Research is finding some clues. . . . ankle plantarflexion. The calf as a locus of impaired walking capacity.
Dr. Ted Carrick was once heard saying that even in the earliest phases of neuropathology, stages possibly so early that neuropathology is absent from most testing results (incidentally, we discuss this on a recent podcast, 137 or 138 and what tests might help in the discovery when things like EMG/NCV are "normal"), that subtle changes in one's gait might be the first sign(s) of aberrant sensory-motor function when all other methods prove unfruitful in the discovery process.
Reduced walking capacity is a hallmark of chronic heart failure (CHF). Why is this? It is reduced fitness ? It is weakness, stiffness, reduced metabolic capacity ? It could be all of them, and many more.
This interesting study found "over two times greater ankle plantarflexion work during stance and per distance traveled is required for a given triceps surae muscle volume in CHF patients. This, together with a greater reliance on the ankle compared to the hip to power walking in CHF patients, especially at faster speeds, may contribute to the earlier onset of fatigue in CHF patients."
This makes sense to us, after all, the much work (perhaps 50%~?) should be provided by the glutes and core in the propulsion phase of gait. But we know that the elderly, and especially the weak elderly, who walk with shorter steps and strides, who walk slower, who are weaker and more fragile, that their capacity for propulsion is notably diminished in the later years. The later years when CHF is also found. Thus, how do these folks find ways to effectively move forward? This study provides one possible clue, the ankle plantarflexors, the gastrocsoleus-achilles complex.
"This observation also helps explain the high correlation between triceps surae muscle volume and exercise capacity that has previously been reported in CHF. Considering the key role played by the plantarflexors in powering walking and their association with exercise capacity, our findings strongly suggest that exercise-based rehabilitation in CHF should not omit the ankle muscle group."
J Biomech. 2014 Nov 28;47(15):3719-25. doi: 10.1016/j.jbiomech.2014.09.015. Epub 2014 Oct 11.
Gait analysis in chronic heart failure: The calf as a locus of impaired walking capacity.
Panizzolo FA1, Maiorana AJ2, Naylor LH1, Dembo L3, Lloyd DG4, Green DJ5, Rubenson J6.