High-Speed Cycling Intervention Improves Rate-Dependent Mobility in Older Adults

Abstract

Purpose: The aim was to determine the feasibility of a 6-wk speed-based exercise program that could be used to initiate new exercise behaviors and to improve rapid movement in older adults approaching frailty.

Methods: The intervention group included 14 older adults (3 males and 11 females; mean ± SD, age = 70 ± 7.6 yr, height = 1.6 ± 0.11 m, mass = 76.8 ± 12.0 kg, body mass index = 27.7 ± 4.7 kg·m). The control group included 12 older adults (6 males and 6 females; mean ± SD, age = 69.2 ± 6.9 yr, height = 1.7 ± 0.09 m, mass = 78.2 ± 10.9 kg, body mass index = 25.3 ± 2.7 kg·m). Subjects included active older adults, including regular exercisers, but none were engaged in sports or exercises with an emphasis on speed (e.g., cycling spin classes or tennis). Stationary recumbent cycling was selected to minimize fall risk, and low pedaling resistance reduced musculoskeletal and cardiovascular load. Two weekly 30-min exercise sessions consisted of interval training in which subjects pedaled at preferred cadence and performed ten 20-s fast cadence intervals separated by 40 s of active recovery at preferred cadence.

Results: Significant group-time interactions (P < 0.05) supported a 2-s improvement in the timed up and go test and a 34% improvement in rapid isometric knee extension contractions in the exercise group but not in controls. Central neural adaptations are suggested because this lower extremity exercise program also elicited significant improvements in the untrained upper extremities of the exercise group (elbow extension rate of force development scaling factor and Nine-Hole Peg Test, P < 0.05).

Conclusion: These results demonstrate that a relatively low dose of speed-based exercise can improve neuromuscular function and tests of mobility in older adults. Such a program serves as a sensible precursor to subsequent, more vigorous training or as an adjunct to a program where a velocity emphasis is lacking.

Figure 1

Experimental arrangement for the measurement of rapid isometric force pulses in elbow extension and knee extension. F indicates the approximate location of force transducers that were rigidly coupled to the distal leg or interfaced with a vertical pole that is pressed against the ground. Participants viewed real time feedback of isometric force (scaled to their maximal voluntary contraction force) on a computer monitor at eye level. Participants were instructed to produce multiple brief force pulses (see inset Figure 2) to approximate force levels of 20, 40, 60 and 80% MVC. Upper and lower extremity force pulses are measured separately as described in methods.

Figure 2

The rate of force development scaling factor (regression slope; RFD-SF) of one representative subject who improved from 8.5 to 10.8 units after six weeks of exercise. The RFD-SF is computed from the linear regression of peak RFD and peak force values taken from several isometric muscle contractions (depicted in inset) produced to a range of submaximal force amplitudes. See methods for further detail.