Body Weight Support Conditions Research Articles

The combined influence of body weight support and running direction on self-selected movement patterns

We investigated metabolic costs, muscle activity, and perceptual responses during forward and backward running at matched speeds at different body weight support (BWS) conditions. Participants ran forward and backward on a lower body positive pressure treadmill at 0%BWS, 20%BWS, and 50%BWS conditions. We measured oxygen uptake, carbon dioxide production, heart rate, muscle activity, and stride frequency. Additionally, we calculated metabolic cost of transport. Furthermore, we used rating of perceived exertion and feeling scale to investigate perceptual responses. Feeling scale during running was higher with increasing BWS (0–50%BWS), regardless of running direction (p < 0.05). Oxygen uptake, heart rate, and metabolic cost of transport were influenced by the interaction of running direction and BWS (p < 0.01). For example, metabolic cost of transport during backward running was greater than when running forward only when running at 0%BWS (i.e., 4.4 ± 1.1 and 5.8 ± 1.4 J/kg/m for forward and backward running, respectively: p < 0.001). However, rectus femoris muscle activity, stride frequency, and rating of perceived exertion during backward running were averages of 113.5%, 11.3%, and 2.8 rankings greater than when running forward, respectively, regardless of BWS (p < 0.001). We interpret our observations to indicate that environment (in the context of effective body weight) is a critical factor that determines self-selected movement patterns during forward and backward running.

Influence of speed on running strategies during forward and backward running with body weight support.

Running with body weight support (BWS) and backward running have been included in exercise programs. However, it is not known how running characteristics of forward and backward running with BWS are influenced by the deviation in the running speed from the preferred speed (PS). The purpose of this study was to investigate how metabolic cost, muscle activity, and perceptual responses of forward and backward running with BWS are influenced by the deviation in running speed from the PS. Eleven participants ran forward and backward at 0%BWS, 20%BWS, and 50%BWS conditions. The running speed conditions were set to their mode-specific PS, PS+10%, and PS-10%. We measured metabolic cost, muscle activity, stride frequency, rating of perceived exertion, and feeling scale. Metabolic cost, muscle activity (rectus femoris and gastrocnemius), and rating of perceived of exertion during running increased with increasing speed, regardless BWS and running direction (P<0.05). For example, a 10% increase in running speed from the PS produced averages of 7.1% and 7.7% increases in oxygen uptake and rectus femoris muscle activity, respectively. However, stride frequency during forward and backward running with BWS did not increase with increasing speed when running speed was manipulated around the PS (i.e., 10% increments: P>0.05), with the exception of forward running at 50%BWS. A 10% increase in running speed from the PS may be useful for individuals who are required to increase their metabolic cost, muscle activity, and perceptual responses during running, regardless of BWS and running direction.

Offloading Effects on Impact Forces and Patellofemoral Joint Loading During Running in Females

BackgroundStructure-specific loading is being increasingly recognized as playing a role in running related injuries. The use of interventions targeted at reducing patellofemoral joint loads have shown effectiveness in reducing symptoms of patellofemoral pain. Use of bodyweight support (BWS) has the potential to reduce loading on the patellofemoral joint during running to augment rehabilitation efforts. Research Question:How is patellofemoral joint loading different when using a harness-based BWS system during running? MethodsTwenty-five healthy females free from lower extremity injury were included. Participants completed four running trials on an instrumented treadmill with varying amounts of BWS using a commercially available harness system. Kinematic data from a 3D motion capture system and kinetic data from the treadmill were combined in a computer model to estimate measures of patellofemoral joint loading, knee kinematics, ground reaction force, and stride frequency. ResultsPeak patellofemoral joint stress and time-integral were reduced when running under BWS conditions compared to control conditions. Incremental decreases in patellofemoral loading were not observed with incremental increases in BWS. Peak knee flexion angle was reduced in all BWS conditions compared to control but was not different between BWS conditions. Knee flexion excursion was reduced in only the high BWS condition. Peak ground reaction force and stride frequency incrementally decreased with increased amounts of BWS. SignificanceHarness-based BWS systems may provide a simple means to reduce patellofemoral joint loading to assist in rehabilitation efforts, such as addressing patellofemoral pain.

Locomotion Synchronization and Gait Performance While Walking With an Overground Body Weight Support System.

Rehabilitation robotics offers new alternatives to patients and therapists to efficiently support walking training using Body Weight Support (BWS) systems. Automating the locomotion of overground BWS systems is one of the feasible approaches to free therapists from manual operation. However, the effect of locomotion control strategies of BWS system on participant's gait performance have not been studied sufficiently. For this reason, in this paper we introduced locomotion synchronization between a participant, a therapist, and a BWS system as control criteria, and investigated its effect on participant's gait performance during walking with an overground BWS system. In the experiment, four healthy participants walked with a BWS system under different BWS conditions, and with/without wearing orthosis which simulates asymmetric gait of actual patients. As the result, it was observed a significant relationship between locomotion synchronization and participants' gait performance, such as walking speed and step time.Clinical relevance - Controlling an overground BWS system's locomotion in synchronizing with the participant's gait has the potential to facilitate the effect of gait rehabilitation.

Neglected physical human-robot interaction may explain variable outcomes in gait neurorehabilitation research.

During gait neurorehabilitation, many factors influence the quality of gait patterns, particularly the chosen body-weight support (BWS) device. Consequently, robotic BWS devices play a key role in gait rehabilitation of people with neurological disorders. The device transparency, support force vector direction, and attachment to the harness vary widely across existing robotic BWS devices, but the influence of these factors on the production of gait remains unknown. Because this information is key to designing an optimal BWS, we systematically studied these determinants in this work. We report that with a highly transparent device and a conventional harness, healthy participants select a small backward force when asked for optimal BWS conditions. This unexpected finding challenges the view that during human-robot interactions, humans predominantly optimize energy efficiency. Instead, they might seek to increase their feeling of stability and safety. We also demonstrate that the location of the attachment points on the harness strongly affects gait patterns, yet harness attachment is hardly reported in literature. Our results establish principles for the design of BWS devices and personalization of BWS settings for gait neurorehabilitation.

Effects of Robot-assisted Gait With Body Weight Support on Torque, Work, and Power of Quadriceps and Hamstring Muscles in Healthy Subjects

Background: Robot-assisted gait training (RAGT) is an effective method for walking rehabilitation. Additionally, the body weight support (BWS) system reduces muscle fatigue while walking. However, no previous studies have investigated the effects of RAGT with BWS on isokinetic strength of quadriceps and hamstring muscles. Objects: The purpose of this study was to investigate the effects of torque, work, and power on the quadriceps and hamstring muscles during RAGT, using the BWS of three conditions in healthy subjects. The three different BWS conditions were BWS 50%, BWS 20%, and full weight bearing (FWB). Methods: Eleven healthy subjects (7 males and 4 females) participated in this study. The Walkbot_S was used to cause fatigue of the quadriceps and hamstring muscles and the Biodex Systems 4 Pro was used to measure the isokinetic torque, work, and power of them. After RAGT trials of each of the three conditions, the subjects performed isokinetic concentric knee flexion and extension, five at an angular velocity of 60°/s and fifteen at an angular velocity of 180°/s. One-way repeated analysis of variance was used to determine significant differences in all the variables. The least significant difference test was used for post-hoc analysis. Results: On both sides, there were significant differences in peak torque (PT) of knee extension and flexion between the three BWS conditions at an angular velocity of 60°/s and 180°/s conditions. A post-hoc comparison revealed that the PT in the BWS 50% was significantly greater than in the BWS 20% and the FWB and the PT in the BWS 20% was significantly greater than in the FWB. Conclusion: The results of this study suggest that the lower BWS during RAGT seems to lower the isokinetic torque, work, and power of the quadriceps and hamstring muscles because of the muscle fatigue increase.

Influence Of Running Direction On Metabolic Costs May Be Attenuated By Body Weight Support

During running on land, backward running produces greater metabolic and muscular demands than when running forward at the same speed. This type of research is important to identify the similarities and differences of forward and backward running, in order to best prescribe backward running as a cross-training stimulus for forward running. PURPOSE: The purpose of this study was to investigate the influence of running direction on metabolic, biomechanical, and perceptual demands during running at different levels of body weight support (BWS). METHODS: Thirteen participants ran forward and backward on a lower body positive pressure treadmill at 0%BWS, 20%BWS, and 50%BWS conditions at the same speed. We measured oxygen uptake (VO2), heart rate (HR), muscle activity (rectus femoris, biceps femoris, tibialis anterior, gastrocnemius), and stride frequency during the tests. Additionally, we calculated metabolic cost of transport (CoT). Furthermore, we used rating of perceived exertion (RPE) and feeling scale to investigate participants’ perceptual demands during the tests. VO2, HR, CoT, RPE, feeling scale, muscle activity, and stride frequency were analyzed using a 2 (directions) x 3 (BWS) repeated measures analysis of variance (α = 0.05). RESULTS: VO2, HR, and CoT were influenced by the interaction of BWS and running direction (P < 0.01). For example, CoT during backward running were greater than when running forward only when running at 0%BWS (4.5 ± 1.1 and 5.8 ± 1.4 J/kg/m in CoT for forward and backward running, respectively: P < 0.001). However, muscle activity from the rectus femoris, stride frequency, and RPE during backward running were averages of 113.5%, 11.3%, and 2.8 rankings greater than when running forward, respectively, regardless of BWS (P < 0.001). CONCLUSIONS: Backward running may require greater biomechanical and perceptual demands compared to forward running at the same speed, regardless of BWS. However, the influence of a change in running direction on metabolic demands may be attenuated by BWS. Supported by JSPS Grant Number 16 K01663.

Analysis of 3-D Kinematics Using H-Gait System during Walking on a Lower Body Positive Pressure Treadmill.

Recently, treadmills equipped with a lower-body positive-pressure (LBPP) device have been developed to provide precise body weight support (BWS) during walking. Since lower limbs are covered in a waist-high chamber of an LBPP treadmill, a conventional motion analysis using an optical method is impossible to evaluate gait kinematics on LBPP. We have developed a wearable-sensor-based three-dimensional motion analysis system, H-Gait. The purpose of the present study was to investigate the effects of BWS by a LBPP treadmill on gait kinematics using an H-Gait system. Twenty-five healthy subjects walked at 2.5 km/h on a LBPP treadmill under the following three conditions: (1) 0%BWS, (2) 25%BWS and (3) 50%BWS conditions. Acceleration and angular velocity from seven wearable sensors were used to analyze lower limb kinematics during walking. BWS significantly decreased peak angles of hip adduction, knee adduction and ankle dorsiflexion. In particular, the peak knee adduction angle at the 50%BWS significantly decreased compared to at the 25%BWS (p = 0.012) or 0%BWS (p < 0.001). The present study showed that H-Gait system can detect the changes in gait kinematics in response to BWS by a LBPP treadmill and provided a useful clinical application of the H-Gait system to walking exercises.

Influence Of Running Speed On Muscle Activity During Backward Running With Body Weight Support

A change in running speed influences gait mechanics of running. PURPOSE: The purpose of this study was to investigate the influence of a change in running speed on muscle activity during forward and backward running at different body weight support (BWS) conditions. METHODS: Eleven participants (29.7 ± 12.3 years) ran forward and backward on a lower body positive pressure treadmill at 0%BWS, 20%BWS, and 50%BWS conditions. The running speed conditions consisted of forward and backward running at preferred speed (PS), PS+10%, and PS-10%. Muscle activity from the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius and stride frequency were measured. Muscle activity and stride frequency were analyzed using a 2 (running direction) x 3 (BWS) x 3 (running speed) repeated measures analysis of variance (α = 0.05). RESULTS: Muscle activity from the rectus femoris (P<0.01) and gastrocnemius (P<0.01) were significantly different between running speeds. For example, muscle activity from the rectus femoris (P<0.05) and gastrocnemius (P<0.05) during running at PS were significantly greater than when running at PS-10%, regardless of running direction and BWS. Furthermore, muscle activity from the rectus femoris (P<0.01) and gastrocnemius (P<0.05) during running at PS+10% were significantly greater than when running at PS, regardless of running direction and BWS. Stride frequency was influenced by the interaction of running direction and running speed (P<0.05). Using the pairwise comparisons, stride frequency during running at PS was significantly higher than that of running at PS-10% only when running forward and backward at 0%BWS (e.g., 84.5 strides/min and 82.0 strides/min for backward running at PS and PS-10% conditions, respectively: P<0.05). Furthermore, stride frequency during running at PS+10% was significantly higher than that of running at PS during forward and backward running at 0%BWS (P<0.05). CONCLUSIONS: Muscle activity from the rectus femoris and gastrocnemius during running may increase with increasing running speed, regardless of BWS and running direction. However, unique biomechanical strategies for the increased muscle activity from the lower extremity may exist for running with BWS.

Simulation of human gait with body weight support: benchmarking models and unloading strategies

BackgroundGait training with partial body weight support (BWS) has become an established rehabilitation technique. Besides passive unloading mechanisms such as springs or counterweights, also active systems that allow rendering constant or modulated vertical forces have been proposed. However, only pilot studies have been conducted to compare different unloading or modulation strategies, and conducting experimental studies is costly and time-consuming. Simulation models that predict the influence of unloading force on human walking may help select the most promising candidates for further evaluation. However, the reliability of simulation results depends on the chosen gait model. The purpose of this paper is two-fold: First, using human experimental data, we evaluate the accuracy of some of the most prevalent walking models in replicating human walking under the influence of Constant-Force BWS: The Simplest Walking model (SW), the Spring-Loaded Inverted Pendulum model (SLIP) and the Muscle-Reflex (MR) gait model. Second, three realizations of BWS, based on Constant-Force (CF), Counterweight (CW) and Tuned-Spring (TS) approaches, are compared to each other in terms of their influence on gait parameters.MethodsWe conducted simulations in Matlab/Simulink to model the behaviour of each gait model under all three BWS conditions. Nine simulations were undertaken in total and gait parameter response was analysed in each case. Root mean square error (mrmse) w.r.t human data was used to compare the accuracy of gait models. The metrics of interest were spatiotemporal parameters and the vertical ground reaction forces. To scrutinize the BWS strategies, loss of dynamic similarity was calculated in terms of root mean square difference in gait dynamics (Δgd) with respect to the reference gait under zero unloading. The gait dynamics were characterized by a dimensionless number Modela-w.ResultsSLIP model showed the lowest mrmse for 6 out of 8 gait parameters and for 1 other, the mrmse value were comparable to the MR model; SW model had the highest mrmse. Out of three BWS strategies, Tuned-Spring strategies led to the lowest Δgd values.ConclusionsThe results of this work demonstrate the usefulness of gait models for BWS simulation and suggest the SLIP model to be more suitable for BWS simulations than the Simplest Walker and the Muscle-reflex models. Further, the Tuned-Spring approach appears to cause less distortions to the gait pattern than the more established Counterweight and Constant-Force approaches and merits experimental verification.

The effects of stride frequency manipulation on physiological and perceptual responses during backward and forward running with body weight support.

We investigated the influence of a change in stride frequency on physiological and perceptual responses during forward and backward running at different body weight support (BWS) levels. Participants ran forward and backward at 0% BWS, 20% BWS, and 50% BWS conditions on a lower body positive pressure treadmill. The stride frequency conditions consisted of forward and backward running at preferred stride frequency (PSF), PSF + 10%, and PSF-10%. We measured oxygen uptake ([Formula: see text]O2), carbon dioxide production, heart rate (HR), muscle activity from the lower extremity, and rating of perceived exertion (RPE). Furthermore, we calculated the metabolic cost of transport (CoT). [Formula: see text]O2, HR, CoT, and muscle activity from the rectus femoris were significantly different between stride frequency conditions (P < 0.05). [Formula: see text]O2, HR, and CoT during running at PSF + 10% were significantly higher than when running at PSF, regardless of running direction and BWS (P < 0.05). However, RPE was not different between stride frequency conditions (P > 0.05: e.g., 12.8-13.8 rankings in RPE for backward running at 0% BWS). Manipulation of stride frequency during running may have a greater impact on physiological responses than on perceptual responses at a given speed, regardless of running direction and BWS. Individuals who need to increase their physiological demands during running may benefit from a 10% increase in stride frequency from the PSF, regardless of BWS and running direction.

Gait asymmetry pattern following stroke determines acute response to locomotor task

BackgroundGiven the prevalence of gait dysfunction following stroke, walking recovery is a primary goal of rehabilitation. However, current gait rehabilitation approaches fail to demonstrate consistent benefits. Gait asymmetry, prevalent among stroke survivors who regain the ability to walk, is associated with an increased energy cost of walking and is a significant predictor of falls post-stroke. Furthermore, differential patterns of gait asymmetry may respond differently to gait training parameters. Research questionThe purpose of this study was to determine whether differential responses to locomotor task condition occur on the basis of step length asymmetry pattern (Symmetrical, NPshort, Pshort) observed during overground walking. MethodsParticipants first walked overground at their self-selected walking speed. Overground data were compared against three task conditions all tested during treadmill walking: self-selected speed with 0% body weight support (TM); self-selected speed with 30 % body weight support (BWS); and fastest comfortable speed with 30 % body weight support and nonparetic leg guidance (GuidanceNP). Our primary metrics were: symmetry indices of step length, stride length, and single limb support duration. ResultsWe identified differences in the response to locomotor task conditions for each step length asymmetry subgroup. GuidanceNP induced an acute spatial symmetry only in the NPshort group and temporal symmetry in the Symmetrical and Pshort groups. Importantly, we found the TM and BWS conditions were insufficient to impact either spatial or temporal gait symmetry. SignificanceTask conditions consistent with locomotor training do not produce uniform effects across subpatterns of gait asymmetry. We identified differential responses to locomotor task conditions between groups with distinct asymmetry patterns, suggesting these subgroups may require unique intervention strategies. Despite group differences in asymmetry characteristics, improvements in symmetry noted in each group were driven by changes in both the paretic and nonparetic limbs.

Harnessing the Power of a Novel Program for Dynamic Balance Perturbation with Supported Body Weight

Self-initiated postural adjustments commonly occur in daily life. To accessibly measure this type of dynamic balance, we developed a simple computer program to induce virtual perturbations and combined it with a commercially available balance board and portable EMG system to measure resulting self-initiated postural adjustments. When performing perturbed balance tests, safety harness with body weight support (BWS) is often used. However, influences of these harnesses on postural reactions are not well known. This study investigated the sensitivity of our assessment tool under different BWS conditions and muscle responses during postural adjustments following perturbation at different directions. Fifteen neurologically intact participants performed self-initiated postural adjustments under conditions with: (1) no harness; (2) harness with no BWS; and (3) harness with 10% BWS. Postural adjustment time and muscle activities of the lower leg were measured. We observed significant increases in postural adjustment time in the harness with no BWS condition and differneces in lower leg muscles response to virtual perturbation. Our findings suggest that the combination of our customized program with EMG is a sensitive and convenient tool to measure postural adjustments that approximate real-world scenarios. This method can be used with light body weight support to ensure safety without influencing muscle synergies.

Influence of stride frequency manipulation on muscle activity during running with body weight support

BackgroundRunning with body weight support (BWS) has been used for physical fitness enhancement. Nevertheless, gait mechanics of running with BWS is not fully understood. Research questionWe investigated influence of stride frequency manipulation on muscle activity during running at various BWS conditions. MethodsNineteen participants (23.8 ± 4.1 years) ran on a lower body positive pressure treadmill at their preferred speed and preferred stride frequency (PSF) for 0%BWS, 50%BWS, and 80%BWS conditions. Preferred speed and PSF were selected for each of the BWS conditions. The stride frequency conditions consisted of running at PSF, PSF+10%, and PSF-10%. Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA) were measured. ResultsRF and BF during running at the PSF+10% were higher than when running at the PSF, regardless of BWS (P < 0.01). Additionally, RF and TA during running at the PSF-10% were higher than when running at the PSF, regardless of BWS (P < 0.05). Furthermore, RF, TA, GA, and PSF during running decreased with increasing BWS (P < 0.05), although preferred speed increased with increasing BWS (P < 0.001). SignificanceThese observations suggest that manipulating stride frequency by 10% from the PSF during running produces greater RF, BF, and TA than when running at the PSF, regardless of BWS. Furthermore, it was suggested that a change in BWS influences RF, TA, GA, PSF, and preferred speed during running. Such information may be useful to enable the practitioner to refine the use of running with BWS in exercise programs.

Effect of body weight support on predicted locomotive physical activity.

[Purpose] This study aimed to evaluate the effect of body weight support with an assistive device on predicted locomotive physical activity measured using triaxial accelerometers in healthy young subjects. [Subjects and Methods] Sixteen healthy subjects aged 21.9 ± 1.1 years walked on a treadmill at speeds of 45 and 55 meters/min under 0%, 10%, 20%, and 30% body weight support conditions. Predicted metabolic equivalents and number of steps were evaluated using triaxial accelerometers. Measured metabolic equivalents and number of steps were evaluated using a metabolic system and observers, respectively. Raw data of synthetic accelerations were also obtained. [Results] Predicted metabolic equivalents and number of steps and raw data of synthetic accelerations decreased with increasing amounts of body weight support. [Conclusion] These findings suggest that accelerometers may underestimate locomotive physical activity with increasing amounts of body weight support using assistive devices. Thus, it is important to consider the amount of body weight support when assessing physical activities in subjects using assistive devices for mobility.

Muscle activity during backward and forward running with body weight support

We investigated muscle activity during backward (BR) and forward (FR) running with body weight support (BWS). Ten participants completed BR and FR on a lower body positive pressure treadmill while selecting a preferred speed (PS) for different BWS conditions (0%, 20%, 40%, 60%, and 80%BWS). Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA), rating of perceived exertion (RPE), preferred stride frequency (PSF), and PS were measured. Magnitude of muscle activity (BF, TA, and GA), RPE, PSF, and PS were not influenced by the interaction of direction and BWS (P>0.05). BF, TA, and GA were not different between directions (P>0.05) but were different between BWS conditions (P<0.01). RF was influenced by the interaction of direction and BWS (P<0.01). RF, BF, TA, and GA during BR were lower with increasing BWS. RF during BR was 59–86% higher than that of FR within BWS condition. RPE was lower with increasing BWS (P<0.001), regardless of direction of locomotion. PSF was lower and PS was higher during BR and FR with increasing BWS (both P<0.001). PSF during BR was 6–9% higher than that of FR. PS during BR was 24–31% lower than that of FR. These observations demonstrate that a change in BWS influences magnitude of muscle activity, PS, PSF, and RPE for both BR and FR. However, a change in direction of locomotion may not influence magnitude of muscle activity or RPE during running for a given BWS, even though muscle activity pattern, PS, and PSF were different between BR and FR.

Frontal brain activation changes due to dual-tasking under partial body weight support conditions in older adults with multiple sclerosis

BackgroundGait impairments present while dual-tasking in older adults with multiple sclerosis (MS) have been associated with an increased risk of falls. Prior studies have examined prefrontal cortex (PFC) activity using functional near infrared spectroscopy (fNIRS) while dual-tasking in older adults with and without cognitive impairment. While the benefits of partial body weight support (PBWS) on gait have been clearly outlined in the literature, the potential use of PBWS to improve the ability to dual task in older adults with and without MS has not been examined. The aim of this study was to examine the effects of PBWS on the PFC activation while dual-tasking in older adults with and without MS.MethodsTen individuals with MS (mean 56.2 ± 5.1 yrs., 8 females) and 12 healthy older adults (HOA) (mean 63.1 ± 4.4 yrs., 9 females) participated in this study. PFC activation (i.e., oxygenated hemoglobin-HbO2) was measured using fNIRS. Assessments were done under two treadmill walking conditions: no body weight support (NBWS) and PBWS. Under each condition, participants were asked to walk at a comfortable speed (W) or walk and talk (WT). Linear mixed models were used to test for differences between cohorts, conditions, and tasks.ResultsHbO2 levels differed significantly between task (p < .001), cohort (p < .001), and BWS (p = .02). HbO2 levels increased under higher cognitive demands (i.e., W vs WT), in individuals with MS, and under different conditions (i.e., NBWS vs PBWS). Post-hoc analysis demonstrated a significant difference between cohorts during the WT and NBWS condition (p = .05). When examining the relative change in HbO2 levels during each task, a significant interaction between task, BWS, and cohort across time was observed (p < 0.01). While HOA increased PFC activation across time, MS exhibited a maintenance of PFC activation patterns during the WT under PBWS condition.ConclusionsThis study establishes the potential impact of PBWS on PFC activation patterns under dual-tasking conditions and sheds light on the ability for PBWS to be used as a therapeutic tool in individuals with neurological conditions to decrease cognitive demands while dual-tasking and thus decrease the risk of falls.

Influence Of Stride Frequency Manipulation On Muscle Activity During Running At Reduced Body Weight

Running with body weight support (BWS) (e.g., running on a lower positive pressure treadmill) has been used for physical fitness enhancement. Nevertheless, gait mechanics of running with BWS is not fully understood. PURPOSE: To investigate influence of stride frequency (SF) manipulation on muscle activity during running at different BWS conditions. METHODS: Nineteen subjects (23.8±4.1 years) ran on a lower body positive pressure treadmill at their preferred running speed (PS) for different BWS conditions (i.e., 0%, 50%, and 80% of BWS conditions). The SF conditions consist of running at preferred SF (PSF), PSF+10%, and PSF-10%. Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA) were measured. In addition, rating of perceived exertion (RPE) and SF were measured. Muscle activity, RPE, and SF were analyzed using a 3 (mode) x 3 (BWS) repeated measures analysis of variance (ANOVA) (α = 0.05). PS was analyzed using a one-way repeated measures ANOVA (α = 0.05). RESULTS: Muscle activity (RF, BF, TA, and GA), RPE, and SF were not influenced by the interaction of BW support and SF (P>0.05). Muscle activity from the RF, TA, and GA were different between BWS conditions (P<0.001). Specifically, muscle activity from the RF, TA, and GA were lower with increasing BWS (e.g., a decrease of 26%~46% between 80%BWS and 0%BWS conditions). Muscle activity from the RF, BF, and TA were different between SF conditions (P<0.05). For example, RF muscle activity during running at PSF was 11%~18% lower than when running at PSF+10%. Additionally, BF muscle activity during running was higher with increasing SF (e.g., a 20% increase in SF resulted in 12%~27% increase in the BF muscle activity). RPE was not different between BWS conditions (P>0.05) and between SF conditions (P>0.05). SF was different between BWS conditions (P<0.001) and between SF conditions (P<0.001). For example, SF was lower with increasing BWS (e.g., a decrease of 15% between 80%BWS and 0%BWS conditions). PS was higher with increasing BWS (9.8±2.1 km/h, 11.0±2.6 km/h, and 11.8±2.8 km/h for 0%, 50%, and 80% of BWS conditions, respectively: P<0.001). CONCLUSION: These observations suggest that a change in SF may influence muscle activity (i.e., RF and TA) during running, regardless of BWS.

Muscle Activity During Backward And Forward Running At Reduced Body Weight

Body weight (BW) support during locomotion is used for both forward and backward locomotion. However, muscle activity during locomotion in different directions at different levels of BW support is not known. PURPOSE: To investigate muscle activity during backward (BR) and forward (FR) running at different BW support conditions. METHODS: Ten subjects (23.1±3.5 yrs) completed BR and FR on a lower body positive pressure treadmill; selecting a preferred speed for different BW support conditions (0%, 20%, 40%, 60%, and 80% of BW). Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA) were measured and averaged across 15 s (zero offset removed, full-wave rectified). In addition, rating of perceived exertion (RPE), preferred stride frequency (PSF), and preferred speed (PS) were measured. All parameters were analyzed using 2 (direction) x 5 (BW) repeated measures ANOVA (α = 0.05). When an interaction effect was observed, post hoc analysis was performed using a Fisher’s protected least significant difference multiple comparison test (α = 0.05). RESULTS: Muscle activity (BF, TA, and GA), RPE, PSF, and PS were not influenced by the interaction of direction and BW support (P>0.05). BF, TA, and GA were not different between directions (P>0.05) but were different between BW support conditions (P<0.05). RF was influenced by the interaction of direction and BW support (P<0.05). For example, RF during BR at 0% BW support condition was significantly higher than that of BR at 40% (P<0.05), 60% (P<0.05), and 80% (P<0.05) BW support conditions. RF, BF, TA, and GA during BR were lower with increasing BW support (e.g., a decrease of 33%~60% between 80% and 0% BW support conditions). RPE during BR and FR were lower with increasing BW support (P<0.05) regardless of direction of locomotion (P>0.05). PSF and PS were different between directions (P<0.05) and between BW support conditions (P<0.05). PSF during BR and FR were lower and PS higher with increasing BW support. PSF during BR was 6%~9% higher than that of FR. PS during BR was 24%~31% lower than that of FR (e.g., 8.9±1.7 km/h vs. 11.9±3.2 km/h for BR and FR at 80% BW support condition, respectively). CONCLUSION: BW support influenced muscle activity whereas direction of locomotion did not even though slower speeds were selected BR vs. FR.

Influence of Body Weight Support and Direction of Locomotion on Preferred Gait

Previously, no research has investigated differences in preferred gait characteristics during forwards and backwards running at varying body weight (BW) support. PURPOSE: To understand how BW support and direction of locomotion influence descriptors of preferred gait. METHODS: Subjects (n=8; 27.0±11.7 years, 173.8±3.5 cm, 74.0±8.7 kg) performed forward and backward running on a lower body positive pressure treadmill at different levels of BW support (i.e., 0%-80% body weight support). Subjects preferred running speed (PS), preferred stride frequency (PSF), and rate of perceived exertion (RPE) were measured. PS, PSF, and RPE were analyzed using a 2(exercise mode: forward and backward locomotion) x 5(BW support: 0%, 20%, 40%, 60%, and 80%) repeated measures analysis of variance (α= 0.05). RESULTS: PS, PSF, and RPE were not influenced by the interaction of exercise mode and BW support (p > 0.05). PS was different between modes (p < 0.001) and between BW support conditions (p < 0.01). For example, PS increased approximately 3.8%-8.5% and 3.0%-11.9% with decreasing BW support for forward and backward running, respectively. Additionally, PS during forward running was higher than that of backward running at reduced BW support (e.g., 3.4±.9 m/s and 2.5±.5 m/s for forward and backward running at 80% BW support, respectively). Furthermore, PSF (p< 0.001) and RPE (p< 0.01) were different between BW conditions but not different between direction of locomotion (p>0.05). Specifically, PSF (e.g., a decrease of 13.2% during forward running at 0% BW support vs. 80% BW support) and RPE (e.g., a decrease of 19.9% during forward running at 0% BW support vs. 80% BW support) during forward and backward running decreased with decreasing BW support. CONCLUSION: It seems that BW support may have more of an influence on preferred gait characteristics than direction of locomotion since PSF and RPE were not different between directions of locomotion.