Relationship between plantar fascia thickness in static standing and calf raise positions and the medial longitudinal arch height ratio in healthy adults.

All 30 participants were healthy and young (average age 25), with no heel pain or foot symptoms, so nothing here applies to patients with plantar fasciitis. Thickness was measured at one point only, 1.5 cm from the heel attachment, on the dominant foot, by one examiner using one ultrasound machine. The plastic sheet placed over the standing measurement window may have reduced image quality, which the authors say could explain why standing readings were less consistent than calf-raise readings. This was a single session with one position change and no follow-up, so there is no information about whether thickness shifts over days, with training, or with symptoms. Many correlations were run across small subgroups (18 men, 12 women) without adjustment for multiple testing, so the one significant subgroup result, age in men, could be chance. The authors themselves note the small per-sex sample as a reason for null subgroup findings. Reliability (how repeatable the measurement was) is reported, but no measurement error is given, and the difference between positions (0.266 mm) is small.

The authors state that the research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors, and that they have no conflicts of interest to declare.

Do not read the thinner calf-raise measurement as evidence that calf raises stretch the plantar fascia or help plantar fasciitis. This was a single ultrasound measurement in 30 healthy young adults with no symptoms, no intervention and no follow-up, so it shows only how the tissue measures while the heel is lifted. Similarly, do not treat the age link seen in men as a real effect; it came from a subgroup of 18 people among many correlations tested.