Effects of a zero-gravity treadmill on body composition and cardiorespiratory fitness after Achilles surgery in a Masters runner.

Zero-gravity treadmills allow alterations in training load. Data are lacking on the utilization of this strategy to allow injured Masters-level athletes to return to activity and regain their fitness. A 6-week training program was designed for a 39-year-old male runner recovering from Achilles surgery using a zero-gravity treadmill. Three training sessions per week were performed with gradually increasing loads. Cardiopulmonary exercise testing and bioelectrical impedance analysis were performed before and after program completion. Following the training program, the athlete was able to return to full weight-bearing running. On cardiopulmonary exercise testing, there were improvements in peak oxygen consumption (42.9 vs 47.3 mL/min/kg; 118.6% vs 130.5% of predicted). On bioelectrical impedance analysis, there were small improvements in total weight, skeletal muscle mass, and adiposity felt to be within the standard of error for bioelectrical impedance analysis. In conclusion, load-altering exercise may be helpful for the Masters-level athlete recovering from Achilles tendon surgery.

Novice Users of a Bodyweight-Supporting Treadmill Require Familiarization.

CONTEXT: Previous work has demonstrated an improvement in running economy during sustained running on a lower body positive pressure treadmill, but neuromuscular and spatiotemporal measures have only been investigated during short-duration running bouts on these devices. The current study sought to replicate the noted metabolic response and investigate whether neuromuscular and/or spatiotemporal adaptations underlie the noted improvements in running economy. DESIGN: Cross-sectional. METHODS: Fifteen trained runners (11 males and 4 females) ran three 15-minute trials with 30% bodyweight support at 70% of the speed that elicited their peak oxygen consumption while running on a standard treadmill. A series of 1-way analyses of variance with repeated measures were used to explore differences in dependent variables over the 45 minutes of running. Dependent variables included oxygen consumption, root-mean-square electromyography of the vastus medialis and medial gastrocnemius during stance, and spatiotemporal parameters. RESULTS: Oxygen consumption decreased after the initial exposure, with no further reductions after 20 minutes. Root-mean-square electromyography of the vastus medialis and medial gastrocnemius also decreased over time, with no further reductions after 20 and 10 minutes, respectively. No differences in spatiotemporal parameters were found. CONCLUSIONS: Future research should provide sufficient time for runners to develop a more economical gait pattern prior to collecting dependent variables, and previous findings using lower body positive pressure treadmills may need to be reconsidered. Athletes using these devices for training or rehabilitation should note that increased economy will lower the intensity of a given treadmill setting over time.

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; VO2max: 60.3 ± 4.2 mL kg-1 min-1) ran at 70% of their individual velocity at VO2max (vVO2max) on a LBPPT at 80% body weight support (80% BWSet) and 90% body weight support (90% BWSet), 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% BWSet and 90% BWSet, 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% BWSet to 90% BWSet, 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% BWSet and 90% BWSet. Those results suggest that on a LBPPT, a 2% incline (at 70% vVO2max) 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% BWSet) 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.

Lower limb EMG activation during reduced gravity running on an incline. Speed matters more than hills irrespective of indicated bodyweight.

BACKGROUND: Progressive loading of the lower limb muscles during running on a positive pressure or reduced gravity (Alter-G™) treadmill is suggested as a rehabilitation strategy after muscle and tendon injury but the influence of running up or downhill and at higher speeds is not known, nor are the interaction effects of speed, inclination, and indicated bodyweight. RESEARCH QUESTION: What are the lower limb EMG activation levels and cadence when running up and downhill in normal and reduced gravity? METHODS: 10 recreationally active male athletes ran on a positive-pressure Alter-G™ treadmill at: 3 indicated bodyweights (60 %, 80 %, and 100 %); 5 speeds (12, 15, 18, 21, and 24 km/h); for incline, decline, and flat conditions (-15 %, -10 %, -5%, 0%, 5%, 10 %, and 15 %); while monitoring the surface EMG of 11 leg muscles as well as cadence (strides per minute). RESULTS AND SIGNIFICANCE: Linear mixed models showed significant effect of running speed, inclination, and indicated bodyweight, with interaction effects observed. Increasing running speed was associated with the largest change in activity, with smaller effects for increasing bodyweight and inclination. Downhill running was associated with reduced activity in all muscle groups, and more tightly clustered activity patterns independent of speed. Substantial variation in sEMG activity occurred in the flat and uphill conditions. Subject responses were quite variable for sEMG, less so for cadence. For the conditions examined, increasing running speed induced the largest changes in EMG of all muscles examined with smaller changes seen for manipulations of inclination and bodyweight.

Gastrocnemius Medialis Contractile Behavior Is Preserved During 30% Body Weight Supported Gait Training.

Rehabilitative body weight supported gait training aims at restoring walking function as a key element in activities of daily living. Studies demonstrated reductions in muscle and joint forces, while kinematic gait patterns appear to be preserved with up to 30% weight support. However, the influence of body weight support on muscle architecture, with respect to fascicle and series elastic element behavior is unknown, despite this having potential clinical implications for gait retraining. Eight males (31.9 ± 4.7 years) walked at 75% of the speed at which they typically transition to running, with 0% and 30% body weight support on a lower-body positive pressure treadmill. Gastrocnemius medialis fascicle lengths and pennation angles were measured via ultrasonography. Additionally, joint kinematics were analyzed to determine gastrocnemius medialis muscle-tendon unit lengths, consisting of the muscle's contractile and series elastic elements. Series elastic element length was assessed using a muscle-tendon unit model. Depending on whether data were normally distributed, a paired t-test or Wilcoxon signed rank test was performed to determine if body weight supported walking had any effects on joint kinematics and fascicle-series elastic element behavior. Walking with 30% body weight support had no statistically significant effect on joint kinematics and peak series elastic element length. Furthermore, at the time when peak series elastic element length was achieved, and on average across the entire stance phase, muscle-tendon unit length, fascicle length, pennation angle, and fascicle velocity were unchanged with respect to body weight support. In accordance with unchanged gait kinematics, preservation of fascicle-series elastic element behavior was observed during walking with 30% body weight support, which suggests transferability of gait patterns to subsequent unsupported walking.

Walking on the Moon: A randomized clinical trial on the role of lower body positive pressure treadmill training in post-stroke gait impairment.

Body weight-supported treadmill training (BWSTT) can be usefully employed to facilitate gait recovery in patients with neurological injuries. Specifically, lower body positive pressure support system (LBPPSS) decreases weight-bearing and ground reaction forces with potentially positive effects on qualitative gait indices. However, which gait features are being shaped by LBPPSS in post-stroke patients is yet poorly predictable. A pilot study on the effects of LBPPSS on qualitative and quantitative gait indices was carried out in patients with hemiparesis due to stroke in the chronic phase. Fifty patients, who suffered from a first, single, ischemic, supra-tentorial stroke that occurred at least 6 months before study inclusion, were enrolled in the study. They were provided with 24 daily sessions of gait training using either the AlterG device or conventional treadmill gait training (TGT). These patients were compared with 25 age-matched healthy controls (HC), who were provided with the same amount of AlterG. Qualitative and quantitative gait features, including Functional Ambulation Categories, gait cycle features, and muscle activation patterns were analyzed before and after the training. It was found that AlterG provided the patients with higher quantitative but not qualitative gait features, as compared to TGT. In particular, AlterG specifically shaped muscle activation phases and gait cycle features in patients, whereas it increased only overall muscle activation in HC. These data suggest that treadmill gait training equipped with LBPPSS specifically targets the gait features that are abnormal in chronic post-stroke patients. It is hypothesizable that the specificity of AlterG effects may depend on a selective reshape of gait rhythmogenesis elaborated by the locomotor spinal circuits receiving a deteriorated corticospinal drive. Even though further studies are warranted to clarify the role of treadmills equipped with LBPPSS in gait training of chronic post-stroke patients, the knowledge of the exact gait pattern during weight-relief is potentially useful to plan patient-tailored locomotor training.

The Effect of Lower Body Positive Pressure on Left Ventricular Ejection Duration in Patients With Heart Failure.

Lower body positive pressure (LBPP) treadmill activity might benefit patients with heart failure (HF). To determine the short-term effects of LBPP on left ventricular (LV) function in HF patients, LV ejection duration (ED), a measure of systolic function was prospectively assessed in 30 men with stable HF with LV ejection fraction ≤ 40% and 50 healthy men (N). Baseline measurements (100% body weight), including blood pressure (BP), heart rate (HR) and LVED, obtained via radial artery applanation tonometry, were recorded after 2 minutes of standing on weight support treadmill and after LBPP achieving reductions of 25%, 50%, and 75% of body weight in random sequence. Baseline, HR, and LVED (251 ± 5 vs 264 ± 4 ms; P = .035) were lower in the HF group. The LBPP lowered HR more (14% vs 6%, P = .009) and increased LVED more (15% ± 7% vs 10% ± 6%; P = .004) in N versus HF. Neither group had changes (Δ) in BP. On generalized linear regression, the 2 groups showed different responses (P < .001). Multivariate analysis showed %ΔHR (P < .001) and HF (P = .026) were predictive of ΔED (r 2 = 0.44; P < .001). In conclusion, progressive LBPP increases LVED in a step-wise manner in N and HF patients independent of HR lowering. The ΔLVED is less marked in patients with HF.

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 VE, 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.

Hamstring and calf muscle activation as a function of bodyweight support during treadmill running in ACL reconstructed athletes.

Rehabilitation after injury and reconstruction to the anterior cruciate ligament is thought to require a gradual reintroduction of loading, particularly during resumption of running. One strategy to achieve this is via the use of a reduced-gravity treadmill but it is unknown, if and how muscle activity varies in the reduced gravity conditions compared to regular treadmill running. Nineteen healthy participants and 18 male patients at the end of their rehabilitation (8 with a bone-patellar-bone graft, 10 with a hamstring graft) participated in this multi-muscle surface electromyography (sEMG) running study. The hamstrings and triceps surae were evaluated during a 16km/h running while at 6 different relative bodyweight conditions from 50% (half weight-bearing) to 100% (full weight-bearing). Muscle activation was examined individually as well as normalized to a composite "entire" activation and considered across the entire gait cycle using Statistical Parametric Mapping. The healthy participants showed differences between the 50-100% BW and 60-100% conditions and in the hamstring graft group for 60-100% and 80-100% conditions. No differences were seen comparing all loading conditions in the bone-patellar-bone graft group. For the hamstrings, from 70% BW and above, there appear to be no difference in activation patterns for any of the groups. The activation patterns of the hamstrings was essentially the same from 70% indicated bodyweight through to full weight bearing when running at 16km/h. Accordingly, when running at this relatively high speed, we do not expect any adverse effects in terms of altered motor patterns during rehabilitation of these muscles.

Peak medial (but not lateral) hamstring activity is significantly lower during stance phase of running. An EMG investigation using a reduced gravity treadmill.

The hamstrings are seen to work during late swing phase (presumably to decelerate the extending shank) then during stance phase (presumably stabilizing the knee and contributing to horizontal force production during propulsion) of running. A better understanding of this hamstring activation during running may contribute to injury prevention and performance enhancement (targeting the specific role via specific contraction mode). Twenty active adult males underwent surface EMG recordings of their medial and lateral hamstrings while running on a reduced gravity treadmill. Participants underwent 36 different conditions for combinations of 50%-100% altering bodyweight (10% increments) & 6-16km/h (2km/h increments, i.e.: 36 conditions) for a minimum of 6 strides of each leg (maximum 32). EMG was normalized to the peak value seen for each individual during any stride in any trial to describe relative activation levels during gait. Increasing running speed effected greater increases in EMG for all muscles than did altering bodyweight. Peak EMG for the lateral hamstrings during running trials was similar for both swing and stance phase whereas the medial hamstrings showed an approximate 20% reduction during stance compared to swing phase. It is suggested that the lateral hamstrings work equally hard during swing and stance phase however the medial hamstrings are loaded slightly less every stance phase. Likely this helps explain the higher incidence of lateral hamstring injury. Hamstring injury prevention and rehabilitation programs incorporating running should consider running speed as more potent stimulus for increasing hamstring muscle activation than impact loading.

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.

Utilization of an Anti-Gravity Treadmill in a Physical Activity Program with Female Breast Cancer Survivors: A Pilot Study.

Breast Cancer survivors can experience a myriad of physical and psychological benefits as a result of regular exercise. This study aimed to build on previous research using lower impact exercise programs by using an antigravity (Alter-G®) treadmill to administer cardiovascular training. The purpose of this study was to determine the effectiveness a physical activity program, including an Alter-G® treadmill, for improving physiological and psychosocial measures in female breast cancer survivors. A 14-week intervention using an AB-AB study design was employed. Six female breast cancer survivors were recruited to participate in the study. Participants attended three 60-minute sessions per week, consisting of a combination of muscular strength/endurance, and cardiovascular endurance exercises. Consistent with current literature and guidelines, exercise interventions were individualized and tailored to suit individuals. Data was collected and analyzed in 2013. Visual inspection of results found improvements in cardiovascular endurance and measures of body composition. Quality of life was maintained and in some cases, improved. Finally, no adverse effects were reported from the participants, and adherence to the program for those who completed the study was 97%. The results of this study suggest that the use of a physical activity program in combination with an Alter-G® treadmill may provide practical and meaningful improvements in measures of cardiovascular endurance and body composition.

Oxygen consumption of elite distance runners on an anti-gravity treadmill®.

Lower body positive pressure (LBPP), or 'anti-gravity' treadmills® have become increasingly popular among elite distance runners. However, to date, few studies have assessed the effect of body weight support (BWS) on the metabolic cost of running among elite runners. This study evaluated how BWS influenced the relationship between velocity and metabolic cost among 6 elite male distance runners. Participants ran three- 16 minute tests consisting of 4 stages of 4 minutes at 8, 7, 6 and 5 min·mile(-1) pace (3.35, 3.84, 4.47 and 5.36 m·s(-1)), while maintaining an aerobic effort (Respiratory Exchange Ratio ≤1.00). One test was run on a regular treadmill, one on an anti-gravity treadmill with 40% BWS and one with 20% BWS being provided. Expired gas data were collected and regression equations used to determine and compare slopes. Significant decreases in oxygen uptake (V̇O2) were found with each increase in BWS (p < 0.001). At 20% BWS, the average decrease in net VO2 was greater than proportional (34%), while at 40% BWS, the average net reduction in VO2 was close to proportional (38%). Across velocities, the slope of the relationship between VO2 and velocity (ΔV̇O2/Δv) was steeper with less support. The slopes at both the 20% and 40% BWS conditions were similar, especially when compared to the regular treadmill. Variability in VO2 between athletes was much greater on the LBPP treadmill and was greater with increased levels of BWS. In this study we evaluated the effect of body weight support on V̇O2 among elite distance runners. We have shown that oxygen uptake decreased with support, but not in direct proportion to that support. Further, because of the high variability in oxygen uptake between athletes on the LBPP treadmill, prediction equations may not be reliable and other indicators (heart rate, perceived exertion or directly measured oxygen uptake) should be used to guide training intensity when training on the LBPP treadmill. Key pointsWith increasing amounts of body weight-support (BWS), the slope of the relationship between velocity and oxygen consumption (ΔVO2/Δv) decreases significantly. This means the change in oxygen consumption (VO2) is significantly smaller over a given change in velocity at higher amounts of BWS.There is a non-linear decrease in VO2 with increasing BWS. As such, with each increment in the amount of BWS provided, the reduction in VO2 becomes increasingly smaller.This paper provides first of its kind data on the effects of BWS on the cost of running among highly trained, elite runners. The outcomes of this study are in line with previous findings among non-elite runners.