The association between premature plantarflexor muscle activity, muscle strength, and equinus gait in patients with various pathologies.
Weak calves, not tight ankles, cause early calf firing—so strengthen before you stretch.
01Research in Context
What this study did
Schweizer et al. (2013) looked back at 716 patients who had a full gait work-up.
They checked who showed early calf-muscle firing and compared it to true equinus and to calf strength.
What they found
Early calf firing linked more to weak plantarflexors than to tight ankles.
Weakness, not ankle tightness, was the main driver of the odd timing.
How this fits with other research
Galli et al. (2011) and Capodaglio et al. (2011) saw the same pattern in Prader-Willi adults: weak, floppy calves wreck balance.
Rigoldi et al. (2013) added that Ehlers-Danlos patients lose the automatic part of sway—again tying poor control to weak support muscles.
All four studies point to the same fix: build strength first, stretch later.
Why it matters
If a client walks on toes and the EMG fires early, test calf strength before you order AFOs or serial casting. Add resisted heel raises, seated calf presses, and gait drills that load the muscle. Re-check timing after strength gains; you may skip the brace entirely.
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02At a glance
03Original abstract
This study provides an overview on the association between premature plantarflexor muscle activity (PPF), muscle strength, and equinus gait in patients with various pathologies. The purpose was to evaluate whether muscular weakness and biomechanical alterations are aetiological factors for PPF during walking, independent of the underlying pathology. In a retrospective design, 716 patients from our clinical database with 46 different pathologies (orthopaedic and neurologic) were evaluated. Gait analysis data of the patients included kinematics, kinetics, electromyographic activity (EMG) data, and manual muscle strength testing. All patients were clustered three times. First, patients were grouped according to their primary pathology. Second, all patients were again clustered, this time according to their impaired joints. Third, groups of patients with normal EMG or PPF, and equinus or normal foot contact were formed to evaluate the association between PPF and equinus gait. The patient groups derived by the first two cluster methods were further subdivided into patients with normal or reduced muscle strength. Additionally, the phi correlation coefficient was calculated between PPF and equinus gait. Independent of the clustering, PPF was present in all patient groups. Weak patients revealed PPF more frequently. The correlations of PPF and equinus gait were lower than expected, due to patients with normal EMG during loading response and equinus. These patients, however, showed higher gastrocnemius activity prior to foot strike together with lower peak tibialis anterior muscle activity in loading response. Patients with PPF and a normal foot contact possibly apply the plantarflexion-knee extension couple during loading response. While increased gastrocnemius activity around foot strike seems essential for equinus gait, premature gastrocnemius activity does not necessarily produce an equinus gait. We conclude that premature gastrocnemius activity is strongly associated with muscle weakness. It helps to control the knee joint under load independent from the underlying disease, and it is therefore a secondary deviation. If treated as primary target, caution should be exercised.
Research in developmental disabilities, 2013 · doi:10.1016/j.ridd.2013.05.025