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Effect of Exercise on OH in SCI

Following exercise, individuals with SCI may experience improvements in the autonomic regulation of their cardiovascular system (Lopes et al. 1984). Exercise, or even passive movement of the legs, could potentially attenuate reduced central blood volume in individuals with SCI during an orthostatic challenge. For example, Dela et al. (2003), found a pronounced increase in BP in individuals with tetraplegia when their legs were passively moved on a cycle ergometer. There is also evidence that exercise training may enhance sympathetic outflow in individuals with SCI, as shown by an increase in catecholamine response to maximal arm ergometry exercise (Bloomfield et al. 1994).

Table 9: Exercise on OH in SCI

Author Year; Country
Score
Research Design
Total Sample Size
MethodsOutcome
Lopes et al. 1984;

USA

PEDro=2

RCT

N=12

Population: 5 tetraplegia, 1 paraplegia; 6 control subjects.

Treatment: Random assignment to active exercise (60 bilateral forearm flexion and extension movements per minute during the first and third minute of each tilt angle) versus no upper limb exercises during tilt from 0-70 degrees by 10 degrees increments at five-minute intervals until BP dropped below 70/40.

Outcome measures: BP, hypotensive symptoms.

1.    No significant difference between the active upper extremity exercise group versus the non-exercise group with reference to orthostatic tolerance to progressive vertical tilt.
Otsuka et al. 2008;

Japan

Prospective controlled trial

N=30

Population: 10 men with tetraplegia, age: 29±6 years who were on a wheelchair basketball team and had physical training for at least 2hr/day, 2 days/week, for 2 years; 10 untrained men with tetraplegia,    age 32±6 years and 10 able-bodied sedentary men, age 23±2 years were included as controls.

Treatment: regular physical activity training

Outcome Measures: HR, BP; electrocardiogram; autonomic nervous system activity in supine and 60° sitting position.

1.   During supine rest, trained subjects with tetraplegia had significantly lower HR than the able-bodied controls.

2.   Increase in HR from supine to sitting position in trained and untrained subjects with tetraplegia.

3.   Untrained subjects with tetraplegia, but not trained subjects with tetraplegia demonstrated significant orthostatic responses (increased sympathetic activity and reduced vagal activity).

Ditor et al. 2005;

Canada

Pre-post

N=8

Population: Sensory incomplete (AIS B-C) cervical SCI (C4-C5).

Treatment: 6 months of body weight-supported treadmill training (BWSTT).

Outcomes measures: HR, BP, and orthostatic responses, heart-rate variability.

1.    Resting HR was reduced but no change in resting BP after BWSTT.

2.    BWSTT did not improve BP or HR during head-up tilt (HUT).

Only three exercise studies have attempted to assess the effect of exercise on orthostatic tolerance in subjects with SCI and protocol differed in each. Lopes et al. (1984) found no effects on orthostatic tolerance with the addition of upper extremity exercises during a progressive head-up tilt (HUT) protocol. Such findings are not surprising given the small muscle mass involved in the upper limbs and the fact that venous pooling occurs primarily in the lower limbs. Ditor et al. (2005) demonstrated that individuals with incomplete tetraplegia retain the ability to make positive changes in cardiovascular autonomic regulation with BWSTT. However, six months of BWSTT did not adversely affect the orthostatic tolerance in subjects with SCI. The authors found this encouraging as it suggests that orthostatic tolerance is retained after exercise training, even though this intervention probably reduced peripheral vascular resistance. Otsuka et al. (2008) found that individuals with complete tetraplegia who were involved in regular physical activity training (2 hrs/day, 2 days/wk, ≥2 yrs) demonstrated greater orthostatic tolerance than inactive individuals with SCI (<30 mins/wk).

Conclusion

There is level 2 evidence (from 1 RCT) (Lopes et al. 1984) that simultaneous upper extremity exercises does not improve orthostatic tolerance during a progressive tilt exercise.

There is level 4 evidence (from 1 pre-post study) (Ditor et al. 2005) that 6 months of BWSTT does not significantly improve orthostatic tolerance during a tilt test.

There is level 4 evidence (from 1 post-test study) (Otsuka et al. 2008) that regular physical activity (2hrs/day, 2x/wk, ≥ 2yrs) may improve orthostatic tolerance during a tilt test.

Simultaneous arm exercise during a tilt test is not effective for improving orthostatic tolerance.

The benefits of body-weight supported treadmill training for management of OH have not been sufficiently proven in SCI.

There is limited evidence that regular physical activity may improve orthostatic tolerance during a tilt test.