Interval training elicits higher enjoyment versus moderate exercise in persons with spinal cord injury

Background: High intensity interval training (HIIT) is a robust and time-efficient approach to improve multiple health indices including maximal oxygen uptake (VO₂max). Despite the intense nature of HIIT, data in untrained adults report greater enjoyment of HIIT versus continuous exercise (CEX). However, this has yet to be investigated in persons with spinal cord injury (SCI).

Objective: To examine differences in enjoyment in response to CEX and HIIT in persons with SCI.

Design: Repeated measures, within-subjects design.

Setting: University laboratory in San Diego, CA.

Participants: Nine habitually active men and women (age?=?33.3?±?10.5 years) with chronic SCI.

Intervention: Participants performed progressive arm ergometry to volitional exhaustion to determine VO₂peak. During subsequent sessions, they completed CEX, sprint interval training (SIT), or HIIT in randomized order.

Outcome Measures: Physical activity enjoyment (PACES), affect, rating of perceived exertion (RPE), VO₂, and blood lactate concentration (BLa) were measured.

Results: Despite a higher VO₂, RPE, and BLa consequent with HIIT and SIT (P?, PACES was significantly higher (P?=?0.03) in response to HIIT (107.4?±?13.4) and SIT (103.7?±?12.5) compared to CEX (81.6?±?25.4). Fifty-five percent of participants preferred HIIT and 45% preferred SIT, with none identifying CEX as their preferred exercise mode.

Conclusion: Compared to CEX, brief sessions of submaximal or supramaximal interval training elicit higher enjoyment despite higher metabolic strain. The long-term efficacy and feasibility of HIIT in this population should be explored considering that it is not viewed as more aversive than CEX.     

Cardiovascular response to peak voluntary exercise in males with cervical spinal cord injury

Context/Objective: Traumatic damage to the cervical spinal cord is usually associated with a disruption of the autonomic nervous system (ANS) and impaired cardiovascular control both during and following exercise. The magnitude of the cardiovascular dysfunction remains unclear. The aim of the current study was to compare cardiovascular responses to peak voluntary exercise in individuals with tetraplegia and able-bodied participants.

Design: A case-control study.

Subjects: Twenty males with cervical spinal cord injury (SCI) as the Tetra group and 27 able-bodied males as the Control group were included in the study.

Outcome Measures: Blood pressure (BP) response one minute after the peak exercise, peak heart rate (HR_peak), and peak oxygen consumption (VO_2peak) on an arm crank ergometer were measured. In the second part of the study, 17 individuals of the Control group completed the Tetra group's workload protocol with the same parameters recorded.

Results: There was no increase in BP in response to the exercise in the Tetra group. Able-bodied individuals exhibited significantly increased post-exercise systolic BP after the maximal graded exercise test (123±16%) and after completion of the Tetra group's workload protocol (114±11%) as compared to pre-exercise. The Tetra group VO_2peak was 59% and the HR_peak was 73% of the Control group VO_2peak and HR_peak, respectively.

Conclusions: BP did not increase following maximal arm crank exercise in males with a cervical SCI unlike the increases observed in the Control group. Some males in the Tetra group appeared to be at risk of severe hypotension following high intensity exercise, which can limit the ability to progressive increase and maintain high intensity exercise.     

Reliability Of Arm Wingate Anaerobic Testing In Persons With Complete Paraplegia

Abstract

Background: Accurate, reliable assessment of upper extremity muscular power in persons with paraplegia caused by spinal cord injury (SCI) would provide an objective indication of their ability to generate the forces necessary for the performance of daily activities. Wingate Anaerobic Testing (WAnT) consists of a 30-second sprint test on a cycle ergometer and has been used widely in both athletic and research settings.

Purpose: To examine test-retest reliability of arm WAnT performance in persons with complete SCI and paraplegia.

Methods: Forty-three participants with thoracic-level paraplegia (T2 through T12) performed 2 trials of arm WAnT with 2 to 7 days between each trial. Testing was performed using a Monarch 834E ergometer with participants seated in their wheelchairs. Participants were directed to crank at maximal pace for 30 seconds against a resistance load equivalent to 3.5% of their body mass. The SMI OptoSensor 2000 system was used to determine values of peak power (P_peak), mean power (P_mean), minimum power, and rate of fatigue, which were compared between trials using 1-way analysis of variance for repeated measures. Coeffi cients of determination (r₂) were calculated between trials for P_peak and P_mean.

Results: No significant diffe rence was found between trials for any of the power output variables. Regression analysis ind icat ed that P_peak and P_mean were closely associated between the 2 trials (r₂= 0.92 and 0.94, respectively).

Conclusion: Arm WAnT is a reliable measurement tool for the assessment of upper extremity muscular power in persons with complete paraplegia.     

Comparison of VO2 Peak during Treadmill and Cycle Ergometry in Severely Overweight Youth

The purpose of this study was to compare peak cardiorespiratory parameters during treadmill and cycle ergometry in severely overweight youth. Twenty-one participants from the Committed to Kids Pediatric Weight Management program at the Louisiana State University Health Sciences Center volunteered. Participants completed peak treadmill and cycle ergometer tests on separate days. In order to examine reliability, six subjects completed a second treadmill test and seven subjects a second cycle test. Physical characteristics included the following: Age (yrs) 12.5 ± 2.8; Body weight (BW) (kg) 78.5 ± 27.0, Height (m) 1.56 ± 0.13; and % fat 42.8 ± 7.5. No statistical significant differences (p ≤ 0.05) were found between treadmill and cycle peak tests. Treadmill VO₂ peak (l·min^-1) averaged 1.57 ± 0.40 and cycle 1.46 ± 0.30 and VO₂ peak relative to BW 21.5 ± 4.1 and 20.3 ± 5.5 for treadmill and cycle ergometry, respectively. Therefore treadmill values were 7.0% and 5.6% higher than cycle values. In normal weight or children and adolescents at risk for overweight, treadmill values typically average from 7 to 12% higher than cycle values. Reliability of VO₂ peak as indicated by intraclass correlation coefficients ranged from 0.70 to 0.96 for a single or repeated tests. Intra individual variability averaged 0.5% for VO₂ peak (l·min^-1) during treadmill ergometry and 5.7% for cycle ergometry. Also, standard errors of measurement were low (40 to 90 ml min or 1.0 to 1.7 ml.kg^-1. min^-1) for the peak treadmill or cycle tests. In summary, our data suggest that both treadmill and cycle ergometry provide reliable methods for determining VO₂ peak in overweight youth.

Key Points

• Treadmill peak VO₂ higher than cycle ergometry in severely overweight youth.
• VO₂peak test-retest or single trial reliability high in both treadmill and cycle VO₂ peak.
• Standard errors of measure low for both treadmill and cycle VO₂peak.

Key Words: VO₂peak, severely overweight youth, treadmill, cycle ergometry     

Exercise testing protocol using a roller system for manual wheelchair users with spinal cord injury

Objective: Determine the validity and reliability of an exercise testing protocol to evaluate cardiorespiratory measures in manual wheelchair users (MWUs) with spinal cord injury (SCI) using a roller-based (RS) wheelchair system.

Design: Repeated measures within-subject design.

Setting: Community-based research laboratory.

Participants: Ten adults with SCI requiring the use of a manual wheelchair.

Interventions: Not applicable.

Outcome measures: Cardiorespiratory measures (peak oxygen consumption [VO₂peak], respiratory exchange ratio [RER], pulmonary ventilation [VE], energy expenditure [EE], heart rate [HR], accumulated kilocalories [AcKcal]) and perceived exertion (RPE) were measured during three separate maximal exercise tests using an arm crank ergometer (ACE) and an RS.

Results: At maximal exertion, there were no significant differences in variables between groups, with moderate-to-strong correlations (P?<?0.05, r?=?0.79–0.90) for VO₂, HR, RPE, AcKcal, and rate of EE between RS and ACE trials. Significant moderate-to-strong correlations existed between RS trials for VO₂, AcKcal, rate of EE, and peak power output (P?<?0.01, r?=?0.77–0.97).

Conclusions: VO_2peak was highly correlated between ACE and RS trials and between the two RS trials, indicating the RS protocol to be reliable and valid for MWUs with SCI. Differences in perceived exertion and efficiency at submaximal workloads and maximal pulmonary ventilation at peak workloads indicated potential advantages to using the RS.     

Biomarkers of cardiometabolic health are associated with body composition characteristics but not physical activity in persons with spinal cord injury

Objective: To examine (i) the associations between physical activity dimensions, cardiorespiratory fitness and body composition and, (ii) the associations between physical activity dimensions, cardiorespiratory fitness, body composition and biomarkers of cardiometabolic health in persons with spinal cord injury (SCI).

Methods: A cross-sectional prospective cohort study with 7-day follow-up was conducted. Body composition, cardiorespiratory fitness and biomarkers of cardiometabolic health were measured in thirty-three participants with SCI (> 1 year post injury). Physical activity dimensions were objectively assessed over 7-days.

Results: Activity energy expenditure (r =.43), physical activity level (r =.39), and moderate-to-vigorous physical activity (MVPA) (r =.48) were significantly (P < 0.001) associated with absolute (L/min) peak oxygen uptake (?O₂ peak). ?O₂ peak was significantly higher in persons performing ≥150 MVPA minutes/week compared to <40 minutes/week (P?=?0.003). Individual physical activity dimensions were not significantly associated with biomarkers of cardiometabolic health. However, body composition characteristics (BMI, waist and hip circumference) showed significant (P < 0.04), moderate (r >.30) associations with parameters of metabolic regulation, lipid profiles and inflammatory biomarkers. Relative ?O₂ peak (ml/kg/min) was moderately associated with only insulin sensitivity (r?=?0.37, P?=?0.03).

Conclusions: Physical activity dimensions are associated with cardiorespiratory fitness; however, stronger and more consistent associations suggest that poor cardiometabolic health is associated with higher body fat content. Given these findings, the regulation of energy balance should be an important consideration for researchers and clinicians looking to improve cardiometabolic health in persons with SCI.     

Training response to high-intensity interval training in a 42-year-old man with chronic spinal cord injury

Objective: To review the outcome of 12 weeks of periodized, high-intensity interval training (HIT) in a man with chronic traumatic spinal cord injury (SCI).

Methods: A 42-year-old man (180?cm tall, 68.4?kg and 32.0% Fat) with a C8/T1 motor complete SCI took part in 12 weeks of 3 days per week arm crank ergometry (ACE) interval training. Training consisted of a combination of HIT that included three times 5 min at ～70% Peak Power (W_Peak) and 5 min recovery (HIT₅); four times 2.5 min at ～85% W_Peak and 5 min recovery (HIT_2.5); ten times 1 min at ～110% W_Peak and 2 min recovery (HIT₁). Heart rate (HR) zones were set as <75% HR_Peak (Z1), 75–89% (Z2), and 90+% (Z3) and used to monitor overall training efficacy.

Results: Thirty-six sessions that included 8 HIT5, 10 HIT2.5, and 5 HIT1 sessions were completed. W_Peak and VO_{2 Peak} improved about 45% and 52%, respectively, by week 6, without further improvement at week 12, HR TRIMP scores and power in training sessions trended upward over the 12-week program.

Conclusions: Twelve weeks of HIT resulted in a large increase in peak aerobic power, as well as submaximal endurance performance in our participant. The early plateau in maximal testing supports the use of submaximal training assessment important in the long-term training monitoring for SCI.     

Physiologic Responses of Paraplegics and Quadriplegics to Passive and Active Leg Cycle Ergometry

ABSTRACT

The purposes of this study were three-fold: (a) to determine acute physiologic responses of spinal cord injured (SCI) subjects to peak levels of leg cycle ergometry utilizing functional neuromuscular stimulation (FNS) of paralyzed leg muscles, (b) to determine the relative contributions of passive and active components of FNS cycling to the peak physiologic responses, and (c) to compare these physiologic responses between persons who have quadriplegia and those who have paraplegia. Thirty SCI subjects (17 quadriplegics and 13 paraplegics) performed a discontinuous graded FNS exercise test from rest to fatigue on an ERGYS 1 ergometer. Steady-state physiologic responses were determined by open-circuit spirometry, impedance cardiography with ECG, and auscultation. In the combined statistics of both groups, it was noted that peak FNS cycling significantly increased (from rest levels) mean oxygen uptake by 255%, arteriovenous O₂ difference VO₂ and V_E, Q and a-vO₂and VCO by 69%, and Stroke Volume by 45%, While total peripheral vascular resistance decreased by 43%. Mean peak power output for paraplegics (15 W) was significantly higher than for quadriplegics (9 W), eliciting higher peak levels of pulmonary ventilation and sympathetically mediated hemodynamic responses such as cardiac output, heart rate, and systolic and diastolic arterial blood pressure. Passive cycling without FNS produced no statistically significant increases in physiologic responses above the resting level in either group. (J Am Paraplegia Soc 1990; 13: 33–39)     

Prediction of thigh skeletal muscle mass using dual energy x-ray absorptiometry compared to magnetic resonance imaging after spinal cord injury

Objectives: A rapid decline in lean mass (LM), fat-free mass (FFM) and increased intramuscular fat (IMF) predispose persons with spinal cord injury (SCI) to chronic medical conditions including dyslipidemia, insulin resistance, type 2 diabetes mellitus and cardiovascular disease. (1) To determine the relationship between dual energy x ray absorptiometry (DXA) and gold standard magnetic resonance imaging (MRI) LM values; (2) to develop predictive equations based on this relationship for assessing thigh LM in persons with chronic SCI.

Study Design: Cross-sectional predicational design.

Settings: Clinical research medical center.

Participants: Thirty-two men with chronic (>1 y post-injury) motor complete SCI.

Methods: Participants completed total body DXA scans to determine thigh LM and were compared to measurements acquired from trans-axial MRI.

Outcome measures: MRI was used to measure whole muscle mass (MM_MRI-WM), absolute muscle mass (MM_MRI-ABS) after excluding IMF, and knee extensor muscle mass (MM_MRI-KE). DXA was used to measure thigh LM (LM_DXA) and (FFM_DXA). To predict MM_MRI-KE, LM_DXA was multiplied by 0.52 and yielded LM_DXA-KE.

Results: LM_DXA predicted MM_MRI-WM [r²_?=?0.90, standard error of the estimate (SEE)?=?0.23?kg, P?<?0.0001] and MM_MRI-ABS (r²?=?0.82, SEE?=?0.28?kg, P?<?0.0001). LM_DXA-KE predicted MM_MRI-KE (r²?=?0.78, SEE?=?0.16?kg, P?<?0.0001).

Conclusion: DXA measurements revealed an acceptable agreement with the gold standard MRI and may be a viable alternative for assessing thigh skeletal muscle mass after SCI.     

Arm crank ergometry improves cardiovascular disease risk factors and community mobility independent of body composition in high motor complete spinal cord injury

Objective: Evaluate the effect of aerobic exercise using arm crank ergometry (ACE) in high motor complete (ISNCSCI A/B) spinal cord injury (SCI) as primarily related to cardiovascular disease (CVD) risk factors and functional mobility and secondarily to body composition and metabolic profiles.

Design: Longitudinal interventional study at an academic medical center.

Methods: Ten previously untrained participants (M8/F2, Age 36.7 y ± 10.1, BMI 24.5 ± 6.0) with high motor complete SCI (C7-T5) underwent ACE exercise training 30 minutes/day?×?3 days/week for 10 weeks at 70% VO_2Peak.

Outcome Measures: Primary outcome measures were pre- and post-intervention changes in markers of cardiovascular fitness (graded exercise testing (GXT): VO₂, VO_2Peak, respiratory quotient [RQ], GXT time, peak power, and energy expenditure [EE]) and community mobility (time to traverse a 100ft-5° ramp, and 12-minute WC propulsion test). Secondary outcome measures were changes in body composition and metabolic profiles (fasting and area under the curve for glucose and insulin, homeostasis model assessment [HOMA] for %β-cell activity [%β], %insulin sensitivity [%S], and insulin resistance [IR], and Matsuda Index [ISI_Matsuda]).

Results: Resting VO₂, relative VO_2Peak, absolute VO_2Peak, peak power, RQ, 12-minute WC propulsion, fasting insulin, fasting G:I ratio, HOMA-%S, and HOMA-IR all significantly improved following intervention (P < 0.05). There were no changes in body composition (P>0.05).

Conclusions: Ten weeks of ACE at 70% VO_2Peak in high motor complete SCI improves aerobic capacity, community mobility, and metabolic profiles independent of changes in body composition.     

Relationships between T-scores at the hip and bone mineral density at the distal femur and proximal tibia in persons with spinal cord injury

Objective: To identify T-score values at the total hip (TH) and femoral neck (FN) that correspond to the cutoff value of <0.60?g/cm² for heightened risk of fracture at the distal femur (DF) and proximal tibia (PT).

Design: Retrospective analysis of data in a research center’s database.

Setting: Community-based individuals with spinal cord injury (SCI).

Participants: 105 unique individuals with SCI.

Outcome Measurements: DXA derived areal BMD (aBMD) and T-score of the DF, PT, TH, and FN.

Results: The aBMD at the DF and PT regions were predictors of T-scores at the TH (R ²?=?0.63, P?<?0.001 and R ²?=?0.65, P?<?0.001) and FN (R ²?=?0.55, P?<?0.001 and R ²?=?0.58, P?<?0.001). Using the DF and PT aBMD of 0.60?g/cm² as a value below which fractures were more likely to occur, the predicted T-score was ?3.1 and ?3.5 at the TH and ?2.6 and ?2.9 at the FN, respectively. However, when the predicted and observed T-score values disagree outside the 95% limit of agreement, the predicted T-score values are lower than the measured T-score values, overestimating the measured values between ?2.0 and ?4.0 SD.

Conclusion: The DF and PT cutoff value for aBMD of 0.60?g/cm² was a moderate predictor of T-score values at the TH and FN, with considerable inaccuracies outside the clinically acceptable limits of agreement. As such, the direct measurement of knee aBMD in persons with SCI should be performed, whenever possible, prior to prescribing weight bearing upright activities, such as robotic exoskeletal-assisted walking.     

Effects of intradialytic cycling exercise on daily physical activity,physical fitness,body composition,and clinical parameters in high-volume online hemodiafiltration patients: a pilot randomized-controlled trial

Purpose

The mortality of dialysis patients treated with high-volume online hemodiafiltration (OL-HDF) is better than hemodialysis, but is still higher than healthy population. Low daily physical activity increases cardiovascular mortality. Addition of intradialytic exercise (IDX) program might improve physical activity and health status in OL-HDF patients. This pilot open-labeled randomized-controlled trial was conducted to evaluate the effects of IDX on physical activity and other clinical parameters in OL-HDF patients.

Methods

Twelve OL-HDF patients were randomized into control (n?=?6) or IDX (n?=?6) groups. The subjects in IDX group were trained to exercise using a cycle ergometer for 60 min during each OL-HDF session. Physical activity measured as daily step count using a wrist-worn triaxial accelerometer, physical fitness, or cardiorespiratory fitness assessed by VO₂max and other physical performance tests, lean body mass determined by the Dual-energy X-ray absorptiometry (DXA), quality of life (QOL), and various parameters were compared between baseline and 6 months.

Results

The baseline physical activity status was comparable. Following 6-month IDX, the physical activity was significantly improved in IDX group [+?1048.79 (+?741.50,?+?2792.54) vs. ? 362.06 (? 1626.82, ? 167.47) steps/day, p?=?0.01], while physical fitness and QOL were unchanged. The lean body mass parameters were preserved in the IDX group while seemed to decrease in the control group. Serum albumin was significantly increased in the IDX group (p?=?0.01). The hemoglobin changes were significantly better (p?=?0.01) and the erythropoietin resistance index was significantly lower in the IDX group (p?=?0.03). Phosphate reduction was significantly greater in the IDX group (p?=?0.04).

Conclusions

IDX could improve physical activity and other metabolic parameters in OL-HDF patients and these might contribute to further improvement in clinical and survival outcomes.

Trial registration

ClinicalTrials.gov Registration: NCT03353844.

     

Physical Performance Variables and Bone Mineral Density in a Group of Young Overweight and Obese Men

The aim of this study was to explore the relationships between performances obtained in different physical tests and bone parameters (bone mineral density [BMD], bone mineral content, hip geometry indices, and trabecular bone score [TBS]) in a group of young Lebanese overweight and obese adult men. Fifty-two overweight and/or obese (body mass index?>?25?kg/m²) young men whose ages range from 18 to 35?yr participated in this study. Weight and height were measured, and body mass index was calculated. Body composition, BMD, cross-sectional area and section modulus (Z) of the femoral neck (FN), and TBS were measured by dual-energy X-ray absorptiometry. Maximum oxygen consumption (VO₂ max, in liter per minute) was determined by direct measurement while exercising on a medical treadmill. One-repetition-maximum half-squat and maximum power (P max) of the lower limbs were measured using validated exercises. Lean mass was a positive determinant of whole-body bone mineral content (r?=?0.71, p?<?0.001), FN cross-sectional area (r?=?0.51, p?<?0.001), and FN Z (r?=?0.58, p?<?0.001). VO₂ max (in liter per minute) was a positive determinant of whole-body BMD (r?=?0.47, p?<?0.001), total hip BMD (r?=?0.43, p?<?0.01), and FN BMD (r?=?0.42, p?<?0.01). VO₂ max (in milliliter per minute per kilogram) was a positive determinant of TBS (r?=?0.30, p?<?0.05). One repetition maximum was a positive determinant of L1–L4 BMD (r?=?0.33, p?<?0.05). This study suggests that VO₂ max (in liter per minute) is a positive determinant of BMD, and VO₂ max (in milliliter per minute per kilogram) is a positive determinant of TBS in overweight and obese men.     

Association of musculoskeletal pain,fear-avoidance factors,and quality of life in active manual wheelchair users with SCI: A pilot study

Objective: Limited evidence examines the association of psychological factors, such as fear of movement and pain catastrophizing, with musculoskeletal pain patterns in active manual wheelchair users with spinal cord injury (SCI). This study investigated the relationship among musculoskeletal pain, fear avoidance factors, quality of life (QoL), activity and duration of injury in individuals with SCI.

Design: Cross-sectional correlational.

Setting: Community setting.

Participants: Twenty-six individuals with SCI (age?=?42?±?14 years, duration manual wheelchair use?=?17?±?13 years, work/school/volunteer hours/week?=?31?±?14; recreation/sports hours/week 10?±?12).

Outcome Measures: Demographics and self-report measures including the Musculoskeletal Pain Survey (MPS), Wheelchair Users Shoulder Pain Index (WUSPI), Tampa Scale of Kinesiophobia (TSK-11), Pain Catastrophizing Scale (PCS), Fear of Pain (FPQ), Subjective Quality of Life Questionnaire (SQoL), and the Social Interaction Inventory (SII). Spearman’s rho (ρ) assessed correlation among measures.

Results: Strong association existed between age and duration of injury (ρ?=?0.66, P?<?0.001). SQoL offered a strong, direct correlation with age (ρ?=?0.63, P?=?0.01), duration of injury (ρ?=?0.70, P?=?0.001), and strong, inverse relationship with MPStotal (ρ?=??0.66, P?=?0.003) and MPS shoulder subscore (ρ?=??0.64, P?=?0.004). WUSPI demonstrated strong, inverse association with self-reported work hours (ρ?=??0.52, P?=?0.02) and a strong, direct relationship to PCS (ρ?=?0.79, P?=?<0001). PCS demonstrated a strong, inverse relationship to work/school/volunteer hours (ρ?=?0.71, P?<?0.001) and strong association to TSK-11_total (ρ?=?0.61, P?=?0.001). A moderate, inverse relationship was identified for recreational/sports hours and FPQ (ρ?=?0.48, P?=?0.03).

Conclusion: This cyclical relationship of musculoskeletal pain, reduced activity, and maladaptive psychological factors allude to interdependence of factors, supporting the multidisciplinary approach to care.     

Robotically assisted treadmill exercise training for improving peak fitness in chronic motor incomplete spinal cord injury: A randomized controlled trial

Objective

To assess the effectiveness of robotically assisted body weight supported treadmill training (RABWSTT) for improving cardiovascular fitness in chronic motor incomplete spinal cord injury (CMISCI).

Design

Pilot prospective randomized, controlled clinical trial.

Setting

Outpatient rehabilitation specialty hospital.

Participants

Eighteen individuals with CMISCI with American Spinal Injury Association (ASIA) level between C4 and L2 and at least one-year post injury.

Interventions

CMISCI participants were randomized to RABWSTT or a home stretching program (HSP) three times per week for three months. Those in the home stretching group were crossed over to three months of RABWSTT following completion of the initial three month phase.

Outcome measures

Peak oxygen consumption (peak VO₂) was measured during both robotic treadmill walking and arm cycle ergometry: twice at baseline, once at six weeks (mid-training) and twice at three months (post-training). Peak VO₂ values were normalized for body mass.

Results

The RABWSTT group improved peak VO₂ by 12.3% during robotic treadmill walking (20.2 ± 7.4 to 22.7 ± 7.5 ml/kg/min, P = 0.018), compared to a non-significant 3.9% within group change observed in HSP controls (P = 0.37). Neither group displayed a significant change in peak VO₂ during arm cycle ergometry (RABWSTT, 8.5% (P = 0.25); HSP, 1.76% (P = 0.72)). A repeated measures analysis showed statistically significant differences between treatments for peak VO₂ during both robotic treadmill walking (P = 0.002) and arm cycle ergometry (P = 0.001).

Conclusion

RABWSTT is an effective intervention model for improving peak fitness levels assessed during robotic treadmill walking in persons with CMISCI.     

The Contribution of "Resting" Body Muscles to the Slow Component of Pulmonary Oxygen Uptake During High-Intensity Cycling

Oxygen uptake (VO₂) kinetics during moderate constant-workrate (WR) exercise (>lactate-threshold (θL)) are well described as exponential. AboveθL, these kinetics are more complex, consequent to the development of a delayed slow component (VO₂sc), whose aetiology remains controversial. To assess the extent of the contribution to the VO₂sc from arm muscles involved in postural stability during cycling, six healthy subjects completed an incremental cycle-ergometer test to the tolerable limit for estimation of θL and determination of peak VO₂. They then completed two constant-WR tests at 90% of θL and two at 80% of ∆ (difference between θL and VO_2peak). Gas exchange variables were derived breath-by-breath. Local oxygenation profiles of the vastus lateralis and biceps brachii muscles were assessed by near-infrared spectroscopy, with maximal voluntary contractions (MVC) of the relevant muscles being performed post-exercise to provide a frame of reference for normalising the exercise-related oxygenation responses across subjects. Above supra-θL, VO₂ rose in an exponential-like fashion ("phase 2), with a delayed VO₂sc subsequently developing. This was accompanied by an increase in [reduced haemoglobin] relative to baseline (∆[Hb]), which attained 79 ± 13 % (mean, SD) of MVC maximum in vastus lateralis at end-exercise and 52 ± 27 % in biceps brachii. Biceps brachii ∆[Hb] was significantly correlated with VO₂ throughout the slow phase. In contrast, for sub- L exercise, VO₂ rose exponentially to reach a steady state with a more modest increase in vastus lateralis ∆[Hb] (30 ± 11 %); biceps brachii ∆[Hb] was minimally affected (8 ± 2 %). That the intramuscular O₂ desaturation profile in biceps brachii was proportional to that for VO₂sc during supra-θL cycle ergometry is consistent with additional stabilizing arm work contributing to the VO₂sc.

Key points

• The source(s) of the "slow component" component of pulmonary oxygen uptake kinetics (VO₂sc) associated with high-intensity exercise remains the source of debate.
• Noninvasive interrogation techniques of the biceps brachii muscle during cycle ergometry suggest that "resting" muscles, such as those of the arms and shoulder girdle, may contribute to the VO₂sc, through stabilising actions (e.g. more forceful pulling on the ergometer handlebars).
• The quantitative contribution of such extra "resting"-muscle work awaits precise determination.

Key words: Muscle oxygenation, near infrared spectroscopy, oxygen uptake kinetics, arm exercise     

Well on wheels intervention: Satisfaction with life and health for adults with spinal cord injuries

Objective/Background: To examine how demographic and injury characteristics identify satisfaction with life (SWL), and assess the differential effects of a wellness intervention by baseline SWL groups.

Design: Baseline and longitudinal analysis of a randomized controlled pilot intervention using decision tree regression and linear mixed models.

Setting: Community based.

Participants: Seventy-two individuals with spinal cord injury (SCI) were randomized to an intervention group (n?=?39) or control group (n?=?33). Participants were aged 44.1?±?13.0 years and 13.1?±?10.6 years post-injury. Most participants were male (n?=?50; 69.4%) and had paraplegia (n?=?38; 52.7%). Participants were classified as high versus low SWL at baseline using a cutoff score of 20.

Interventions: The intervention aimed to increase self-efficacy, and in turn, increase engagement in health-promoting behaviors related to SWL. Six 4-hour in-person workshops were conducted over a 3-month period led by experts and peer-mentors who were available for support.

Outcome measure(s): Self-efficacy for health practices, secondary condition severity, health-promoting behaviors, perceived stress, and SWL.

Results: At baseline, participants with low SWL were recently injured (<4.5 years), while persons with high SWL were married and younger (<49 years old). Intervention participants with low SWL at baseline significantly improved SWL over time compared to those with high SWL (P?=?0.02).

Conclusion: Certain injury and demographic characteristics were associated with SWL, and intervention participants with low SWL at baseline improved their SWL over 2 years. Healthcare providers should consider time post-injury, marital status, and age in identifying individuals at risk for low SWL that may benefit from wellness interventions.     

Provocative Stimulation of Growth Hormone: A Monozygotic Twin Study Discordant for Spinal Cord Injury

Abstract

Background/Objective: A blunted growth hormone (GH) response to provocative testing and/or low levels of plasma insulin-like growth factor-1 (IGF-I) have been reported in persons with spinal cord injury (SCI). A reduction in activity of the GH-IGF-I axis may have deleterious effects on body composition and function. Provocative testing for GH stimulation was performed to determine the response in monozygotic twins that were discordant for SCI.

Methods: GH stimulation testing was performed by the administration of intravenous arginine.

Results: Nine SCI twins with paraplegia, a mean age of 39 ± 9 years, and duration of injury of 14 ± 9 years were studied. The twins with SCI had a significantly lower body mass index than non-SCI twins (22.5 ± 4.0 vs 25.1 ± 4.2 kg/m²; P < 0.05); percent fat mass was greater in the twins with SCI (30 ± 11 % vs 22 ± 10%; P < 0.05). Baseline serum GH was correlated with percent fat only in the SCI twins. The response to GH provocative stimulation was less in the twins with SCI: peak GH response was 5.8 ± 6.6 vs 13.0 ± 7.3 ng/mL (P < 0.05), and sum GH response was 15.7 ± 15.6 vs 30.2 ± 17.3 ng/mL (P = 0.06). Although baseline serum GH was correlated with stimulated response in the SCI twins, this relationship was not found in the non-SCI twins. Adiposity was positively related to the provocative serum GH response in twins with SCI rather than negatively related, as noted in the non-SCI twins.

Conclusions: This study confirms and extends prior work that reported a reduction in stimulated GH release in persons with SCI, which was related to baseline values.