Table 2.
Summary of included studies. Information were extracted with regard to the effect of locomotor adaptability (i.e., difference between the recovery response following an unexpected perturbation and the response after subsequent movement perturbations) and its distinct predictive (i.e., difference prior to/at the potential perturbation between baseline and an after-effect condition) and reactive (i.e., difference between the recovery response following an unexpected perturbation and the response after an again unexpected perturbation) components
| Study | Participantsa, b | Method | Measure | Outcome |
|---|---|---|---|---|
| Bhatt et al. [72] | O: Single session: n = 25 (73 ± 5 years), 13 F Dual session: n = 13 (70 ± 5 years) 7 F Healthy ([61, 72–74] same pool) |
Design: Disturbed trail walking (same as in [61, 72–74]) Perturbation: Slip [i.e., hidden free moveable platforms (90 cm forward, 58 cm backward)] Protocol: Baseline, 8 slips, 3 non-slips, 8 slips, 3 non-slips, 15 mixed trials |
Parameters: Stability, fall incidence, loss of balance, limb support Magnitude of stability at TD slipping foot (predictive) and magnitude of stability and limb support at lift-off trailing limb (LA) as well as fall incidence and loss of balance between the baseline or first slip trial and last slip trial |
The older adults significantly reduced their fall incidence and loss of balance (LA) and increased their pre-slip (predictive) and post-slip stability (LA) by the end of the session |
| Bierbaum et al. [16] | O: n = 13 (67 ± 3 years), 0 F Y: n = 10 (26 ± 3 years), 0 F Active, healthy |
Design: Disturbed trail walking (60 % of walk-to-run transition velocity) Perturbation: Trip (i.e., change hard to soft surface) Protocol: Baseline followed by adaptation phase with 19 trials on soft or hard surface (2nd, 8th and 19th) |
Parameters: Margin of stability (and components), base of support, GRF Rate and magnitude of LA (TD recovery leg) and predictive adjustments (TD disturbed leg) |
Despite an age-related reduced recovery performance after the first unexpected perturbation, young and older adults showed similar significant LA and predictive stability control. Predictive adjustments were present directly after the first perturbation trial in both age groups. Adaptive motor adjustments (LA) improved over consecutive trials |
| Bierbaum et al. [17] | O: n = 14 (67 ± 4 years), 0 F Y: n = 14 (25 ± 2 years), 0 F Active, healthy |
Design: Disturbed trail walking (60 % of walk-to-run transition velocity) Perturbation: Trip (i.e., change hard to soft surface) Protocol: Baseline followed by 5 unexpected perturbation trials, each after 4–8 unperturbed trials (wash-out phase) |
Parameters: Margin of stability (and components), base of support Rate and magnitude of reactive adjustments |
Reactive adaptive adjustments significantly improved over the 5 unexpected perturbations. Young adults showed a tendency towards greater reactive adaptability compared with older adults |
| Bohm et al. [36] | Control group O: n = 14 (70 ± 4 years), 0 F Y: n = 15 (26 ± 3 years), 0 F Active, healthy |
Design: Disturbed trail walking (self-selected speed) Perturbation: Trip (i.e., change hard to soft surface) Protocol: Baseline followed by adaptation phase with 15 trials on soft or hard surface (2nd, 7th and 13th) (comparable to [16]) |
Parameters: Margin of stability (and components), base of support Rate and magnitude of LA (TD recovery leg) and predictive adjustments (TD disturbed leg) |
Young and older adults showed similar significant LA and predictive stability control. Predictive adjustments were present directly after the first perturbation trial in both age groups. Adaptive motor adjustments (LA) improved over consecutive trials |
| Bruijn et al. [63] | O: n = 12 (73 ± 5 years), 3 F Y: n = 8 (22 ± 4 years), 4 F Healthy |
Design: Disturbed treadmill walking Perturbation: Different speeds of the belts (0.5 and 1.0 m/s) Protocol: Tied-belt (baseline, 5 min), split-belt (10 min), tied-belt (after-effect condition, 5 min) |
Parameters: Step length symmetry, stride length, swing time, swing speed Rate and magnitude of adaptation to split-belt condition (LA) and after-effect condition (predictive) |
The older adults adapted less and more slowly to split-belt walking (LA) and showed fewer after-effects (predictive adaptation) than young adults |
| Chambers and Cham [64] | O: n = 9 (60 ± 4 years), ? F Y: n = 11 (23 ± 2 years), ? F Healthy |
Design: Disturbed trail walking (self-selected speed) Perturbation: Slip (i.e., slippery solution on the surface) Protocol: Baseline followed by unexpected slip and 5 consecutive non-slip trials (alert dry) |
Parameters: Activation (EMG, onset, duration, power, co-contraction index) of lower limb muscles during stance phase (heel contact to toe off) Magnitude and time of muscle activation at heel contact and toe off during baseline and alert dry trials (predictive) |
The muscle activation following the unexpected slip was scaled to slip severity. The younger adults showed a more powerful and longer activity. Young and older adults similarly presented a more powerful muscle activation and co-contraction at the ankle and knee as well as earlier onsets and longer durations in the posterior muscles during the alert dry trials. These predictive changes were partly enhanced in the young adults |
| Van Hedel and Dietz [112] | O: n = 9 (63 ± 7 years), 2 F, (−1) Y: n = 9 (23 ± 3 years), 2 F Healthy |
Design: Disturbed treadmill walking Perturbation: Obstacle (i.e., foam stick at speed of the walking velocity, task: stepping over obstacle as low as possible) Protocol: Blocks of trails (3 × 50 steps, ~12 min, 5-min breaks) with acoustic signal of upcoming obstacle (every 6–11 steps) and acoustic feedback of foot clearance after passing the obstacle |
Parameters: Obstacle hits, foot-obstacle clearance, muscle activity (EMG) of lower limbs, joint angles, swing phase duration Step adjustments (LA) over the obstacles [first 4 steps (onset) vs. last 4 steps (end)] in the same block and between trial blocks (block 1 vs. 2 vs. 3) |
Young and older adults presented similar significant LA of stepping performance (foot-obstacle clearance) within the first block while the younger had less obstacle hits. Muscle activity decreased in both age groups, however, significantly only in the elderly. Joint angles and swing phase remained unaffected |
| Karamanidis et al. [81] | O: n = 11 (62–76 years), 11 F Y: n = 11 (22–30 years), 11 F |
Design: Disturbed treadmill walking (self-selected speed) Perturbation: Trip (i.e., external resistance on the right leg during swing phase) Protocol: Baseline, unexpected trip and 6 recovery steps followed by unperturbed wash-out phase, 11 consecutive disturbed steps and a final undisturbed step (after-effect condition) |
Parameter: Margin of stability, base of support Rate and magnitude of LA and predictive adjustments at TD |
Although older adults needed more steps to recover after the unexpected trip compared with the young adults, they preserved their LA following consecutive step perturbations. However, responses were delayed compared with young adults. After-effects were unaffected by age (predictive adaptation) |
| Pai et al. [37] | O: n = 41 (73 ± 5 years), 21 F Healthy (same as [37, 40, 46, 71]) |
Design: Disturbed sit-to-stand (‘stand up as quick as possible’) Perturbation: Slip (i.e., 24 cm forward slide of the surface) Protocol: Baseline trials followed by 5 slips and a reslip after 3–4 non-slip trials (same as in [37, 40, 46, 71]) |
Parameter: Stability, fall incidence, loss of balance Magnitude of stability at seat-off (predictive) as well as fall incidence and loss of balance (LA) |
Older adults significantly reduced their risk of falling and balance loss (LA) attributable to improved predictive motor adjustments |
| Pai et al. [71] | Walking: O: n = 38 (71 ± 5 years), 19 F; Y: n = 35 (26 ± 5 years), 18 F ([61, 72–74] same pool) Sit-to-stand: O: n = 41 (73 ± 5 years), 21 F; Y: n = 60 (25 ± 5 years), 44 F (same as [37, 40, 46, 71]) |
Walking: Design, perturbation and protocol see Bhatt et al. [72] (same as in [61, 72–74]) Sit-to-stand: Design, perturbation and protocol see Pai et al. [37] (same as in [37, 40, 46, 71]) |
Parameter: Stability, fall incidence, loss of balance and limb support Magnitude of LA of stability and limb support (300 ms after slip onset) and associated fall incidence and loss of balance |
Older adults fall over twice as likely as young adults following the first unexpected slip in both tasks. Both age groups rapidly adapted in walking and sit-to-stand task by improved control of stability and limb support (LA), leading to a significant reduction of falls and balance loss after 5 slips |
| Pai et al. [73] | O: n = 73 (≥65 years), ? F Healthy ([61, 72–74] same pool) |
Design, perturbation and protocol see Bhatt et al. [72] (same as in [61, 72–74]) | Parameter: Stability, fall incidence Magnitude of stability at TD (30–50 ms prior slip) slipping foot (predictive) and at TD (300–500 ms after slip onset) trailing foot (LA and reactive) as well as fall incidence between the first and last slip trial |
Significantly reduced fall rate based on significant LA due to predictive as well as and reactive stability adjustments after the slip and non-slip trials |
| Pai et al. [74] | O: n = 67 (72 ± 6 years), 44 F Healthy ([61, 72–74] same pool) |
Design, perturbation and protocol see Bhatt et al. [72] (same as in [61, 72–74]) | Parameter: Fall incidence Fall incidence of the first slip trial and last slip trial (LA) |
Reduced fall incidence comparing the first with the last slip trial (indicating LA) |
| Pavol et al. [46] | O: n = 41 (73 ± 5 years), 21 F Y: n = 60 (25 ± 5 years), 44 F, (−7) Healthy (same as [37, 40, 46, 71]) |
Design, perturbation and protocol see Pai et al. [37] (same as in [37, 40, 46, 71]) | Parameter: Fall incidence, recovery step (occurrence, direction, number) Fall incidence and recovery step characteristics of the first compared with the last trial of young and older adults |
Although older adults fell more frequently following the first unexpected perturbation, the fall incidence decreased with repeated slip exposure similarly in both age groups, which was accompanied by changes of the recovery step (LA) |
| Pavol et al. [40] | O: n = 41 (73 ± 5 years), 21 F, healthy Y: n = 60 (25 ± 5 years), 44 F, (−9) (same as [37, 40, 46, 71]) |
Design, perturbation and protocol see Pai et al. [37] (same as in [37, 40, 46, 71]) | Parameter: Position and velocity of CoM at seat-off (predictive) Falls, recovery step (length, duration and direction), extrapolated CoM position and hip height (step TD) (LA and reactive) Rate and magnitude of LA (slip 1–5) and magnitude of predictive and reactive (slip–reslip) adjustments |
Young and older adults adjusted their CoM position and velocity during seat-off after the 5 perturbation trials (i.e., similar predictive motor adaptations) and therewith contributed to a decrease of fall incidence and changes of recovery step incidence and direction. Predictive and reactive adjustment magnitudes were greater in the young adults |
| Roemmich et al. [62] | O: n = 15 (65 ± 8 years), ? F Y: n = 15 (23 ± 2 years), ? F Healthy |
Design: Disturbed treadmill walking Perturbation: Different speeds of the belts (100 % and 50 % of fastest comfortable speed) Protocol: Tied-belt (baseline), split-belt for 10 min (early: mean of first 5 steps; mid: mean of 5 steps after 5 min; late: mean of last 5 steps), wash-out, split-belt for 2 min (readapt: mean of first 5 steps) and again tied-belt (post-tied: mean of 5 steps) |
Parameter: Step length, stride length and stance time asymmetry Intra-limb (stride length and stance time asymmetry) and inter-limb (step length asymmetry) LA as well as predictive (baseline vs. post-tied) and reactive (early vs. readapt) adaptive changes |
Similar predictive and reactive adaptive responses of young and older adults to the sequence of tied- and split-belt walking |
| Sakai et al. [113] | O: n = 45 (71 ± 4 years), 26 F Healthy |
Design: Disturbed treadmill walking (2 km/h) Perturbation: Slip (i.e., decelerating right belt for 500 ms at TD of the heel) Protocol: 20 perturbations repeatedly in a 5-min walk |
Parameter: Sway, muscle activity (EMG) of lower limbs and trunk, stride time Magnitude of LA as difference between average of 10 early (first half) and 10 late (second half) subsequent perturbations steps |
Older adults showed reduced sway (i.e., more stable) in the second half of 20 disturbed steps (LA). While muscle EMG latencies were unchanged, two muscles of the limb indicated reduced EMG magnitude in the second half |
| Tseng et al. [114] | O: n = 18 (72 ± 4 years), 12 F Y: n = 36 (26 ± 4 years), 13 F Healthy |
Design: Disturbed stepping movements (‘step fast and accurate’) Perturbation: Left or right shift of visual step target during volitional step initiation Protocol: 20 baseline steps followed by a block of 30 adaptation trials (target shift) |
Parameter: Step accuracy (foot position), duration (total, response time, weight transfer, stepping execution) Magnitude of LA as difference of early (first 3 of 30 steps) and late adaptation trials (last 3 of 30 steps) |
Older adults adapted stepping accuracy almost equivalent to young adults but showed slowness during the stepping movement in the early adaptation phase. With practice, older adults reduced their movement times to levels similar to young adults |
| Yang and Pai [61] | O: n = 73 (73 ± 5 years), 46 F ([61, 72–74] same pool) | Design, perturbation and protocol see Bhatt et al. [72] (same as in [61, 72–74]) | Parameter: Stability, fall incidence, analysis of gait pattern, kinematic (trunk, knee, foot) Magnitude of stability, gait pattern and kinematics at TD slipping foot (predictive) and at lift-off trailing limb as well as fall incidence (LA) between the first and last slip trial |
Older adults improved gait stability by forward positioning of their CoM in relation to their base of support [shorter steps and forward trunk leaning and flat foot landing with knee flexed (LA and predictive)] following the trial session (first vs. last trial) |
CoM center of mass, EMG electromyography, F female, GRF ground reaction force, LA locomotor adaptability, O older adults, TD touchdown of respective foot, Y young adults, ? not reported
aAge data are mean ± SD or range
bNegative numbers in parentheses indicate numbers of participants who were excluded during the course of the study (e.g., due to technical issues)