March 2025

Walking Economy & Preferred Gait Speed in the Aged

Studies of gait have determined that even older runners use less of their plantar flexors – calf muscles – as they age compared to younger runners. To substitute, they use more of their hip flexors to swing their leg forward and their hip extensors/gluteals to push their weight forward. This is referred to as a distal (calf) to proximal (hips) shift that, unfortunately, costs the body more energy per unit distance. Hence, with age, gait becomes less energetically efficient; that is, the cost of walking (CoW) increases. Furthermore, gait speed changes inversely: the older you are, even if fit, the slower your preferred speed (PWS) is. “Why” is the driving question of a group of French biomechanists.

Three groups of men were assessed on anthropometric measures, aerobic capacity, neuromuscular function, and gait: young men (YM), old men (OM: ~71 yrs), and very old men (VOM: ~86 years). The integrative approach included % body fat, maximal O2 capacity, subjective measures of overall fatigue, maximal isometric strength of the knees, calfs, and dorsiflexors (which pull the toes upward), balance, mobility, and CoW at PWS.

They concluded that (1) net CoW increased with age especially in the VOM; (2) the main parameters of this increased cost were step frequency and the coefficient of variation of stride time in older subjects; (3) maximal strength of the quadriceps and calf muscles impacted CoW more in men over 80 when walking at a pre-determined faster rate than their PWS, and, most critically, (4) PWS is “mainly related to the level of physical activity in old and very old adults”.

The bottom line: move more, move faster while you’re still young, and don’t let the old man move in!         

MSSE Feb. 2025

Plantar Fasciitis: Risk & Preventive Factors

Plantar fasciitis (PF) is an inflammation of the ligaments that support the arch of the foot and cause excruciating heel pain. It is one of the more chronic and debilitating injuries many runners face, especially if they take on too many miles, too soon in their training, in the wrong shoes. Over 1200 participants (563 females, 643 males, with 715 runners and 491 non-runners) were filmed while running to gather biomechanical data with self-reported running distances included in the analysis. They were followed for 12 months with weekly call-ins to track PF occurrences. Data was analyzed “to reveal potential associations between running distance and biomechanical risk factors and PF while controlling for running distance, sex, and age.”

Only 28 subjects developed PF – 18 runners, 10 non-runners – making firm conclusions suspect. However, runners who logged more than 40 km/wk (25 miles/wk) had a six-times higher rate of PF than those who ran between 6 and 20 km/wk. Increasing age increased the probability of developing PF by 3.9% per year.

More importantly, those who had less ankle abduction during gait, that is, less pronation during the stance phase, might be at greater risk for PF.

In sum, “Regular running with a moderate weekly volume and more toeing out of the foot relative to the shank may reduce the risk against PF in runners…”

This is contrary to what had been deemed a cause of higher risk – over-pronation – but may have something to do with the timing of pronation during plantar flexion. More on that when the scientists figure it out.                                                

Published ahead of print MSSE Nov. 2024

Tid Bits