Muscle fatigue after Achilles tendon rupture: A limited heel-rise test with electromyography
reveals decreased endurance
Sammanfattning
Measuring the maximal number of heel-rises is the clinical standard to quantify plantarfl exor
strength. However, this activity
can be diffi cult and uncomfortable after Achilles tendon rupture (ATR) and may capture aspects other
than muscle
strength and endurance. Therefore, the aim of this study project was to evaluate muscle fatigue with
a limited number of
heel-rises. Fifty-two patients with ATR were evaluated 2.0-6.7 years after injury. Patients performed
the heel-rise test with
surface electromyography (sEMG) of the gastrocnemius muscles. Muscle fatigue was operationally
defi ned as the slope of
the sEMG signal frequency. Subjects performed signifi cantly fewer heel-rises on the injured side
compared with the uninjured
side (25.5 9.3 vs 33.6 15.1; p 0.001). Subjects also had greater muscle fatigue on the injured side
compared
with the uninjured side for the lateral gastrocnemius ( 31.1 13.9 vs -26.2 14.8; p 0.048), but not
the medial gastrocnemius
( p 0.074). There was a signifi cant increase in fatigue of both the lateral and medial gastrocnemius
on the injured
side over the fi rst 10 repetitions ( p 0.001). Our fi ndings demonstrate that subjects have increased
gastrocnemius muscle
fatigue even several years after ATR and muscle fatigue can be detected with a limited number of
heel-rises.
Key