Date of Award


Degree Type

Creative Project

Degree Name

Master of Science (MS)


Kinesiology and Health Science

Committee Chair(s)

Brennan Thompson


Brennan Thompson


David Bolton


Sara Harper


Background: Falls are a primary cause of mortality and morbidity in older adults. In an effort to assess falls, a number of studies have measured neurological, biomechanical, and neuromuscular function in relation to fall risk. Despite efforts, falls continue to affect the older adult population leading to subsequent impaired mobility and function. Multiple factors contribute to fall risk among older adults, however, a factor that has shown a consistent relationship with the prevalence of future falls is reduced muscle characteristics. Moreover, the ability to rapidly accelerate a limb, as captured by rate of power development (RPD), rate of velocity development (RVD), and peak power (PP) could have important role in balance recovery. When stepping to avoid a fall, the ability to move a limb is critical, therefore and step time provide insight into these relationships. Our overarching purpose was to determine how time to peak values, not solely peak values, were associated with reactive balance performance.

Research Question: Will RPD, RVD, and PP have a strong, positive relationship with maximal lean angle as well as strong, negative relationship with step time following a temporally unpredictable perturbation? We hypothesized that older adults would have a strong, positive relationships among RPD, RVD, PP and maximal lean angle as well as strong, negative relationships with step time when compared to young adults.

Methods: Females and males between 18 and 35 years old, and those between 55 and 85 years old were recruited to complete a cross-sectional design. Subjects reported for two visits to the Neuromuscular Research Laboratory and the Movement Analysis Laboratory. After a dynamic warm-up, subjects performed the stretches by alternating limbs and performed experimental strength testing and balance (rapid step) protocols. The strength testing protocol involved three maximal vertical jumps while standing on a jump mat and a seated isometric, isokinetic, and isotonic dynamometer test was used to assess leg extension/flexion and hip extension/flexion in which peak torque (PT), RPD, RVD, and PP were measured. The rapid step protocol involved temporally unpredictable perturbations, in which each trial began at a lean angle of 10° and progressed by 5° increments with successful completion. Trials consisted of three attempts to regain balance following a postural perturbation, and two successful completions were required. Outcome measures maximal lean angle and step time were expected to have a strong, positive correlation with, RPD, RVD muscle characteristics.

Results: A total of 35 participants completed the two visits including young (n = 26) and older adults (n = 9). Young adults did have significant associations between isometric, knee extension PT (e.g., step time r = .407, p = .024), older adults did have a significant, positive association between maximal lean angle and PT (r = .607, p = .042). Among young adults, no significant associations were present between step outcomes (maximal lean angle and step time) and PP, RVD, or RPD variables. However, among older adults, maximal lean angle, and PP (r = .640, p = .032), RVD (r = .608, p = .041), and RPD (r = .751, p = .010) all reported significant, positive associations.

Significance: Our results suggest older adults’ muscle characteristics (e.g., PP, PT, RVD, RPD) have strong, positive relationships with the achieved maximal lean angle. While young adults did have significant associations between isometric, knee extension PT (e.g., step time r = .407, p = .024). When stepping to avoid a fall, the ability to rapidly move a limb is critical and time- dependent muscle capacities (e.g., RPD, RVD, and PP) are important determinants of limb movement.