GAYLB, DAVlS, POHLMAN, AND GLASER

RBSBARCH QUARTBRLY

FOR EXERCISE AND SPORT

1990, VOL. 61, No.3, pp. 224-232

Cardiorespiratory and Perceptual Responses to Arm Crank and Wheelchair Exercise Using Various Handrims in Male Paraplegics G. Wll.LIAM GAYLE, ROBERTA L. POID...MAN, AND ROGER M. GLASER Wright State University GLEN M. DAVIS Cumberland College of Health Sciences

The purpose ofthe present study was to determine the effects of 10-in {0.25-m} versus 16-in {0.41-m} wheelchair handrims on cardiorespiratory and psychophysiological exercise responses during wheelchair propulsion at selected velocities. Fifteen male paraplegics (27.0 ± 5.5 yrs) performed three discontinuous exercise tests (ACE = arm crank ergometer; WERG = wheelchair roller ergometer) and two 1600-m performance-based track trials (TRACK) under simulated race conditions. There were no significant differences inHR, V0 2, VE , HLa, or category-ratio ratings of perceived exertion (RPE) using different handrims during wheelchair propulsion at 4 km-h:', In contrast, at 8 km-k! subjects demonstrated a 13% lower steady state V0 2 (p < .05) using the 10-in handrims, coincident with a 23% lower VE • Steady state HR during WERG at 8 km-k! using the 10-in (124.4 ± 39 b-minl] or 16-in (130.6 ± 4.6 b-min") handrims were not significantly different. There were also no significant differences between ACE or WERG conditions during maximal effortfor V0 2 or VE • However, HRpeak during ACE was 7% higher than HRpeak during WERG16 (183 ± 15 b-min! vs. 171 ± 12 b-min", p < .05), and whole blood HLa during ACE was also significantly higher (by 23-2.5 mmol; p < .05) compared to WERG. There were no significant differences for HR, performance time, or RPE between trials using different handrim diameters during the 1600-m event. In contrast, HLa was significantly lower using smaller handrims (9.9 mmol) compared with larger handrims (113 mmol), paralleling a similar difference in the laboratory. Although these data demonstrated few significant differences ofphysiologic responses between trials using different handrims, there was a tendency for a lower metabolic stress using the smaller handrims.

cally or biomechanically. This eventually culminated in 1980 with the National Wheelchair Athletic Association relaxing certain physical requirements on wheelchairs used for sanctioned competition, which precipitated a revolution of wheelchair frame design, wheel diameter, and handrim sizes. However, due to the lack of research regarding appropriate wheelchair design, most athletes today still acquire their knowledge through trial and error, from other athletes, or from their coaches. Voight and Bahn (1969) and Glaser, Foley, Laubach, Sawka, and Suryaprasad (1978) have reported that the standard wheelchair is inefficient and physiologically stressful on the cardiovascular and muscular systems of untrained paraplegics. However, several investigators have reported that a significant positive relationship exists between optimal sport wheelchair design variables (e.g., seat angle, frame length, or wheel placement) and improved physical performance (Brubaker, McClay, & McLaurin, 1984; Higgs, 1983). In addition, Van der Woude et al. (1988) found significant differences in cardiorespiratory parameters between 0.300.35-m handrims and 0.56-m wheelchair handrims. Therefore, the purpose of the present investigation was to determine the effects oftwo different handrim sizes on cardiorespiratory and psychophysiological exercise responses of male paraplegics performing wheelchair propulsion at selected velocities.

Key words: wheelchair exercise, cardiorespiratory response,

Method

paraplegic, handrims As wheelchair track- and road-racing have become more popular in the United States, athletes with spinal cord injuries (SCI) have looked to extensive equipment modifications that might result in performance advantages either physiologi-

Subjects Fifteen asymptomatic SCI males (M age =27.0 ± 5.5 yrs), significantly disabled by lower-limb neuromuscular deficits,

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with the laboratory procedures, including two "habituation" exercise tests.

were recruited for the present investigation from the university campus and surrounding community. Three subjects had been previously involved in competitive wheelchair track competitions and twelve were active in recreational activities. All subjects gave informed consent and underwent detailed medical examination in accordance with a protocol approved by the University Internal Review Board. A physician evaluated the subjects for significant cardiorespiratory or orthopedic limitations that might contraindicate vigorous exercise. and one subject was excluded from the study as a result of the medical screening. Physicalcharacteristics and disability assessment. At a preliminary visit, body length was assessed in the supine position with manual stretching of the limbs (Davis & Shephard, 1988). Body mass was determined in the sitting position on a standard hospital scale (Toledo Electroscale Model 570 Weightmetre, Dayton, am, and anthropometric measurements were assessed. Subcutaneous body fat was measured by Lange skinfold calipers at three upper-body sites (subscapular, chest, triceps; Pollock, Wilmore, & Fox, 1984). A generalized regression equation for predicting body density and percent body fat in adult males was utilized (Brozek, Grande, Anderson, & Keys, 1963; Pollock. Schmidt, & Jackson,1980) because ofthe lack ofSCI population-specific formulas. The site and degree of spinal cord injury (see Table 1) was determined during the physical examination from selfreport. Prior to exercise testing, each subject was familiarized

Exercise Testing Exercise tests were conducted on separate days. at least 24 hrs apart at the same time of day. Subjects fasted 3-5 hrs before each test and were instructed to avoid vigorous exercise for 12 hrs prior to testing sessions. All tests were conducted in a temperature- and humidity-controlled laboratory (TA = 21.5 0-23.00 C, RH = 70-79%). The first exercise test evaluated peakpower output. heart rate (HR), and metabolic variables using a discontinuous multistage arm cranking protocol (Davis & Shephard, 1988; see Table 2). Following a warm-up of three submaximal exercise stages, subjects performed progressive resistance arm crank exercise (ACE) to volitional fatigue or until they were unable to maintain the required arm cranking cadence (60 rev-min"). Although the primary focus of this investigation was on wheelchair ergometry (WERG), we were initially concerned that our SCI subjects might not exhibit a "true" centrally limited maximum effort during wheelchair propulsion. A previous investigation (Wicks. Oldridge, Cameron. & Jones, 1983) had demonstrated minimal differences of VO,yeak between ACE and WERG in elite SCI athletes our use of the arm cranking protocol was to validate this finding in the general paraplegic population. Furthermore.

Table 1 Subject Characteristics

Subject

JB KC RF JR JG DH AK GL TL PN RO AS WS KW RW

M SEM

Lesion Level

T11 T10 TlI-10

~-4

Ll-2 T1D-11 T11.12 TS-9 TlI-10 L1 L1 T1D-l1 Ts Ts Ts

Body Mass (kg)

Percent Fat

172.5 179.9 185.4 175.3 162.0 175.0 179.1 185.4 179.1 165.1 182.3 168.5 180.3 198.1 179.0

56 52 82

177.4 2.4

Age (yrs)

Height (cm)

26 23 34 35 19 24 21 27 31 29 33 23 27 20 34 27 1

(%)

ACE V0 2peak (l-rnin')

ACE HRmax (b-mln')

95 65 85 98 71

12.9 9.0 17.8 9.7 7.4 7.8 9.0 17.8 19.8 24.4 20.6 7.8 24.8 16.3 16.1

1.56 1.47 1.54 1.97 2.27 2.58 2.22 1.75 1.77 2.20 1.92 2.13 1.89 2.33 1.62

190 214 180 192 158 184 204 160 180 196 174 194 180 172 174

73.4 3.7

14.7 1.6

1.95 0.09

184 4

72

56 68 63 77 88 72

Note. Lesion level refers to approximate site of spinal cord injury. Percent fat represents estimate from able-bodied

regression equations. ACE represents maximal arm cranking.

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comparison ofWERG test results to the ACE test alsojustified repeating the former if the difference between modalities exceeded 10%. The wheelchair used during WERG testing was a standard track-racing chair (Stainless Medical Products Racer, San Diego, CA) modified to heighten the back support to 24 in (0.61 m) in compensation for subjects with varying levels ofbalance. Mainwheel axles were lengthened by 6 in (0.15 m) so that the width of the chair could be adjusted for each subject. The handrims were either 10-in (0.25-m) or 16-in (0.41-m) foam-covered handrims, which were attached directly to the spokes ofthe 27 .5-in (0.70-m) mainwheels. Our use ofnonmetric units to describe handrim diameters throughout this manuscript is based on the common convention for marketing these devices in the U.S., as well as for ready identification on the part of adapted physical educators, coaches, and disabled athletes. The wheelchair roller consisted of a commercial device (Pioneers of America Wheelchair Roller, Burnaby, Canada) with an added electronic speed display and wheel revolution counter to permit precise monitoring of the distance traveled during a given time period (R. M. Glaser, personal communication, June 1, 1986). Heart rate and metabolic variables were also evaluated during the discontinuous wheelchair roller test (see Table 2) using lO-in (WERGlOprotoeol) or 16-in (WERG16 protocol) handrims. Subjects propelled the modified track wheelchair at

three submaximal velocities consisting of 4 km-h" (without body mass loading), 4 km-h", and 8 km-h" (both velocities with body mass loading). "Body mass loading" refers to the mass of the subject and the track wheelchair either resting on the rollers (viz., body mass loading) or elevated above the rollers (viz., without body mass loading). Each submaximal effort lasted 5 min with a 4-min recovery between phases. Following submaximal WERG exercise, subjects performed a progressive velocity test (l-min stages of I km-h' increments) to volitional fatigue or until they were unable to maintain the required velocity displayed on an electronic speedometer and monitored by the investigator. During ACE and WERG maximal effort tests, verbal encouragement was provided to ensure optimal effort.

Physiological measurements and ratings of perceived exertion During exercise tests, air was inspired through a lowresistance two-way valve (dead space =82 ml; Hans Rudolf #2700, Kansas City, KS) connected to a dry-gas meter previously calibrated against a 120-L Tissot spirometer. Expired gas was pumped from an 8-L plexiglass mixing chamber to paramagnetic 02 and infrared CO 2 analyzers previously calibrated with cylinder mixtures analyzed by the Lloyd Haldane method (Haldane & Priestley, 1935). Metabolic and respiratory variables (V02' VC02, RER, V E' VT) were calculated

Table 2 ACE and WERG Test Protocols Time (min)

Condition

0-5

Rest Stage 1 Work

5-10

Stage 2 Work

10-14 14-20

Recovery Stage 3 Work

20-24 24-30

Recovery

Recovery Stage 4 Work

ACE (60 rev-min")

30-34 34-35 35-36 36-37 37-38 38-39

Load set to elicit HR of 115-125 b-mirr' (approx. 60% HRmax)

Loadless

Load set to elicit HR of 125-135 b-min' (approx. 65% HRmax)

4

Load set to elicit HR of 135-145 b-mlrr' (approx. 70% HRmax)

8

Load increased by 8.5 W to volitional fatigue

8 9 10 11 12

Note. ACE represents arm crank exercise; WERG represents wheelchair roller exercise. RBsBARCII QuARTERLY POR ExBRCISB AND SPoRT, VOL. 61, No.3

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every 30 s using a computerized system (Vista Model 1700, Vacumetrics, Inc., Ventura, CA). The exercise electrocardiogram was continuously monitored (CMs lead placement) via cardiotachometer (GEDCO CT-2, GEDCO Assoc., Huntington, NY). Fingertip blood lactate samples (100 tanl) were collected 3 min after submaximal or maximal exerciseperiods for subsequent enzymatic analysis (YSI Whole Blood Llactate Analyzer, Yellow Springs Instruments, Yellow Springs, OR). Differentiated category-ratio ratings of perceived exertion (RPE) on a 0.5- to lO-point scale were requested from subjects at rest and immediately following exercise bouts (pandolf, 1982). Subjects were asked to rate their perception ofeffort arising from "central" cues (sensations ofstress from the cardiopulmonary system), "peripheral" cues (local sensations of strain in the exercising muscles and joints), and "overall" cues (an overall sensation of exertion integrating their "central" and "peripheral" cues with whatever ratings they deemed appropriate). A complete description of each scale was presented prior to testing during the "habituation" exercise sessions.

ously described. Each subject was strongly encouraged to propel the track chair as quickly as possible over the 1600-m course.

1600-mperformance test

The subjects' lesion levels and physical characteristics are reported in Table 1. Their mean maximal HR (HRpeak) and peakoxygen intake (VO:J>e8k) during arm cranking were 184 ± 4 b-mirr' and 1.95 ± 0.12 l-mirr', respectively. Mean VIJ>e8k during ACE was 74.5 ± 4.0 l-min", commensurate with a postexercise HLa of 13.2 ± 0.6 mmol (see Table 3). Differentiated category-ratio RPE arising from central, peripheral, and overall cues during ACE were 8.4 ± 0.5, 8.8 ± 0.4, and 9.0± 0.3, respectively. These perceptual cues were not significantly different from those derived during maximal wheelchair exercise (see Table 3). During loadless and body mass loaded wheelchair propulsion at4 km-lr' (see Figures 1-4), there were no significant differences of steady state cardiorespiratory or perceptual responses between WERGlO and WERGI6. Similarly, there were no significant differences of metabolic, respiratory, or

Statistical analysis All tests were randomly assigned and counterbalanced, with subjects completing each test. A two-way blocked ANOV A was utilized to compare group means for metabolic and RPE responses during submaximal efforts (i.e., WERG 10 vs, WERG 16at4 km-h' and 8 krn-h"). One-way ANOVA was used to compare group means for ACE versus WERGI0 or WERG16 data and for TRACKlO versus TRACK16 scores. Duncan's multiple range a posteriori test (95% confidence interval) was utilized to determine where significant differences occurred when significant F-ratios (p < .05) were reported.

Results

In addition to the laboratory assessments of cardiorespiratory responses during ACE, WERGlO, and WERGI6, subjects underwent two 1600-m performance tests using lO-in (TRACKI0) or 16-in (TRACKI6) handrims. These tests were conducted on an all-weather track on separate days, in either the morning or evening when environmental conditions permitted maximal outdoor effort (TA = 16.10-28.3 0 C, RH = 44-96%, ground wind velocity = 0-4.9 m-s"). The wide range ofenvironmental data represents a distinct limitation to "field" testing under ambient conditions. During the track tests, HR was monitored via PM-tape telemetry (Marquette Holter Monitor, Marquette, Inc., Milwaukee, WI) and race time was recorded. Immediately following each test, fmgertip lactate samples and RPE were collected as previ-

Table 3 Physiological and Perceived Extrtlon Responses During Maximal Arm Crank and Wheelchair Roller Exercise ACE HRpeak (b'min") V02peak (l-mlrr') VEpeak(l-mirr') HLapeak (mmol)' Rating Perceived Exertion Central Peripheral Overall

WERG10

184 1.95 74.5 13.2

± ± ± ±

4 0.09 4.0 0.6

176 1.98 74.0 10.7

8.4 8.8 9.0

± ± ±

0.5 0.4 0.3

7.7 8.8 8.6

± 2 ± 0.10 ± 3.5 ± 0.4 ± ± ±

0.5 0.4 0.4

WERG16 171 1.94 73.1 10.8

± ± ± ±

4 0.10 4.5 0.4

7.7 8.5 8.5

± ± ±

0.5 0.4 0.4

Note. Values are means ± SEM. ACE represents arm crank exercise. WERG1 a represents wheelchair roller exercise using 10-in handrims. WERG16 represents wheelchair roller exercise using 16-in handrims. Possible range of perceived exertion is 0.5 to 10 units. *Ace > WERG 10 and WERG16 (p < .05). RBsEARCII QuAR1llRLY POR ExIlRCSIl AND SPORT, VOL.

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RPE scores during maximal wheelchair effort between handrim diameters (see Table 3). Maximum wheelchair velocities for WERG10 and WERG16 were 12.9 ± 0.4 km-lr and 11.8 ± 0.5 km-h", respectively. However, in contrast to the low velocity (4 km-h") and maximal velocity (11.8-12.9 km-lr') conditions, subjects performing WERG16 at 8 km-lr developed a 13% higher steady state VOz' F(l, 42) = 3.5, p < .05, compared with WERGI0 (see Figure 1). Similarly, VB was elevated by 23%, F(l, 42) =4.01, p < .05, during wheelchair propulsion at 8 km-lr for WERG16 versus WERGlO (32.0 ± 2.11·min" vs. 26.0 ± 1.1 f-min", respectively). Postexercise fmgertip Hl.a was also significantly increased, by 56% (see Figure 3) at 8 km-h", using the larger handrims, F(I, 42) = 5.35, p < .05.

2.15

o 10 lnell Hlnclrlm 1151nc1l Hlndrlm



Category-ratioRPE scores were usually 1.0- 1.4points higher using the larger handrims for central, F(I, 42) = .5.27; for peripheral, F(I, 42) = 2.97; and for overall, F(I, 42) = 4.36. P < .05 (see Figure 4). In contrast to the metabolic, respiratory. and perceptual responses at 8 km-h", steady state HR (see Figure 2) was not significantly different between WERG10 (124.4 ± 3.9 b-min:') and WERG16 (130.6 ± 4.6 b-mirr'). During the 1600-m performance event, elapsed times were comparable for subjects using the 10-in (611.8 ± 28.4 s) versus 16-in (611.9 ± 32.6 s) handrims. Similarly, HR responses wereidentical (172.9±4.0b·min") duringTRACKIO and TRACKI6. In contrast. postexercise fingertip lactate samples differed by 1.4 mmol, F(I, 14) = 10.04, p < .05, in favor of the smaller handrims. This difference corresponded to a 14% increase when using the larger handrims. Yet there were no statistically significant differences of central (7.4 ± 0.5 vs. 7.3 ± 0.3), peripheral (8.2 ± 0.3 vs. 7.8 ± 0.4), or overall (7.6 ± 0.4 vs. 7.7 ± 0.4) perceptions of exertion between TRACKI0 and TRACK16 performances.

2

1.5

VO z

Discussion 1

0.5

o Rest

Loadle.. 4 km'h"

4 kin· h"

8 km· h"

Maximal Effort

WHEEL VELOCI1Y Figure 1. Relationship between oxygen Intake (VOz; l-mlrr'') and wheel velocity using 10-ln or 16-ln handrlms. Values are means (SEM too small to be shown). Asterisk (*) denotes significant difference (p < .05) between handrim diameters.

The results of the present study reflect the cardiorespiratory and psychophysiological responses of nonathletic SCI subjects performing arm crank exercise (ACE) and wheelchair propulsion using 10-in (WERGI0) or 16-in (WERGI6) handrims. The mean V0ztreak and HRpeak values (1.95 l-mirr and 184 b-mirr', respectively) of our subjects, while consistent with or slightly higher than previous investigations of "active" SCI males (Gass & Camp, 1984; Pitetti, Snell, & Stray-Gunderson. 1987; Van Loan, McCluer, Loftin. & Boileau, 1987; Wicks et al.• 1983). are lower than other studies focusing on wheelchair sportsmen (Jackson, Davis. Kofsky, 14

o 10 InCh Handrlm

12



10

18 Inch Handrlm

160

HLae

140

15

HR 120

o 10 Inch Handrlm •

18 lnell Handrlm

*

4

100

Rest Rest

Load.... 4 km'h"

4 km- h"

8 km· h'

Maximal Effort

Loadl... 4 km .h"

4 km· h"

8 kin· h"

Maximal Effort

WHEEL VELOCI1Y

WHEEL VELOCITY Figure 2. Relationship between heart rate (HR; b'mln-') and wheel velocity using 10-ln or 16·ln handrlms. Values are means ± SEM.

Figure 3. Relationship between blood lactate (HLa; mmol) and wheel velocity using 10-ln or 16-ln handrlms. Values are means ± SEM . Asterisk (*) denotes significant difference (p < .05) between handrlm diameters.

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Keene, & Shephard, 1981; Kofsky, Shephard, Davis, & Jackson, 1984; Zwiren & Bar-Or, 1975). Response to maximum exercise. Expressed relative to their body mass, the subjects of the present investigation developed a mean VOzt>eakduring maximal arm cranking of 27.5 ml-kgv-mirr' (vs. 40-50 ml-kgv-min" for able-bodied individuals of similar age performing treadmill running; Skinner, 1987). However, this mass-adjusted index must be interpreted with some caution, as its relevance might be questioned for subjects whose body mass is supported in a wheelchair. Moreover, arm cranking is not a "natural" mode of daily ambulation for the SCI population since it utilizes a dissimilar biomechanical technique to wheelchair propulsion (Davis, Ferrara, & Byrnes, 1988; Glaser & Davis, 1989). Nevertheless, the similarity between VOzt>eak achieved during maximal ACE orWERG (1.94-1.981·min·1; see Table 3) reinforces the view that either modality may be used to assess the cardiorespiratory fitness of wheelchair users (Glaser & Davis, 1989; Kofsky, Davis, Shephard, Keene, & Jackson, 1983; Pitetti et al., 1987). The similarity of maximal exercise responses between WERGI0 and WERG16 also suggests that these handrim

diameters do not play an independent role in eliciting peak cardiorespiratory performance in SCI subjects. Although wheelchair rollers do not permit the accurate measurement of power output, peak Val' V gPeak, HRpeak, and Hl.a peak (see Table 3) were comparable between wheelchair handrim sizes, implying that the degree of exercise stress was similar. This view was supported by subjective ratings of perceived exertion during maximal WERG that were nearly identical for central (7.7), peripheral (8.5-8.8), or overall (8.5-8.6) perceptions of effort VOzt>eak was not significantly different among ACE, WERGI0, and WERG16, supporting the view that either modality may be utilized to elicit VOzt>eak in the lower-limb disabled (Davis & Shephard, 1988; Glaser & Davis, 1989; Wicks et al., 1983). Interestingly, ACE HRpeak was 8-13 b-mirr' higher than WERG HRpeak, supporting a slightly greater "central" perception of exertion (8.4 vs. 7.7; p > .05). Similarly, ACE Hl.apeak (13.2 mmol) was higher than WERGIO or WERG16 lll..apeak (10.7 mmoland 10.8 mmol, respectively). These data strongly suggest that, in untrained subjects, maximum velocity wheelchair propulsion may be limited more by a subject's muscular strength and lower mechanical efficiency during WERG than central cardiovascular factors such as heart rate or left ventricular stroke volume. The higher exercise heart rates and blood lactate concentrations, together with a smaller differential between central and peripheral RPE scores during ACE, would tend to support this viewpoint. The factors contributing to the superior efficiency and power production of maximum ACE include (a) use of both flexor and extensor muscles for force production (Glaser, Laubach, Sawka, & Suryaprasad, 1978), (b) inherent neural pathways that favor asynchronous limb movements (Glaser, Sawka, Young, & Suryaprasad, 1980; Marincek & Valencic, 1978), (c) advantageous gear ratios of arm crank ergometers (Engel & Hildebrandt, 1974; Glaser, Young, & Suryaprasad, 1977), (d) transmission of torque by a handle rather than intermittent "stroking" of 10-in or 16-in handrims (Engel & Hildebrandt, 1974; Wicks et al., 1983), and (e) reduced isometric muscle activity for trunk stabilization during WERG (Marincek & Valencic, 1978). Response to submaximum exercise. At 4 km-h", the addition of body mass loading over the wheelchair rollers produced an increase in steady state Val of only 0.17-0.18 l-mirr' using la-in or 16-in handrims (see Figure 1). Similarly, there was only a slight elevation of HR (by 2-3 b-mirr': see Figure 2) and VB (by 21·min·1) between the mass-supported versus unsupported conditions. Clearly, the main factor contributing to higher metabolic stress during wheelchair propulsion at low velocities is rhythmic arm movement not present under resting conditions. Studies of mechanical efficiency (Gaesser & Brooks, 1975; Stuart, Howley, Gladen, & Cox, 1981) have demonstrated that energy lost to internal work of muscle and joint movements comprises a large proportion of the total metabolic energy production during exercise. The negligible increment of cardiorespiratory or perceptual responses during wheelchair exercise using lO-in or 16-in

10 010 Inch Handrlm

8

C



16 Inch Handrlm

6 4

2 0 10

8

P

6 4

2 0 10

8

0

*

6 4

2 0

Rest

Loadless 4 km: h"

4 km- h"

8 km- h'

Maximal Effort

WHEEL VELOCITY Figure 4. Relationship between central (e), peripheral (P) and overall (0) ratings of perceived exertion and wheel velocity using 10-ln or 16-ln handrlms. Values are means (SEM too small to be shown). Asterisk (*) denotes significant difference (p< .05)between handrlm diameters. RBsBAROI QuARTERLY POR

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handrims at 4 km-h" with body mass loading would tend to support this judgment Steady state VO~ during WERG 10 was only 9% lower (p » .05) than WERG16 (0.59 l-min" vs. 0.64 l-min"; see Figure 1) for submaximal wheelchair propulsion at 4 km-h", Similarly, HR, VB' BLa, and RPE scores revealed negligible differences of exercise stress between handrim diameters for the low velocity condition (see Figures 2-4). These fmdings may be explained by improved postural positioning (e.g., trunk stabilization and/or lower center of gravity) using a track-type wheelchair compared with the "standard" medical model (Steadward, 1980), together with the low metabolic stress of4 km-h? propulsion. Both factors may have rendered wheelchair propulsion so efficient that any possible advantage of either handrim diameter was minimized. Based on the cardiorespiratory evidence and subjective responses of our subjects, we conclude that, for untrained wheelchair users performing steady state exercise, there exists no psychophysiological difference using lO-in and 16-in handrim diameters at low wheelchair velocities. Unlike the metabolic responses at 4 km-h" wheelchair velocity, there were significant differences at 8 km-h" between the WERG10 and WERG 16 tests. Steady state oxygen intake during WERGIO was 13% lower than WERG16 (p < .05), matching a 23% lower VB (p < .05). Why significant differences for steady state V02 and VB emerged at 8 krn-h", but not at the lower velocity, may be explained by likely postural differences required for highintensity wheelchair propulsion and a subsequent change in the point where the hands contact the handrims. At 8 krn-h", users alter their contact point on the handrim to a more forward-striking position (Tupling, Davis, Pierrynowski, & Shephard, 1986). Although wedidnotdirectly quantify power output or mechanical efficiency during wheelchair propulsion, it is likely that a smaller handrim diameter would engender a superior biomechanical advantage on the basis of a more forward-leaning body position during handrim impact and lowered "wasted" trunk/arm movements. Furthermore, using smaller handrims, "striking force" would be less isometric and more forward, resulting in an increased translational force.' In their time-velocity analyses of wheelchair propulsion dynamics, Vander Woude, Veeger, and Rozendal (1987) proposed that force generation arising from different movement techniques may be more important then pushing time on the handrim, recovery time after pushing, or total cycle time. In a subsequent study, the same authors (Vander Woude et al., 1988) noted that SCI sportsmen developed lower steady state cardiorespiratory responses over a range of treadmill speeds using 0.30-0.35-m handrims compared to 0.56-m handrims. They attributed these differences to decreased arm segment excursions at higher wheelchair velocities (7-14 km-h") using smaller handrims. An additional biomechanical factor mitigating against the larger diameter handrims (WERGI6) is a lowered drive ratio due to force application with a longer lever arm. Although this might initially require less force to turn the

wheelchairmainwheels at 8 km-h", the stroking velocity must

also be high, thereby elevating steady state cardiorespiratory responses. Conversely, although WERGIO may initially require greater force to turn the wheelchair mainwheels, stroking velocity is necessarily lower, producing a decreased drive ratio and reduced metabolic or cardiopulmonary stresses. A limitation to the present study was our lack of measured stroke length, stroke rate, or stroke force data using 10-in versus 16in handrims. At 8 km-h", WERG 10 HLa (2.5 mmol) was significantly attenuated compared to WERG16 (4.0 mmol). Similarly, category-ratio RPE were lower (p < .05) during WERG 10 than WERG16 for central (2.8 vs. 3.9), peripheral (3.5 vs. 4.6), or overall (3.2 vs. 4.6) perceptions of effort. It was interesting to observe that peripheral RPE responses were consistently higher at each wheelchair velocity than central or overall responses (see Figure 4). These data suggest that local muscular factors (i.e., peripheralresponses) sometimes "overpower" central cues of exertion (Noble. Borg, Jacobs, Ceci, & Kaiser, 1983). 1600-m Performance Test. The comparison of exercise HR during a simulated 1600-m race demonstrated an analogous cardiorespiratory stress (eliciting a mean HR of 173 b-mirr') using lO-in or 16-in handrims. Previous researchers (Crews, Wells, Burkett, & Hopkins, 1982) have found similar HR responses (167 b-min") in wheelchair athletes during outdoor performance events. It appears that, even with verbal encouragement, external environmental variables and motivation tend to influence a subject's performance outside of the clinical setting. Similarly, there were no appreciable differences of mean wheelchair velocity during TRACKIO (2.69 m-sec") and TRACK16 (2.7 m-sec"). In contrast, there was a significant difference of HLa concentrations in favor of the small diameter handrims (9.9 mmol vs. 11.3 mmol for TRACKIO vs. TRACKI6, respectively; p < .05), which paralleled the blood lactate data collected during wheelchair propulsion at 8 km-h" in the laboratory. While there were no significant differences in RPE between conditions, peripheral cues were again elevated over central or overall perceptions of effort. This reinforces the concept that peripheral responses "overpower" central cues, regardless of environmental conditions (Noble et aI., 1983).

Conclusions Clinical and research assessment of cardiorespiratory performance for individuals with lower-limb impairments suffers from the widespread proliferation and variability of wheelchair ergometers, treadmills, and roller systems. This difficulty often complicates comparisons between studies, as no single device has emerged as a valid measurement standard for use in the field. However, the authors have

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demonstrated the similarity of maximal exercise responses betweenan acceptedmodeof clinicalassessment(ACE)and an exercise-specific apparatus (WERG; trackwheelchair and rollers),reinforcingthe viewthateithermodality maybe used by physicaleducators, rehabilitation specialists, or clinicians to assess VOzt>eak in SCI subjects. Accommodating the principleof exercise specificity, we furtherrecommend that theWERGbe givena higherpriorityin a clinicalsettingwhen both submaximal and maximal exercise assessments are desired. Although thesedatademonstrated few significant differences betweenhandrimdiameters,there was a tendency to a lowermetabolic stressand reducedperceivedexertionscores using lO-in handrimsat 8 km-h:'. Therefore,we recommend that wheelchair athletes use smaller diameter handrims for continuous steady state exercise (e.g., track competitions lasting longer than 5-7 min). Whether the smaller handrim diameterofferssimilaradvantages for non-steady-state exercise (e.g., tracksprintraces or roadracesover hillyterrain) is worthyof furtherresearch.

References Brozek, J., Grande, F.• Anderson, J. T .• & Keys. A. (1963). Densitometric analysis of body composition: Revision of some quantitative assumptions. Annals ofthe New York Academy of Science, 110, 113-140. Brubaker, C. E., McClay. I. S., & McLaurin, C. A. (1984). The effect of mechanical advantage on handrim propulsion efficiency. Proceedings ofthe Seventh Annual Conference ofRehabilitation Engineering, 4, 15-16 Crews. D., Wells, C. L., Burkett. L.• & Hopkins, Y. (1982). A physiological profile of four wheelchair marathon racers. Physician and Sportsmedicine,10, 134-143. Davis. G. M .• & Shephard, R. J. (1988). Cardorespiratory fitness in highly-active versus inactive paraplegics. Medicine and Science in Sports and Exercise, 20, 463-468. Davis, R., Ferrara, M .• & Byrnes. D. (1988). The competitive wheelchair stroke. National Strength and Conditioning Association Journal, 10,4-10. Engel. P., & Hildebrandt, G. (1974). Wheelchair design: Technological and physiological aspects. Proceedings of the Royal Society ofMedicine, 67.409-411. Gaesser, G. A., & Brooks, G. A. (1975). Muscular efficiency during steady-rate exercise: Effects of speed and work. Journal of Applied Physiology, 38, 1132-1139. Gass, C. G., & Camp, E. M. (1984). The maximum physiological responses during incremental wheelchair and arm cranking exercise in male paraplegics. Medicine and Science in Sports and Exercise, 16, 355-359. Glaser, R. M., & Davis, G. M. (1989). The wheelchair dependent individual. In B. A. Franklin, S. Gordon, & G. C. Timmis (Eds.), Exercise in Modem Medicine: Testing and Prescription in Health and Disease (pp. 237-267). Baltimore: Williams and Wilkins. Glaser, R. M., Foley, D. M., Laubach, L. L., Sawka. M. N., & Suryaprasad, A. G. (1978). An exercise test to evaluate fitness for wheelchair activity. Paraplegia, 15. 252-261.

Glaser. R. M .• Laubach. L. L., Sawka, M. N., & Suryaprasad, A. G. (1978). Exercise stress fitness evaluation and training of wheelchair users. In A. S. Leon & G. 1. Amundson (Eds.), Proceedings of the First International Conference on Lifestyle and Health (pp. 167-193). Minneapolis: University of Minnesota Press. Glaser, R. M., Sawka. M. N., Young, R. E., & Suryaprasad, A. G. (1980). Applied physiology for wheelchair design. Journal of Applied Physiology, 48,41-44. Glaser. R. M., Young. R. E., & Suryaprasad, A. G. (1977). Reducing energy cost and cardiopulmonary stresses during wheelchair activity. Federation Proceedings. 36, 580. Haldane. J. S., & Priestley, J. G. (1935). Respiration (pp. 124-129). Oxford: Clarendon. Higgs. C. (1983). An analysis of racing wheelchairs used at the 1980 Olympic Games for the Disabled. Research Quarterly for Exercise and Sport, 54, 229-233. Jackson, R. W., Davis, G. M., Kofsky, P. R., Keene, G. C. R., & Shephard, R. 1. (1981). Fitness levels in the lower-limb disabled. Transactions ofthe 27th Annual Orthopedic Research Society, 6,9-13. Kofsky, P. R., Davis, G. M., Shephard, R. 1., Keene, G. C. R., & Jackson, R. W. (1983). Field testing: Assessment of physical fitness of disabled adults. European Journal ofApplied Physiology, 51,109-120. Kofsky, P. R., Shephard, R. J., Davis, G. M., & Jackson, R. W. (1984). Fitness classification tables for lower-limb disabled individuals. InC. Sherill (Ed.). Sport andDisabledAthletes (pp. 147-155). Champaign, IL: Human Kinetics. Marincek, C. R. T., & Yalencic, Y. (1978). Arm cyclo-ergometry and kinetics ofoxygen consumption in paraplegics. Paraplegia, 15, 178-185. Noble, B. 1., Borg. G. Y., Jacobs, I., Ceci, R., & Kaiser, P. (1983). Category-ratio perceived exertion scale: Relationship to blood and muscle lactates and heart rate. Medicine and Science in Sports and Exercise, 15, 523-528. Pandolf, K. B. (1982). Differentiated ratings of perceived exertion during physical exercise. Medicine and Science in Sports and Exercise, 14, 397-405. Pitetti. K. H., Snell, P. G., & Stray-Gunderson, 1. (1987). Maximal response of wheelchair-confined subjects to four types of arm exercise. Archives ofPhysicalMedicine and Rehabilitation, 86, 10-13. Pollock, M. L., Schmidt, D. H., & Jackson, A. S. (1980). Measurement of cardiorespiratory fitness and body composition in the clinical setting. Comprehensive Therapy, 12. 12-27. Pollock. M. L., Wilmore, 1. H., & Fox, S. M. (1984). Exercise in health and disease-evaluation and prescription for prevention and rehabilitation (pp. 205-228). Philadelphia: W. B. Saunders. Skinner. J. S. (1987). Exercise testing and exercise prescription for special cases (pp. 37-39). Philadelphia: Lea and Febiger. Steadward, R. D. (1980). Analysis of wheelchair sports events. In H. Natvig (Ed.), First International Medical Congress on Sports for theDisabled(pp.184-192). Oslo: Royal Ministry ofChurch and Education. Stuart, M. K., Howley. E. T., Gladen, L. B., & Cox, R. H. (1981). Efficiency of trained subjects differing in maximum oxygen uptake and the type of training. Journal ofApplied Physiology, 50,444-449. Tupling. S. J.• Davis, G. M., Pierrynowski, M. R., & Shephard, R. J. (1986). Arm strength and impulse generation: Initiation of

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Authors' Notes The authors wish to acknowledge funding support for this project by the Department of Health, Physical Education and

Recreation, College ofEducation and Human Services, Wright State University, and the Rehabilitation Research and Development Service, United States Veterans Administration. The authors also wish to thank Production Research Corporation, College Park, MD, for providing wheelchair equipment and Yellow Springs Instruments, Yellow Springs, OH, for use of their lactate analyzer. The experiment reported in this paper formed part of the doctoral dissertation (Ohio State University) of the principal author. An abstract of this paper has been presented at the 35th Annual Meeting of the American College of Sports Medicine, Dallas, TX, 1988.

Submitted: October 21,1988 Revision accepted: June 11,1989

G. William Gayle is an assistant professor and Roberta L. Pohlman is an associate professor in the Department of Health. Physical Education and Recreation, Wright State University. Glen M. Davis is a lecturer with the Department ofBiological Science. Rehabilitation Research Centre, Cumberland College of Health Sciences. Lidcombe, New South Wales. Australia. Roger M. Glaser is a professor in the Department ofPhysiology and Biophysics and Acting Director of the Department of Rehabilitation Medicine and Restorative Care. School ofMedicine. Wright State University. Dr. Davis and Dr. Glaser are fellows in the American College of Sports Medicine. Requests for reprints should be sent to G. William Gayle, PhD., College of Education and Human Services, Department ofHealth. Physical Education and Recreation, Wright State University, Dayton, OH 45435, (513)873-3223.

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Cardiorespiratory and perceptual responses to arm crank and wheelchair exercise using various handrims in male paraplegics.

The purpose of the present study was to determine the effects of 10-in [0.25-m] versus 16-in [0.41-m] wheelchair handrims on cardiorespiratory and psy...
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