Differences Between Men and Women in Balance and Tremor in Relation to Plantar Fascia Laxity During the Menstrual Cycle.

CONTEXT: Although much attention has been paid to the effect of estrogen on the knee ligaments, little has been done to examine the ligaments in the foot, such as the plantar fascia, and how they may be altered during the menstrual cycle.
OBJECTIVE: To (1) examine sex differences in plantar fascia thickness and laxity and postural sway and (2) identify any menstrual cycle effects on plantar fascia laxity, postural sway, and neuromuscular tremor between menstruation and the ovulation phase.
DESIGN: Case-control study.
SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Fifteen healthy women (age = 25.9 ± 1.8 years) and 15 healthy men (age = 27.3 ± 2.0 years) volunteered to participate in this study. INTERVENTION(S): We asked participants to perform 8 balance tasks on a force platform while we assessed postural sway and tremor. MAIN OUTCOME MEASURE(S): Plantar fascia length and thickness unloaded and loaded with body weight were measured via ultrasound. Postural sway and tremor were measured using a force platform.
RESULTS: Plantar fascia length and thickness with pressure were greater in ovulating women compared with men ( P < .001), but no differences were found between women during menstruation and men. Postural sway and tremor were greater at ovulation than during menstruation ( P < .05), and men had less sway than ovulating women on the 3 most difficult balance tasks ( P < .01).
CONCLUSIONS: Plantar fascia laxity was increased and postural sway and tremor were decreased at ovulation compared with menstruation in women. Postural sway and tremor in men were the same as in women during menstruation. These findings support the need to be aware of the effect of sex hormones on balance to prevent lower extremity injuries during sport activities.