Standardizing fatigue-resistance testing during electrical stimulation of paralysed human quadriceps muscles, a practical approach.
Martin Schmoll, Ronan Le Guillou, David Lobato Borges and 3 others
PMID 33478556WHAT IT FOUND
Distributed stimulation did not improve fatigue resistance in three men with spinal cord injury during dynamic knee extension.
The protocol standardized testing at 40% of maximal evoked torque, but no electrode configuration significantly outperformed conventional stimulation.
Key findings
01No tested electrode configuration showed a statistically significant difference in the fatigue index compared to conventional stimulation.
02Alternative configurations required significantly lower stimulation amplitudes to reach the target torque compared to conventional stimulation.
03The study standardized fatigue testing at 40% of the maximal evoked contraction (MEC) to allow for better comparison between muscles.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
Very small sample size (n=3 participants, 6 legs) limits generalizability. The study was a pilot/feasibility trial, not powered to detect small differences in fatigue. One electrode configuration (POS1) was excluded from analysis due to technical issues with unfused contractions. Results may not apply to untrained patients, as all participants had at least 14 months of prior FES training. The high stimulation intensities used (to reach 40% MEC) may have reduced the selectivity of distributed stimulation, potentially masking benefits seen at lower intensities in other studies.
Declared interests
The authors declared no competing interests. The study was supported by the Swiss National Science Foundation and the European Commission Horizon 2020 programme.
The easy way to misread this
Do not assume that distributed stimulation is ineffective for all FES applications. This pilot used high stimulation intensities (40% of maximal evoked contraction) in a small group of highly trained individuals. Previous literature shows benefits at lower intensities or in different contexts, and the lack of statistical significance here may be due to the small sample size and the specific high-force conditions tested.