Influence of Hand Cycling on Physical Capacity in the Rehabilitation of Persons With a Spinal Cord Injury: A Longitudinal Cohort Study

Participants 

The study was part of the Dutch research program “Physical Strain, Work Capacity, and Mechanisms of Restoration of Mobility in the Rehabilitation of Persons With a Spinal Cord Injury.” Patients who were admitted to 1 of the 8 main Dutch SCI rehabilitation centers during the period 1999 to 2004 were included if they (1) had acute SCI, (2) had a prognosis of “mainly wheelchair-bound,” (3) had a lesion level of C5 or lower (and consequently were expected to be able to propel a hand cycle), (4) were aged between 18 and 65 years, (5) had sufficient knowledge of the Dutch language, and (6) did not have a progressive disease or psychiatric problem. Patients were (temporarily) excluded if they had cardiovascular contraindications or serious musculoskeletal complaints.

After being informed about the study, the patients were screened by a physician and signed a written informed consent on a voluntary basis.

Study Design 

Trained research assistants performed the standardized measurement protocol, which was approved by the Medical Ethics Committee of the VU University Medical Center. The study included 3 measurements: at the start of active rehabilitation when each subject could sit in a wheelchair for at least 3 hours (t1), on discharge (t2), and 1 year after discharge (t3).

All subjects performed an aerobic exercise test in a handrim wheelchair to determine POpeak and Vo2peak. Subjects who were not yet able to perform the exercise test at t1 performed the test 3 months after t1. The exercise test was performed in a handrim wheelchair, because this was most closely related to subjects' everyday mobility and because testing in a hand cycle would put those not hand cycling at a disadvantage. In addition, muscle strength and pulmonary function, both considered to be possible contributors to the level of POpeak and Vo2peak,16 were also evaluated. Hand cycle use was monitored retrospectively at both t2 and t3 with a specifically designed questionnaire in which questions were asked about the frequency and duration of hand cycle use in the previous 3 months. From the answers to these questions we defined regular hand cycling as hand cycling once a week or more (hand cycling group). Not hand cycling was defined as hand cycling less than once a week or not hand cycling at all (not hand cycling group).

All subjects followed the usual care rehabilitation program in their own rehabilitation centers. The SCI rehabilitation programs in The Netherlands have been standardized considerably over the past decade17 in the 8 specialized rehabilitation centers. In the present study, hand cycling was defined as both hand cycle use and/or hand cycle training.

Measures 

Data Analyses 

Subject characteristics and baseline values for the physical capacity outcome measures at the start of clinical rehabilitation (t1) and at the start of the postclinical rehabilitation period (t2) were compared between the hand cycling group and the nonhand cycling group with an independent t test (P≤.05).

A multilevel regression analysisd was applied to investigate the relationship between hand cycling and changes in physical capacity. The main advantage of this statistical method is that it corrects for the dependency of repeated measures within subjects and rehabilitation centers. Separate models were constructed for subjects with paraplegia and tetraplegia and for the clinical rehabilitation period and postrehabilitation period. The physical capacity outcome measures at t2 (for the clinical rehabilitation period) and t3 (for the postclinical rehabilitation period) were used as dependent variables in the respective models. Group (nonhand cycling=0, hand cycling=1) and the baseline value of the physical capacity variable at t1 (for the clinical rehabilitation period) or at t2 (for the postclinical rehabilitation period) were included as independent variables. For example, the following model reflects the difference in improvement in POpeak between the hand cycling group and the nonhand cycling group during clinical rehabilitation:

As possible confounders, the following independent variables were added one by one to the initial model: completeness of the lesion (motor complete=1, motor incomplete=0), sex (man=1, woman=0), age (y), time since injury at t1 (in days), length of active rehabilitation defined as time between t1 and t2 (in days), and participation in other aerobic sport activities (in h/wk). Hand cycle use during clinical rehabilitation (yes=1, no=0) was added as a possible confounder to the second model (postrehabilitation period). Variables that changed the regression coefficient of hand cycling by at least 10% were identified as confounders and were included in the final model, as was previously described by Maldonado and Greenland26 The level of significance was set at P less than or equal to .05.

Characteristics of the Hand Cycling Group and the Nonhand Cycling Group 

Data on hand cycle use was available for 137 subjects in the clinical rehabilitation period and for 131 subjects in the postrehabilitation period. Data on 106 subjects were available for both periods. In total, 162 (different) subjects participated in the study. Table 1 shows the characteristics of the hand cycling group and the nonhand cycling group during and after clinical rehabilitation. Except for age in the tetraplegic group, no significant differences in characteristics were found between the hand cycling group and the nonhand cycling group at the start of clinical rehabilitation (baseline t1). At the start of the postclinical rehabilitation period (baseline t2), no significant differences in personal characteristics were found between the hand cycling group and the nonhand cycling group.

Table 1. Characteristics of the 2 Groups, Hand Cycling or Not Hand Cycling, During and After Rehabilitation

	Characteristics	Subject (n)	ASIA Grade A or B (% yes)	Mean Age ± SD (y)	Mean Body Weight ± SD (kg)	Mean Height ± SD (cm)	Sex (% men)	Mean TSI at t1 ± SD (d)	Mean Time t1 − t2 ± SD (d)	Mean Aerobic Sports ± SD (h/wk)
	During rehabilitation (at baseline t1)									Questionnaire at t2
	Paraplegia
	Non-HC	56	71	42±14	72.3±15.2	177±10	73	92±57	153±68	1.9±2.3
	HC	35	80	40±15	76.1±13.4	179±10	67	97±67	177±113	2.1±1.5
	P		.64	.50	.29	.38	.36	.71	.23	.78
	Tetraplegia
	Non-HC	26	58	44±14	69.0±11.6	176±8	69	120±98	226±145	1.1±1.3
	HC	20	80	33±10	68.8±14.2	177±10	80	110±58	254±198	1.1±1.1
	P		.11	.007	.93	.91	.41	.67	.61	.94
	After rehabilitation (at baseline t2)									Questionnaire at t3
	Paraplegia
	Non-HC	60	70	48±15	75.8±16.0	178±10	70	NA	NA	0.7±1.4
	HC	34	71	39±15	75.2±11.8	177±8	77	NA	NA	0.8±2.0
	P		.72	.12	.83	.83	.50			.61
	Tetraplegia
	Non-HC	28	50	38±14	70±13.2		68	NA	NA	0.4±0.9
	HC	9	56	33±7	75±17.9	181±11	89	NA	NA	0.8±1.0
	P		.67	.26	.38	.11	.22			.27

NOTE. Sex with only the percentage of men described (with the percentage of woman added equals 100%), ASIA grade A or B with only the percentage of subjects with ASIA grade A or B described (with the percentage of subjects with ASIA grade C or D added equals 100%). Aerobic sports: other aerobic sports apart from hand cycling, during and after rehabilitation obtained from a questionnaire at t2 and t3, respectively. Abbreviations: ASIA Grade A or B, motor complete lesion; HC, hand cycling group; NA, not applicable; Non-HC, nonhand cycling group; SD, standard deviation.

Table 2, Table 3, Table 4 describe the physical capacity outcomes of the hand cycling group and the nonhand cycling group during and after clinical rehabilitation. For each outcome measure, only subjects who completed both the baseline and follow-up tests were included. Because not all subjects were able to perform all tests on all occasions, a variable number of subjects is presented for each outcome measure. At the start of the active rehabilitation (t1), no differences in baseline values were found between the hand cycling group and the nonhand cycling group. At the start of the postclinical rehabilitation period (t2), subjects with paraplegia in the hand cycling group had significantly higher values for muscle strength (MMT total, P=.04; HHD elbow extension, P=.018) compared with the nonhand cycling group. No differences in baseline values were found in subjects with tetraplegia for the postrehabilitation period.

Table 2. Cross-Sectional Values of the Outcome Measures at Baseline (t1) and at Follow-Up (t2) During Rehabilitation

	During Rehabilitation Outcome Measures	Paraplegia			Tetraplegia
		n	t1	t2	n	t1	t2
	POpeak (W)
	Hand cycling	28	37.3±19.6	52.8±23.6	12	15.3±7.4	27.0±11.6
	Nonhand cycling	40	38.0±20.3	48.1±20.7	14	14.8±10.0	23.4±15.9
	Vo2peak (L/min)
	Hand cycling	29	1.10±0.23	1.42±0.45	11	0.86±0.32	1.07±0.37
	Nonhand cycling	38	1.22±0.48	1.32±0.47	12	0.97±0.38	1.05±0.38
	Vo2peak (mL·kg−1·min−1)
	Hand cycling	29	14.6±6.0	18.5±6.3	9	10.8±3.4	13.6±4.9
	Nonhand cycling	36	16.3±6.0	18.1±6.2	11	13.5±4.3	14.5±4.5
	MMT total
	Hand cycling	36	58.2±3.3	59.5±2.1	20	38.3±14.9	45.6±14.2
	Nonhand cycling	55	56.0±12.3	57.0±12.1	24	43.0±12.2	49.8±12.2
	HHD elbow flexion (l+r) (n)
	Hand cycling	26	487±133	546±153	17	310±125	416±138
	Nonhand cycling	40	487±153	533±146	19	308±113	407±137
	HHD elbow extension (l+r) (n)
	Hand cycling	28	320±118	417±129	7	208±130	249±105
	Nonhand cycling	47	342±107	393±109	15	151±90	216±103
	FVC (%)
	Hand cycling	33	77.5±22.5	87.1±19.5	19	59.9±24.2	73.8±25.8
	Nonhand cycling	49	80.2±27.6	88.5±24.0	23	69.3±23.2	79.9±18.0
	PEFR (%)
	Hand cycling	33	62.2±17.1	71.1±15.5	19	45.4±22.1	56.6±20.7
	Nonhand cycling	49	58.7±24.2	66.8±20.3	23	52.3±18.2	58.7±16.1

NOTE. Values are mean ± SD. For each outcome measure, only subjects with baseline and follow-up measurements are included. There were no significant differences at baseline during rehabilitation (t1) between the hand cycling group (hand cycling) and the nonhand cycling group (nonhand cycling) (P≤.05). Abbreviations: l, left; r, right.

Table 3. Cross-Sectional Values of the Outcome Measures at Baseline (t2) and at Follow-Up (t3) After Rehabilitation

	After Rehabilitation Outcome Measures	Paraplegia			Tetraplegia
		n	t2	t3	n	t2	t3
	POpeak (W)
	Hand cycling	26	54.6±22.6	57.8±25.0	4	29.9±19.7	33.3±22.2
	Nonhand cycling	36	46.9±22.1	49.5±23.9	12	22.9±14.3	23.2±13.1
	Vo2peak (L/min)
	Hand cycling	26	1.38±0.46	1.45±0.57	4	0.99±0.46	1.16±0.74
	Nonhand cycling	33	1.26±0.46	1.33±0.52	14	0.99±0.34	1.05±0.30
	Vo2peak (mL·kg−1·min−1)
	Hand cycling	26	18.8±6.6	19.0±8.9	4	11.1±6.2	12.6±9.9
	Nonhand cycling	33	17.5±5.9	17.9±6.6	14	13.9±3.4	14.1±3.4
	MMT total
	Hand cycling	33	60.0±0.2⁎	59.9±0.5	6	50.3±9.4	51.0±10.1
	Nonhand cycling	53	59.0±2.6	59.6±1.6	28	48.6±9.4	49.3±8.9
	HHD elbow flexion (l+r) (n)
	Hand cycling	21	568±128	581±154	6	419±138	419±205
	Nonhand cycling	34	499±140	508±138	18	440±145	448±123
	HHD elbow extension (l+r) (n)
	Hand cycling	26	427±99⁎	453±104	3	214±87	241±70
	Nonhand cycling	41	367±95	373±109	13	202±78	230±96
	FVC (%)
	Hand cycling	30	89.9±20.6	93.0±18.8	8	79.2±18.7	82.1±32.2
	Nonhand cycling	46	90.9±18.9	91.0±21.0	22	75.9±20.0	83.2±18.2
	PEFR (%)
	Hand cycling	30	69.9±14.5	72.8±19.3	8	52.2±22.8	55.9±28.8
	Nonhand cycling	46	69.9±20.6	70.8±18.1	22	57.9±14.8	63.5±15.4

NOTE. Values are mean ± SD. For each outcome measure, only subjects with baseline and follow-up measurements are included.

⁎ Significant differences at baseline (after rehabilitation; at t2) between the hand cycling group and the nonhand cycling group (P≤.05).

Table 4. The Regression Equation of Hand Cycling (β2 regression coefficient) After Adding All Confounders (that change β2 >10%) to the Model

	Outcome Measures	During Rehabilitation						After Rehabilitation
		Paraplegia			Tetraplegia			Paraplegia
		n	β2 ± SE	P	n	β2 ± SE	P	n	β2 ± SE	P
	PO (W)	68	6.2±2.4	.00	26	2.6±2.8	0.35	62	0.3±2.9	0.92
	V̇o2 (L/min)	67	0.21±0.07	.00	23	0.11±0.11	.32	59	0.01±0.07	.89
	V̇o2 (mL·kg−1·min−1)	65	1.55±0.96	.11	20	0.81±1.50	.59	59	−0.9±0.9	.32
	MMT total	88	0.4±0.6	.51	44	−1.5±1.6	.35	86	−0.1±0.2	.44
	HHD elbow flexion (n)	66	5±18	.78	36	−9.7±25.7	.71	56	23±24	.34
	HHD elbow extension (n)	75	43±17	.01	22	−41.8±28.1	.14	67	28±13	.03
	FVC (%)	82	0.4±3.2	.90	42	0.7±4.7	.88	76	3.1±2.6	.23
	PEFR (%)	82	2.1±3.1	.51	42	3.5±4.1	.39	76	2.5±2.8	.37

Abbreviation: SE, standard error.

Hand Cycling During Clinical Rehabilitation 

During clinical rehabilitation subjects in the hand cycling group and the nonhand cycling group on average improved on all outcome measures (see table 2).

Hand Cycling in the Postrehabilitation Period 

During the year after clinical rehabilitation subjects in both the hand cycling group and the nonhand cycling group improved only marginally on all outcome measures (see table 3).

In contrast to the results during clinical rehabilitation, no significant effect of hand cycling was found on POpeak and Vo2peak, muscle strength (MMT total, elbow flexion strength), or pulmonary function (PEFR, FVC).

Hand cycling during rehabilitation appeared to be a confounder for the effect of hand cycling in the postrehabilitation period in most outcome measures. A large number of subjects (≈25% in all outcome measures) had missing values for this confounder. Therefore, we performed a multilevel regression analysis without this confounder (see table 4). In addition, we also performed an analysis with this confounder on the subgroup of subjects with data on hand cycling during rehabilitation. Results were the same, except for elbow extension strength. After adding the confounder hand cycling during the rehabilitation, no significant effect of hand cycling on elbow extension strength was found in a subgroup of 53 subjects (P=.83).

Because of the low number of subjects and the unequal distribution over the hand cycling group and the nonhand cycling group, a multilevel regression analysis could not be performed after clinical rehabilitation for subjects with tetraplegia.

POpeak and Vo2peak 

Other Outcome Measures 

Study Limitations 

One limitation of the present study is that missing values are considerable, because data on an outcome measure had to be available for 2 sequential measurement moments. Not all subjects were able to perform the tests on all occasions, and this applies in particular to the peak wheelchair exercise test. It appeared that, despite a test protocol that was especially designed for subjects with the lowest physical capacity, 50% of those with a lesion level of C5 or C6 were not able to perform the test in the first 3 months of active rehabilitation, although some of them were hand cycling during rehabilitation. There were also subjects with incomplete lesions and a relatively high physical capacity who dropped out of the project because they regained walking ability during rehabilitation. Therefore, the results of POpeak and Vo2peak apply only to subjects with SCI who depend on a wheelchair and are able to propel a wheelchair independently.

In the present study, the relationship between hand cycling and the outcome measures of physical capacity is not necessarily a causal relationship. Because this study was designed as an observational cohort study, no controlled training protocol was imposed and no randomized control group was included. The frequency (and intensity) of training was reported by subjects themselves and is therefore subjective. A hand cycle frequency of at least once a week is rather low to induce training effects; nevertheless, we found positive effects in subjects with paraplegia during the rehabilitation period.

Another limitation of this observational design is that subjects who are doing well are more likely to hand cycle regularly. However, this is not supported by our results, which show equal baseline values on all outcome measures in the hand cycling group and the nonhand cycling group at the start of rehabilitation. The higher baseline values in the hand cycling group at the start of the postrehabilitation period may support the assumption of a selection bias, although this can also be explained by the fact that half of the subjects in the hand cycling group had already started hand cycling during rehabilitation. A more suitable design to investigate the effects of hand cycle training would be a randomized controlled trial. We are currently investigating the effects of structured hand cycle training (interval training twice a week) on physical capacity in subjects with SCI.