We estimated energy expenditure with the Physiological
Cost Index (PCI) [35]. The PCI was assessed on a treadmill.
First, participants stood still for 2 min and the mean
heart rate of the last 10 s was used as heart rate at rest.
Then they walked for 3 min at the same speed as previously
determined in their first 10MWTat preferred speed.
The PCI was calculated as follows: PCI = (steady-state
heart rate – heart rate at rest)/ambulatory velocity.
We assessed symmetry of gait, which has been shown
to improve after locomotor-specific training in patients
with iSCI [20]. It is an important marker for the quality
of gait and an accurate indicator of changes in the walking
pattern, even on a sub-clinical level [36]. There is
evidence that gait symmetry also improves after lower
extremity strength training in patients with stroke [37].
Gait symmetry was measured by comparing lengths of
stance and swing phases of each single leg (by dividing
stance time [in % of whole step] right by stance time
left) with portable insoles. If the value was >1, it was
inverted to ensure comparability. Gait symmetry was measured
in 8 participants only, due to infrastructural issues.