Incremental Visual Occlusion During Split-Belt Treadmill Walking Has No Gradient Effect on Adaptation or Retention.

Split-belt treadmills have become an increasingly popular means of quantifying ambulation adaptability. Multiple sensory feedback mechanisms, including vision, contribute to task execution and adaptation success. No studies have yet explored visual feedback effects on locomotor adaptability across a spectrum of available visual information. In this study, we sought to better understand the effects of visual information on locomotor adaptation and retention by directly comparing incremental levels of visual occlusion. Sixty healthy young adults completed a split-belt adaptation protocol, including a baseline, asymmetric walking condition (adapt), a symmetric walking condition (de-adapt), and another asymmetric walking condition (re-adapt). We randomly assigned participants into conditions with varied visual occlusion (i.e., complete and lower visual field occlusion, or normal vision). We captured kinematic data, and outcome measures included magnitude of asymmetry, spatial and temporal contributions to step length asymmetry, variability of the final adapted pattern, and magnitude of adaptation. We used repeated measures and four-way MANOVAs to examine the influence of visual occlusion and walking condition. Participants with complete, compared to lower visual field visual occlusion displayed less consistency in their walking pattern, evident via increased step length standard deviation (p = .007, d = 0.89), and compared to normal vision groups (p = .003 d = 0.81). We found no other group differences, indicating that varying levels of visual occlusion did not significantly affect locomotor adaptation or retention. This study offers insight into the role vision plays in locomotor adaptation and retention with clinical utility for improving variability in step control.

Leg press and chest press strength normative values by half-decades in older persons.

Evaluating muscular strength is vital to the application of effective training protocols that target quality of life and independence in older individuals. Resistance training is a valuable tool to improve functional capacity, strength, and power in this population; however, the lack of normative values for common lifts such as the leg press (LP) and chest press (CP) reduce its utility. This study developed age- and sex-specific normative strength values for older individuals. LP and CP 1-repetition maximum (1RM) values on Keiser A420 pneumatic machines were compiled from 445 older adults, ages 60-85y. Descriptive statistics and quartile rankings are reported, and two-way ANOVAs were conducted to determine differences between sex and age groups. There were significant sex x age group interactions for LP and CP. Men were significantly stronger than women across all age groups for both exercises (p < .01); however, the mean difference decreased with age. For men, no differences were seen among the 60-64 (237 ± 39 kg), 65-69 (223 ± 43 kg) and 70-74 (219 ± 50 kg) age groups; but the 60-64 group showed higher strength values than the 75-79 group (193 ± 52 kg) and all three groups contained higher strength values than the 80-85 group (172 ± 40 kg). Similarly, for relative strength, the 60-64 group (2.80 ± 0.53 kg·kgBM) surpassed values for all groups but the 65-69, and the 65-69 (2.70 ± 0.54 kg·kgBM) produced greater strength values than the 70-74 (2.45 ± 0.47 kg·kgBM), 75-79 (2.09 ± 0.37 kg·kgBM) and 80-85 (2.19 ± 0.38 kg·kgBM) groups. In contrast, no significant differences in absolute or relative strength were seen among age groups for the women. Our study establishes absolute and relative age- and sex-specific normative values for the LP1RM and CP1RM in older individuals. These values allow practitioners and researchers to interpret the results of various interventions, and evaluate their importance to evaluation of sarcopenia, injury risk, functional mobility and quality of life. Additionally, our results reveal that age-related declines in strength are prominent for male LP and CP, but not female CP or LP.