Maximal Physiological Parameters during Partial Body-Weight Support Treadmill Testing

Effect of anti-gravity treadmill (Alter G) training on gait characteristics and postural stability in adult with healed burns: A single blinded randomized controlled trial

BACKGROUND

Burns constitute one of the foremost contributors to premature mortality and morbidity, and the recovery process from burn injuries is characterized by its intricate and protracted nature.

OBJECTIVE

The principal aim of this study was to assess the influence of an anti-gravity treadmill (Alter G) training program on both gait characteristics and postural stability indices (PSI) in adult individuals who have recovered from burns.

DESIGN

This study followed a single-blind, randomized, controlled design.

METHODS

A total of 45 adults, aged 18-35 years, with healed lower extremity burns that were circumferential and encompassed 35-50% of their total body surface area (TBSA) were randomly allocated to either the anti-gravity treadmill (Alter G) Training group (n = 22) or the traditional physical therapy program (TPTP) group (n=23). The TPTP group received conventional physical therapy, while the anti-gravity treadmill (Alter G) training group engaged in anti-gravity treadmill exercises alongside the traditional physical therapy program. The primary outcome measures, evaluated at both baseline and the conclusion of the 12-week intervention, included gait characteristics assessed using the GAITRite system and PSI measured by the Biodex Balance System (BBS).

RESULTS

The anti-gravity treadmill (Alter G) training group exhibited significantly greater enhancements than the TPTP group in terms of mean values and percentage changes in gait characteristics and PSI. Specifically, the percentage changes for the Alter G group were as follows: stride length (20.57%), step time (22.58%), step length (20.47%), velocity (15.67%), cadence (23.28%), and double support time (29.03%). In contrast, the TPTP group's percentage changes were: 6.73%, 8.19%, 7.65%, 7.75%, 8.89%, and 9.37%, respectively. Concerning PSI, the Alter G group exhibited percentage changes of 55.17% for the medio-lateral stability index (MLI), 48.21% for antero-posterior stability index (API), and 48.48% for the overall stability index (OSI). The TPTP group's corresponding percentage changes were 20%, 14.03%, and 16.41%.

CONCLUSIONS

The amalgamation of anti-gravity treadmill training with the traditional physical therapy program yields greater efficacy than TPTP in isolation. Consequently, the findings underscore the efficiency of anti-gravity treadmill (Alter G) Training as a valuable tool for rehabilitating patients with burn injuries.

Hydrodynamic Flow Characteristics of a Recirculating Pool: Examining the Ecological Validity for Training and Testing

ABSTRACT

Krajewski, KT, Beethe, AZ, Dever, DE, Johnson, CD, Nindl, BC, Lovalekar, MT, Flanagan, SD, and Connaboy, C. Hydrodynamic flow characteristics of a recirculating pool: examining the ecological validity for training and testing. J Strength Cond Res 37(10): 2023-2031, 2023-Recirculating swimming flumes (RSFs) with elliptical multifeature designs have grown in popularity due to their multifunctionality for rehabilitation and training. Because of their smaller footprint, laboratories have adopted their use to investigate swimming and underwater treadmill running. However, little is known about the hydrodynamic characteristics of these RSFs and how they might influence outcomes. The purpose was to determine hydrodynamic flow characteristics of an RSF at the manufacturers' set "speeds" around the centroid of flow projection. Hydrodynamic velocity profiles were collected through a 3D profiling velocimeter, sampling at 200 Hz in an RSF. Data were collected 0.5 and 1.5 m from the projection channel at designated flume "speeds" of 30-95 (+99) in 5-unit increments. Velocity data were collected for 1 minute per trial (location × speed) to determine mean flow velocity (MFV) for 10, 20, 30, and 40 cm2 cross-sectional areas (CSAs). A two-way ANOVA was conducted comparing CSAs from the surface by distance from the current channel (4 × 2). Separate ANOVAs were conducted to assess differences in MFV across each CSA. Significant differences between flow CSAs indicated that MFV is less for a larger area at the same speed, indicative of variable and turbulent flow characteristics across the respective CSAs. Mean flow velocity was further diminished by distance from the flow channel as supported by the main effect, thus exposing an individual to variant flow velocities simultaneously. Limited stability of the flow velocity centroid could affect swim mechanics making the movement pattern no longer analogous to traditional pool and open water swimming, rather resembling swimming upstream in a river with turbulent flow.

Neuromuscular adjustments to unweighted running: the increase in hamstring activity is sensitive to trait anxiety

Introduction: Originally developed for astronauts, lower body positive pressure treadmills (LBPPTs) are increasingly being used in sports and clinical settings because they allow for unweighted running. However, the neuromuscular adjustments to unweighted running remain understudied. They would be limited for certain lower limb muscles and interindividually variable. This study investigated whether this might be related to familiarization and/or trait anxiety. Methods: Forty healthy male runners were divided into two equal groups with contrasting levels of trait anxiety (high, ANX⁺, n = 20 vs. low, ANX^-, n = 20). They completed two 9-min runs on a LBPPT. Each included three consecutive 3-min conditions performed at 100%, 60% (unweighted running), and 100% body weight. Normal ground reaction force and electromyographic activity of 11 ipsilateral lower limb muscles were analyzed for the last 30 s of each condition in both runs. Results: Unweighted running showed muscle- and stretch-shortening cycle phase-dependent neuromuscular adjustments that were repeatable across both runs. Importantly, hamstring (BF, biceps femoris; STSM, semitendinosus/semimembranosus) muscle activity increased during the braking (BF: +44 ± 18%, p < 0.001) and push-off (BF: +49 ± 12% and STSM: +123 ± 14%, p < 0.001 for both) phases, and even more so for ANX⁺ than for ANX^-. During the braking phase, only ANX⁺ showed significant increases in BF (+41 ± 15%, p < 0.001) and STSM (+53 ± 27%, p < 0.001) activities. During the push-off phase, ANX⁺ showed a more than twofold increase in STSM activity compared to ANX^- (+119 ± 10% vs. +48 ± 27, p < 0.001 for both). Conclusion: The increase in hamstring activity during the braking and push-off phases may have accelerated the subsequent swing of the free-leg, likely counteracting the unweighting-induced slowing of stride frequency. This was even more pronounced in ANX⁺ than in ANX^-, in an increased attempt not to deviate from their preferred running pattern. These results highlight the importance of individualizing LBPPT training and rehabilitation protocols, with particular attention to individuals with weak or injured hamstrings.

The Safety and Feasibility of Lower Body Positive Pressure Treadmill Training in Individuals with Chronic Stroke: An Exploratory Study

BACKGROUND

Lower body positive pressure (LBPP) may provide a novel intervention for gait training in neurological conditions. Nonetheless, studies investigating the safety and feasibility of LBPP in patients with stroke are insufficient.

OBJECTIVES

The purpose of this study was to evaluate the safety and feasibility of LBPP as a rehabilitation intervention for individuals with chronic stroke.

METHODS

Individuals with chronic stroke were recruited from the community to participate in LBPP gait training three times a week for six weeks. The LBPP's safety and feasibility were documented throughout the study and at the end of six weeks. Safety and feasibility referred to the incidence of adverse events, complications, the participant and therapist satisfaction questionnaire, and the device limitation including but not limited to technical issues and physical constraints. In addition, blood pressure, pulse rate, and oxygen saturation were taken pre- and post-session. Dependent t-tests were used to analyze the difference between assessments. A Wilcoxon test was used to assess the ordinal data (Trial registration number NCT04767334).

RESULTS

Nine individuals (one female, eight males) aged 57 ± 15.4 years were enrolled. All participants completed the intervention without adverse events. All participants reported positive scores from 4 (very satisfying) to 5 (extremely satisfying) in the safety and feasibility questionnaire. No significant differences were observed in blood pressure and oxygen saturation during the intervention sessions. However, significant increases were observed in heart rate from 82.6 ± 9.1 beats/min (pre-session) to 88.1 ± 6.8 beats/min (post-session) (p = 0.027).

CONCLUSIONS

LBPP is a safe and feasible rehabilitation tool to use with individuals with chronic stroke.

Role of Antigravity Training in Rehabilitation and Return to Sport After Running Injuries

Anti-gravity treadmill training is a therapeutic option to help recovering runners return to activity after injury. This current concept paper provides a synopsis of the latest evidence of the biomechanical and metabolic changes that occur with body weight support (BWS) treadmill training, effects of antigravity treadmill training on clinical outcomes and clinical case studies in injured runners. Literature searches identified studies with descriptive, experimental and interventional designs and case studies that examined acute and chronic use of antigravity treadmills in runners and relevant populations. Laboratory-based studies were included to provide technical considerations for rehabilitation programming. Antigravity treadmills use causes reductions in cadence, ground reaction forces (GRF), GRF impulses, knee and ankle range of motion, and vertical stiffness, with elevations in stride duration, flight time, ground contact time, and plantarflexion. Antigravity treadmills appear useful across a spectrum of injuries in runners, including postsurgical repair of osteochondral defect, stress reactions (medial tibia, pelvis), and lumbar disc herniation. Runners may preserve aerobic fitness, muscle activation patterns, and muscle mass during recovery compared to traditional rehabilitation protocols. Technical considerations for accurate loading include treadmill frame adjustment to appropriate height to ensure accuracy of level of BWS while running, and monitoring for fast cadence to ensure impact loading rates remain low. Speed or grade can be increased to maintain metabolic demand and fitness while minimizing bone and tissue loading. Monitoring for symptom provocation will guide protocol adjustments to BWS and prescriptions. Once able to run pain-free (sustained or interval) >95% BWS for >30 min, the runner is likely ready to safely transition to ground running. Antigravity treadmill training can be considered when available to facilitate smooth transition back to ground running in a conditioned state.

AlterG Anti-Gravity Treadmill Accuracy of Unloading Is Affected by Support Frame Height

ABSTRACT

de Heer, HD, Kaufman, A, Repka, CP, Rojas, K, Charley, B, and Bounds, R. AlterG Anti-Gravity Treadmill accuracy of unloading is affected by support frame height. J Strength Cond Res 35(10): 2910-2914, 2021-The AlterG Anti-Gravity Treadmill uses air pressure to provide partial body-weight support (BWS), lowering impact forces and metabolic demand of walking and running. Users wear specialized shorts that zip onto a bag supported by a metal bar frame covering the treadmill. The frame is placed at hip height in positions numbered 1-9, adjusted up or down based on preference. Machine accuracy in providing BWS is important to achieve desired training effects, but it is unknown whether frame placement impacts accuracy. Twenty subjects (10 men/women) were weighed in 10% increments from 0 to 60% BWS with the frame at hip height (iliac crest), the "neutral" position, and reweighed with the frame placed up to 3 numbers above or below hip height. Although the machine displayed the same proportion BWS, placing the frame higher than the neutral position resulted in significantly more support, whereas placing the frame lower led to less support. At 10% BWS, placing the frame 3 positions higher resulted in 3% more support compared with the neutral position (13.1% BWS, p < 0.001) and 3 positions lower in 4.7% less support (5.3% BWS, p < 0.001). Deviances were greater with more BWS. At 60% BWS, 3 positions higher than neutral resulted in 71.2% BWS (11.2% more than expected, p < 0.001) and 3 below 48.1% BWS (12.9% below expected, p < 0.001), total 24.1% difference. These findings suggest that the position of the support frame significantly impacts the AlterG accuracy in providing BWS, with placement higher than hip height resulting in more support than displayed by the machine and lower placement resulting in less support.

Effect of Uphill Running on VO2, Heart Rate and Lactate Accumulation on Lower Body Positive Pressure Treadmills

Lower body positive pressure treadmills (LBPPTs) as a strategy to reduce musculoskeletal load are becoming more common as part of sports conditioning, although the requisite physiological parameters are unclear. To elucidate their role, ten well-trained runners (30.2 ± 3.4 years; VO_2max: 60.3 ± 4.2 mL kg^-1 min^-1) ran at 70% of their individual velocity at VO_2max (vVO_2max) on a LBPPT at 80% body weight support (80% BW_Set) and 90% body weight support (90% BW_Set), at 0%, 2% and 7% incline. Oxygen consumption (VO₂), heart rate (HR) and blood lactate accumulation (LA) were monitored. It was found that an increase in incline led to increased VO₂ values of 6.8 ± 0.8 mL kg^-1 min^-1 (0% vs. 7%, p < 0.001) and 5.4 ± 0.8 mL kg^-1 min^-1 (2% vs. 7%, p < 0.001). Between 80% BW_Set and 90% BW_Set, there were VO₂ differences of 3.3 ± 0.2 mL kg^-1 min^-1 (p < 0.001). HR increased with incline by 12 ± 2 bpm (0% vs. 7%, p < 0.05) and 10 ± 2 bpm (2% vs. 7%, p < 0.05). From 80% BW_Set to 90% BW_Set, HR increases of 6 ± 1 bpm (p < 0.001) were observed. Additionally, LA values showed differences of 0.10 ± 0.02 mmol l^-1 between 80% BW_Set and 90% BW_Set. Those results suggest that on a LBPPT, a 2% incline (at 70% vVO_2max) is not yet sufficient to produce significant physiological changes in VO₂, HR and LA-as opposed to running on conventional treadmills, where significant changes are measured. However, a 7% incline increases VO₂ and HR significantly. Bringing together physiological and biomechanical factors from previous studies into this practical context, it appears that a 7% incline (at 80% BW_Set) may be used to keep VO₂ and HR load unchanged as compared to unsupported running, while biomechanical stress is substantially reduced.

Making the Grade: An Exploration of Incline Running on a Bodyweight-Supportive Treadmill

CONTEXT

Bodyweight-supporting treadmills are popular rehabilitation tools for athletes recovering from impact-related injuries because they reduce ground reaction forces during running. However, the overall metabolic demand of a given running speed is also reduced, meaning athletes who return to competition after using such a device in rehabilitation may not be as fit as they had been prior to their injury.

OBJECTIVE

To explore the metabolic effects of adding incline during bodyweight-supported treadmill running.

DESIGN

Cross-sectional.

SETTING

Research laboratory.

PARTICIPANTS

Fourteen apparently healthy, recreational runners (6 females and 8 males; 21 [3] y, 1.71 [0.08] m, 63.11 [6.86] kg).

INTERVENTIONS

The participants performed steady-state running trials on a bodyweight-supporting treadmill at 8.5 mph. The control condition was no incline and no bodyweight support. All experimental conditions were at 30% bodyweight support. The participants began the sequence of experimental conditions at 0% incline; this increased to 1%, and from there on, 2% incline increases were introduced until a 15% grade was reached. Repeated-measures analysis of variance was used to compare all bodyweight-support conditions against the control condition.

MAIN OUTCOME MEASURES

Oxygen consumption, heart rate, and rating of perceived exertion.

RESULTS

Level running with 30% bodyweight support reduced oxygen consumption by 21.6% (P < .001) and heart rate by 12.0% (P < .001) compared with the control. Each 2% increase in incline with bodyweight support increased oxygen consumption by 6.4% and heart rate by 3.2% on average. A 7% incline elicited similar physiological measures as the unsupported, level condition. However, the perceived intensity of this incline with bodyweight support was greater than the unsupported condition (P < .001).

CONCLUSIONS

Athletes can maintain training intensity while running on a bodyweight-supporting treadmill by introducing incline. Rehabilitation programs should rely on quantitative rather than qualitative data to drive exercise prescription in this modality.

Effects of body weight support and gait velocity via antigravity treadmill on cardiovascular responses early after total knee arthroplasty

To investigate the effects of body weight support (BWS) and gait velocity on cardiovascular responses during walking on an antigravity treadmill early after unilateral and bilateral total knee arthroplasty (TKA).This study was a cross-sectional study design. Fifty patients (7 males and 43 females; average age, 72.0 ± 5.1 years) at 4 weeks after unilateral (n = 25) and bilateral (n = 25) primary TKA were enrolled in the study. Subjects walked on an antigravity treadmill at speeds of 2.5 km/hour and 3.5 km/hour with 3 levels (50%, 25%, and 0%) of BWS. Cardiovascular responses were monitored by measuring oxygen consumption (VO2), heart rate (HR), systolic and diastolic blood pressure (SBP/DBP), the respiratory exchange ratio (RER), and rate pressure product (RPP). Borg rating of perceived exertion (RPE) and a visual analog scale (VAS) of knee pain were recorded immediately after each trial.There were no significant differences in cardiovascular responses between the unilateral and bilateral TKA groups. In the repeated measures Analysis of Variance, VO2 levels, HR, RPP, RPE, RER, and VAS were significantly increased in proportion to 3 levels (50%, 25%, and 0%) of BWS for unilateral and bilateral TKA groups, respectively. Meanwhile, SBP and DBP were unaffected by differences in BWS. At 3.5 km/hour, VO2, RPE, and RER values were statistically greater than those at 2.5 km/hour under the same BWS conditions.We found that the reduction in the metabolic demand of activity, coupled with positive pressure on the lower extremities, reduced VO2 and HR values as BWS increased.Cardiovascular responses vary according to BWS and gait velocity during antigravity treadmill walking. BWS rather than gait velocity had the greatest effect on cardiovascular responses and knee pain.

Mechanical Determinants of the U-Shaped Speed-Energy Cost of Running Relationship

Purpose: The aim of this study was to investigate the relationship between the energy cost of running (Cr) and speed and its mechanical determinants by comparing running in normal [100% body weight (BW)] and reduced (20% and 60% BW) gravity conditions at several speeds (2.25, 3.17, 4.08, and 5.00 m·s⁻¹) in experienced runners.

Methods: Twelve experienced runners (24.6 ± 5.4 year) ran on an AlterG treadmill in a partially randomized order at the four running speeds and at the three gravity conditions in order to assess Cr, spatiotemporal parameters, spring-mass characteristics and elastic energy (EL) during running.

Results: For the three gravity conditions, the speed-Cr per kg of body mass relationship was curvilinear (significant speed effect: P < 0.001) and was significantly downward shifted with reduced gravity (100%>60%>20% BW; P < 0.001). EL, expressed in J·step⁻¹, was significantly higher at 100% BW than at 60 and 20% BW and at 60% BW than at 20% BW (significant gravity effect: P < 0.001) with a significant increase in EL per step at faster speeds for the 3 gravity conditions (P < 0.001). EL, expressed in J·kg⁻¹·m⁻¹, was significantly downward shifted with gravity (100%>60%>20% BW; P < 0.001), with no significant speed effect (P = 0.39).

Conclusions: Our findings showed that, for the three gravity conditions, the speed-Cr relationship was curvilinear, and the optimization of the stretch-shortening cycle and muscle activation in the muscle-tendon unit may be involved to explain these U-shaped relationships, especially at normal terrestrial gravitational conditions (100% BW). The U-shaped speed-Cr per kg of the body mass relationship was shifted downward in hypogravity conditions, which was characterized by decreased EL compared to 100% BW. These mechanisms may contribute to the less than proportional decrease in Cr per kg of body mass relative to gravity.

Physiological Responses to Treadmill Running With Body Weight Support in Hypoxia Compared With Normoxia

CONTEXT

Anecdotal reports suggest elite sports clubs combine lower-body positive-pressure rehabilitation with a hypoxic stimulus to maintain or increase physiological and metabolic strain, which are reduced during lower-body positive pressure. However, the effects of hypoxia on cardiovascular and metabolic response during lower-body positive-pressure rehabilitation are unknown.

OBJECTIVE

Evaluate the use of normobaric hypoxia as a means to increase physiological strain during body-weight-supported (BWS) running.

DESIGN

Crossover study.

SETTING

Controlled laboratory.

PARTICIPANTS

Seven familiarized males (mean (SD): age, 20 (1) y; height, 1.77 (0.05) m; mass, 69.4 (5.1) kg; hemoglobin, 15.2 (0.8) g·dL^-1) completed a normoxic and hypoxic (fraction of inspired oxygen [O₂] = 0.14) trial, during which they ran at 8 km·h^-1 on an AlterG™ treadmill with 0%, 30%, and 60% BWS in a randomized order for 10 minutes interspersed with 5 minutes of recovery.

MAIN OUTCOME MEASURES

Arterial O₂ saturation, heart rate, O₂ delivery, and measurements of metabolic strain via indirect calorimetry.

RESULTS

Hypoxic exercise reduced hemoglobin O₂ saturation and elevated heart rate at each level of BWS compared with normoxia. However, the reduction in hemoglobin O₂ saturation was attenuated at 60% BWS compared with 0% and 30%, and consequently, O₂ delivery was better maintained at 60% BWS.

CONCLUSION

Hypoxia is a practically useful means of increasing physiological strain during BWS rehabilitation. In light of the maintenance of hemoglobin O₂ saturation and O₂ delivery at increasing levels of BWS, fixed hemoglobin saturations rather than a fixed altitude are recommended to maintain an aerobic stimulus.

Can anti-gravity running improve performance to the same degree as over-ground running?

This study examined the changes in running performance, maximal blood lactate concentrations and running kinematics between 85%BM anti-gravity (AG) running and normal over-ground (OG) running over an 8-week training period. Fifteen elite male developmental cricketers were assigned to either the AG or over-ground (CON) running group. The AG group (n = 7) ran twice a week on an AG treadmill and once per week over-ground. The CON group (n = 8) completed all sessions OG on grass. Both AG and OG training resulted in similar improvements in time trial and shuttle run performance. Maximal running performance showed moderate differences between the groups, however the AG condition resulted in less improvement. Large differences in maximal blood lactate concentrations existed with OG running resulting in greater improvements in blood lactate concentrations measured during maximal running. Moderate increases in stride length paired with moderate decreases in stride rate also resulted from AG training. The use of AG training to supplement regular OG training for performance should be used cautiously, as extended use over long periods of time could lead to altered stride mechanics and reduced blood lactate.

The Effect of Lower-Body Positive Pressure on the Cardiorespiratory Response at Rest and during Submaximal Running Exercise

Anti-gravity treadmills facilitate locomotion by lower-body positive pressure (LBPP). Effects on cardiorespiratory regulation are unknown. Healthy men (30 ± 8 y, 178.3 ± 5.7 cm, 70.3 ± 8.0 kg; mean ± SD) stood upright (n = 10) or ran (n = 9) at 9, 11, 13, and 15 km.h⁻¹ (5 min stages) with LBPP (0, 15, 40 mmHg). Cardiac output (CO), stroke volume (SV), heart rate (HR), blood pressure (BP), peripheral resistance (PR), and oxygen uptake (VO₂) were monitored continuously. During standing, LBPP increased SV [by +29 ± 13 (+41%) and +42 ± 15 (+60%) ml, at 15 and 40 mmHg, respectively (p < 0.05)] and decreased HR [by −15 ± 6 (−20%) and −22 ± 9 (−29%) bpm (p < 0.05)] resulting in a transitory increase in CO [by +1.6 ± 1.0 (+32%) and +2.0 ± 1.0 (+39%) l.min⁻¹ (p < 0.05)] within the first seconds of LBPP. This was accompanied by a transitory decrease in end-tidal PO₂ [by −5 ± 3 (−5%) and −10 ± 4 (−10%) mmHg (p < 0.05)] and increase in VO₂ [by +66 ± 53 (+26%) and +116 ± 64 (+46%) ml.min⁻¹ (p < 0.05)], suggesting increased venous return and pulmonary blood flow. The application of LBPP increased baroreflex sensitivity (BRS) [by +1.8 ± 1.6 (+18%) and +4.6 ± 3.7 (+47%) at 15 and 40 mmHg LBPP, respectively P < 0.05]. After reaching steady-state exercise CO vs. VO₂ relationships remained linear with similar slope and intercept for each participant (mean R² = 0.84 ± 0.13) while MAP remained unchanged. It follows that (1) LBPP affects cardiorespiratory integration at the onset of exercise; (2) at a given LBPP, once reaching steady-state exercise, the cardiorespiratory load is reduced proportionally to the lower metabolic demand resulting from the body weight support; (3) the balance between cardiovascular response, oxygen delivery to the exercising muscles and blood pressure regulation is maintained at exercise steady-state; and (4) changes in baroreflex sensitivity may be involved in the regulation of cardiovascular parameters during LBPP.

Physiological and Biomechanical Responses of Highly Trained Distance Runners to Lower-Body Positive Pressure Treadmill Running

Background

As a way to train at faster running speeds, add training volume, prevent injury, or rehabilitate after an injury, lower-body positive pressure treadmills (LBPPT) have become increasingly commonplace among athletes. However, there are conflicting evidence and a paucity of data describing the physiological and biomechanical responses to LBPPT running in highly trained or elite caliber runners at the running speeds they habitually train at, which are considerably faster than those of recreational runners. Furthermore, data is lacking regarding female runners’ responses to LBPPT running. Therefore, this study was designed to evaluate the physiological and biomechanical responses to LBPPT running in highly trained male and female distance runners.

Methods

Fifteen highly trained distance runners (seven male; eight female) completed a single running test composed of 4 × 9-min interval series at fixed percentages of body weight ranging from 0 to 30% body weight support (BWS) in 10% increments on LBPPT. The first interval was always conducted at 0% BWS; thereafter, intervals at 10, 20, and 30% BWS were conducted in random order. Each interval consisted of three stages of 3 min each, at velocities of 14.5, 16.1, and 17.7 km·h⁻¹ for men and 12.9, 14.5, and 16.1 km·h⁻¹ for women. Expired gases, ventilation, breathing frequency, heart rate (HR), rating of perceived exertion (RPE), and stride characteristics were measured during each running speed and BWS.

Results

Male and female runners had similar physiological and biomechanical responses to running on LBPPT. Increasing BWS increased stride length (p < 0.02) and flight duration (p < 0.01) and decreased stride rate (p < 0.01) and contact time (p < 0.01) in small-large magnitudes. There was a large attenuation of oxygen consumption (VO₂) relative to BWS (p < 0.001), while there were trivial-moderate reductions in respiratory exchange ratio, minute ventilation, and respiratory frequency (p > 0.05), and small-large effects on HR and RPE (p < 0.01). There were trivial-small differences in V_E, respiratory frequency, HR, and RPE for a given VO₂ across various BWS (p > 0.05).

Conclusions

The results indicate the male and female distance runners have similar physiological and biomechanical responses to LBPPT running. Overall, the biomechanical changes during LBPPT running all contributed to less metabolic cost and corresponding physiological changes.

Effects of different percentages of body weight support on spatiotemporal step characteristics during running

This study aimed to determine the effect of different percentages of body weight support (BWS) on spatiotemporal step characteristics during running. 26 endurance runners (age: 37 ± 9 years) completed a running treadmill protocol consisting of 6 different conditions (BWS combinations: 0-50%), with velocity maintained at 12 km/h. Each condition lasted 1 minute. Step angle, ground contact time (CT), flight time (FT), step length (SL) and frequency (SF), and duration of phases during stance time (phase1: initial contact; phase2: midstance; phase3: propulsion) were measured for every step during the test using a photoelectric cell system. Compared with the baseline condition (100% BW), FT was longer, CT was shorter, SL was longer, SF was lower, and the step angle was higher with each increase in BWS (p < 0.05). Also, some changes were observed in the duration of phases during stance time: phase1 did not experience changes across experimental conditions (p = 0.096), phase2 decreased and phase3 increased as BW was supported (p < 0.05). These results indicate that as BW was supported, runners showed longer FT and SL, shorter CT, lower SF, and greater step angle as well as some changes in the phases during the ground contact. Therefore, this study highlights the effect of different percentages of BWS on spatiotemporal parameters.

Anti-gravity treadmill can promote aerobic exercise for lower limb osteoarthritis patients

[Purpose] The anti-gravity treadmill (Alter-G^®) allows the load on the lower limbs to be adjusted, which is considered useful for patients with lower limb osteoarthritis. The aim of the present study was to examine the effects of aerobic exercise using an anti-gravity treadmill in patients with lower limb osteoarthritis by using a cardiopulmonary exercise load monitoring system. [Subjects and Methods] The subjects were 20 patients with lower limb osteoarthritis. These subjects walked naturally for 8 minutes and then walked on the Alter-G for 8 minutes at their fastest speed at a load where lower limb pain was alleviated. [Results] Subjective and objective exercise intensity did not differ significantly between level ground walking and Alter-G walking neither before nor after walking. Pain before walking did not differ significantly between level ground walking and Alter-G walking, but pain after walking was significantly greater with level ground walking than with Alter-G walking. [Conclusion] Exercise therapy using an anti-gravity treadmill was useful for patients with lower limb osteoarthritis in terms of cardiopulmonary function, which suggested that this could become a new form of exercise therapy.

Heart rate and VO2 responses to treadmill running with body weight support using the GlideTrak™

BACKGROUND/OBJECTIVE

The heart rate (HR) and metabolic (VO2) responses to treadmill running using the GlideTrak™ body weight support system have not been reported. The purpose of this study was to compare the submaximal and maximal HR and VO2 responses to normal-weight treadmill running (TMR) to treadmill running with body weight support provided by the GlideTrak™ (GTR).

METHODS

Twenty participants (11 males; 9 females) 18 to 26 years of age voluntarily participated in this study. Each participant completed two exercise tests in each mode of running: a maximal graded exercise test to compare maximal HR and VO2 values and a submaximal exercise test to compare the HR-VO2 relationship.

RESULTS

Maximal HR and VO2 values were significantly (p < 0.001) lower during GTR (183.4 ± 9.1 bpm, 38.1 ± 7.2 mL kg-1 min-1) compared to TMR (194.3 ± 8.6 bpm, 49.5 ± 8.9 kg-1 min-1). There was a significant difference in the HR-VO2 relationship between GTR and TMR. Compared to TMR, exercising at a HR of 140 bpm resulted in a VO2 that was 4.0 mL kg-1 min-1 lower during GTR. At the VO2 associated with a HR of 140 bpm during TMR, the HR during GTR was 16 bpm higher. During GTR at intensities of exercise up to an RER of 1.0, only 8 participants achieved vigorous intensities of aerobic exercise defined as 64-90% of VO2max.

CONCLUSION

Exercising with the GlideTrak™ body weight support system may not provide the same cardiorespiratory training stimulus as normal-weight treadmill running.

Physiological Responses During the Lower Body Positive Pressure Supported Treadmill Test

Objective

To quantify changes in cardiopulmonary function using a lower body positive pressure supported (LBPPS) treadmill during the exercise tolerance test (ETT) in healthy subjects before applying the LBPPS treadmill in patients with gait problems.

Methods

We evaluated 30 healthy subjects who were able to walk independently. The ETT was performed using the Modified Bruce Protocol (stages 1–5) at four levels (0%, 40%, 60%, and 80%) of LBPPS. The time interval at each level of the LBPPS treadmill test was 20 minutes to recover to baseline status. We measured systolic blood pressure, diastolic blood pressure, peak heart rate (PHR), rating of perceived exertion (RPE), metabolic equivalents (METs), and oxygen consumption rate (VO₂) during each LBPPS condition.

Results

Systolic blood pressure increased as the LBPPS level was increased (40% to 80%). PHR, RPE, METs, and VO₂ were negatively associated with the LBPPS condition, although they were not always significant different among the LBPPS levels. The equation from a random effect linear regression model was as follows: VO₂ (mL/kg/min)=(2.75×stage)+(–0.14×LBPPS level)+11.9 (r²=0.69).

Conclusion

Detection of the changes in physiological parameters during a submaximal ETT using the LBPPS system may be helpful for applying the LBPPS treadmill in patients who cannot perform the ETT due to gait problems, even at submaximal intensity.

Running speed increases plantar load more than per cent body weight on an AlterG® treadmill

AlterG® treadmills allow for running at different speeds as well as at reduced bodyweight (BW), and are used during rehabilitation to reduce the impact load. The aim of this study was to quantify plantar loads borne by the athlete during rehabilitation. Twenty trained male participants ran on the AlterG® treadmill in 36 conditions: all combinations of indicated BW (50-100%) paired with different walking and running speeds (range 6-16 km · hr^-1) in a random order. In-shoe maximum plantar force (Fmax) was recorded using the Pedar-X system. Fmax was lowest at the 6 km · hr^-1 at 50% indicated BW condition at 1.02 ± 0.21BW and peaked at 2.31 ± 0.22BW for the 16 km · hr^-1 at 100% BW condition. Greater increases in Fmax were seen when increasing running speed while holding per cent BW constant than the reverse (0.74BW-0.91BW increase compared to 0.19-0.31BW). A table is presented with each of the 36 combinations of BW and running speed to allow a more objective progression of plantar loading during rehabilitation. Increasing running speed rather than increasing indicated per cent BW was shown to have the strongest effect on the magnitude of Fmax across the ranges of speeds and indicated per cent BWs examined.

Cardiovascular responses in older adults with total knee arthroplasty at rest and with exercise on a positive pressure treadmill

PURPOSE

We investigated cardiovascular responses at rest and during submaximal exercise on a lower body positive pressure treadmill in older adults with total knee arthroplasty (TKA).

METHODS

Twenty-four adults (mean age 64.6 ± 7.9 SD) with unilateral TKA participated (median time since surgery 8.0 weeks). Heart rate and blood pressure responses were measured at rest standing on the positive pressure treadmill with 0, 10, 20, and 30 mmHg applied. Heart rate, blood pressure, oxygen consumption, minute ventilation, knee pain and perceived exertion were measured during submaximal exercise tests (0 and 40% body weight support) conducted 1 week apart.

RESULTS

At rest there were no differences in blood pressure across different treadmill pressures, but heart rate was significantly lower when 30 mmHg was applied compared to ambient pressure conditions (P < 0.05). Participants averaged 5.1 exercise test stages with 0% body weight support (maximum speed 2.5 mph, 0% incline) and 6.4 stages with 40% body weight support (maximum speed 3.0 mph, 10% incline). During exercise, heart rate, systolic blood pressure, oxygen consumption, and minute ventilation were lower when 40% body weight support was provided for a given test stage (P < 0.01). Diastolic blood pressure, knee pain and perceived exertion did not differ with body weight support but increased with increasing exercise test stages (P < 0.05).

CONCLUSIONS

Provision of body weight support allowed TKA patients to walk at faster speeds and/or to tolerate greater incline with relatively lower levels of heart rate, blood pressure, and oxygen consumption.

Lower body positive pressure: an emerging technology in the battle against knee osteoarthritis?

Background

Knee osteoarthritis (OA) is the most prevalent medical condition in individuals over the age of 65 years, and is a progressive joint degenerative condition with no known cure. Research suggests that there is a strong relationship between knee pain and loss of physical function. The resulting lifestyle modifications negatively impact not only disease onset and progression but also overall health, work productivity, and quality of life of the affected individual.

Purpose

The goal of this investigation was to examine the feasibility of using an emerging technology called lower body positive pressure (LBPP) to simulate weight loss and reduce acute knee pain during treadmill walking exercise in overweight individuals with radiographically confirmed symptomatic knee OA.

Design

Prospective case series.

Methods

Twenty-two overweight individuals with knee OA completed two 20-minute treadmill walking sessions (one full weight bearing and one LBPP supported) at a speed of 3.1 mph, 0% incline. Acute knee pain was assessed using a visual analog scale, and the percentage of LBPP support required to minimize knee pain was evaluated every 5 minutes. Knee Osteoarthritis Outcome Scores were used to quantify knee pain and functional status between walking sessions. The order of testing was randomized, with sessions occurring a minimum of 1 week apart.

Results

A mean LBPP of 12.4% of body weight provided participants with significant pain relief during walking, and prevented exacerbation of acute knee pain over the duration of the 20-minute exercise session. Patients felt safe and confident walking with LBPP support on the treadmill, and demonstrated no change in Knee Osteoarthritis Outcome Scores over the duration of the investigation.

Conclusion

Results suggest that LBPP technology can be used safely and effectively to simulate weight loss and reduce acute knee pain during weight-bearing exercise in an overweight knee OA patient population. These results could have important implications for the development of future treatment strategies used in the management of at-risk patients with progressive knee OA.