A prospective study of the muscle strength and reaction time of the quadriceps, hamstring, and gastrocnemius muscles in patients with plantar fasciitis

BACKGROUND: Muscle weakness is an important etiological factor in plantar fasciitis (PF), but available data on the role of the quadriceps, hamstring, and gastrocnemius (GCM) muscles are limited. The aim of this study was to compare the strength and reaction time of the quadriceps, hamstring, and GCM muscles and foot pressure between patients with PF and normal controls. METHODS: A total of 21 PF patients and 21 normal controls were enrolled. Muscle strength was measured by the peak torque per body weight (Nmkg(− 1) × 100). Muscle reaction time was evaluated by the acceleration time (AT, milliseconds). Foot pressure and posture were assessed by pedobarography [valgus/varus index (VV index), %]. RESULTS: The strength of the quadriceps was significantly lower in the affected ankles of the PF group than in the control group (p = 0.005). The AT of the quadriceps and hamstring muscles was significantly increased in the affected ankles of the PF group than in the control group (quadriceps: p = 0.012, hamstring: p = 0.001), while the AT of the GCM muscle was significantly decreased (p = 0.009) and significantly correlated negatively with quadriceps muscle strength (r = −.598, p = 0.004) and AT (r = −.472, p = 0.031). Forefoot (p = 0.001) and hindfoot (p = 0.000) pressure were significantly greater, with the VV index showing hindfoot valgus, in the affected ankles in the PF group compared to the control group (p = 0.039). CONCLUSIONS: This study demonstrated weakness and delayed reaction time of the quadriceps and hamstring muscles, with a rapid reaction time of the GCM muscle, in patients with PF. CLINICAL RELEVANCE: Clinicians and therapists should assess the function of the quadriceps and hamstring muscles when planning the management of PF patients without muscle tightness.