Effects of Task-Specific Step Training on Reactive Balance

Not Applicable

Completed

Interventions: Behavioral: non-treadmill trip training
Behavioral: treadmill trip training

Brief Summary: The goal of this study is to investigate the effects of a novel form of balance training called trip training. Trip training typically involves repeatedly exposing an individual to trip-like losses of balance on a specialized treadmill. This repeated exposure can lead to improvements in responses to trips while walking in the future, thereby reducing the risk of falling after a trip. Trip training typically is commonly conducted using a costly specialized treadmill. This study will evaluate the efficacy of a trip training protocol that does not require a treadmill. Adults age 65-80 will be assigned to either 1) non-treadmill trip training, 2) treadmill trip training, or 3) no intervention. The investigators hypothesized that responses to laboratory-induced trips would be better after non-treadmill trip training compared to no intervention, and that there would be no statistical difference between responses to laboratory-induced trips after non-treadmill trip training and treadmill trip training. The results from this work will advance the use of trip training, and may enable its wider use by establishing a protocol that does not require a costly treadmill.

Recruitment & Eligibility

Inclusion Criteria

Exclusion Criteria

participants must pass a health screening involving a questionnaire that will be reviewed by a health care specialist.
participants must not have clinical osteoporosis as indicated by a bone mineral density of the lumbar vertebra and proximal femur of t<-2.0 as obtained from dual energy x-ray absorptiometry (DEXA), or a DEXA scan completed within the last year.

Arm && Interventions

Group	Intervention	Description
non-treadmill trip training	non-treadmill trip training	Two training sessions per week will be completed for three consecutive weeks. Each training session will last 0.5-1 hour with an active training time of 30 minutes per participant. Training will involve repeated volitional and reactive stepping movements that mimic the movements necessary to recover balance after tripping while walking.
treadmill trip training	treadmill trip training	Two training sessions per week will be completed for three consecutive weeks. Each training session will last 0.5-1 hour with an active training time of 30 minutes per participant. Training will involve repeated exposure to simulated trips on a treadmill. To simulate a trip, participants first stand on the stationary treadmill belt. A sudden and unexpected increase in backward treadmill belt speed induces a forward loss of balance similar to when tripping. Participants are then required to take steps to recover balance and establish a stable gait pattern before the trial ends. Trials are repeated using pseudo-random speeds that provide variability and are individualized to each participant's capabilities.

Primary Outcome Measures

Name	Time	Method
Trunk angle at touchdown of the first recovery step	during the week after the 3-weeks of intervention	After a laboratory-induced trip: Angle from vertical of a line connecting midpoint of greater trochanter markers and midpoint of the acromion markers
Trip outcome	during the week after the 3-weeks of intervention	This is a binary variable that has a value of either "fall" or "recovery." After a laboratory-induced trip, trip outcome will be assign to one of the following two values: "fall" if a participant is fully and continuously supported by the harness as observed from video, or if the harness force applied to the participant, integrated over time from trip onset until 1 second after touchdown of the first recovery step, is greater than 40% of body weight \* seconds. The harness force will be measured by a uniaxial load cell. "recovery" if the harness force applied to the participant, integrated over time from trip onset until 1 second after touchdown of the first recovery step, is less than 40% of body weight \* seconds. The harness force will be measured by a uniaxial load cell.

Secondary Outcome Measures

Name	Time	Method
Recovery step length	during the week after the 3-weeks of intervention	After a laboratory-induced trip, the distance between a lateral malleolus marker of the stance limb and a lateral malleolus marker of the stepping foot at touchdown
Average step speed	during the week after the 3-weeks of intervention	After a laboratory-induced trip, the distance between a lateral malleolus marker of the stance limb and a lateral malleolus marker of the stepping foot at touchdown divided by the time from impact with the trip obstacle and touchdown of the initial recovery step.
Minimum hip height after trip onset	during the week after the 3-weeks of intervention	After a laboratory-induced trip, the minimum distance between the walkway and the greater trochanter marker on the non-tripping limb during trip recovery.
Trunk angular velocity at touchdown of the first recovery step	during the week after the 3-weeks of intervention	After a laboratory-induced trip: time derivative of trunk angle, and its value at the instant of touchdown of the first recovery step.
Gait speed	during the week after the 3-weeks of intervention	The average forward speed of the participant prior to the laboratory-induced trip.