@article{conway_crudup_lewek_franz_2021, title={Effects of Horizontal Impeding Force Gait Training on Older Adult Push-Off Intensity}, volume={53}, ISSN={["1530-0315"]}, DOI={10.1249/MSS.0000000000002500}, abstractNote={ABSTRACT
          
            Introduction
            Aging and many gait pathologies are often characterized by deficits in push-off intensity (i.e., propulsive ground reaction forces and peak ankle moment and power output) during walking. Unfortunately, conventional interventions such as progressive resistance training, designed to enhance calf muscle mechanical output, generally fail to translate strength gains to functional improvements in habitual push-off intensity.
          
          
            Methods
            Horizontal impeding forces applied to the body’s center of mass systematically augment the mechanical output required from muscle–tendon units spanning the ankle during the push-off phase of walking, which could convey long-term benefits via training. Therefore, the purpose of this study was to investigate the preliminary efficacy of a 6-wk horizontal impeding force training paradigm on improving habitual push-off intensity in 11 healthy but not physically active older adults (age = 76 ± 4 yr, 6 females and 5 males).
          
          
            Results
            We found that older adults significantly (P < 0.05) increased measures of isometric strength by 18%, maximum walking speed by 10%, and 6-min walk test distance by 9% as a result of horizontal impeding force training. As a more clinically significant contribution of this work, we found that those subjects also increased habitual peak ankle moment and peak ankle power during push off after training by a significant 10% and 15%, respectively (P ≤ 0.036).
          
          
            Conclusions
            We conclude that the use of horizontal impeding forces in older adults improves their maximum muscular and walking capacities while encouraging access to newfound strength gains, thereby improving habitual push-off intensity during walking.
          }, number={3}, journal={MEDICINE AND SCIENCE IN SPORTS AND EXERCISE}, author={Conway, Katie A. and Crudup, Keyaira L. and Lewek, Michael D. and Franz, Jason R.}, year={2021}, month={Mar}, pages={574–580} }
 @article{conway_franz_2020, title={Increasing the Propulsive Demands of Walking to Their Maximum Elucidates Functionally Limiting Impairments in Older Adult Gait}, volume={28}, ISSN={["1543-267X"]}, DOI={10.1123/japa.2018-0327}, abstractNote={The authors elucidated functional limitations in older adult gait by increasing horizontal impeding forces and walking speed to their maximums compared with dynamometry and with data from their young counterparts. Specifically, the authors investigated which determinants of push-off intensity represent genuine functionally limiting impairments in older adult gait versus biomechanical changes that do not directly limit walking performance. They found that older adults walked at their preferred speed with hallmark deficits in push-off intensity. These subjects were fully capable of overcoming deficits in propulsive ground reaction force, trailing limb positive work, trailing leg and hip extension, and ankle power generation when the propulsive demands of walking were increased to maximum. Of the outcomes tested, age-related deficits in ankle moment emerged as the lone genuine functionally limiting impairment in older adults. Distinguishing genuine functional limitations from age-related differences masquerading as limitations represents a critical step toward the development and prescription of effective interventions.}, number={1}, journal={JOURNAL OF AGING AND PHYSICAL ACTIVITY}, author={Conway, Katie A. and Franz, Jason R.}, year={2020}, month={Feb}, pages={1–8} }
 @article{conway_franz_2020, title={Shorter gastrocnemius fascicle lengths in older adults associate with worse capacity to enhance push-off intensity in walking}, volume={77}, ISSN={["1879-2219"]}, DOI={10.1016/j.gaitpost.2020.01.018}, abstractNote={Reduced push-off intensity during walking is thought to play an important role in age-related mobility impairment. We posit that an age-related shift toward shorter plantarflexor operating lengths during walking functionally limits force generation, and thereby the ability of those muscles to respond to increased propulsive demands during walking. To determine whether gastrocnemius muscle fascicle lengths during normal walking: (1) are shorter in older than young adults, and (2) correlate with one's capacity to increase the propulsive demands of walking to their maximum. We used in vivo cine B-mode ultrasound to measure gastrocnemius fascicle lengths in 9 older and 9 young adults walking at their preferred speed, their maximum speed, and with horizontal impeding forces that increased in a ramped design at 1%BW/s to their maximum. A repeated measures ANOVA tested for effects of age and walking condition, and Pearson correlations assessed the relation between fascicle outcomes and condition performance. A tendency toward shorter medial gastrocnemius muscle fascicle lengths in older versus young adults was not statistically significant. However, older adults walked with reduced peak fascicle shortening during all conditions compared to young adults – an outcome not explained by reduced muscle-tendon unit shortening and exacerbated during tasks with greater than normal propulsive demand. As hypothesized, we found a strong and significant positive correlation in older subjects between gastrocnemius fascicle lengths during normal walking and performance on the ramped impeding force condition (p = 0.005, r² = 0.704), even after controlling for isometric strength (p = 0.011, r² = 0.792) and subject stature (p = 0.010, r² = 0.700). Our findings provide muscle-level insight to develop more effective rehabilitation techniques to improve push-off intensity in older adults and assistive technologies designed to steer plantarflexor muscle fascicle operating behavior during functional tasks.}, journal={GAIT & POSTURE}, author={Conway, Katie A. and Franz, Jason R.}, year={2020}, month={Mar}, pages={89–94} }