Acute energy cost of multi-modal activitybased therapy in persons with spinal cord
injuryEric Turner Harness 1, Todd A. Astorino 2
1

Project Walk Spinal Cord Injury Recovery Center, Carlsbad, CA, USA, 2Department of Kinesiology, California State
University San Marcos, CA, USA
Objective: To examine acute energy costs of multi-modal activity-based therapy (ABT) in men and women withspinal cord injury (SCI).
Study design: Descriptive case series.
Setting: An outpatient center in California.
Participants: Seven men and women (age = 28.3 ± 11.6 years; duration of injury = 4.3 ± 2.5 years) with injury
levels ranging from C5 to T8.
Intervention: Activity-based therapy.
Outcome measures: Oxygen uptake (VO2), energy expenditure (kcal/minute), SCI Metabolic Equivalent of Task
(MET) (1 MET = 2.7 ml/kg/minute).
Results: Oxygen uptake (VO2) during ABT ranged from 5.10 to 8.62 ml/kg/minute, with VO2 consistently higher
during modalities involving load bearing versus non-load bearing (P = 0.08). SCI MET values ranged from 1.89
to 3.24 and were significantly higher in subjects with mid-thoracic injury versus low-cervical injury (P = 0.01).
Conclusion: Data reveal that multi-modal ABT increases VO2 in persons with SCI, but energy expenditure isrelatively low. Strategies must be identified to optimize energy expenditure in the SCI to reduce health risks.
Modalities involving load bearing seem to be superior to non-load-bearing activities. VO2 was greater in
response to load-bearing modalities than non-load-bearing modalities. It remains to be determined whether
chronic ABT enhances cardiovascular fitness and reduces disease risks in this population.
Keywords: Activity-based therapy, Spinal cord injuries, Rehabilitation, Paraplegia, Tetraplegia, Energy expenditure, MET, Resistance training, Ergometry,
Functional electrical stimulation, Assisted standing

Introduction
Approximately, 12 000 spinal cord injuries (SCIs) occur
annually, with 80% of injuries occurring in men.1 Onset
of SCI often reduces participation in physical activity
and is consequent with alterations in endocrine function, body composition, and vitality.2 One result of
reduced physical activity is the increased incidence ofobesity that contributes to enhanced risk of cardiovascular disease and diabetes.3–5 Consequently, effective rehabilitation is needed in persons with SCI to reduce theseverity of co-morbidities associated with SCI.
Initially, the primary modality used to rehabilitate
persons with SCI was arm ergometry as it targets thearms, which are needed for day-to-day wheelchair operation, and promotes increases in aerobic fitness.6 As
Correspondence to: Eric Turner Harness, Project Walk SCI Recovery
Center, 2738 Loker Avenue West, Carlsbad, CA 92010, USA.
Email: eharness@projectwalk.org© The Academy for Spinal Cord Injury Professionals, Inc. 2011
DOI 10.1179/2045772311Y.0000000027

early as 1989, studies were published revealing changes
in VO2 in response to acute functional electrical stimulation (FES) and/or hybrid FES-training/rowing inpersons with SCI. FES is a practical therapy in thispopulation as it minimizes excess strain on the upper
extremities while activating the paralyzed musculature
to stimulate hypertrophy, improve circulation, andenhance aerobic fitness.7,8 Mean VO2 during FES
widely varies across individuals, ranging from 0.57 l/minute in persons with injury at C4–T10 to 2.12 l/minute in males with thoracic injury.9,10 Anotherpopular modality is resistance training, as it augments
muscular strength in this population.11 For example,
Nash et al. 12 reported that circuit training increased
energy expenditure to values approximating 40%VO2
max in 17 individuals with complete injury (T4–L1).
Finally, locomotor training in the form of bodyweight-supported treadmill training has been applied

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Acute energy cost of multi-modal ABT in persons with SCI

in this population to improve functional capacity andenhance muscle mass.13,14 Overall, these modalities are
effective to improve physical function and reduce morbidity in persons with SCI.
Recently, activity-based therapy (ABT) has become apopular modality to treat persons with SCI at facilities
across the world. This mode of therapy consists of thefollowing components: patterned motor activation via
locomotor training and/or FES, patterned and nonpatterned activation through task-specific rehabilitationand strengthening, including circuit and/or resistancetraining, and sensory stimulation through sensorimotor
therapy.15 It is unique from traditional therapies in thatit does not focus on teaching compensatory techniques,but targets recovery of neural function. The primary
goal of this therapy is to promote recovery of motorand sensory function below the injury location.15,16
Preliminary data show that ABT promotes neural recovery in rats completing gait training as well as increases
cardiovascular fitness in persons with SCI performing
FES.17,18 Nevertheless, acute physiological responses
to ABT consisting of multiple exercise modalities are
not well documented.
The primary aim of this study was to examine acuteresponses to multi-modal ABT in men and womenwith SCI and to use this information to begin to build
a database of energy costs for these activities. The treatment modalities included in this research were employed
in studies showing greater bone mineral density and leanbody mass, increased lower-extremity strength, andimproved (P < 0.05) motor function in men andwomen with SCI after 6 months of training.16,19,20
Collins et al. 21 recently published a compendium ofenergy cost requirements of various physical activities
and activities of daily living for individuals with SCI,
and this study may help to expand upon these findings.

Methods
Subjects
Participants in this study included seven men andwomen with SCI. They were categorized by neurologicalinjury location either low tetraplegia (C5–C8) or midthoracic (T1–T8). Their demographic characteristics
are shown in Table 1. There were no differences (P >0.05) in any characteristic between groups. Due to thesmall sample size, motor complete- and motor incomplete injuries, defined through the American Spinal
Injury Association Impairment Scale (AIS) as A or B
(motor complete) and C or D (incomplete), were combined. Subjects were currently completing rehabilitation
2–3 days/week at a facility in Southern California.
Participants were free of known cardiac, pulmonary,496

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Table 1 Demographic characteristics of subjects

Sample size (n)Age (year)
Height (cm)Mass (kg)Injury duration (year)
Male/female
Motor complete/motor
Incomplete

Upper-level injury(C5–C8)Mid-level injury(T1–T8)3
28.0 ± 14.8
183.3 ± 14.2
74.3 ± 20.5
4.7 ± 2.9
2/1
2/1

4
28.4 ± 11.0
178.7 ± 12.8
76.2 ± 19.3
3.5 ± 2.5
3/1
3/1

Values are mean ± standard deviation.
No statistical difference between groups (P > 0.05).

or metabolic disease, and were not on medications that
affect cardiovascular or metabolic function. Subjects
filled out a health history questionnaire and provided
informed consent before participating in the study. All
experimental procedures were approved by the
University Institutional Review Board. We certify that
all applicable institutional and governmental regulations concerning the ethical use of human volunteers
were followed during the course of this research.

DesignSubjects refrained from exercise for 24 hours prior to thesession and were 2 hours post-absorptive. They completed a 2–3-hour session of ABT, during which
expired air via indirect calorimetry was continuously
obtained. All activities were supervised by trained
personnel.

Exercise protocol
ABT as completed in this study included the following
modalities:
1. Active assistive exercise: While in a supine or prone
position, the subjects’ limbs were assisted throughdifferent ranges of motion and provided a resistanceless than gravity. The subjects were instructed toattempt or visualize actively assisting or resisting the
movement performed.
2. Standing/standing frame (Easystand Evolv, Altimate
Medical, Morton, MN, USA): The subject was
raised into, or if able, raised themselves into a standing
position to load the lower extremities. While in thisposition, the subject performed various lower- andupper-body extremity exercises to exhaustion.
3. Total gym (EFI Inc., San Diego, CA, USA): Subjects
completed active and/or active assistive squat exercises
while loading the lower extremities at 65% of bodyweight.
4. Hands and knees/kneeling: Subjects were placed on thefloor with the knees and hips flexed 90°, the shoulder
flexed 90°, and the elbow extended 180° so that bodyweight is evenly distributed between the upper andlower body (Fig. 1A). During kneeling, subjects wereHarness and Astorino

placed on the floor with the knees flexed 90° and thehips extended 180° so that body weight is supportedby the lower body (Fig. 1B). Various upper- andlower-body movements were performed in this position.
5. Spin bike: The subject was seated on a modified stationary bike (V-Bike, Star Trac, Irvine, CA, USA) with a
22 kg fly wheel. The modifications included a wider
seat and a back support and, if necessary for the
person with tetraplegia, a platform walker was used inplace of the standard handle bars (Figs 2A and B).
Load bearing occurred through the upper limbs(Figs 2C and D). The subject attempted to pedal thebike under his/her own power; if unable to do so, thesubject was assisted by staff to complete the movement.
6. FES leg ergometry (Restorative Therapies, Baltimore,
MD, USA): While seated in a wheelchair, the subjects’
gluteus maximus, hamstrings, and quadriceps muscles
were stimulated with surface electrodes at 140 mA,
with a pulse width of 250 μs at a frequency equal to33.3 Hz. Ergometer control speed was set at 45 rpm
with a resistance of 1.00 Nm.

Participants completed an average of four of thesemodalities during a single day of training. A basesequence was implemented that consisted of active assistive exercise first, followed by load-bearing exercises,
and finishing with FES. The sequence and incorporation of the different load-bearing modes were different
across subjects due to different levels of physical function and injury location. With the exception of FES,
all modalities were performed at an intensity that the
subjects considered was their maximum effort for theduration of the exercise. Approximately 5–15 minutes
recovery was provided between exercises to allow

Acute energy cost of multi-modal ABT in persons with SCI

subjects to rest, transfer to the next modality, anddrink water ad libitum. During recovery, the respiratory
mask was removed. Gas exchange data were continuously obtained during each modality, which lasted aminimum of 8 minutes to achieve a steady state.

Assessment of gas exchange data
A portable metabolic cart (Jaeger OxyCon, Viasys
HealthCare, Yorba Linda, CA, USA) was used toacquire breath-by-breath gas exchange data throughout
exercise. Initially, the device was calibrated to room air
as well as a standard gas mixture equal to 16.0% O2
and 4.0% CO2. A vest was placed on participants’chest containing the gas analyzers and flow turbine,
and a respiratory mask was used to collect expired air.
VO2 (in ml/kg/minute and ml/minute) was time-averaged every 30 seconds during exercise and used to calculate energy expenditure (in kcal/minute) using
respiratory exchange ratio as well as in METs, using
the constant proposed by Collins et al. 21 for SCI
where 1 MET = 2.7 ml/kg/minute (SCI MET).

Statistical analysis
Data were analyzed using JMP (SAS, Cary, NC, USA)for normality of distribution using the Shapiro–Wilk
test. Normally distributed data were tested using thematched-pairs t-test, and non-parametric statistics(Wilcoxon rank-sum) were used on non-normal data.
Both were used to determine if there were significant
differences in sample characteristics and measured parameters between injury-level categories. All analyses were
two-tailed, with alpha = 0.05. Data are reported asmean ± standard deviation where applicable.

Figure 1 (A) Hands and knees, during which subjects were placed on the floor and required to support their body weight throughthe upper and lower extremities while performing various upper- and lower-body exercises. (B) Kneeling, during which subjects
were placed on the floor and required to support their body weight through the lower extremities while performing various upperand lower-body exercises.

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Figure 2 (A) Spin bike, Low cervical set up, platform walker secured in place of handle bars, upper extremities were loaded throughplacement of forearms on the walker. (B) Spin bike, Mid-thoracic set up, upper extremities were loaded through placement of thehands on the handle bars. (C) Spin bike, Low cervical set up showing subject positioning. (D) Spin bike, Mid-thoracic set up showing
subject positioning.

Results
Due to the heterogeneity of those with SCI (i.e. variations in injury level, existing motor and sensory function, and response to treatment), the selection of
specific modalities within ABT programs is very individualized and is performed to best take advantage of thefunctional abilities of each client. As participants variedwith regard to injury level, injury duration, and physicalfunctioning, they did not complete identical exercise
programs during the study. This also required that exercises be performed in a manner and sequence that weremost advantageous to the individual in that session. We
believe that it was important to capture this aspect;
therefore, data were recorded throughout each modality
during each exercise session. This may present a more
realistic representation of the actual energy costs ofthese activities. Consequently, data are presented for

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six activities that were performed by at least two subjects
in a single-injury category.

VO2 and energy expenditure data
Oxygen uptake (ml/kg/minute and ml/minute), energy
expenditure (kcal/minute), and SCI MET equivalents
for each modality are presented in Table 2. VO2 andcalorie expenditure during exercise were consistently
lower in subjects with low cervical injury versus thosewith mid-thoracic injury. Modalities providing skeletalloading in subjects with mid-thoracic injuries (standing/standing frame, total gym, and spin bike) tended
to reveal greater oxygen consumption than modalities
in which subjects were seated or lying down (FES andactive assistive exercise) (P = 0.08). VO2 during standing/standing frame was significantly higher in subjects

Harness and Astorino

Table 2

Acute energy cost of multi-modal ABT in persons with SCI

Energy expenditure during acute ABT

Activity-injury group
Active assistive exercise
C5–C8
T1–T8
Standing/standing frame
C5–C8
T1–T8
Total gym
C5–C8
T1–T8
Hands and knees/kneeling
C5–C8Spin bike
C5–C8
T1–T8
FES leg ergometry
T1–T8

n

VO2 (ml/minute)Kcal/minute

VO2 (ml/kg/minute)

SCI MET2
4

411.74 ± 80.51
471.12 ± 199.57

2.00 ± 0.40
2.29 ± 0.97

5.10 ± 1.92
6.08 ± 1.75

1.89
2.25

3
4

391.74 ± 36.86*
655.56 ± 178.65

1.90 ± 0.18
3.18 ± 0.87

5.54 ± 1.56*
8.62 ± 0.77

2.05
3.19

2
3

422.39 ± 8.45
551.61 ± 166.18

2.05 ± 0.04
2.67 ± 0.83

5.13 ± 1.07
7.01 ± 0.72

1.90
2.60

2

387.60 ± 23.19

1.95 ± 0.01

6.45 ± 1.37

2.39

3
2

387.11 ± 76.73
595.05 ± 160.09

1.88 ± 0.37
2.89 ± 0.78

5.57 ± 2.35
8.76 ± 0.12

2.06
3.24

3

559.10 ± 30.91

2.71 ± 0.15

6.84 ± 0.96

2.53

Values are mean ± standard deviation.
FES, functional electrical stimulation; SCI MET, 2.7 ml/kg/minute.
*P < 0.05 between groups for this modality.

with mid-thoracic injuries than those with low cervicalinjuries (P = 0.03; Table 2).

Discussion
The primary aim of this study was to describe the energy
cost of acute multi-modal ABT in persons with SCI.
Results revealed that prolonged bouts of ABT increased
VO2 with magnitude of these increases higher in individuals with mid-thoracic compared to low cervical injury.
Standing demonstrated the highest VO2 in participants
with mid-thoracic injuries, with values similar to thosereported for wheelchair ambulation, FES-cycling, andarm ergometry, yet greater than observed with circuit
training.6,12,22,23
The energy expenditure and VO2 reported in thepresent study differ somewhat from previously demonstrated values. Results from Perret et al. 24 revealed
higher mean calorie expenditure equal to 4.8 kcal/
minute during 60 minutes of FES in men and womenwith complete thoracic injury. This population,
however, did not include men and women with cervicalinjury who tend to reveal lower exercise tolerance thanpersons with a thoracic/lumbar-level injury.
In the Collins et al. 21 compendium of energy costrequirements for individuals with SCI, subjects in the
low cervical and mid-thoracic groups exhibited higher
energy cost during arm cranking at 32–96 W and wheelchair ambulation (2.60–6.33 SCI METs) compared toactivities including aerobics, circuit training, andweight training (1.83–3.41 SCI METs). However, novalues were reported for rehabilitation-type exercises
including active assistive exercise, FES, and other
ABT modalities as presented in the current study. SCI

METs for these activities range from 1.89 to 3.24,
which is comparable to traditional exercise including
aerobics, circuit training, and weight lifting. The one
activity included in Collins et al. 21 which is similar tothat presented here was ‘assisted standing’. In persons
with lower-level thoracic injuries (T9–L4), an oxygen
uptake, energy expenditure, and SCI MET cost equal
to 238.0 ± 5.7 ml/minute, 1.23 ± 0.03 kcal/minute,and 1.17 MET cost were reported. All subjects in thepresent study exhibited higher values for these parameters during standing/standing frame exercise(Table 2), which could be explained by the greater familiarity of our subjects with this exercise modality andthe need to perform other exercises while in this position, including isolated upper-extremity movements
and assisted squats, which require additional active
muscle mass and thus oxygen uptake.
It has been recommended for persons with SCI to
expend 1000–2200 kcal/week to reduce disease risks.25
Perret et al. 24 showed that 4–8 hours/week of FES isadequate to meet this criterion. However, our results
show lower energy expenditure for multi-modal ABT
ranging from 1.88 to 3.18 kcal/minute, which would
require between 5.2 and 8.9 hours of activity per week
to expend this amount of calories. It is plausible thatexercise that activates a large muscle mass, such as
FES or standing, should be emphasized in rehabilitation
regimens to optimize calorie expenditure and potentiallyreduce health risks, as greater durations of exercise may
be contraindicated in this population due to lack ofadherence, increased injury risk, or simply lack of feasibility. Identifying suitable exercise regimens in patientswith cervical injury is needed too, as their lower physical

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Acute energy cost of multi-modal ABT in persons with SCI

function reduces calorie expenditure and thus theirability to meet this standard.
This study faced a few limitations. First, data can only
be applied to men and women with SCI completing
ABT and not arm ergometry, athletics, or activities ofdaily living. Second, subjects had chronic SCI, and sotheir responses cannot be compared with responses of
persons with acute or sub-acute injury (<6 months
post-injury). Participants’ VO2 max was not obtained,
and so it is unknown as to what fraction of maximal
aerobic power subjects were exercising. In addition, participants typically exercised at a self-imposed maximum,and so data may represent sub-maximal effort. Finally,
the number of females participating in the study was
small, which limits its generalizability to the entire
female population.

Conclusion
The types of exercise modalities employed in the present
study are gaining prominence in the field of SCI rehabilitation due to their promotion of functional recovery
below the neurological injury level.15,16 Considering
the low levels of physical fitness in persons with SCI
and consequent enhanced risks of chronic disease, identifying calorie expenditure for ABT modalities and subsequently educating clientele with regard to meeting
minimum duration of these activities seems paramountto reduce morbidity and mortality in this population.
The current report is a first step in understanding theacute physiological responses to acute ABT and may
allow clinicians to better match participants’ caloric
intake to expenditure. Further study is merited to
examine the effects of chronic ABT on cardiorespiratory
fitness, muscular function, and disease prevention inpersons with SCI.

Acknowledgment
The authors thank Fred Kolkhurst, PhD, for providing
the portable metabolic unit used in this study, andKimberly Howell for her assistance with data analysis.

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