Comparing the efficacy of metronome beeps and stepping stones to adjust gait: steps to follow!

Abstract

Acoustic metronomes and visual targets have been used in rehabilitation practice to improve pathological gait. In addition, they may be instrumental in evaluating and training instantaneous gait adjustments. The aim of this study was to compare the efficacy of two cue types in inducing gait adjustments, viz. acoustic temporal cues in the form of metronome beeps and visual spatial cues in the form of projected stepping stones. Twenty healthy elderly (aged 63.2 ± 3.6 years) were recruited to walk on an instrumented treadmill at preferred speed and cadence, paced by either metronome beeps or projected stepping stones. Gait adaptations were induced using two manipulations: by perturbing the sequence of cues and by imposing switches from one cueing type to the other. Responses to these manipulations were quantified in terms of step-length and step-time adjustments, the percentage correction achieved over subsequent steps, and the number of steps required to restore the relation between gait and the beeps or stepping stones. The results showed that perturbations in a sequence of stepping stones were overcome faster than those in a sequence of metronome beeps. In switching trials, switching from metronome beeps to stepping stones was achieved faster than vice versa, indicating that gait was influenced more strongly by the stepping stones than the metronome beeps. Together these results revealed that, in healthy elderly, the stepping stones induced gait adjustments more effectively than did the metronome beeps. Potential implications for the use of metronome beeps and stepping stones in gait rehabilitation practice are discussed.

Fig. 1

Overview of the experimental setup (i.e., stepping stones condition)

Fig. 2

Schematic representation of phase-delay (+60° phase shifts) perturbations in the sequence of metronome beeps (a gray and black thick lines indicate metronome onsets and thin line segments represent beeps if the perturbation would not have occurred) and stepping stones (d gray and black patches indicate projected stepping stones and the partly occluded white patches represent stepping stones if the perturbation would not have occurred). For both cueing conditions, representative gait events are indicated by diamond markers (representing time instants of heel strike and the center position of the foot in a and d, respectively). In this schematic representation, belt speed was 1.0 m/s, so m in (d) is comparable to s in (a). b and e depict corresponding relative phase time series ϕ and ϕ* for S ₋₃ to S ₅ for metronome and stepping stones conditions, respectively; note that in (e) ϕ ≈ ϕ*. c and f depict associated %Corr for S ₀–S ₅ for metronome and stepping stones conditions, respectively. See text for further details

Fig. 3

Mean normalized step times (a, T _step) and step lengths (b, Y _step) for S ₁–S ₂₀ for the perturbation conditions. Note that following phase-advance (−60°) perturbations, a shorter-step response was observed (with both T _step and Y _step < 100% regardless of the cueing type); after phase-delay (+60°) perturbations, a longer-step response was observed (with both T _step and Y _step > 100% regardless of the cueing type). For both phase-shift directions, significant differences between cueing types for a given S _n are indicated by an open symbol for the T _step or Y _step that deviated most from 100%; initial step-time and step-length adjustments were faster and larger for the stepping stone (S) than metronome beep (M) conditions

Fig. 4

Relative phase time series for S ₋₁₀ to S ₂₀ for perturbation (a, b) and switching (c, d) conditions. Thin and thick lines represent individual and averaged relative phase time series, respectively. Dark and bright thick gray lines represent relative phase time series of footfalls with metronome beeps (M) and stepping stones (S), respectively

Fig. 5

Mean percentage correction for S ₁–S ₂₀ for perturbation (a) and switching (b) conditions. Open symbols represent significant differences between phase shift directions (advance vs. delay)