Step Length & Step Frequency: Effect on Lower Limb Function
Last year I finally splurged and purchased a treadmill that has force platforms within it. Somehow the treadmill talks to a tablet and I can immediately see gait biomechanics.
The below abstract grabs my attention. For many older adults with balance deficits, I observe very short step lengths. After surgical procedures, I observe an odd mixture of short step lengths with high percentages of asymmetry. The focus I've been taking is to normalize step length.
Increasing step length takes a lot of concentration and work. It's nice to see a bit of what I tell patients substantiated in the abstract. In order to change their gait, I mention they need to use their powerhouse muscles: their buttocks and thighs. When they focus and change their gait pattern, the exact muscles that are mentioned in the abstract are reported to be sore.
My thought: it isn't the reduced strength that created the gait pattern we see. I have a feeling the gait pattern is due to fear of falling. The fear of falling alters the gait pattern such that the individual's gait has reduced step length. And over the years of walking with shorter step lengths, the muscles become weaker.
Below you will find a quick view of the abstract.
Effects of step length and step frequency on lower-limb muscle function in human gait.
The aim of this study was to quantify the effects of step length and step frequency on lower-limb muscle function in walking. Three-dimensional gait data were used in conjunction with musculoskeletal modeling techniques to evaluate muscle function over a range of walking speeds using prescribed combinations of step length and step frequency. The body was modeled as a 10-segment, 21-degree-of-freedom skeleton actuated by 54 muscle-tendon units. Lower-limb muscle forces were calculated using inverse dynamics and static optimization. We found that five muscles - GMAX, GMED, VAS, GAS, and SOL - dominated vertical support and forward progression independent of changes made to either step length or step frequency, and that, overall, changes in step length had a greater influence on lower-limb joint motion, net joint moments and muscle function than step frequency. Peak forces developed by the uniarticular hip and knee extensors, as well as the normalized fiber lengths at which these muscles developed their peak forces, correlated more closely with changes in step length than step frequency. Increasing step length resulted in larger contributions from the hip and knee extensors and smaller contributions from gravitational forces (limb posture) to vertical support. These results provide insight into why older people with weak hip and knee extensors walk more slowly by reducing step length rather than step frequency and also help to identify the key muscle groups that ought to be targeted in exercise programs designed to improve gait biomechanics in older adults.
J Biomech. 2017 Mar 21. pii: S0021-9290(17)30146-X. doi: 10.1016/j.jbiomech.2017.03.004. [Epub ahead of print]