Reliability and minimal detectable change of a new treadmill-based progressive workload incremental test to measure cardiorespiratory fitness in manual wheelchair users

Background: Cardiorespiratory fitness training is commonly provided to manual wheelchair users (MWUs) in rehabilitation and physical activity programs, emphasizing the need for a reliable task-specific incremental wheelchair propulsion test.

Objective: Quantifying test-retest reliability and minimal detectable change (MDC) of key cardiorespiratory fitness measures following performance of a newly developed continuous treadmill-based wheelchair propulsion test (WPT_Treadmill).

Methods: Twenty-five MWUs completed the WPT_Treadmill on two separate occasions within one week. During these tests, participants continuously propelled their wheelchair on a motorized treadmill while the exercise intensity was gradually increased every minute until exhaustion by changing the slope and/or speed according to a standardized protocol. Peak oxygen consumption (VO_2peak), carbon dioxide production (VCO_2peak), respiratory exchange ratio (RER_peak), minute ventilation (VE_peak) and heart rate (HR_peak) were computed. Time to exhaustion (TTE) and number of increments completed were also measured. Intra-class correlation coefficients (ICC) were calculated to determine test-retest reliability. Standard error of measurement (SEM) and MDC_90% values were calculated.

Results: Excellent test-retest reliability was reached for almost all outcome measures (ICC=0.91-0.76), except for RER_peak (ICC=0.58), which reached good reliability. TTE (ICC=0.89) and number of increments (ICC=0.91) also reached excellent test-retest reliability. For the main outcome measures (VO_2peak and TTE), absolute SEM was 2.27?mL/kg/min and 0.76 minutes, respectively and absolute MDC_90% was 5.30?mL/kg/min and 1.77 minutes, respectively.

Conclusion: The WPT_Treadmill is a reliable test to assess cardiorespiratory fitness among MWUs. TTE and number of increments could be used as reliable outcome measures when VO₂ measurement is not possible.     

Longitudinal relationship between wheelchair exercise capacity and life satisfaction in patients with spinal cord injury: A cohort study in the Netherlands

Abstract

Objective

To examine the relationship between wheelchair exercise capacity and life satisfaction in persons with spinal cord injury from the start of active inpatient rehabilitation up to 5 years after discharge.

Design

Prospective cohort study.

Subjects

Persons with spinal cord injury, aged 18–65 years, and wheelchair dependent at least for long distances.

Method

Measurements at the start of active rehabilitation, after 3 months, at discharge from inpatient rehabilitation, and 1 and 5 years after discharge. A peak wheelchair exercise test was performed to record peak oxygen uptake (VO_2peak) and peak power output (PO_peak). Life satisfaction was measured as current life satisfaction and change of life satisfaction in comparison with life after spinal cord injury. Relationships between (changes in) exercise capacity and (changes in) life satisfaction were analyzed random coefficient analysis, corrected for possible confounders (age, gender, level of lesion, functional status, secondary impairments, pain, and sports activity) if necessary.

Results

Of 225 persons included, 130 attended two or more peak exercise tests, who were include in the analyses. Mean age at start was 39 years, 75% were male, 73% had paraplegia, and 76% had a traumatic lesion. Mean PO_peak increased during the study from 32.9 to 55.9 Watts, mean VO_2peak from 1.02 to 1.38 l/minute, and mean life satisfaction from 5.7 to 7.8. An increase of PO_peak with 10 W was associated with a 0.3-point increase of life satisfaction (P = 0.01). An increase of VO_2peak with 0.1 l/minute was associated with a 0.1-point increase of life satisfaction (P = 0.049).

Conclusion

High(er) wheelchair exercise capacity is related to high(er) life satisfaction in spinal cord injury patients.     

Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review

ContextThis review synthesizes the findings of previous research studies on the cardiovascular and metabolic benefits of aerobic exercise for individuals with tetraplegia secondary to spinal cord injury. They are often less active due to muscular paralysis, sensory loss, and sympathetic nervous system dysfunction that result from injury. Consequently, these persons are at higher risk for exercise intolerance and secondary health conditions.ObjectiveTo evaluate the evidence concerning efficacy of aerobic exercise training for improving health and exercise performance in persons with tetraplegia from cervical injury.MethodsThe search engines PubMed and Google Scholar were used to locate published research. The final 75 papers were selected on the basis of inclusion criteria. The studies were then rank-ordered using Physiotherapy Evidence Database.ResultsStudies combining individuals with tetraplegia and paraplegia show that voluntary arm-crank training can increase mean peak power output by 33%. Functional electrical stimulation leg cycling was shown to induce higher peak cardiac output and stroke volume than arm-crank exercise. A range of peak oxygen uptake (VO_2peak) values have been reported (0.57–1.32 L/min). Both VO_2peak and cardiac output may be enhanced via increased muscle pump in the legs and venous return to the heart. Hybrid exercise (arm-crank and functional electrical stimulation leg cycling) can result in greater peak oxygen uptake and cardiovascular responses.ConclusionEvidence gathered from this systematic review of literature is inconclusive due to the lack of research focusing on those with tetraplegia. Higher power studies (level 1–3) are needed with the focus on those with tetraplegia.     

Physiological Responses to Exergaming After Spinal Cord Injury

Purpose:

To investigate whether exergaming satisfies guideline-based intensity standards for exercise conditioning (40%/50% oxygen uptake reserve [VO₂R] or heart rate reserve (HRR), or 64%/70% of peak heart rate [HR_peak]) in persons with paraplegia.

Methods:

Nine men and women (18-65 years old) with chronic paraplegia (T1-L1, AIS A-C) underwent intensity-graded arm cycle exercise (AE) to evaluate VO2_peak and HR_peak. On 2 randomized nonconsecutive days, participants underwent graded exercise using a custom arm cycle ergometer that controls the video display of a Nintendo Gamecube (GameCycle; Three Rivers Holdings LLC, Mesa, AZ) or 15 minutes of incrementally wrist-weighted tennis gameplay against a televised opponent (XaviX Tennis System; SSD Co Ltd, Kusatsu, Japan).

Results:

GameCycle exergaming (GCE) resistance settings ≥0.88 Nm evoked on average ≥50% VO₂R. During XaviX Tennis System exergaming (XTSE) with wrist weights ≥2 lbs, average VO₂ reached a plateau of ~40% VO₂R. Measurements of HR were highly variable and reached average values ≥50% HRR during GCE at resistance settings ≥0.88 Nm. During XTSE, average HR did not reach threshold levels based on HRR for any wrist weight (20%-35% HRR).

Conclusions:

On average, intensity responses to GCE at resistance setting ≥0.88 Nm were sufficient to elicit exercise intensities needed to promote cardiorespiratory fitness in individuals with SCI. The ability of XTSE to elicit cardiorespiratory fitness benefits is most likely limited to individuals with very low fitness levels and may become subminimal with time if used as a conditioning stimulus.     

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.     

Effects of arm cranking exercise on muscle oxygenation between active and inactive muscles in people with spinal cord injury

Objective: We investigated the effects of the incremental arm-cranking exercise (ACE) on tissue oxygen saturation (StO₂) between active and inactive muscles, and the relationship between peak oxygen uptake (VO_2peak) and changes in the StO₂ in inactive muscles.Design: Observational study.Setting: Community-based supervised intervention.Participants: The participants were individuals with motor and sensory complete spinal cord injury (complete SCI; n = 8) and motor complete but sensory incomplete SCI (incomplete SCI; n = 8), and able-bodied (AB) individuals (n = 8) matched for age, height, and body mass index.Intervention: The ACE was performed at a rate increasing by 10 watts min⁻¹ until exhaustion.Outcome Measures: VO_2peak, heart rate (HR), and StO₂.Results: While VO_2peak was similar among the groups, peak HR was significantly higher in both SCI groups than in the AB (P < 0.05). In active muscles (biceps brachii), no differences in the StO₂ were observed among the groups (P > 0.05). In inactive muscles (vastus lateralis), the StO₂ in the AB and the incomplete SCI began to decrease at approximately 40% of the peak work rate; however, they remained unchanged in the complete SCI. The reductions in StO₂ in the AB were significantly greater than in the incomplete SCI.Conclusions: These results suggest that sympathetic vasoconstriction occurred in the incomplete SCI and AB, although it did not occur in the complete SCI, probably due to a reduction in sympathetic nerve activity. Sympathetic vasoconstriction in inactive muscles may not contribute to an individual’s VO_2peak regardless of their group.     

Adaptation to reduced lung function in children and young people with spinal deformity

BackgroundSevere scoliosis can affect respiratory function in growing patients and produce cardiopulmonary complications, leading to significant morbidity. The development of spinal deformity may impact on young patients’ level of function and reported quality of life (QOL). The aim of this study was to investigate the relationship between lung function, exercise capacity and quality of life in young patients with spinal deformity.MethodsThis is a retrospective analysis of 104 patients (31% male, 69% female with mean age 14.9yrs). 77% of patients had an adolescent idiopathic scoliosis, with the remainder having other scoliosis diagnoses or Scheuermann’s kyphosis. Principal outcomes included Spirometry [FEV₁, FVC], Whole Body Plethysmography, Cardiopulmonary Exercise Testing [CPET] and patient outcome questionnaires (with SRS-22). CPET measures included maximal exercise capacity [VO_2peak] as well as VO₂ at ventilatory threshold [VT] expressed as %predicted VO_2max-a measure of physical conditioning, and minute ventilation [V_E] from which breathing reserve [BR] could be calculated.ResultsMean (±SD) main thoracic scoliosis was 59.9⁰ (±15.2⁰), and mean kyphosis in those with Scheuermann’s condition was 95.3⁰ (±11.5⁰). No correlation was elicited between FEV₁ or FVC (%predicted) and VO_2peak (%predicted) in this patient cohort. Greater thoracic curves were associated with lower FEV₁ (%predicted), r = −0.343, p = 0.001, FVC (%predicted), r = −0.307, p = 0.003 and BR (%) at the end of exercise (r = −0.-0.459, p < 0.001). The patient cohort had a mean (sd) VO₂peak of 98(17) %predicted, with greater VO₂peak levels recorded in female subjects, those of younger age and those with higher scoliosis angles. Those with better lung function [FEV₁ (%predicted)] had better BR (%) at the end of exercise (r = 0.483, p < 0.001). SRS-22 scores correlated significantly with VO_2peak (%predicted) (total SRS-22 versus VO_2peak (%predicted), r = 0.336, p = 0.002).ConclusionLarger thoracic scoliotic curves are associated with poorer lung function but better exercise capacity, likely related to higher levels of physical conditioning. Higher QOL scores were recorded in patients who had greater VO_2peak levels, suggesting that exercise capacity may be a protective factor for emotional well-being in patients with spinal deformity.     

High‐Intensity Interval Training Improves Peak Oxygen Uptake and Muscular Exercise Capacity in Heart Transplant Recipients

Heart transplant (HTx) recipients usually have reduced exercise capacity with reported VO_2peak levels of 50–70% predicted value. Our hypothesis was that high‐intensity interval training (HIIT) is an applicable and safe form of exercise in HTx recipients and that it would markedly improve VO_2peak. Secondarily, we wanted to evaluate central and peripheral mechanisms behind a potential VO_2peak increase. Forty‐eight clinically stable HTx recipients >18 years old and 1–8 years after HTx underwent maximal exercise testing on a treadmill and were randomized to either exercise group (a 1‐year HIIT‐program) or control group (usual care). The mean ± SD age was 51 ± 16 years, 71% were male and time from HTx was 4.1 ± 2.2 years. The mean VO_2peak difference between groups at follow‐up was 3.6 [2.0, 5.2] mL/kg/min (p < 0.001). The exercise group had 89.0 ± 17.5% of predicted VO_2peak versus 82.5 ± 20.0 in the control group (p < 0.001). There were no changes in cardiac function measured by echocardiography. We have demonstrated that a long‐term, partly supervised and community‐based HIIT‐program is an applicable, effective and safe way to improve VO_2peak, muscular exercise capacity and general health in HTx recipients. The results indicate that HIIT should be more frequently used among stable HTx recipients in the future.     

Low-Frequency Fatigue in Individuals With Spinal Cord Injury

Abstract

Background/Objective: This study examined magnitude and recovery of low-frequency fatigue (LFF) in the quadriceps after electrically stimulated contractions in spinal cord-injured (SCI) and able-bodied subjects.

Subjects: Nine SCI (ASIA A-C, levels C5-T9, injured 13.6 ± 12.2 years) and 9 sedentary able-bodied subjects completed this study.

Methods: Fatigue was evoked in 1 thigh, and the nonfatigued leg served as a control. The fatigue test for able-bodied subjects lasted 15 minutes. For SCI, stimulation was adjusted so that the relative drop in force was matched to the able-bodied group. Force was assessed at 20 (P20) and 100 Hz (PI 00), and the ratio of P20/P100 was used to evaluate LFF in thighs immediately after, at 10, 20, and 60 minutes, and at 2, 4, 6, and 24 hours after a fatigue test.

Results: The magnitude of LFF (up to 1 hour after fatigue) was not different between able-bodied and patients with SCI. However, recovery of LFF over 24 hours was greater in able-bodied compared with patients with SCI in both the experimental (P < 0.001) and control legs (P < 0.001). The able-bodied group showed a gradual recovery of LFF over time in the experimental leg, whereas the SCI group did not.

Conclusions: These results show that individuals with SCI are more susceptible to LFF than able-bodied subjects. In SCI, simply assessing LFF produced considerable LFF and accounted for a substantial portion of the response. We propose that muscle injury is causing the dramatic LFF in SCI, and future studies are needed to test whether “fatigue” in SCI is actually confounded by the effects of muscle injury.     

Effect of High Intensity Exercise on Peak Oxygen Uptake and Endothelial Function in Long‐Term Heart Transplant Recipients

Coronary allograft vasculopathy is a well‐known long‐term complication after cardiac transplantation. Endothelial dysfunction is involved and may be prevented by aerobic exercise. The purpose of this study was to examine whether high intensity aerobic exercise improves peak oxygen uptake (VO_{2 peak}) and endothelial function in heart transplant (HT) recipients. Twenty‐seven long‐term HT recipients were randomized to either 8‐weeks high intensity aerobic exercise or no training. Flow mediated dilation of the brachial artery (FMD) was measured by ultrasound and VO_{2 peak} by the analysis of expired air. Blood pressure and biomarkers were measured before and after 8 weeks. VO_{2 peak} increased significantly in the exercise group (VO_{2 peak} 23.9 ± 1.79 to 28.3 ± 1.63 mL/kg/min compared to controls (VO_{2 peak} 24.6 ± 1.38 to 23.4 ± 1.58, p < 0.001 exercise vs. control).FMD increased in the exercise group compared to controls (8.3 ± 1.1% to 11.4 ± 1.2% vs. 5.6 ± 1.0% to 5.3 ± 1.7%, p = 0.024). No increase in nitroglycerin‐induced vasodilation was observed. Systolic blood pressure fell in the exercise group (142 ±4.2 mmHg to127 ± 3.4 mmHg, p = 0.01) and was unchanged in controls (141 ± 4.2 mmHg to 142 ±6.4 mmHg, NS). High intensity aerobic exercise reduces systolic blood pressure and improves endothelial function in HT recipients.     

Effective training for patients with intermittent claudication

Objective. Current guidelines for treatment of intermittent claudication (IC) do not include a specific recommendation for the intensity of exercise therapy. Thus, the purpose of this study was to determine the relative effectiveness of high versus low intensity exercise for patients with IC, and further to study the effect of such training on blood flow to the legs during exercise. Design. The effect of eight weeks of supervised endurance training was examined in 16 patients with IC. The patients were randomly assigned to training at intensities corresponding to either 60% or 80% of their peak oxygen consumption (VO_2peak), respectively. Results. VO_2peak and time to exhaustion increased significantly (9% and 16%, respectively) more in the high intensity group (p<0.05). Blood flow to the legs did not change after training in any of the groups. Conclusion. High intensity training gave larger improvements in VO_2peak and time to exhaustion than low intensity training. As blood flow did not change after the exercise program, it is likely that the observed different increase of VO_2peak was due to changed mitochondrial oxidative capacity and/or skeletal muscle diffusive capacity.     

Change in exercise capacity measured by Cardio-pulmonary Exercise Testing (CPET) in Danish people with cystic fibrosis after initiation of treatment with Lumacaftor/Ivacaftor and Tezacaftor/Ivacaftor

BackgroundSince 2015, when the first cystic fibrosis transmembrane conductance regulator (CFTR) modulators were approved for people with cystic fibrosis (CF) homozygous for F508del-CFTR, studies have shown improved lung function after initiation of the treatment and patients experience improved physical capacity. The aim of this study was to investigate change in exercise capacity after initiation of Lumacaftor/Ivacaftor and Tezacaftor/Ivacaftor treatment (LUM/IVA, TEZ/IVA).MethodsWe performed a single group prospective observational cohort study with follow-up at six and 12 months. The study examined change in exercise capacity in people with CF initiating treatment with LUM/IVA and TEZ/IVA, measured by cardio-pulmonary exercise testing (CPET). Inclusion criteria were people with CF homozygous for F508del-CFTR aged 12 years or older eligible for LUM/IVA and TEZ/IVA treatment from June 2017 until June 2019. Primary outcomes were change in VO_2peak and maximal workload. Secondary outcomes were change in muscle strength, muscle power and body composition in a subgroup of the study population.ResultsA total of 91 patients were included in the analysis. The mean change in VO_2peak and VO_2peak divided by body weight from baseline to 12-months follow-up was 145.7 (91.2;200.2) ml/min and 1.07 (95% CI 0.19;1.95) ml/min/kg, respectively. The mean change in maximal workload between baseline and 12 months was 14.2 Watt (95% CI 9.1;19.2). All improvements in exercise capacity were statistically significant.ConclusionsPatients in this study improved their exercise capacity by a statistically significant increase in VO_2peak and maximal workload 12 months after initiation of treatment with LUM/IVA and TEZ/IVA.     

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.     

Aquatic,deep water peak VO2 testing for individuals with spinal cord injury

Objective: To determine the reliability of peak VO₂ testing for individuals with spinal cord injury (SCI) in deep water and on land; and to examine the relationship between these two testing conditions.

Design: Reliability study.

Setting: Comprehensive rehabilitation center in Baltimore, MD, USA.

Participants: 17 participants (13 men, 4 women) with motor complete and incomplete SCI. Participants were randomized into either aquatic or arm cycle ergometer first measurements.

Intervention: Pilot study to assess peak VO₂.

Outcome measures: Peak VO₂ measured with metabolic cart in supported deep water with the addition of Aquatrainer® connection, and on land with arm cycle ergometer. Two trials were conducted for each condition with 48?h separating each test.

Results: Peak oxygen consumption reliability was statistically significant for both conditions, aquatic (r?=?0.93, P?<?0.001) and arm cycle ergometry (r?=?0.96, P?<?0.001). Additionally, aquatic and arm cycle peak VO₂ correlation existed (r?=?0.72, P?<?0.001). For these 17 participants, lower extremity motor score influenced supported, deep water peak VO₂, B?=?0.57, P?<?0.02, whereas age, sex, and weight did not impact deep water or ergometer values.

Conclusion: Determining peak VO₂ for individuals with SCI is highly reproducible for arm cycle ergometry and in deep water assessment. Additionally, aquatic, deep water peak VO₂ testing is valid when compared to arm cycle ergometry. Although the peak VO₂ relationship between deep water and arm cycle ergometry is high, variance in the two conditions does exist. Therefore, it is important to assess peak VO₂ via the same exercise modality utilized in the treatment intervention.     

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.     

Lipid profiles are influenced by arm cranking exercise and training in individuals with spinal cord injury

STUDY DESIGN: A prospective, two-group comparative intervention study. OBJECTIVE: To determine the acute and training effects of arm cranking exercise on blood lipid profiles in wheel chair bound individuals with spinal cord injury (SCI) and normal able-bodied subjects. SETTING: Faculty of Science, School of Sport and Exercise Science, Liverpool John Moores University, England. METHODS: Total cholesterol, triglyceride and high-density lipoprotein cholesterol (HDL-C) at rest and in response to arm cranking exercise before and after 12 weeks of training were compared between individuals with SCI (N = 5) and able-bodied subjects (N = 7). Following the determination of peak oxygen consumption (VO2peak), all subjects performed a submaximal arm cranking exercise at an intensity corresponding to 60-65% VO2peak for 30 min. Venous blood samples were obtained before and after submaximal exercise and measured for total cholesterol, triglycerides and HDL-C concentrations. These lipid parameters were remeasured in all subjects at rest and in response to the same submaximal arm cranking exercise after 12 weeks of individually supervised arm cranking training programme. RESULTS: Before training, the resting mean value of triglyceride in individuals with SCI was significantly (P < 0.05) higher than that found in able-bodied persons. Acute arm cranking exercise did not change total cholesterol or triglyceride concentrations in either the SCI or the able-bodied groups. However, HDL-C increased significantly following exercise in the able-bodied subjects. Following training, the resting mean value of total cholesterol in the group with SCI was significantly (P < 0.05) higher compared with able-bodied individuals. Furthermore, the resting and post submaximal arm cranking exercise mean values of total cholesterol in the able-bodied group, but not in the group with SCI, were significantly lower than those observed before training. While the resting mean value of HDL-C before training in the group with SCI was lower than that found in the able-bodied, this difference did not reach the designated level of significance (P > 0.05). Submaximal arm cranking exercise was followed by a significant increase in HDL-C only in the able-bodied individuals. Compared to pretraining, the resting and post arm cranking exercise levels of HDL-C in the group with SCI increased significantly (P < 0.05) after training. CONCLUSION: It is concluded that acute arm cranking exercise and training in individuals with SCI is associated with favourable effects on HDL-C, whereas total cholesterols and triglycerides were not altered. The mechanism responsible for the increase in HDL-C with training in individuals with SCI is not known, but it is likely to be related to increased activity of cholesterol transport enzymes lipoprotein lipase and acyltransferase.     

Physiologic Responses of Elite Paraplegic Road Racers to Prolonged Exercise

ABSTRACT

The purpose of this study was to determine cardiopulmonary and selected metabolic responses in spinal cord injured (SCI) paraplegics during prolonged arm crank exercise (ACE). Six male and one female elite SCI paraplegic (T4-12 lesions) road racers performed 40 continuous minutes of ACE at 60% of peak ACE oxygen uptake (VO₂). Blood samples (30 ml) were collected via antecubital venipuncture at rest and minutes 20 and 40 of ACE for determinations of hemoglobin, hematocrit, serum free fatty acid (FFA), and blood lactate (LA) concentrations. No significant differences were observed over time for V0₂ or pulmonary ventilation. Heart rate recorded at minutes 30 and 40 was significantly elevated’ above HR at minutes 10 and 20 of ACE indicating the presence of an upward drift in HR in paraplegics performing prolonged ACE. Compared to rest, LA concentration was significantly higher at minute 20 and remained relatively stable thereafter. A significant increase in FFA concentration at minute 40 combined with a significant decline in the respiratory exchange ratio suggested a preference for lipid substrate utilization by exercising muscle as ACE continued. The data indicate that the autonomic sympathetic nervous system impairment associated with paraplegia had no apparent adverse effects on cardiopulmonary or metabolic adjustments to prolonged ACE in these well-trained subjects.     

The Effects of Intermittent Exercise on Physiological Outcomes in an Obese Population: Continuous Versus Interval Walking

This study compared the effects of 12 weeks of caloric restriction and interval exercise (INT) and caloric restriction and continuous aerobic exercise (CON) on physiological outcomes in an obese population. Forty-four individuals (BMI ≥ 30 kg·m^-2) were randomised into the INT or CON group. Participant withdrawal resulted in 12 and 14 participants in the INT and CON groups, respectively. All participants were on a strict monitored diet. Exercise involved two 15-min bouts of walking performed on five days per week. Interval exercise consisted of a 2:1 min ratio of low-intensity (40-45% VO_2peak) and high- intensity (70-75% VO_2peak) exercise, while the CON group exercised between 50-55% VO_2peak. Exercise duration and average intensity (%VO_2peak) were similar between groups. There were no significant differences (p > 0.05) between the two groups for any variable assessed apart from very low density lipoprotein (VLDL-C), which significantly decreased over time in the INT group only (p < 0.05, d = 1.03). Caloric restriction and interval exercise compared to caloric restriction and continuous aerobic exercise resulted in similar outcome measures apart from VLDL-C levels, which significantly improved in the INT group only.

Key points

• Twelve weeks of interval exercise and caloric restriction resulted in significant improvement in very low density lipoprotein cholesterol in an obese population, as compared to continuous aerobic exercise and caloric restriction.
• Twelve weeks of either interval exercise or continuous exercise resulted in similar improvements in aerobic fitness in an obese population.

Key words: Interval training, body fat, fitness, metabolism