cosmed K4and determined the “accumulated oxygendeficit”. At the same time, they calculated theanaerobic intervention on the basis of theblood lactate levels taken after the test and ofestimate of the energy derived from phos-phocreatine. In practice, these authors simul-taneously evaluated 400m runners with thecriteria previously used by the other authorsmentioned.

New Studies in Athletics • no. 2/2008

The aerobic mechanism in the 400 metres

16

Table 1: Contribution of the aerobic energetic mechanism and anaerobic energetic mechanismsin the 400m according to selected authors (Data are recorded with values for the aerobic con-tribution in ascending order.)

Author(s) Publication Date Aerobic Contribution Anaerobic Contribution

Foss & Keteyan 1998 18% 82%

Newsholme et al. 1992 25% 75%

Lacour et al. 1990 28% 72%

Reis & Miguel 2007 32% 68%

Hill 1999 37-38% 62-63%

Nummela & Rusko 1995 37-46% 54-63%

Duffield et al. 2005 41-45% 55-59%

Spencer & Gastin 2001 43% 57%

Weyand et al. 1994 67-70% 30-36%

Reasons why the percentage of the aero-bic contribution is considered different bydifferent authors

Differences between men and womenFor the purposes of establishing a greater

or lesser level of intervention of the aerobicmechanism, we must first take into accountwhether the 400m runners are men orwomen. ARCELLI (1995) showed that whentwo athletes, one male and the other female,obtained identical results in the 400m (forexample 48 sec), the woman produced morelactic acid. Thus, since the energetic expendi-ture (expressed in ml/kg-1) is similar in bothathletes, and in the woman there is a greaterquantity of energy derived from the glycoliticmechanism, the percentage of aerobic workturns out to be higher in the man.

However, this is not true when consideringperformances that are not equal from achronometric point of view but do have acomparable value, so as, for example, to

occupy similar positions in male and femalerankings, respectively, on a national and worldlevel. WEYLAND et al. (1994), for example,indicate values for aerobic intervention thatare of 64-67% in men and 66-70% in women,for whom the aerobic mechanism thus turnsout to be more important than for men. HILL(1999) gives the aerobic mechanism 37% ofthe energetic contribution in men and 38% inwomen. In turn, DUFFIELD et al. (2005) showthe aerobic contribution as equal to 41% inmales and 45% in females. With all thingsconsidered, it can be said that the consensusof all of the authors we have referred to is thatin the 400m women athletes use a slightlyhigher percentage of aerobic energy (from+1% to +4%) when compared to men ath-letes (see Table 2).

Differences between sprinters andendurance athletes

The physiological characteristics of the ath-letes studied certainly influence the findingson the degree of intervention of the energetic



Table 2: Contribution of the aerobic and anaerobic energetic mechanism in male and female400m runners according to selected authors

Table 3: Contribution of the aerobic and anaerobic energetic mechanisms in the 400m per-formed by sprinters and by endurance athletes according to selected authors

Author(s) SubjectGroup

PublicationDate

AerobicContribution

AnaerobicContribution

Weyand et al. Men 1994 64-67% 33-36%

Weyand et al. Women 1994 66-70% 30-34%

Hill Men 1999 37% 63%

Hill Women 1999 38% 62%

Duffield et al. Men 2005 41% 59%

Duffield et al. Women 2005 45% 55%

Authors SubjectGroup

PublicationDate

AerobicContribution

AnaerobicContribution

Weyand et al. Sprinters 1994 64-66% 34-36%

Weyand et al. Endurance Athletes 1994 67-70% 30-33%

Nummela & Rusko Sprinters 1995 37.1% 62.9%

Nummela & Rusko Endurance Athletes 1995 45.6% 54.4%

mechanisms. In fact, “sprinter” type athletes(e.g. the ones who have good results in 200m)have greater anaerobic tendencies and hencederive a lower percentage of energy from theaerobic mechanism. The converse is true forrunners who are more inclined to longer dis-tances through genetics or training. WEYLAND et al. (1994), for example, showthat in sprinters the contribution of the anaer-obic mechanism is equal to 36% in men andto 34% in women athletes; however, inendurance athletes these authors determinedthe contribution to be 33% in men and 30%in women. In subjects that obtained 400mtimes that were approximately equal, NUM-MELA & RUSKO (1995) arrived at an aerobiccontribution of 37.1% in sprinters (averagetime 49.5 ± 6.0 sec) and 45.6% in enduranceathletes (average time 49.4 ± 5.3 sec). As canbe seen in Table 3, the aerobic mechanismintervention has been found to be 3-8% high-er in the athletes who come from longerevents.

Influence of methodologies usedThe criteria used to calculate the total ener-

gy expenditure and the intervention of theenergetic mechanisms are also important.DUFFIELD et al. (2005) obtained values forthe aerobic contribution that turned out to behigher when measured with the “accumulatedoxygen deficit” method (41.9% in men and44.5% in women) in comparison to dataderived from evaluation of the blood lactateand estimation of phosphocreatine consump-tion (39.2% in men and 37.0% in women).The difference between the two methods was6.1% in men and 7.5% in women respective-ly (see Table 4).

According to BANGSBO (1996), the“accumulated oxygen deficit” method tendsto underestimate the “estimated cost” inhigh intensity tests, which the 400m can beconsidered. In this way, the percentage ofaerobic intervention was overestimatedwhile the percentage of anaerobic interven-tion was underestimated. Moreover, it isentirely probable that in the final stretch ofthe 400m, there is an increase in the cost ofthe run.

HILL (1999) states that in laboratory exper-iments on the treadmill (as in NUMMELA &RUSKO, 1995, SPENCER & GASTIN, 2001,and WEYLAND et al., 1993) athletes are lessmotivated than in races and it is quite likelythat this enables them to obtain the maximumintervention of the aerobic mechanism but notof the anaerobic mechanism. This point couldalso apply to the findings of DUFFIELD et al.(2005), who evaluated lactate production inrunners during a test on the track that simu-lated a race but that was not competition. Itshould be noted that only LACOUR et al.(1990) and HILL (1999) evaluated lactate pro-duction in race conditions.

Differences caused by performance levelAt this point, we can establish how much

influence the different performance levels ofthe athletes studied have in determining thedifferent contributions of the energetic mech-anisms. Table 5 shows various data in the lit-erature for male and female 400m runners.For the women, when performance in the400m gets worse, there does not seem to bea corresponding increase in the percentage ofaerobic work. However, in the case of the



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Table 4: Contribution of the aerobic and anaerobic energetic mechanisms in 400m tests evalu-ated with two different methods reported by Duffield et al. (2005)

Method Subject Group Aerobic Contribution Anaerobic Contribution

Accumulated oxygen deficit Men 41.9% 58.1%

Accumulated oxygen deficit Women 44.5% 55.4%

Lactate + phosphocreatine Men 39.2% 60.8%

Lactate + phosphocreatine Women 37.0% 63.0%

men, taking into account that the values werecalculated with dissimilar criteria and withgreater inclinations towards sprinting ortowards endurance tests, it can be noted thatthe better the results, the lesser the aerobiccontribution.

In any event, this result becomes moreevident if, based on the literature on the sub-ject, a theoretical calculation of the energeticcharacteristics in terms of the times obtainedfor the 400m is carried out, as indicated inTable 6.

In Table 6 it is possible to see that theanaerobic contribution (of which the pre-dominant part is glycolitic) falls rapidly witha decrease in the 400m performance levelof the subject athletes. In fact, the reduc-tion is greater than the decrease in the totalexpenditure. Passing, for example, from atime of 44 sec to a time of 48 sec, the totalexpenditure falls from 119.2 to 104.4 ml/kg-1,a percentage fall of 12.4%. At the same

time, the anaerobic work carried out pass-es from 90.1 to 70.1 ml/kg-1, a reduction of22.2%. If, instead, the performance goesfrom 48 to 52 sec, the total expenditurefalls from 104.4 to 93.4 ml/kg-1, (a fall of21.6%), while the anaerobic work goesfrom 70.1 to 53.2 ml/kg-1 (a fall of 41.0%).At the same time, the aerobic contributionincreases as a consequence of the extend-ed duration of the race, being 24% for aperformance of 44 sec, 33% for 48 sec and43% for 52 sec.

In the first moments of a 400m race therunner utilises mainly anaerobic mechanisms,since the quantity of oxygen he/she can man-age to use is limited, but as the time of phys-ical exertion is prolonged the use of oxygen isincreased.

In other words, it happens that on the onehand, the faster athlete produces morelactate and on the other, has less possibility ofusing the aerobic mechanism. Thus for



Table 5: Performance level and percentage of aerobic contribution in the 400m found by select-ed authors

Author(s) andSubject Group

PublicationDate

Average performancefor the 400m (sec)

AerobicContribution

Male Subjects

Lacour et al. 1990 45.48-47.46 28.0%

Hill 1999 49.3 37.0%

Spencer and Gastin 2001 49.3 43.0%

Nummela & Rusko (endurance athletes) 1995 49.4 45.6%

Nummela & Rusko (sprinters) 1995 49.5 37.1%

Weyand et al. (sprinters) 1994 50.5 64.0%

Reis & Miguel 2007 50.6 32.0%

Duffield et al. 2005 52.2 41.3%

Weyand et al. (endurance athletes) 1994 58.5 67.0%

Female Subjects

Weyand et al. (sprinters) 1994 57.9 66.0%

Duffield et al. 2005 60.2 44.5%

Weyand et al. (endurance athletes) 1994 70.6 70.0%

Hill 1999 71.2 38.0%

Calculating Energy Expenditure in the 400m

Energetic expenditure for 400m runners can be considered as equal to: Cna + Ca + Ck,

In this sum:• Cna is the non-aerodynamic cost of the run, that is, according to DI PRAMPERO (1985),

the energy the athlete expends (1) to lift his/her body at every stride; (2) to accelerate thecentre of gravity at every stride; (3) for friction at the point where the foot meets theground; (4) for the internal work load; (5) for the muscular contractions necessary to main-tain posture; (6) for the work of the respiratory muscles and the heart;

• Ca is the cost to overcome air resistance;• Ck is the cost to accelerate the body in the start phase of the race.

The energetic expenditure of the run, including the non-aerodynamic component and thecomponent to overcome air resistance (Cna + Ca), is constant and expressed in ml of oxygenper kg of body weight and per km run. According to ARCELLI et al. (2006), it is equal to 4v2 – 25 v + 175, with v being the speed of the athlete in m/s-1.

Since the distance of the race is 400m (= 0.4 km):

• Cna + Ca = 1.6 v2 – 10 v + 70

This cost is expressed in ml/kg-1.

The cost to accelerate the body – also expressed in ml/kg-1 – is, according to ARCELLI andDOTTI (2000), as follows:

• Ck = 0.0957/v2.

The energetic expenditure to run 400m is sustained by the intervention of different energeticmechanisms. Thus:

Cna + Ca + Ck = Laer + Llatt + Lalatt.

• By Lae we mean the energy derived from the aerobic energetic mechanism; • By Llatt, we mean the energy derived from the anaerobic lactacid mechanism. • By Llatt, we mean the energy derived from the anaerobic alactacid mechanism.

As far as Llatt is concerned, LACOUR et al. (1990) found that the lactate produced in the400m race turned out to be equal to 8.8 v – 54.3, with v being the average speed in m/s-1.In this case, the formula these authors indicated for times between 45.45 and 49.07 sec isextrapolated for both slightly better and considerably worse performances. A caloric equiva-lent for lactate equal to 3 ml/kg-1 for each 1 mmol/l-1 increase of blood lactate with respect tothe basal count (considered as equal to 1 mmol/l-1) must also be taken into account. Lalatt,then, must be considered as equal to 16 ml/kg-1. Laer is then calculated by difference, thatis to say, by subtracting Llatt + Lalatt from Cna + Ca + Ck.

In this way, we derived the data used to construct the last four columns of Table 6.



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him/her, anaerobic intervention is more impor-tant. The contrary is true of the slower runner,who uses a greater quantity of energy fromthe aerobic mechanism. The better the per-formance, the greater the anaerobic contribu-tion and the lesser the aerobic contribution.

Performance capacity, therefore, definitive-ly represents the most important quantitativefactor for the purposes of explaining the dif-ferent intervention of the aerobic mechanism.

Figure 1 shows the curve of the contribu-tion of the aerobic mechanism for male run-ners in percentage according to performance

times, calculated theoretically on the basis ofwhat has been stated above and the datagiven in Table 5.

Oxygen consumption during the 400m andmaximum oxygen consumption

Athletes never reach their maximum oxygenconsumption (VO2max) in the 400m. Accord-ing to NUMMELA & RUSKO (1995), they havea peak oxygen consumption that is equal to79% VO2max; according to SPENCER &GASTIN (2001), they reach 89%; according toDUFFIELD et al. (2005), both men andwomen use 81.6%. NUMMELA & RUSKO



Table 6: Fall in the total energetic expenditure and anaerobic contribution with slower perform-ances in the 400m (male athletes only)

Figure 1: Contribution of the aerobic mechanism in the 400m for male runners by race timeaccording to selected authors (Note both Nummela & Rusko and Weyand et al. show separatedata for sprinters and endurance athletes; the straight line shows the contribution of the aero-bic mechanism according to performance time calculated theroreticly on the basis of data givenin Table 3.)

400m performance(sec)

Energeticexpenditure(ml/kg-1)

Anaerobiccontribution(ml/kg-1)

Anaerobiccontribution (%)

Aerobiccontribution(ml/kg-1)

Aerobiccontribution (%)

44 119.2 90.1 75.6 29.1 24.2

46 111.1 79.7 71.7 31.4 28.3

48 104.4 70.1 67.1 34.3 32.9

50 98.5 61.3 62.2 37.2 37.8

52 93.4 53.2 56.9 40.2 43.1

also found that after mid-race, oxygenconsumption never tended to increase andthat, in both in sprinters and endurance ath-letes, it even tended to reduce in the laststretch. According to REIS & MIGUEL (2007),in the course of a 400m race simulation, run-ners barely reached 63% of their maximumrate of oxygen consumption in the final part ofthe race.

In tests where VO2max was determinedduring the run, higher values were reached.Thus it happened that, in the time phase inwhich the efficiency of oxygen contributionto the muscles increases, running speed islow or medium-low and in the musclesemployed, Type I fibres (aerobic musclefibres that can externalise reduced strengthvalues) are mainly used. Only in the laterphases of the race, when the intensity isalready close to or above VO2max and whenthe mechanisms that allow the arrival of oxy-gen in the fibres are already activated, doType II fibres work intensively, and thesefibres are on the average endowed withgreater levels of strength. Instead, even atthe start of the 400m, when the oxygen con-tribution to the fibres is still not very high,since the running speed is very high, a signif-icant percentage of Type II fibres are calledupon to work, both of the Sub-type IIa, aswell as the Sub-type IIx (those that, in olderterminology were called IIb); but the latter arenot very resistant.

We think that the explanation for the factthat after 150-200m in competition theconsumption of oxygen has a minimum oreven zero tendency to increase and comeclose to VO2max levels, and that it eventends to become lower in the final phase ofthe race (NUMMELA & RUSKO, 1995), isthat many of the Type II fibres are placed“out of action” since they have arrived at acritical pH level. Thus, because of the inhi-bition of glycolysis enzymes, they cannotuse the aerobic mechanism. This might alsobe the reason for the decrease in strengthafter the first 100m found by NUMMELA etal. (1992).

Conclusion

Both aerobic and anaerobic (alactic andlactic) mechanisms provide the requiredenergy in the 400m. Many researches havetried to show the percentage of the totalenergy provided by these mechanisms but,unfortunately, their findings have divergedgreatly.

We have identified several aspects thatcan affect the findings of research in thisarea. One of these is the gender of theathlete. Considering the same national andinternational ranking, women use the aero-bic mechanism more than men. It is alsoimportant to consider the physiologicalabilities of a 400m runner. Sprint type athletes(e.g. the ones who have good results in the200m) use anaerobic mechanisms morethan those athletes who have higher aerobicabilities through genetics or training. Anothersignificant aspect that can affect theobtained results is the different methodolo-gies used in the research. Based on analyti-cal evaluations of literature data, we havedetermined that the slower the performance,the greater the aerobic contribution and thatperformance level is the most important fac-tor in the relative contribution of the severalenergetic mechanisms.

We also looked at how the oxygen uptakechanges during the 400m. It does not reachthe maximum value (VO2max), and in the finalpart of the race it slightly decreases. Oneexplanation is that the increased pH levelcaused by the anaerobic work done in thefirst part of the race inhibits the glycolysisenzymes and thus stops the Type II musclefibres from using the aerobic mechanism.

Further analysis is required to understandthe factors responsible for this reduction ofoxygen consumption, and how the consump-tion can differ between different athletes.

Please send all correspondence to:Giampiero [email protected]



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ARCELLI, E. (1995). Acido lattico e prestazione. Vigevano:Cooperativa Dante editrice.

ARCELLI, E. & DOTTI, A. (2000). Mezzofondo veloce. Dallafisiologia all’allenamento. Roma: FIDAL.

ARCELLI, E.; LA TORRE, A.; DOTTI, A. & ALBERTI, G. P.(2006). Origine dell’energia e spesa energetica nei 100metri, Atleticastudi, 1, 3-10.

BANGSBO, J. (1996). Oxygen deficit: a measure of the anaerobic energy production during intense exercise? Canadian Journal of Applied Physiology, 21 (5):347-349.

DI PRAMPERO, P.E. (1985). La locomozione humana suterra, in acqua, in aria. Edi-Ermes editore, Milano.

DUFFIELD, R.; DAWSON, B. & GOODMAN, C. (2005).Energy system contribution to 400 metre track running.Journal of Sports Sciences, 23, 299-307.

FOSS, M.L. & KATEYAN, S.J. (1998). Fox’s PhysiologicalBasis for Exercise and Sport, 6th edition. Dubuque:McGraw-Hill (cited by Hill, 1995).

HILL, D.W. (1999). Energy system contributions in middledistance running events. Journal of Sports Sciences, 17,477-483.

LACOUR, J.R.; BOUVAT, E. & BARTHÉLÉMY, J.C. (1990).Post-competition blood lactate concentration as indicatorsof anaerobic energy expenditure during 400m and 800mraces, European Journal of Applied Physiology, 61,172-176.

LETZELTER, S. & EGGERS, R. (2006). L’andamento dellavelocità nei 400 m delle atlete e degli atleti di classe mon-diale, Atleticastudi, 2, 19-28.

MCARDLE, W.D.; KATCH, F.I. & KATCH, V.L. (1998). Fisi-ologia applicata allo sport (Table 7.1, p. 132). Milano: CasaEditrice Ambrosiana,

MEDBO, J.I.; MOHN, A.C.; TABATA, I.; BAHR, R. & VAAGE,O. (1988). Anaerobic capacity determined by maximal accu-mulated O2 deficit. Journal of Applied Physiology, 64, 50-60.

NEWSHOLME, E.A. et al. (1992). Physical and mentalfatigue, metabolic mechanism and importance of plasmaamino acids. British Medical Bulletin, 48, 477 (cited byMcArdle et al.,1998).

NUMMELA, A. & RUSKO, H. (1995). Time course of anaer-obic and aerobic energy expenditure during short-termexhaustive running in athletes. International Journal ofSports Medicine, 16, 522-527.

NUMMELA, A.; RUSKO, H. & MERO, A. (1994). EMGactivities and ground reaction forces during fatigued andnonfatigued sprinting. Medicine and Science in Sport Exer-cise, 26: 605-609, 1994.

NUMMELA, A.; VUORIMAA T. & RUSKO, H. (1992).Changes in force production, blood lactate and EMG activ-ity in the 400m sprint. Journal of Sports Sciences, 10, 3,217-228.

REIS, M. & MIGUEL, P. (2007). Changes in the accumulat-ed oxygen deficit and energy cost of running 400 metres.New Studies in Athletics, 22, 2, 49-56.

SPENCER, M.R. & GASTIN, P.-B. (2001). Energy systemcontribution during 200- to 1500-m running in highlytrained athletes. Medicine and Science in Sports and Exer-cise, 33, 157-162.

WEYAND, P.G.; CURETON, K.; CONLEY, D. S. &SLONIGER, M. A. (1993). Percentage anaerobic energyutilized during track running events. Medicine and Sciencein Sports and Exercise, 25, S105, 1993.

WEYAND, P.G.; CURETON, K.; CONLEY, D. S.; SLONIGER,M. A. & LIU, Y. L. (1994). Peak oxygen deficit predicts sprintand middle-distance track performance. Medicine andScience in Sports and Exercise, 26, 9, 1174-1180.

REFERENCES

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