The effect of weighted vest walking on metabolic responses and ground reaction forces

Acute effect of resistive aquatic high-intensity interval training on metabolic costs in adults

Background

The effects of Aquatic High-Intensity Interval Training (AHIIT) and resistive AHIIT (Resistive AHIIT) to improve metabolic responses were not yet known.

Objective

This study was to compare the metabolic responses and perceived effort in young healthy adults in a single session of AHIIT and resistive AHIIT.

Methods

20 healthy subjects (9 females, 11 males) performed a stationary running at a matched exercise intensity prior AHIIT and resistive AHIIT [10 × 1-min bouts of stationary running at 90% maximum heart rate (HR max) separated by 1-min active recovery] to examine the metabolic and cardiometabolic outcomes. Mixed effects models were applied to analyze the effects of group, time, and the interaction between group and time on both outcomes. The level of correlations between metabolic variables was checked by Pearson's linear correlation.

Results

There are significant differences on pre and post resting energy expenditure (REE) within both AHIIT and resistive AHIIT groups (p < 0.01) respectively as well as the subjective rate of perceived exertion (RPE) (p < 0.01) within RAHIIT group. A moderate correlation found on respiratory exertional ratio (RER) and RPE in resistive AHIIT (r = 0.534). No significant differences between groups in terms of HR max, mean heart rate (HR mean), peak oxygen consumption (VO2 peak) and total energy expenditure (TEE) (p = 0.50, p = 0.48, p = 0.81, p = 0.59).

Conclusion

Resistive AHIIT provides comparable benefits of metabolic outcomes with AHIIT. Comparable results allowed AHIIT and resistive AHIIT prescriptions precisely.

Effect of Weighted Vest at 0%, 5% and 10% of Body Mass on Gasometry Biomarkers and Performance during a Rectangular Test in Trained Trail Runners

Trail runners (TRs) must carry an extra load of equipment, food (bars and gels) and liquids, to delay the anticipation of fatigue and dehydration during their competitions. Therefore, we aimed to evaluate how an extra load can influence the metabolic level. Thirteen well-trained trail runners performed a randomized crossover study (total n = 39), completing three treadmill running sessions with a weighted vest of 0%, 5% and 10% of their body mass during a combined test (rectangular test + ramp test). In addition, biomarkers of oxygen metabolism, acid-base and electrolyte status pre-, during and post-test, as well as the rectangular from capillary blood of the finger and time to exhaustion, were analyzed. Repeated-measures ANOVA showed no significant difference between conditions for any of the analyzed biomarkers of blood gas. However, one-way ANOVA showed a significant difference in trial duration between conditions (p ≤ 0.001). Tukey's post hoc analysis observed a significant decrease in time to exhaustion in the weighted vest of 10% compared to 0% (p ≤ 0.001) and 5% (p ≤ 0.01) and 5% compared to 0% (p = 0.030). In addition, repeated-measures ANOVA detected a significant difference in pH in the group x time interaction (p = 0.035). Our results show that increasing the weighted vest (5% and 10%) anticipates fatigue in runners trained in TR. In addition, increasing the load decreased pH by a smaller magnitude at 10% compared to 0% and 5% at the end of the exercise protocol.

Physiological Responses in Trail Runners during a Maximal Test with Different Weighted-Vest Loads

During some trail running races, athletes have to carry hydration support, food, and technical and safety equipment, which generates an additional load that must be mobilized during the race. The aim of the present study was to determine the physiological responses to overload running and the effect they may have on metabolic zones. Seventeen well-trained male trail runners (n = 17) completed three maximal treadmill tests with weighted vests at 0%, 5%, and 10% of their body mass (L0, L5, and L10). Their gas exchange was monitored to assess their ventilatory thresholds 1 (VT1) and 2 (VT2), maximal fat oxidation zone (FatMax), and peak oxygen consumption (VO2peak). Their heart rate (HR), power, and velocity (V) were tracked to compare their behavior. One-way ANOVA showed significant differences in the V (p < 0.001; ηp2 = 0.4620) as a limitation for reaching the peak velocity (Vpeak), with a significant decrease in the Vpeak with the L10 compared to the L0 (p = 0.002) and L5 (p = 0.004). In addition, one-way ANOVA showed significant differences in the peak absolute power (p < 0.001; ηp2 = 0.468) among the groups, detecting higher power production between the L10 and L0 (p < 0.001) and between the L10 and L5 (p = 0.015). Loads higher than L5 could generated important physiological and mechanical modifications, while a load of L5 managed to maintain the working conditions without overloading. These insights shed light on nuanced strategies for optimizing performance and endurance, offering valuable considerations for athletes seeking to enhance their training regimens during overload conditions.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis

BACKGROUND

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat.

OBJECTIVE

The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel.

ELIGIBILITY CRITERIA

Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6 weeks were included.

DATA SOURCES

MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022.

RISK OF BIAS

A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias.

DATA SYNTHESIS

A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated.

RESULTS

Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19 °C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6 beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24 °C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7 beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01 L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation.

CONCLUSIONS

Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length.

PROSPERO REGISTRATION

CRD42022337761.

The assessment of a novel lower body resistance garment as a mechanism to increase the training stimulus during running: a randomised cross-over study

BACKGROUND

This study examined the physiological and perceived impact of wearing a novel lower body resistance garment during exercise and recovery.

METHODS

Using a randomised cross-over design, 15 recreationally-active males performed 2 × 10-min steady-state runs followed by a 10-min passive recovery with concomitant monitoring of oxygen consumption (V̇O2), heart rate (HR) and rating of perceived exertion (RPE; exercise portion only), wearing either the resistance garment (experimental) or running shorts (control).

RESULTS

During exercise, there was a trend for V̇O2 and RPE to be higher (4.5% and 7.7% respectively) in experimental than control (V̇O2: r = 0.24, p > 0.05; RPE: r = 0.32, p > 0.05) and for HR to be lower (- 0.4%, r = - 0.05, p > 0.05). During recovery, V̇O2 and HR tended to be lower (4.7% and 4.3% respectively) in experimental than control (V̇O2: r = - 0.32, p > 0.05; HR: r = - 0.27, p > 0.05).

CONCLUSIONS

Though effects were trivial to small, and not statistically significant, these findings provide proof of concept and suggest that this garment design may increase the training stimulus during running and aid post-exercise recovery.

Weighted vests in CrossFit increase physiological stress during walking and running without changes in spatiotemporal gait parameters

This study quantified the physiological and biomechanical effects of the 20 lb (9.07 kg, males) and 14 lb (6.35 kg, females) weighted vest used in CrossFit, and whether they were predisposed to injury. Twenty subjects (10 males, 10 females) undertook walking (0%, 5% and 10% gradient) and running trials in two randomised study visits (weighted vest/no weighted vest). Physiological demand during walking was increased with the vest at 10% but not 5% or 0% with no change in gait variables. In the running trial, the weighted vest increased oxygen uptake (males; females) (+0.22L/min, p < 0.01; +0.07 L/min, p < 0.05), heart rate (+11bpm, p < 0.01; +11bpm, p < 0.05), carbohydrate oxidation (+0.6 g/min, p < 0.001; +0.2 g/min, p < 0.01), and energy expenditure (+3.8 kJ/min, p < 0.001; +1.5 kJ/min, p < 0.05) whilst blood lactate was increased only in males (+0.6 mmol/L, p < 0.05). There was no change in stride length or frequency. Weighted vest training increases physiological stress and carbohydrate oxidation without affecting measured gait parameters. Practitioner summary: We examined the effect of weighted vest training prescribed in CrossFit (20 lb/9.07 kg, males and 14 lb/6.35 kg, females) in a randomised controlled trial. We found that physiological stress is increased in both sexes, although three-fold greater in males, but with no change in biomechanical gait that predisposes to lower-limb injury.

Increased velocity at VO2max and load carriage performance in army ROTC cadets: prescription using the critical velocity concept

The purpose of this study was to evaluate the effects of using the critical velocity (CV) concept to prescribe two separate high-intensity interval training (HIT) exercise programs aimed at enhancing CV and load carriage performance. 20 young adult participants (male = 15, female = 5) underwent a 4-week training period where they exercised 2 d wk^-1. Participants were randomly assigned into two groups: (1) HIT or (2) Load Carriage-HIT (LCHIT). Pre- and post-training assessments included running 3-minute All-Out Test (3MT) to determine critical velocity (CV) and distance prime (D') and two load carriage tasks (400 and 3200 m). There were significant increases in CV (p = 0.005) and velocity at V˙ O_2max (vV˙ O_2max) (p = 0.037) among the sample but not between training groups. Improvements were observed in 3200 m load carriage performance time (p < 0.001) with a 9.8 and 5.4% decrease in the LCHIT and HIT groups, respectively. Practitioner summary: Critical velocity has shown efficacy as a marker for performance in tactical populations. With the addition of load carriage, there is a reduction in the individual's CV. The CV-concept-prescribed exercises (HIT and LCHIT) 2 days per week for 4 weeks showed improvements in CV, vV˙ O_2max and load carriage performance. The use of the CV concept provides a method to prescribe HIT to increase running and load carriage performances in tactical populations.

Methods for improving thermal tolerance in military personnel prior to deployment

Acute exposure to heat, such as that experienced by people arriving into a hotter or more humid environment, can compromise physical and cognitive performance as well as health. In military contexts heat stress is exacerbated by the combination of protective clothing, carried loads, and unique activity profiles, making them susceptible to heat illnesses. As the operational environment is dynamic and unpredictable, strategies to minimize the effects of heat should be planned and conducted prior to deployment. This review explores how heat acclimation (HA) prior to deployment may attenuate the effects of heat by initiating physiological and behavioural adaptations to more efficiently and effectively protect thermal homeostasis, thereby improving performance and reducing heat illness risk. HA usually requires access to heat chamber facilities and takes weeks to conduct, which can often make it impractical and infeasible, especially if there are other training requirements and expectations. Recent research in athletic populations has produced protocols that are more feasible and accessible by reducing the time taken to induce adaptations, as well as exploring new methods such as passive HA. These protocols use shorter HA periods or minimise additional training requirements respectively, while still invoking key physiological adaptations, such as lowered core temperature, reduced heart rate and increased sweat rate at a given intensity. For deployments of special units at short notice (< 1 day) it might be optimal to use heat re-acclimation to maintain an elevated baseline of heat tolerance for long periods in anticipation of such an event. Methods practical for military groups are yet to be fully understood, therefore further investigation into the effectiveness of HA methods is required to establish the most effective and feasible approach to implement them within military groups.

A comparison of economy between two different backpack designs for runners

We compared two backpack designs (back/front or back only) in twelve recreational runners (age 22.0 ± 1.7years). An initial incremental exercise test (VO₂max 52.2 ± 4.7 ml kg^-1.min^-1) was conducted, followed by four tests of 20 min duration (running speed 9.8 ± 1.1 km/h) with loads carried of 0, 1 kg, 3 kg, and 6 kg with the two backpack designs in a randomized order. Economy was assessed by energy cost of running (CR), oxygen cost (O₂ cost), heart rate (HR) and rate of perceived exertion (RPE). Repeated measure ANOVA revealed a non-significant main effect for CR, O₂ cost, HR, RPE between systems. Post-hoc comparison of significant time × position interaction showed for CR, F(3,33) = 5.34, p < .01, η_p² = 0.33, and O₂ cost, F(3,33) = 5.15, p < .01, η_p² = 0.32, that carrying weight in the back/front were significantly lower after 20 min (CR: p = .02 and O₂ cost: p = .03). These results suggest, that for longer runs the equal distribution of weight is advantageous.

Aerobic Exercise Performance During Load Carriage and Acute Altitude Exposure

Coffman, KE, Luippold, AJ, Salgado, RM, Heavens, KR, Caruso, EM, Fulco, CS, and Kenefick, RW. Aerobic exercise performance during load carriage and acute altitude exposure. J Strength Cond Res 34(4): 946-951, 2020-This study quantified the impact of combined load carriage and acute altitude exposure on 5-km running time-trial (TT) performance and self-selected pacing strategy. Furthermore, this study developed a velocity prediction tool (nomogram) for similar aerobic exercise tasks performed under various combinations of altitude and load stress. Nine volunteers (6M/3F, age: 24 ± 7 years, height: 171 ± 6 cm, body mass: 72 ± 7 kg, and V[Combining Dot Above]O2peak: 50.5 ± 5.2 ml·min·kg) completed a randomized, repeated-measures design protocol. Volunteers performed 3 familiarization (FAM) trials at sea level (SL; 250 m) with no-load carriage. Experimental testing included 3 self-paced, blinded 5-km running TT on a treadmill while carrying a 30% body mass external load at SL, moderate altitude (MA; 2000 m), and high altitude (HA; 3000 m). At SL, load carriage resulted in a 36% decrement in 5-km exercise performance in comparison with FAM trials (43 ± 7 vs. 32 ± 3 minutes; p < 0.001). Time required to complete the 5-km distance while carrying an external load was increased by 11% when performed at HA vs. SL (48 ± 7 vs. 43 ± 7 minutes; p = 0.001). TT pace was not different among experimental conditions (load carriage at SL, MA, and HA) until after 1 km of the running distance had been completed. Heart rate was not different among experimental conditions throughout the entire TT (170 ± 17 b·min). These data quantify the anticipated reduction in aerobic exercise performance under various combinations of acute altitude exposure and load carriage conditions. The self-paced running TT approach used presently allowed for development of an altitude-load nomogram for use in recreational, occupational, or military settings.

Functional resistance training during walking: Mode of application differentially affects gait biomechanics and muscle activation patterns

BACKGROUND

Task-specific loading of the limbs-termed as functional resistance training-is commonly used in gait rehabilitation; however, the biomechanical and neuromuscular effects of various forms of functional resistance training have not been studied systematically. This information is crucial for correctly selecting the appropriate mode of functional resistance training when treating individuals with gait disorders.

RESEARCH QUESTION

To comprehensively evaluate the biomechanical (i.e., joint moment and power) and muscle activation changes with different forms of functional resistance training that are commonly used in clinics and research using biomechanical simulation-based analyses.

METHODS

We developed simulations of functional resistance training during walking using OpenSim (Gait2354, 23 degrees of freedom and 54 muscles) and custom MATLAB scripts. We investigated five modes of functional resistance training that have been commonly used in clinics or in research: (1) a weight attached at the ankle, (2) an elastic band attached at the ankle, (3) a viscous device attached to the hip and knee, (4) a weight attached at the pelvis, and (5) a constant backwards pulling force at the pelvis. Lower-extremity joint moments and powers were computed using inverse dynamics and muscle activations were estimated using computed muscle control while walking with each device under multiple resistance levels: normal walking with no resistance, and walking with 30, 60, and 90 Newtons of resistance.

RESULTS

The results indicate that the way in which resistance is applied during gait training differentially affects the internal joint moments, powers, and muscle activations as well as the joints and phase of the gait cycle where the resistance was experienced.

SIGNIFICANCE

The results highlight the importance of understanding the joints and muscles that are targeted by various modes of functional resistance training and carefully choosing the best mode of training that meets the specific therapeutic needs of the patient.

Influence of excess weight on lower-extremity vertical stiffness and metabolic cost of walking

The purpose was to test whether lower-extremity vertical stiffness and gait mechanics explain differences in energy cost of walking (Cw) between individuals with normal weight (NW) and obesity (OB). Ten OB (33.1 ± 2.0 kg m^-2) and 10 NW (24.2 ± 1.3 kg m^-2) walked for six minutes on an instrumented treadmill at 1.25 m s^-1 while Cw, lower-extremity kinematics, and vertical stiffness (K _vert) were measured. NW completed another trial with a loaded vest (NWL) to simulate the BMI of the obese group. Cw was 24% greater in OB (277.5 ± 45.3 J m^-1) and 23% greater in NWL (272.7 ± 35.7 J m^-1) than NW (211.0 ± 27.0 J m^-1, P < 0.005). Mass-specific Cw (Cw_kg) wasn't different between conditions (P = 0.085). Lower-extremity K _vert was 40% higher in OB (32.7 ± 5.2 kN m^-1) than NW (23.3 ± 4.7 kN m^-1, P < 0.001), but neither was different from NWL (27.5 ± 3.4 kN m^-1, P > 0.05). Mass-specific K _vert (P = 0.081) was similar across conditions. K _vert was related to Cw (r = 0.55, P = 0.001). Cw_kg wasn't different between NW or OB, but there was a negative correlation between BMI and Cw_kg driven by lower Cw_kg in NWL. Cw and K _vert covaried in proportion to body mass, but mass-specific K _vert was unrelated to Cw_kg. Mass-specific K _vert was lower in NWL than OB due to NWL's greater angle of attack, center of mass displacement, and joint range of motion.

Acute Metabolic Changes with Thigh-Positioned Wearable Resistances during Submaximal Running in Endurance-Trained Runners

The aim of this study was to determine the acute metabolic effects of different magnitudes of wearable resistance (WR) attached to the thigh during submaximal running. Twenty endurance-trained runners (40.8 ± 8.2 years, 1.77 ± 0.7 m, 75.4 ± 9.2 kg) completed six submaximal eight-minute running trials unloaded and with WRs of 1%, 2%, 3%, 4% and 5% body mass (BM), in a random order. The use of a WR resulted in a 1.6 ± 0.6% increase in oxygen consumption (VO₂) for every 1% BM of additional load. Inferential based analysis found that the loading of ≥3% BM was needed to elicit any substantial responses in VO₂, with an increase that was likely to be moderate in scale (effect size (ES) ± 90% confidential interval (CI): 0.24 ± 0.07). Using heart rate data, a training load score was extrapolated to quantify the amount of internal stress. For every 1% BM of WR, there is an extra 0.17 ± 0.06 estimated increase in training load. A WR ≥3% of BM was needed to elicit substantial responses in lactate production, with an increase which was very likely to be large in scale (ES ± 90% CI: 0.41 ± 0.18). A thigh-positioned WR provides a running-specific overload with loads ≥3% BM, resulting in substantial changes in metabolic responses.

Metabolic Costs of Standing and Walking in Healthy Military-Age Adults: A Meta-regression

INTRODUCTION

The Load Carriage Decision Aid (LCDA) is a U.S. Army planning tool that predicts physiological responses of soldiers during different dismounted troop scenarios. We aimed to develop an equation that calculates standing and walking metabolic rates in healthy military-age adults for the LCDA using a meta-regression.

METHODS

We searched for studies that measured the energetic cost of standing and treadmill walking in healthy men and women via indirect calorimetry. We used mixed effects meta-regression to determine an optimal equation to calculate standing and walking metabolic rates as a function of walking speed (S, m·s). The optimal equation was used to determine the economical speed at which the metabolic cost per distance walked is minimized. The estimation precision of the new LCDA walking equation was compared with that of seven reference predictive equations.

RESULTS

The meta-regression included 48 studies. The optimal equation for calculating normal standing and walking metabolic rates (W·kg) was 1.44 + 1.94S + 0.24S. The economical speed for level walking was 1.39 m·s (~ 3.1 mph). The LCDA walking equation was more precise across all walking speeds (bias ± SD, 0.01 ± 0.33 W·kg) than the reference predictive equations.

CONCLUSION

Practitioners can use the new LCDA walking equation to calculate energy expenditure during standing and walking at speeds <2 m·s in healthy, military-age adults. The LCDA walking equation avoids the errors estimated by other equations at lower and higher walking speeds.

Effects of upper and lower body wearable resistance on spatio-temporal and kinetic parameters during running

Wearable resistance training involves added load attached directly to the body during sporting movements. The effects of load position during running are not yet fully established. Therefore, the purpose of this research was to determine spatio-temporal and kinetic characteristics during submaximal running using upper, lower and whole-body wearable resistance (1-10% body mass (BM)). Twelve trained male runners completed eight 2-min treadmill running bouts at 3.9 m/s with and without wearable resistance. The first and last bouts were unloaded, while the middle 6 were randomised wearable resistance conditions: upper body (UB) 5% BM, lower body (LB) 1%, 3%, 5% BM and whole body (WB) 5%, 10% BM. Wearable resistance of 1-10% BM resulted in a significant increase in heart rate (5.40-8.84%), but minimal impact on spatio-temporal variables. Loads of 5% BM and greater caused changes in vertical stiffness, vertical and horizontal force, and impulse. Functional and effective propulsive force (2.95%, 2.88%) and impulse (3.40%, 3.38%) were significantly (p < 0.05) greater with LB5% than UB5%. Wearable resistance may be used to increase muscular kinetics during running without negatively impacting spatio-temporal variables. The application of these findings will vary depending on athlete goals. Future longitudinal studies are required to validate training contentions.

Effect of exercises with weight vests and a patient education programme for women with osteopenia and a healed wrist fracture: a randomized, controlled trial of the OsteoACTIVE programme

Background

Exercise programmes have shown to be important for the prevention of fractures in patients with established osteoporosis. However, few studies have evaluated the effect of such programmes for women with low bone mineral density (BMD) (osteoporosis or osteopenia) who have already suffered a fracture. Studies have indicated that exercise programmes concentrating on muscular strength and dynamic balance have a positive effect on significant risk factors for falls such as quadriceps strength and balance. The aim of the present study was to assess the effect of a 6-month exercise programme and a patient education component (OsteoACTIVE) on quadriceps strength, BMD, dynamic balance, walking capacity, physical activity level and quality of life in postmenopausal women with osteopenia and a previous wrist fracture.

Methods

Eighty postmenopausal women with low BMD and a healed wrist fracture were randomized to OsteoACTIVE (n = 42) (age 65.5, range 51.2–79.2 years) or patient education only (control group) (n = 38) (age 63.9, range 52.7–86.8 years). Follow-up was conducted after 6 months (end of intervention) and 1 year. Outcome measures included quadriceps strength, BMD, dynamic balance, walking capacity, physical activity level and quality of life.

Results

Thirty-five participants (83 %) completed the OsteoACTIVE programme. Mean adherence to OsteoACTIVE was 87 % (range 48–100 %). Twenty-five participants (72 %) met the a priori goal of 80 % adherence to the program. No adverse events were reported. There were no significant differences between the two groups over the 1-year follow-up for any of the outcome measures.

Conclusion

The OsteoACTIVE rehabilitation programme revealed no significant effect on quadriceps strength, BMD, dynamic balance, walking capacity or self-reported functional outcomes over the 1-year follow-up.

Trial registration

NCT01357278 at ClinicalTrials.gov (date of registration2010-04-21).

Exercises including weight vests and a patient education program for women with osteopenia: a feasibility study of the OsteoACTIVE rehabilitation program

STUDY DESIGN

Prospective case series with 1-year follow-up.

OBJECTIVES

The primary aim was to describe the OsteoACTIVE rehabilitation program and evaluate its feasibility in terms of progression, adherence, and adverse events in patients with low bone mineral density (BMD) and a healed forearm fracture. The secondary aim was to assess changes in measures of function and quality of life.

BACKGROUND

Previous studies have shown benefits of weight-bearing activities, resistance exercises, and balance and coordination training for women with low BMD and older adults. However, no studies, to our knowledge, have described or examined a rehabilitation program combining the use of weight vests and patient education in patients with low BMD.

METHODS

Forty-two postmenopausal women with osteopenia and a healed forearm fracture attended the OsteoACTIVE program for 6 months (3 sessions of 60 minutes per week). Feasibility was assessed by documenting training progression (load and exercises), program adherence (aiming for greater than 80%), and adverse events (joint pain, muscle soreness, and falls). Secondary measures included quadriceps strength, BMD, dynamic balance, walking ability, and self-report functional outcome measures. All outcome measures were recorded preintervention (baseline), postintervention, and at 1-year follow-up.

RESULTS

Thirty-five women (83%) completed the 6-month program and 31 women (74%) attended all the follow-up measurement sessions. All participants progressed during the rehabilitation program for both load and type of exercises. Furthermore, 87% of the participants met the a priori goal of 80% adherence, and no participants reported adverse events. Improvements in quadriceps strength and BMD of the femoral trochanter were noted at the end of the 6-month training period (P<.05). At 1-year follow-up, there were significant improvements in quadriceps strength and dynamic balance compared to baseline (P<.05).

CONCLUSION

The OsteoACTIVE rehabilitation program was feasible and achieved progression of training level, had high adherence, and had no adverse events. Positive improvements were established in lower extremity function and femoral trochanter BMD. Clinical trial registered at ClinicalTrials.gov (NCT01357278).

LEVEL OF EVIDENCE

Therapy, level 4.

Effect of air-filled vest on exercise-heat strain when wearing ballistic protection

OBJECTIVES

The purpose was to determine if an air-filled vest worn under ballistic protection reduces physiological strain during exercise in the heat either while wearing a tactical military (TM) protective vest or a law enforcement (LE) concealable vest.

METHODS

Sixteen men (24.5±3.9 years; 179.5±5.6 cm; 84.6±12.3kg) performed either two or four trials of treadmill walking (1.34 m s(-1); 2% grade) over 120 min in a hot, dry environment (37°C, 30% relative humidity, wind speed 3.5 m s(-1)). Participants completed trials wearing a TM or LE, with either the air-filled vest (TMa; LEa) or no vest (TMc; LEc) in random order. During trials, participants wore Army Combat Uniform pants. Physiological variables measured every 5min included gastrointestinal temperature (T GI), mean skin temperature (T sk), and heart rate (HR). Sweat rate (SR) was calculated based on fluid intake and body mass measures.

RESULTS

In the tactical trial (TMa versus TMc), no differences in final T GI (38.2±0.4 versus 38.3±0.4°C), T sk (35.0±0.9 versus 35.0±1.0°C), HR (142±19 versus 143±23 bpm) existed (P>0.05). In the LE trials (LEa versus LEc), no differences in final T GI (38.0±0.4 versus 38.1±0.3°C), T sk (35.3±1.1 versus 35.6±0.9°C), HR (132±20 versus 135±20 bpm) existed (P>0.05). Despite slightly higher SR, there was no statistical difference in TM (1.15±1.13 versus 1.54±0.46 l h(-1); P=0.10) or in LE (1.39±0.52 versus 1.37±0.18 l h(-1); P=0.35) during trials.

CONCLUSION

When participants exercised with a TM or LE while wearing the air-filled vest, there were no thermoregulatory and physiological differences compared to control trials. In our testing conditions, the air-filled device had little effect on physiological responses during prolonged mild exercise in the heat.

Test-retest reliability and minimum detectable change using the K4b2: oxygen consumption, gait efficiency, and heart rate for healthy adults during submaximal walking

PURPOSE

Oxygen consumption (VO2; mLO2/kg/min), gait efficiency (GE; mlO2/kg/m) and heart rate (HR; beats per minute) are measures of physiological gait performance. However, the collection device, procedures for data normalization, and biological factors can affect measurement variability. The purpose of this study was to determine the test-retest reliability and minimum detectable change (MDC) for VO2, GE, and HR with the K4b2 at submaximal walking speeds in healthy young adults. A second purpose was to determine if net measures improved reproducibility.

METHOD

Twenty-two participants completed 2 identical treadmill tests on separate days at submaximal walking speeds from 0.71 m/s to 1.65 m/s.

RESULTS

Intraclass correlation coefficient (ICC) values for gross VO2, gross GE, and HR were greater than .85 for all walking speeds. Associated MDC values were approximately 7% to 10% for gross VO2 and GE, and approximately 9% to 12% for HR. ICC values for resting VO2 were lower, with MDC values approaching 25%. Subtracting out resting values to derive net VO2 and GE values produced ICC values below .76 for the 2 slowest speeds but ICC values greater than .83 for the faster speeds. MDC values for net VO2 and GE were up to 20% for the slowest speeds.

CONCLUSIONS

The results demonstrate metabolic cost can be assessed reliably using the K4b2 during submaximal walking and that gross measures are more reliable than net measures. Furthermore, changes at self-selected speeds exceeding 1.0 mLO2/kg/min in gross VO2 and 0.01 mLO2/kg/m in gross GE can be considered a true change in walking performance.

Lower extremity mechanics during marching at three different cadences for 60 minutes

During group marches, soldiers must walk in step with one another at the same imposed cadence. The literature suggests that shorter trainees may be more susceptible to injury due to overstriding that can occur when taller recruits dictate marching cadence. This study assessed the effects of fixed cadence simulated marching at cadences above and below preferred step rate (PSR) on lower extremity joint mechanics in individuals who were unaccustomed to marching. During three separate visits, 13 volunteers walked with a 20 kg load on a force-sensing treadmill at self-selected PSR, PSR+15% (shorter strides), and PSR-15% (longer strides) at 1.3 m/s for 60 min. Two-way RM ANOVAs (cadence by time) were performed during the stance phase. Ranges of motion and anteroposterior ground reaction force increased significantly as cadence decreased (P < .03). Knee extension moment increased slightly when step rate decreased from PSR+15% (shortest strides, 0.85 ± 0.2 N m/kg) to PSR (0.87 ± 0.3 N m/kg, 3% increase); however, this increase was substantially greater (20% increase) when cadence was decreased from PSR to PSR-15% (longest strides, 1.09 ± 0.3 N m/kg). Our results indicate that overstriding during fixed-cadence marching is a factor that can substantially increase mechanical stress on lower extremity joints.

Strategies used during a challenging weighted walking task in healthy adults and individuals with knee osteoarthritis

Knee osteoarthritis (OA) is a disease that affects millions of people. While numerous gait differences have been identified between healthy adults and adults with knee OA under normal and challenging conditions, adults with knee OA have not been studied during a challenging weighted walking task. Investigation of the effect of weighted walking on the initial contact and loading response phases of gait was undertaken in 20 healthy and 20 knee OA subjects ages 40-85 years old walking at 1.0m/s while unweighted and weighted with 1/6th of their body weight in a weight vest. Subjects were grouped according to their Kellgren and Lawrence radiographic score and healthy subjects were age-matched to those with knee OA. ANOVA revealed significant effects for hip flexion angle at initial contact, step length, initial double support percent, and load rate. Post hoc t-tests revealed that subjects with knee OA had a larger initial double support percent and hip flexion angle at initial contact and a decreased load rate compared to unweighted, healthy adults. Also, both groups increased their initial double support percent in response to the challenging weighted walking task, but only the healthy adults increased their hip flexion angle at initial contact and decreased their load rate. During the weighted condition, the knee OA group had a shorter step length compared to the healthy group. Because the knee OA group only made minor compensations to their gait strategy, it appears that they may be unable or prefer not to adjust their gait mechanics due to underlying issues.

Riding a bicycle: do we need more than a helmet?

BACKGROUND

To assess pediatric bicycle-related traumatization in view of types of injuries, incidence and modes of prevention.

METHODS

Retrospective study of pediatric cases admitted to the pediatric intensive care unit of a university-affiliated level II trauma hospital in Israel over 12 consecutive years.

RESULTS

Forty-six patients (three girls, 43 boys) with bicycle-related injuries formed 1% of the total pediatric intensive care unit admissions during the study period. The number of patients with bicycle-related injuries increased significantly during recent years (1996-2001 vs 2002-07: P = 0.003). Most of the cases presented abdominal injuries (54.4%) followed by head (32.6%) and chest (13%) injuries. The median age of patients with abdominal trauma was significantly lower in comparison to patients with other types of injuries (P = 0.002). Abdominal cases required longer hospitalization compared with other patients (P = 0.003). Falling from a bicycle was the main mechanism of injury in abdominal cases (88%) (P = 0.003). Motor vehicle impacts were the main mechanism of injury in patients with head (60%) and chest (66.6%) trauma.

CONCLUSION

The incidence of severe bicycle-related injuries requiring intensive care hospitalization is increasing and abdominal trauma forms the main portion of those injuries. We suggest introducing a trunk-protective measure for young bicyclists. Exact information on the mechanism of the injury is important for evaluating the injured patient more accurately.