Effect of experimental alterations in excess weight on aerobic capacity

MEDICINE AND SCIENCE IN SPORTS Vol 10. No. 3. pp. 194-199. 1978

Effect of experimental alterations in excess weight on aerobic capacity and distance running performance K. J. CURETON, P. B. SP.4RLING. B. W. EVANS, S. M. JOHNSON, U. D. KONG, .AND J. W. PURVIS Human Performance Lclboratory Dicision of Health, Physical Educutwn and Rec~eation Unicersity of Georgia Athens, Georgia 30602

ABSTRACT CURETON. K.J.. P.B. SP.lFiLING, B.W. EVANS, S.%1. JOHNSON. U.D. KONG, and J.W. PURVIS. Effect of experimental alterations in excess welght on aerobic capac~tvand distance running performance. .Med. Sci. Sports. Vol. 10, No. 3, pp. 194-199, 1978.-To experimentallv investigate the effect of excess bodv weight or fat on maximal oxvgen uptake (V* max) and distance running performance, the metabolic response to maximal and submaximal treadmill runninq and the 12-min run performance were measured In SIX subjects under each of four added-weiqht (AW) conditions: normal bodv w e ~ & tand 5. 10. and 15% additional external welqht, added to the trunk. AW was found to svstemat~callvand sisp~hcantlvdecrease V* rnax expressed relative to the total w e ~ q h tc a r r ~ e dtml/min.kg TI!'), maxirnal treadmill (TM)run t ~ m and e 12-rnln run distance, but not to svstematicallv affect V* rnax 1 llmini or V*max (ml/min.kq FFW). An Increase of 5% A\V was found, on the averaqe, to d e c r e a e V s ma.; cml/ min-kg TIV) 2.4 rnl. the TSI run time 35 sec and the 12-min run distance 89 m. These decreases were a direct consequence of the increased e n e r q cost of runnlnK at submax~malspeeds. It was concluded that chanqes in excess bodv weiqht can Influence V s rnax expressed relative to b d v weiqht and distance run performance independent of anv chanqe in cardiovascular capacltv. Failure to d~stinmishthe metabol~ceffects of hodv fatness from the influence of cardiorespiratorv capacitv rnav result in mislead~nq interpretation of distance nm test scores.

BODY COXIPOSITION. 5lAXIMAL OXYGEN UPT;IKE, ENDURANCE PERFOHMASCE

Distance running performance tests. due to their rnoderatelv-high, pos~tiverelationship with maximal oxvgen ) relative to hodv 'iveiqht iml/ uptake lVoz ~ n a x expressed rnin-kg BW), have been interpreted as indicative of cardiovascular fitness ( 6 ) ,cardiorespiratory endurance I 23). or cardovascular eficiencv ( 1). implyins that individual differences in performance on these tests predomlnatelv reflect variations in cardiorespiratorv capacity. .Although Vo2 mas iml/rnin.kq B\\'\ is. theoretically. an important determinant of tasks r e c ~ u i r i nrelativelv-prolond. ~ exhaustive. ~ v e i ~ h t - l ~ e a r work i n c such as distance rilnnlnq (.7,3) and moderatelv hich relatio~ishipshave I~eenfound S ~ ~ l , r n ~for l l dm ~ l , l ~ c a t t oonv r r n l , e r . 1477

\cceptd tor n~~nllcatlon Fel~rrlarv.1Y74.

between distance running performance tests and Voz rnax (ml/min.kg BCV) (3,6,11,15,20), the v a l i l t y of interpreting &stance run test scores as measures of carlorespiratory capacity in groups of normal indviduals mav be questioned. In populations of individuals who vary in bodv composition, Vo2 rnax (ml/min.kg BW) is not a pure measure of carlorespiratory capacity, but also reflects differences in body fatness (5,9,25). Bodv fat. hecause it increases the I)odv weight without contributing to the bodv's capacity to utilize oxygen, lowers the V O ~m a (rnl/min.kg BW). \loderate. inverse relationships have been reported between percentase bodv fat (% fat) andVo2 rnax (ml/rnin.k? BIV) in various groups of subjects (5.8.11.12.16.25). Furthermore, when C'oq lnax is expressed relative to fat-free \veiqht (FF\V), correlations with distance running performance have been found to be considerablv '-lower (8,12!.16). suggestinq that part of the higher relationships hetween vo2 jml/min.kq BLVI and distance running performance is due to the influence of bodv fatness on V O ~max tml/min.kg BD'). T h e influence of bodv fatness on distance run performance is generally not considered in interpretations of distance n m tests (1,6,23). hlanv studies. however. have reported si_pificant,inverse relationships between bodv fatness and l s t a n c e running performance or related tests of physical work capacity (5,10,11.12.16.17.18,27~,which suqgests that body fatness is a factor that influences d s tance running performance. Buskirk and Tavlor (3) and iVelch et al. (25) have hvpothesized that bodv fat should decrease performance in relativelv-prolonged. exhaustive. weight-bearing work such as &stance runninq because 1)ody fat increases the total bodv weight and. therefore. the ener? requirement of performine anv given level of \vork. without a correspondne increase in maximal oxvSen uptake. Recognuin2 the rneta1)olic etfect of 1)ody fatness and cardiol-espiratory capac~tyas separate tactors inHuencing tl~stanceI-unninq performance 1s Important 51nc.e the two have different 111edicali~llplicatio~ih. Pool- clistance 1.~111-

EXCESS WEIGHT,

\jo2 MAX AND

ninq capability and low Vo2 max (ml/min-kg BW), although indicative of poor physical work capacity, are not necessarily incliiative of poor cardiorespiratory function due to pathological impairment or inactivity. The distinction is also important in accurately interpreting distance r u n test scores in t e r m s of t h e i r t r u e biological determinants. The present study was conducted to experimentally investigate the influence of excess weight on maximal oxygen uptake and distance running performance. The objective was to use the addition of external weight to the body as a model to investigate the consequences of changes in body fatness on Vo2 Inax and runniny: performance.

METHODS The subjects (Ss) for this studv were six young adults. four males and two females, who regularlv engaged in distance n~nninq.Trained rather than untrained individuals were selected as subjects because it was assumed thev could more effectively pace themselves during the distance run tests and had greater pro1)al)ility for sr~ccesshl completion of the 5-week studv without the occurrence of a training effect due to the testing or attrition due to injurv or sickness. The Ss were all volunteers who gave informed consent. The experiment was condi~ctedover a %week period. Durinq week 1, i u ~ t h r o p o ~ ~ ~ eand t r i choclv composition ilieasrlres were 111ade. Bodv weiqht was nleasrired on a Horns scale to the nearest 23 gms. Percent fat ('!hfat) was estimated fro^^^ I)oclv densitv ( 4 ) determined I)v rmderwater \veiyhing winq ii C h a t i l l o ~autopsy ~ scale. Resiclual volriune was ineasr~l-edr~sinyan oxygen-re\)reuthi~~il tread~liill test alld the 12-111inr111i to I ) e c o ~ ~ta~niliar le \vith the pacing iiild esertion reclriirecl. D r ~ r i n\\.eeks ~ -7 throllgh 5. ei~cliS \\.as testecl rii~clei.eacli of the torlr coilclitions: 11 nor~nal I ~ o dn.eiqht. -7) 5"L iicldetl \\.eiyht (.A\\'\, ;3) 101'6:I\\.'.;itid 4 1 \\it. Tlie Ilotl\ \vciqht ~lleasuredi l l \veeli 1 wa5 ritilizecl to cleter~iii~~e tlie iiillonnt of \veight acldecl. The orclei.;)f the four coiiditioi~h\vah rotated to ~ ~ i i i ~ i i l~~1i 1zbe1e ~ cl~iwiti:ilt e s t ~ ~effect. ~ g Tlie Ss \\.ere instrr~cteclto ~.efraiii ~ I - O I I I , c ~ i v tl-iciniilg tlril-iriq testiiig cl:i!.s. slid other\vi\e to ~ ~ ~ ; c i i i t : c [lie i i ~ \ ; I I I I ~ le\,el vt t r i i i ~ i i ~ they ~ q e~igiigetl111 prior to tI1c \ t l l < I \ . . .\ co11ti11lioii5. l ) e e J - i i ~ c r e ~ l ~ e~~~~r toct od c \\.:i> o l 115etlfor tile ti-c;itiii~ill\ t i . ? h s test. .\ttei- ,I 5-111ii1 \viii-iii-111)\\iclkii~~: ict j.,?I I I ~ I ~1I0." # 1qi.;ctle. tollo\\ecll)~ h i n ~ not rest. tlie S 11e"in I ~ I I I ~ aItI ~I II III rnin run measured under the for~r.I\\' conditions are presented in Table 2. .o2 m u r l i ~ n i n and r associated measures of mawimal i ' Vo2(~nl/rnin-kq ~. B\V\. HR and R were not svste~nTABLE i Phvslcal character~stlcso i sualects. Age

Ht

Wt

Fat

.

FFW

Subiect Sex (yrs) (cm) (kg) (%) (kg) -

: _1

3 2

5 i

4 M !vl 'ul F F

391 5 32.1 :: 6 i 0 !53.7 79 4 11 8 70.0 !68.3 60.1 6 56.3 ! 8 1 9 6 4 2 ;0.9 5 7 2 26 i69.5 60 1 ;9.9 28 1 ?O 163.7 53 2 21.5 :! 7 --

?7

29 25 30

h2ma: (ml/min*kg BW)

52.2

%I? max (ml/min.kg FFW)

07 6

57 5

654

55.4

52.2 52.3 38.4 63.3

56.1 7

17

19 9

.MEDICINE AND SCIENCE IN SPORTS

TABLE 2. Means rt SD and F rat~osfor phys~olog~cal vartahles measured durlng maxl. ma1 treadm~llrunnlng and 12-mln performance for the four added we~ght(AW) condltions. N = 6

VE (I/min)

105.3

* 19.3 3.605

ib2 (I/min)

106.4

g (ml/m~n-kg BW) FRY)

ib2 (ml/mtn-kp TW) TM run time (mln)

HR (bpm)

R 12-min run (m)

103.4

106.9

2.68

rt 21.0 k 2 1 . 8 rt 18.9

3.587

k ,822 rt.837

g (ml/rnln-kg

F ratio

% AW

Variable

3.537

3.644

3.47a

r ,854 r ,776

55.3 54.5 54.1 r5.5 ~ 5 . 5 ~ 6 . 63.2 62.9 61.9 2 3 . 1 rt3.3 r 3 . 5 55.3 51.9 49.1 +. 5.5 rt 5.2 k 5.5 14.8 14.3 13.7 k 2 . 3 k 2.4 2.2 194 193 193 rt8 *9 57 1.19 1.20 1.18 rt .04 lt .05 rt.06 3230 3104 3043 2 3 0 6 k 2 7 7 +263

*

55.7 1 *5.4 64.1 r3.3 48.4 rt 4.7 13.2 k 1.8 192 k 8 1.20 r .04 2953 5254

2.08 3.488 48.11b 20.16h

< 1.00 < 1.00 46.26h

ap, different for the folly .i\V couditiolls. This finding .\ measure of the excess ~veiqhtt E \ f 7 carried duriny the form and eeciency were not ha111indicates that r~unl~in< rlms in this study can I)e co~npirtedI)? adding the fat I)ered I)? carryiulj the and that the i~lcl-eahein i i o z (I/ \vei