Upper-body exercise performance: comparison ...

ERGONOMICS, 1986, VOL. 29, No.1, 145-154

Upper-body exercise performance: comparison between women and men By JEFFREY E. FALKEL, MICHAEL N. SAWKA, LESLIE LEVINE,

NANCY A. PIMENTAL and KENT B. PANDOLF

U.S. Army Research Institute of Environmental Medicine, Natick,

Massachusetts 01760, U.S.A.

Keywords: Arm crank and cycle exercise; Arm volume; Prolonged exercise,

Gender differences; Maximal power output; Peak VOz'

This study compared upper-body (arm crank) aerobic fitness for a group of women (n = 8) and men (n = 9) matched for lower-body (cycle)aerobic fitness (X ± S.E. = 50 ± 2 ml kg - 1 min - 1) and also examined the influence selected physiological factors

had on upper-body exercise performance. The components of upper-body exercise studied included maximal power output (POmaJ, peak oxygen uptake (peak VOz), elbow isokinetic strength and endurance, arm volume and endurance time at 80'!~ arm crank peak VOz' During maximal effort upper-body exercise, there was no difference in peak VOz (ml kg -1 min - 1) between the genders despite the men's significantly greater strength, arm volume and pam ax ' Likewise, there was no difference in upper body endurance time at 80% peak VOz between the genders. These data indicated that (i) women are not at a disadvantage in performing aerobic upper-body exercise, (ii) skeletal muscle strength provides a relatively minor influence on both maximal effort and prolonged upper-body exercise; and (iii) individuals can perform prolonged upper-body exercise at relative intensities greater than that needed to elicit an aerobic training effect.

1. Introduction Previous investigators have reported that an individual will achieve lower peak power output (Asmussen and Henningsen 1958, Astrand et al. 1965, Bergh et al. 1976, Bobbert 1960, Davies and Sargeant 1974), and peak oxygen uptake (Bevegard et al. 1966, Stenberg et al. 1967) during upper-body exercise compared with lower­ body exercise. Additional data have implied that prolonged aerobic exercise is more difficult to perform for the upper than for the lower-body muscle groups (Ekelund 1967, Pimental et al. 1984). There have been several physiological factors suggested as contributing to this reduced upper-body exercise performance. The relatively smaller muscle mass involved during upper-body exercise probably results in a limitation of peak oxygen uptake via peripheral circulatory factors as opposed to central circulatory factors (Sawka et al. 1982). The peripheral factors suggested to be responsible for a lower peak oxygen uptake during arm exercise may include: (i) the use of relatively weak muscle groups in the upper body (Glaser et at. 1980, Kamon and Pandolf 1972), (ii) inadequate blood perfusion due to intramuscular pressure exceeding perfusion pressure (Sawka et al. 1983 b, Simmons and Shephard 1971), and (iii) the limited oxidative capacity of the upper-body musculature (Sawka et al. 1983 a). Relatively little research has been conducted on the ability of women to perform upper-body exercise. It has been documented that women have a smaller upper-body muscle mass (Hettinger 1961, Ikai and Fukunaga 1968),have lower strength values for © Copyright

u.s. Government 1985

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upper-body muscle groups (Laubach 1976), have a lower maximal oxygen uptake during lower-body exercise (Asmussen and Henningsen 1958, Bergh et al. 1976) and have a lower maximal cardiac output during exercise compared with men (Astrand et al. 1965,Bevegard et al. 1966).Thus, it seems that women might be less able than men to perform upper-body exercise. The only study that compared gender differences for upper-body exercise did not match populations for pertinent physiological variables (Washburn and Seals 1984). These investigators matched only for age, and assumed similar relative levels of physical activity. They reported that while the men had significantly higher peak power output and peak VOz values; there was no significant difference between genders when peak VOz was corrected for arm volume. Since it is difficult to match genders based on activity, research needs to be conducted to examine gender differences during upper-body exercise when the populations are matched for lower-body aerobic fitness. The authors recognize that if genders are matched for aerobic fitness they may differ in activity level. The purpose of this investigation was twofold: (i) to compare upper-body aerobic fitness for a group of women and men matched for lower-body aerobic fitness and (ii)to examine the influence of various physiological factors upon upper-body exercise performance between the genders.

2. Methods 2.1. Subjects Eight women and nine men volunteers participated in this investigation. The women had a mean (± S.£.) age of 24 ± 2 years, weight of 58·9 ± 2 kg, height of 163 ± 2 cm and body fat of 23·2 ± 1%. The men had a mean (± S.E.) age of 26 ± 2 years, weight of 77 ± 3 kg, height of 177 ± 2 em and body fat of 14·1 ± 1%.

2.2. Procedures Prior to experimental testing, each subject completed a number of practice sessions on an arm crank (ACE) and cycle (CYE) ergometer. Each subject completed a continuous progressive intensity protocol maximal CYE test (McArdle et al. 1973). Two days later each subject underwent a series of upper-body exercise tests on a specially constructed ACE (Sawka et al. 1983 b). Each ofthese tests was separated by at least 2 days. The first test was a continuous progressive intensity maximal effort ACE test (Sawka et al. 1983b). The second test was a progressive intensity, discontinuous ACE protocol (Sawka et al. 1983b). This second test was used to determine the power output (PO) that would elicit 80% of their ACE peak VOz' The third test was a prolonged ACE test that consisted of each subject exercising at a submaximal PO equal to 80% of their ACE peak VOz until exhaustion, or until they could no longer maintain a 70 r.p.m. crank rate. Five minutes after the start of the prolonged ACE test, the submaximal PO was adjusted to obtain 80% ACE peak VOz, and then this submaximal PO was maintained throughout the remainder of the prolonged ACE exercise trial. Isokinetic elbow flexion (EF) and elbow extension (EE) strength (S) as well as endurance(E) were determined on an isokinetic dynamometer (Cybex II) at a limb velocity of30° s- 1 and 1800 s - 1, respectively. Isometric handgrip strength (HG) was determined by an electromechanical handgrip dynamometer with a digital readout. The procedures described by Ramos and Knapik (1978)were employed for all strength measurements. Each subject's percent fat was estimated by hydrostatic weighing and arm volume (AV) was determined using the water-displacement method.

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2.3. Measurements Oxygen uptake and pulmonary ventilation were determined by open circuit spirometry. Subjects breathed via a two-way breathing valve (Otis-McKerrow) and expired gases were collected in 150 I Douglas bags. Expired gases were then analysed for O 2 and CO 2 concentrations using an electrochemical O 2 analyser (Applied Electrochemistry S-3A) and an infrared CO 2 analyser (Beckman LB-2), respectively. Minute volumes of expired gases were determined with a 120I Tissot gasometer. The electrocardiogram was obtained from chest electrodes (CM-5 placement). Venous blood samples were collected before and after the maximal effort ACE test, and every 10 min during the prolonged ACE test from an indwelling catheter placed in a superficial forearm vein. Patency was maintained with heparinized saline. Previous research has indicated minimal sampling bias from forearm venous sampling during upper-body exercise (Pimental et al. 1984). Blood lactate was determined by an enzymatic method. 2.4. Statistical Treatment Means, standard deviations, standard errors of the mean, simple correlation coefficients and independent t-tests were performed on a programmable calculator (Hewlett-Packard 9815A). In addition, analyses of variance were performed (with a group factor for gender comparisons and repeated measures factor for ergometer and time comparisons) and any significant effects were tested using a Scheffe' post hoc analysis. Forward selection multiple regression analyses were performed to calculate the R 2 coefficients. In addition, a dummy variable was used to test for gender effect in the multiple regression analyses. Statistical significance was accepted at the p < 0·05 level.

3. Results Table 1 presents the PO and physiological responses to maximal effort ACE and CYE exercise. ACE exercise elicited lower (p < 0'05) PO max values than CYE exercise for both the women (54%) and men (49%). The women had lower (p ACE peak V0 2 (ml kg -1 min -1) and endurance time as the dependent variables. The independent variables were the upper-body strength and endurance, measurements of arm volume, CYE peak V0 2 , ACE peak V0 2 , CYE PO max and ACE PO max' These independent variables were entered by the computer by a stepwise

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Table 5. Results of the mulitple regression analyses for upper-body exercise performance. Step

Independent variables

r

R Z x 100

Women

1 2 3

ACE peak VOz HGS AV

0·86 0·17 0·12

74 87 94

Men

1 2 3

EFE AV EFS

0'71 0·54 0·09

50 70 76

Peak VOz (mlkg- 1min- 1)

1 2 3

CYE peak VOz EFS EEE

0·89 0·48 0'41

79 81 82

Endurance time

1 2 3

CYE peak VOz EFS EFEEEE- 1

0·56 0·22 0·25

31 38 40

Department variables PO m• x

forward selection procedure. Since a significant gender effect was found for ACE PO m • x, a separate regression analysis was made for women and men for this variable. For women, ACE PO m • x was best predicted by the equation Y=O·11 AV + 1·36 HG +2'70ACEpeakVO z-73'19 (R 2=0'94), and for men the equation Y=0·02AV + 1·44 EFS + 1·05 EFE - 34·27 (R 2 = 0,76) was generated. Since no gender effect was found for ACE peak V0 2 or endurance time, only one equation was developed for each of these variables. ACE peak V0 2 was best predicted by the equation, Y=0·03 EFE -0,01 EEE+0·70 CYE V0 2 (R 2 =0'82) and endurance time was best predicted by the equation Y=0·17 EFS+0·86 CYE peak V0 2 -4,60 EFE EEE- 1-2l-36 (R 2 =0,40).

4. Discussion Previous investigations of upper-body exercise have almost exclusively studied men with little data collected on women. The studies which have reported upper-body exercise peak V0 2 data for women either did not attempt to make comparisons to a group of men (Asmussen and Henningsen 1958, Astrand et al. 1965, Glaser et al. 1981) or did not match genders for pertinent physiological factors (Stenberg et al. 1967, Washburn and Seals 1984).Washburn and Seals (1984)reported upper-body peak V0 2 values for a group of men and women matched for age and with similar physical activity levels. Since activity levels are difficult to quantitate, that may not be the best method to match test populations. The present investigation matched the men and women subjects for cycle exercise aerobic fitness. Since aerobic fitness values are easily quantifiable, they provide a good index to match subject populations. However, we recognize that, in order to match genders for lower-body aerobic fitness, the women were probably more active than the men. Our data clearly show that women are not at a disadvantage for aerobic upper­ body exercise. When women and men have equal lower-body exercise peak V0 2 levels, they achieve equal peak V0 2 for upper-body exercise. Washburn and Seals (1984)

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reported that peak val values needed to be corrected for AV to obtain similar values for women and men. The AV corrections for peak Val are assumed to remove differences relative to the size of the active muscle mass. However, we believe this to be a poor assumption because: (i)chest, back and shoulder muscle groups are not quantified in AV measurements, but clearly participate in upper-body exercise; and (ii) the relationship between AV and active arm musculature is not established, but is probably low. The present study found no differences between the genders for peak val when expressed in ml kg - 1 min - 1 or when corrected for AV in ml mlAV -1 min - 1. In comparison with our men, our women had smaller absolute AV values and smaller AV per kilogramme body weight values. Although the relationship of AV per kilogramme was significantly different, it was not large enough to result in a significant difference in the ml mlAV-I min - 1 values. Although the AV correction has been used to remove the gender differences for upper-body peak val> our data show that the AV expression of peak Val accounted for only 52% of the variance of the more traditional ml kg -1 min -1 expression of peak Val' Also, our findings suggest that there may not be a substantial physiological basis to correct upper-body peak Val for AV. We found a correlation of only r = 0·20 between AV and upper-body peak Val' This finding was further supported by Sawka et al. (1983 a) who found a correlation of r = 0·25 between AV and ACE peak Val' Differences III upper-body skeletal muscle mass may be a factor when comparing between genders for maximal power output (PO max) during ACE exercise. Despite the fact that both groups gave a maximal effort as evidenced by the magnitude of the physiological responses in Table 1, the men were able to achieve significantly greater PO max values. A larger upper-body muscle mass may have enabled the men to generate more force and achieve the greater PO max for ACE exercise. The forward selection multiple regression identified ACE Val and EFE as the variables which explained the most variance for the women and men, respectively. Then for both genders, AV and a measure of strength explained the most variance of all the remaining variables. The primary predictor for the men, EFE, represents contributions of both aerobic power and muscular strength; as EFE was highly related to both ACE VO l m ax (r=0'71, p < 0'05) and EFS (r = 0'70, p < 0'05). In addition, AV and strength measures were highly interrelated. The present investigation was the first to have subjects perform prolonged (greater than 20 min) upper-body exercise at a relative intensity capable of eliciting a training effect.The only other study of prolonged upper-body exercise employed a 60% relative intensity (Pimental et al. 1984),but varied the power output to keep their male subjects exercising at a constant oxygen uptake equal to 60% ACE peak Val' We maintained a constant power output that initially elicited 80% ACE peak Val' Our data showed a significant increase in submaximal oxygen uptake (by ~ 8%) during prolonged ACE exercise. This increase in submaximal Val during prolonged upper-body exercise has not been previously reported. During prolonged lower-body exercise, oxygen uptake has been reported to increase (Costill et al. 1971) over time. In addition, we found that plasma lactate concentration also increased over time and approached maximal exercise levels. For prolonged lower-body exercise, LA values have been reported to remain relatively constant over time at similar relative intensities (Costill et al. 1971, Saltin and Stenberg 1964).These elevated oxygen uptake and lactate values indicated that an increased energy cost to perform a given power output level over time resulted in a reduced efficiency. We believe that the reduced efficiency was the result of altered propulsion biomechanics, As subjects began to fatigue, they probably recruited

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additional muscle groups in order to continue exercise. This was supported by an observation of greater extraneous movements and an apparent greater use of the torso muscle groups as the exercise continued. The present investigation's findings have a number of industrial and clinical implications. Traditionally, the evaluation and preparation of individuals to perform sustained upper-body exercise has primarily focused on muscular strength. In addition, muscular-strength development has been emphasized in rehabilitation medicine to improve wheelchair exercise performance in individuals who cannot use their legs for locomotion. The present investigation found muscular strength to provide a minor contribution to both maximal and prolonged upper-body exercise performance. Lower-body cardiovascular fitness was the primary factor determining upper-body exercise performance. Therefore, aerobic training programmes need to be emphasized for appropriate industrial and clinical communities. Our study also demonstrates for the first time that individuals can perform prolonged upper-body exercise at a relative intensity great enough to elicit an aerobic training effect. Studies that have attempted to aerobically train the upper-body employed interval training programmes because of muscular fatigue.

Acknowledgments Recognition is due to Mr. Larry Drolet for statistical analyses, Ms Colleen McDermott and SP4 Darren Billings for assistance with the data collection and to Ms Pat Basinger and Ms Patti DeMusis for technical assistance in preparing the manuscript. The views, opinions and/or findings contained in this report are those of the authors, and should not be construed as an official Department of the Army position, policy or decision, unless so designated by other official documentation. Approved for public release, distribution unlimited. Cette etude compare I'aptitude aerobique de la portion superieure du corps (manivelage)des

hornmes (n = 9) a celie des femmes (n = 8) apparies sur la base de leur capacite aerobique de la portion inferieure (sur ergocycle): X ± E.T. = 50± 2 ml kg- 1 min - I; elle se propose egalernent de

rechercher quelle influencecertains facteurs physiologiques ont sur les performances de la region superieure. Les composantes de l'exercise se rapportant a la portion superieure comportaient Ie rendement maximum (PO max), la consommation de crete d'oxygene (pic V0 2 ) , la force isocinetique et I'endurance au niveau du coude, Ie volume du bras et Ietemps d'endurance a 80% du pic V0 2 pour Ie travail du bras. Pendant I'effetmaximal de cet exercice on n'a pas observe de differencedans Ie pic de V0 2 (ml kg- 1 min -1) entre les sexes,en depit de la force, du volume du bras et du PO max significativement plus Cleves chez les hommes. De meme il n'y avait pas de differenceentre sexes dans les temps d'endurance a 80% du pic de V0 2 . Ces resultats indiquent que (a) les femmes ne sont pas desavantagees dans ce genre de travail; (b) la force des muscles du squelette exerce une influence relativement faible sur l'effort maximal, ainsi que sur Ie travail prolonge de la portion superieure du corps et (c) les individus puevent effectuerces exercicesades intensites relatives plus importantes que cellesnecessaires pour entrainer un effetaerobique dQ a l'exercice. Diese Studie verglich das aerobische Arbeitsvermogen des oberen Korpers (Armkurbel) mit dem des unteren Korpers (Fahrradergometer), bei einer Gruppe von 8 Frauen und 9 Mannern (X ± SE, 50± 2 ml kg- 1 min - I). Dariiber hinaus wurde der Einfluf ausgewahlter physiologischer Parameter auf das Arbeitsverrnogen des Oberkorpers untersucht. Die Parameter, die bei der Arbeit an der Armkurbel beriicksichtigt wurden waren die Maximalleistung, maximales Sauerstoffaufnahmevermogen, die isokinetische Kraft und Ausdauer des Unterarms, Armvolu­ men und die Ausdauer bei 80% von V0 2 max. Wiihrend der Maximalleistung war kein signifikanter Unterschied beziiglich der Sauerstoffaufnahme zwischen den Geschlechtern trotz der signifikant hoheren Kraft, _Armvolumen und Maximalleistung der Manner, Bei den

Upper-body exercise

153

Ausdauerversuchen mit 80% V0 2 max konnte ebenfalls kein Unterschied zwischen den Geschlechtern festgestellt werden. Diese Daten zeigen, daf (a) Frauen nicht benachteiligt sind bei der Ausiibung von aerobischer Arbeit des Oberkorpers, (b) die Starke der Skelettmuskulatur hat ein relativ geringeren EinfluB auf das max. Arbeitsvermogen und die Ausdauer bei Arbeit des Oberkorpers, (c) Individuen konnen langere Zeit eine hohere Leistung erbringen, als fiir einen aerobischen Trainingszuwachs notig ist. *liif§'i';fj:rclqll'O)f'f~*ttf;$:iJ (El~.!IL:::!n l'[flI~

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