Active after Stroke

Each year 47.000 people in the Netherlands suffer a stroke for the first time,
in total 129 people per day. In 2011 the costs of care for stroke survivors
were estimated to be 970 million euro for males and 1.3 billion for females
(top 10 of most expensive conditions). Rehabilitation of stroke survivors is
aimed at gaining as much independence as possible in their own environment.
After discharge from the hospital stroke survivors need to stay or become
physically active to keep or regain their aerobic capacity as an important part
of integration into society.
Research shows that almost 80% of the stroke survivors has reduced strength and
an aerobic capacity between 12-20 ml/kg/min. According to Shephard a minimum
VO2max of 15 ml/kg-1/min-1 is needed to perform functional activities for
independent living. Cardiopulmonary capacity (i.e., aerobic capacity or VO2max)
is defined as the highest rate at which oxygen can be taken up and consumed by
the body during intense exercise18. Obtaining a valid measure of aerobic
capacity in stroke survivors is important for the purpose of determining
exercise capacity, training prescription, treatment efficacy evaluation, and/or
investigation of exercise-induced adaptations of the oxygen
transport/utilization system. The current gold standard for the assessment of
aerobic capacity is considered to be the maximal cardiopulmonary exercise test
(CPET) with measurements of ventilation and gas exchange, for direct
assessment of maximal oxygen uptake (VO2max). VO2max is the accepted indicator
of aerobic capacity and reflects the limits of the cardiorespiratory system to
respond to exercise.
The assessment of aerobic capacity in persons after stroke is more challenging
than in healthy subjects because they present with stroke-specific impairments
such as muscle weakness, fatigue, poor balance, contractures and spasticity,
which can compromise CPET outcome. Marzolini et al. for instance, reported that
at the start of an exercise training intervention only 68.4% of CPETs (n=98)
provided information sufficient to prescribe exercise intensity in persons with
chronic stroke, suggesting that many persons after stroke do not reach the
limits of their cardiopulmonary system before training. In the search for a
CPET protocol that allows persons after stroke to reach the limits of their
cardiopulmonary system, a multitude of different protocols have been developed
using treadmill, body weight supported treadmill, (recumbent) leg cycle
ergometry and recumbent stepper exercise. However, the majority of subjects did
not reach the limits of their cardiopulmonary system in these protocols. Given
the reported difficulty of measuring VO2max in persons after stroke, we may
need to consider an alternative, for instance, the determination of the
ventilatory threshold, or respiratory compensation point (RCP). The RCP is
recommended as an appropriate target intensity level for the prescription of
exercise as it is an effort independent measure and maximum testing is not
necessary. Measuring RCP in persons after stroke is feasible for the majority
of subjects as evidenced by the reports of 5 studies. Recent studies have
found the determination of RCP to have reasonably good reliability (ICC3,1 =
0.77 (95% CI 0.24, 0.87) in persons after stroke. Since CPET requires
expensive equipment and trained personnel, not available to many clinicians,
there is an urgent need for a valid and reproducible field test to assess at
least the RCP and if possible, VO2max. In clinical settings field tests of
walking ability are often used. These usually comprise a self-paced test in
which the patient walks as far as possible in either six or twelve minutes.
Despite the wide use in stroke rehabilitation, the 6MWT requires a long walking
track, it can only be performed on an individual basis, and participants may be
influenced by self-paced walking speed, motivation, and encouragement that
cannot be standardized and might influence the level of exertion. Their very
simplicity, however, limits the information that can be obtained from them
about the physiological and symptomatic changes that occur during exercise.
Therefore, the Shuttle Walk Test, initially developed for persons with COPD,
may be of more use. The protocol was modified from that of a progressive,
externally paced 20 meter shuttle running test, widely used as a field test of
functional capacity in athletes. The protocol has been adapted or modified for
patients with a variety of chronic diseases for adults and children and has
been found to be safe and have acceptable psychometric properties. A systematic
review reported the correlations between distance walked in the SWT and VO2peak
to range from 0.67 to 0.95 (p<0.01) for criterion validity. ICCs for test
retest reliability ranged from 0.76 to 0.99. To date the SWT has not been
tested or applied in subjects after stroke. For many adults with physical
disabilities, the original 20-m shuttle test is not suitable, because the
starting speed (8 km/h) and increase (0.5 km/h) every minute are beyond their
capabilities. A continuous progressive exercise lasting between 6 and 17
minutes is optimal for achieving a maximal effort.
Verschuren et al. developed a modified Shuttle Test (ST) for children with
cerebral palsy, which, compared with the original SWT, uses smaller increments
in walking or running speed over a 10-m course. There are 2 protocols available
for this 10-m shuttle test. The Level I shuttle test (ST-I) starts at 5 km/h.
The Level II shuttle test (ST-II) starts at 2 km/h. Speed is increased 0.25
km/h every level (minute) for both tests. These protocols might be a more
suitable functional walk/run test for individuals with motor deficits,
including subjects after stroke.
Since most subjects after stroke that participated in the SUSTAIN study (n=60)
walked less than 3.5 km/hr during a 6 minute walk test, we will investigate the
validity and reproducibility of the ST-II test (that starts at 2 km/hr) for
measuring cardiopulmonary capacity.

Primary Objective: to investigate the validity and reproducibility of the ST
for measurement of cardiopulmonary capacity in stroke survivors.
Secondary Objective(s): To establish 1. the reproducibility of the exercise
time during the ST, 2. safety of the ST in stroke survivors, 3. possible
differences in the reproducibility and validity of the ST between patients with
subacute stroke and patients with chronic stroke.

This is a test-retest study.
Subjects will be asked to perform the Shuttle Test (ST) twice, about one week
apart. After the ST and appropriate rest a validation procedure will be
performed lasting 3 minutes.

We will ask people after stroke to come 2 x 1 hour for testing. We will
exclude subjects at risk for potential problems with maximal exercise testing
(such as fall prone subjects and subjects with severe cardioascular disease.
During the test the researcher accompanies the subject. We therefore estimate
the burden and risks associated with participation as low.This study will
provide insight into the validity and reproducibility of the ST for people
after stroke. This field test has the potential to provide information on a
subject*s exercise capacity, to be used to determine exercise intensity and
treatment outcomes. The individual subjects will get insight into their
exercise capacity and will be given a report on their exercise capacity to
share with their attending physical therapist and/or physician if they should
wish to do so.