Predicting peak oxygen uptake from submaximal exercise after spinal cord injury

Effects of two external cooling strategies on physiological and perceptual responses of athletes with tetraplegia during and after exercise in the heat

Athletes with tetraplegia may experience marked hyperthermia while exercising under environmental heat stress due to their limited ability to dissipate heat through evaporative means. This study investigated the effectiveness of two external cooling strategies (i.e., spraying water onto the body surface or using a cooling vest) on physiological and perceptual variables in tetraplegic athletes during and after an aerobic exercise session in a hot environment. Nine male wheelchair rugby players performed an incremental test to determine their maximum aerobic power output. After that, they were subjected to three experimental trials in a counter-balanced order: control (CON, no body cooling), cooling vest (CV), and water spraying (WS). During these trials, they performed 30 min of a submaximal exercise (at 65% of their maximum aerobic power) inside an environmental chamber set to maintain the dry-bulb temperature at 32 °C. The following variables were recorded at regular intervals during the exercise and for an additional 30 min following the exertion (i.e., post-exercise recovery) with the participants also exposed to 32 °C: body core temperature (TCORE), skin temperature (TSKIN), heart rate (HR), rating of perceived exertion (RPE), thermal comfort (TC), and thermal sensation (TS). While exercising in CON conditions, the tetraplegic athletes had the expected increases in TCORE, TSKIN, HR, RPE, and TC and TS scores. HR, TC, and TS decreased gradually toward pre-exercise values after the exercise, whereas TCORE and TSKIN remained stable at higher values. Using a cooling vest decreased the temperature measured only on the chest and reduced the scores of RPE, TC, and TS during and after exercise but did not influence the other physiological responses of the tetraplegic athletes. In contrast, spraying water onto the athletes' body surface attenuated the exercise-induced increase in TSKIN, led to lower HR values during recovery, and was also associated with better perception during and after exercise. We conclude that water spraying is more effective than the cooling vest in attenuating physiological strain induced by exercise-heat stress. However, although both external cooling strategies do not influence exercise hyperthermia, they improve the athletes' thermal perception and reduce perceived exertion.

Validity of the two-minute walk test to assess exercise capacity and estimate cardiorespiratory fitness in individuals after stroke: a cross-sectional study

OBJECTIVES

The purpose of this study was to investigate the construct validity of the 2-minute walk test (2MWT) to assess the exercise capacity and the criterion-concurrent validity of the 2MWT and the 6-minute walk test (6MWT) to estimate the cardiorespiratory fitness of ambulatory individuals with chronic stroke. In addition, to provide an equation to predict the distance covered in the 6MWT and another to predict the peak oxygen consumption (VO2peak) for these individuals.

METHODS

This is a cross-sectional and prospective study. A convenience sample with 57 individuals with chronic stroke was recruited. The 2MWT, the 6MWT and the cardiopulmonary exercise test (CPET) were performed in a laboratory. The Spearman's correlation coefficient was used to investigate the validity. To develop the equations, stepwise multiple linear regression analysis was used.

RESULTS

A significant correlation of very high magnitude between the distance covered in the 2MWT and the 6MWT was found (rs = 0.93; p < 0.001). A significant correlation of moderate magnitude between the distance covered in the 2MWT and the VO2peak (rs = 0.53; p < 0.001) similar to the correlation between the 6MWT and the VO2peak (rs = 0.55; p < 0,001) were found. Furthermore, an equation was developed to predict the VO2peak (R2 = 0.690; p < 0.001; VO2peak = 13.532 + 0.078*distance walked in the 2MWT +4.509*sex-0.172*age), and another to predict the distance covered in the 6MWT (R2 = 0.827; p < 0.001; MWT = -1.867 + 3.008*distance walked in the 2MWT).

CONCLUSION

2MWT showed adequate construct and concurrent validity. Furthermore, it is possible to use the prediction equations developed to estimate the VO2peak or the distance covered in the 6MWT.

Estimation of peak oxygen consumption in individuals with spinal cord injury patients using multiple linear regression analysis: a preliminary study

PURPOSE

This study aims to develop a regression model to estimate peak oxygen consumption (VO2peak) in individuals with spinal cord injury (SCI) by employing different variables.

METHODS

In this study, 34 participants were divided into two groups: 19 with cervical injury (CI) and 15 with thoracic injury (TI). Key measurements included VO2peak and related factors such as age, height, weight, body mass index (BMI), fat-free mass, body fat percentage, limb and trunk circumferences, spinal cord independence (SCIM III), Korean activities of daily living (K-ADL), and respiratory functions (forced vital capacity (FVC), peak expiratory flow (PEF), and maximum voluntary ventilation (MVV)). Statistical analyses were conducted using forward selection regression to examine the relationships between these variables.

RESULTS

Height, calf circumference, SCIM III score, and PEF were key variables in all patients with SCI (TSCI). For patients with CI, the key variables were height, calf circumference, and MVV, whereas for patients with TI, the key variable was calf circumference. The average explanatory powers of the VO2peak regression model for TSCI were 70.3% (R2) and 66.2% (adjusted R2), with an average standard error of estimate (SEE) of 2.94 ml/kg/min. The average explanatory power for patients with CI was 71.7% (R2) and 66.1% (adjusted R2), with an average SEE of 1.88 ml/kg/min. The average explanatory power for patients with TI was 55.9% (R2) and 52.5% (adjusted R2), with an average SEE of 3.41 ml/kg/min. There was no significant difference between the VO2peak measured and predicted VO2peak for each type of injury.

CONCLUSION

The regression model for estimating VO2peak in SCI patients in this preliminary study is as follows: TSCI=39.684-0.144×(Height)-0.513×(Calf)+0.136×(SCIM III)+1.187×(PEF), CI=38.842-0 .158×(Height) - 0.371×(Calf)+0.093×(MVV), TI=42.325-0.813×(Calf).

Exercise prescription for persons with spinal cord injury: a review of physiological considerations and evidence-based guidelines

Persons with spinal cord injury (SCI) experience gains in fitness, physical and mental health from regular participation in exercise and physical activity. Due to changes in physiological function of the cardiovascular, nervous, and muscular systems, general population physical activity guidelines and traditional exercise prescription methods are not appropriate for the SCI population. Exercise guidelines specific to persons with SCI recommend progressive training beginning at 20 min of moderate to vigorous intensity aerobic exercise twice per week transitioning to 30 min three times per week, with strength training of the major muscle groups two times per week. These population-specific guidelines were designed considering the substantial barriers to physical activity for persons with SCI and can be used to frame an individual exercise prescription. Rating of perceived exertion (i.e., perceptually regulated exercise) is a practical way to indicate moderate to vigorous intensity exercise in community settings. Adapted exercise modes include arm cycle ergometry, hybrid arm-leg cycling, and recumbent elliptical equipment. Body weight-supported treadmill training and other rehabilitation modalities may improve some aspects of health and fitness for people with SCI if completed at sufficient intensity. Disability-specific community programs offer beneficial opportunities for persons with SCI to experience quality exercise opportunities but are not universally available.

Intervention Design of High-Intensity Interval Training in Individuals With Spinal Cord Injury: Narrative Review and Future Perspectives

Background

Individuals with spinal cord injury (SCI) have lower levels of physical activity compared to the nondisabled population. Exercise guidelines recommend moderate or vigorous exercise to improve cardiovascular health and reduce cardiometabolic risk factors in persons with SCI. High-intensity interval training (HIIT) is a popular exercise choice and encompasses brief periods of vigorous exercise paired with intermittent periods of recovery.

Objectives

This review describes the available literature on HIIT for individuals with SCI, including differences in protocol design and suggested areas of further investigation.

Methods

Our institution's library system performed the comprehensive search. The primary keywords and phrases used to search included spinal cord injury, high-intensity interval training, tetraplegia, paraplegia, and several other related terms.

Results

Initially 62 records were screened, and 36 were deemed outside the scope of this review. Twenty-six studies published between 2001 and 2021 fulfilled the eligibility criteria and were divided among two researchers for review and analysis. All records required persons with SCI and a standardized HIIT intervention. Study design varied widely with respect to mode of exercise, prescribed intensity, duration of performance intervals, and session duration. This variability necessitates further investigation into the specifics of a HIIT prescription and the associated outcomes for persons with SCI.

Conclusion

Standardization of HIIT protocols may lead to more robust conclusions regarding its effects on cardiorespiratory fitness as well as mitigation of cardiometabolic risk factors. Meta-analyses will eventually be needed on proper dosing and session parameters to improve cardiorespiratory fitness and cardiometabolic risk factors.

Predicting Maximum Oxygen Uptake from Non-Exercise and Submaximal Exercise Tests in Paraplegic Men with Spinal Cord Injury

This study aimed to develop prediction equations for maximum oxygen uptake (VO₂max) based on non-exercise (anthropometric) and submaximal exercise (anthropometric and physiological) variables in paraplegic men with a spinal cord injury. All participants were tested on an arm ergometer using a maximal graded exercise test. Anthropometric variables such as age, height, weight, body fat, body mass index, body fat percentage, and arm muscle mass and physiological variables such as VO₂, VCO₂, and heart rate at 3 and 6 min of graded exercise tests were included in the multiple linear regression analysis. The prediction equations revealed the following. Regarding non-exercise variables, VO₂max was correlated with age and weight (equation R = 0.771, R² = 0.595, SEE= 3.187). Regarding submaximal variables, VO₂max was correlated with weight and VO₂ and VCO₂ at 6 min (equation R = 0.892, R² = 0.796, SEE = 2.309). In conclusion, our prediction equations can be used as a cardiopulmonary function evaluation tool to estimate VO₂max simply and conveniently using the anthropometric and physiological characteristics of paraplegic men with spinal cord injuries.

Toward a Standardized and Individualized Laboratory-Based Protocol for Wheelchair-Specific Exercise Capacity Testing in Wheelchair Athletes: A Scoping Review

ABSTRACT

Previous studies on handrim wheelchair-specific (an)aerobic exercise capacity in wheelchair athletes have used a diversity of participants, equipment, and protocols. Therefore, test results are difficult to compare among studies. The first aim of this scoping review is to provide an overview of the populations studied, the equipment and protocols used, and the reported outcomes from all laboratory-based studies on wheelchair-specific exercise capacity in wheelchair athletes. The second aim is to synthesize these findings into a standardized, yet individualized protocol. A scoping literature search resulted in 10 anaerobic and 38 aerobic protocols. A large variety in equipment, protocol design, and reported outcomes was found. Studies that systematically investigated the influence of protocol features are lacking, which makes it difficult to interpret and compare test outcomes among the heterogeneous group of wheelchair athletes. Protocol design was often dependent on a priori participant knowledge. However, specific guidelines for individualization were missing. However, the common protocol features of the different studies were united into guidelines that could be followed when performing standardized and individualized wheelchair-specific exercise capacity tests in wheelchair athletes. Together with guidelines regarding reporting of participant characteristics, used equipment, and outcome measures, we hope to work toward more international agreement in future testing.

Peak oxygen uptake in sportsmen with spinal cord injury: importance of body composition

BACKGROUND

Although peak oxygen uptake (VO<inf>2peak</inf>) is considered the most useful index of functional capacity, it's difficult to interpret the results of cardiopulmonary exercise testing (CPET) in individuals with spinal cord injury (SCI). In fact, VO<inf>2peak</inf> is usually normalized for total body weight, but body composition in persons with SCI largely varies depending on physical activity and time since injury, with a progressive loss of fat-free mass (FFM). This can lead to a misinterpretation of the cardiopulmonary fitness in this population.

AIM

Our study proposes a methodology of evaluation, based on bioelectrical impedance analysis (BIA), which could provide more individualized and accurate data in sportsmen with SCI.

DESIGN

Case-control study.

POPULATION

Ambulatory patients at the Sports Medicine Unit of the IRCCS A. Gemelli University Polyclinic Foundation, Rome, Italy.

METHODS

Comparison of data derived from BIA, echocardiography and CPET between 10 male sportsmen with complete, high SCI (group T) and 10 able-bodied controls (group C).

RESULTS

Mean VO<inf>2peak</inf>, weight-normalized VO<inf>2peak</inf>, fat-free mass (FFM)-normalized VO<inf>2peak</inf> and body cellular mass (BCM)-normalized values were significantly lower in group T. At the same heart rate (on average the 55% of the maximal theoretical for age), mean of absolute VO<inf>2</inf>, weight-normalized VO<inf>2</inf> and FFM-normalized VO<inf>2</inf> were still significantly lower in group T. Considering the BCM-normalized VO<inf>2</inf>, the group T showed greater values than controls, 39.4±7.8 vs. 31.1±8.5 mL/kg/min.

CONCLUSIONS

Body composition is a crucial factor for properly interpreting a CPET in individuals with SCI. In particular, normalization of VO<inf>2peak</inf> values for the BCM seems the most reliable tool to assess the real functional capacity in this population.

CLINICAL REHABILITATION IMPACT

A more accurate definition of the aerobic power and functional capacity of people with SCI can improve the monitoring of rehabilitations protocols and physical exercise in this population.

Assessment of mitochondrial respiratory capacity using minimally invasive and noninvasive techniques in persons with spinal cord injury

Purpose

Muscle biopsies are the gold standard to assess mitochondrial respiration; however, biopsies are not always a feasible approach in persons with spinal cord injury (SCI). Peripheral blood mononuclear cells (PBMCs) and near-infrared spectroscopy (NIRS) may alternatively be predictive of mitochondrial respiration. The purpose of the study was to evaluate whether mitochondrial respiration of PBMCs and NIRS are predictive of respiration of permeabilized muscle fibers after SCI.

Methods

Twenty-two individuals with chronic complete and incomplete motor SCI between 18–65 years old were recruited to participate in the current trial. Using high-resolution respirometry, mitochondrial respiratory capacity was measured for PBMCs and muscle fibers of the vastus lateralis oxidizing complex I, II, and IV substrates. NIRS was used to assess mitochondrial capacity of the vastus lateralis with serial cuff occlusions and electrical stimulation.

Results

Positive relationships were observed between PBMC and permeabilized muscle fibers for mitochondrial complex IV (r = 0.86, P < 0.0001). Bland-Altman displayed agreement for complex IV (MD = 0.18, LOA = -0.86 to 1.21), between PBMCs and permeabilized muscles fibers. No significant relationships were observed between NIRS mitochondrial capacity and respiration in permeabilized muscle fibers.

Conclusions

This is the first study to explore and support the agreement of less invasive clinical techniques for assessing mitochondrial respiratory capacity in individuals with SCI. The findings will assist in the application of PBMCs as a viable alternative for assessing mitochondrial health in persons with SCI in future clinical studies.

The Relationship Between Athletic Performance and Physiological Characteristics in Wheelchair Basketball Athletes

Purpose: This study was aimed to investigate the relationship between athletic performance and physiological characteristics in wheelchair basketball (WB) athletes with different classification scores. Methods: Twenty-six (24 male and 2 female) WB athletes were involved into the study. The participants were divided into two functional categories (Category A:1.0-2.5 points, category B: 3.0-4.5 points) according to the IWBF rules. Shoulder internal (IR) and external rotation (ER) muscle strengths were evaluated with the ISOMED 2000® isokinetic dynamometer. Handgrip strength was evaluated with hydraulic hand dynamometer. Custom ramp protocol on treadmill was employed to measure aerobic capacity. Anaerobic capacity was evaluated with Wingate anaerobic power test in standard laboratory conditions. The athletic performance was assessed by 20 m Sprint test, Slalom Test, and Zone Shot tests. Results: Category B athletes achieved significantly better results in the measurements of shoulder IR and ER muscle strength, aerobic and anaerobic capacity, and athletic performance while the grip strength was found similar in the categories. There was a significant correlation between the athletic performance and shoulder IR and ER muscle strength, and aerobic and anaerobic capacities in two categories. There was no significant relationship between grip strength and athletic performance parameters in two categories. Conclusion: It was concluded that athletic performance in WB athletes with different classification scores is related to upper extremity muscle strength, aerobic, and anaerobic capacity. Additionally, upper limb muscle strength, athletic performance, aerobic and anaerobic capacity assessments to be made will contribute positively to the planning of individual training and exercise programs.

Construct validation of the leisure time physical activity questionnaire for people with SCI (LTPAQ-SCI)

STUDY DESIGN

Cross-sectional construct validation study.

OBJECTIVES

To test the construct validity of the Leisure Time Physical Activity Questionnaire for People with Spinal Cord Injury (LTPAQ-SCI) by examining associations between the scale responses and cardiorespiratory fitness (CRF) in a sample of adults living with spinal cord injury (SCI).

SETTING

Three university-based laboratories in Canada.

METHODS

Participants were 39 adults (74% male; M age: 42 ± 11 years) with SCI who completed the LTPAQ-SCI and a graded exercise test to volitional exhaustion using an arm-crank ergometer. One-tailed Pearson's correlation coefficients were computed to examine the association between the LTPAQ-SCI measures of mild-, moderate-, heavy-intensity and total minutes per week of LTPA and CRF (peak volume of oxygen consumption [V̇O_2peak] and peak power output [PO_peak]).

RESULTS

Minutes per week of mild-, moderate- and heavy-intensity LTPA and total LTPA were all positively correlated with V̇O_2peak. The correlation between minutes per week of mild intensity LTPA and V̇O_2peak was small-medium (r = 0.231, p = 0.079) while all other correlations were medium-large (rs ranged from 0.276 to 0.443, ps < 0.05). Correlations between the LTPAQ-SCI variables and PO_peak were also positive but small (rs ranged from 0.087 to 0.193, ps > 0.05), except for a medium-sized correlation between heavy-intensity LTPA and PO_peak (r = 0.294, p = 0.035).

CONCLUSIONS

People with SCI who report higher levels of LTPA on the LTPAQ-SCI also demonstrate greater levels of CRF, with stronger associations between moderate- and heavy-intensity LTPA and CRF than between mild-intensity LTPA and CRF. These results provide further support for the construct validity of the LTPAQ-SCI as a measure of LTPA among people with SCI.

Comparison of the 6-Min Propulsion and Arm Crank Ergometer Tests to Assess Aerobic Fitness in Manual Wheelchair Users With a Spinal Cord Injury

OBJECTIVE

The 6-Min Manual Wheelchair Propulsion Test is proposed to easily and rapidly assess aerobic fitness among long-term (≥3 mos) manual wheelchair users with spinal cord injury. However, aerobic responses to this test have not been established. This study aimed (1) to characterize aerobic responses during the 6-Min Manual Wheelchair Propulsion Test, (2) to establish parallel reliability between the 6-Min Manual Wheelchair Propulsion Test and the Maximal Arm Crank Ergometer Test, and (3) to quantify the strength of association between the total distance traveled during the 6-Min Manual Wheelchair Propulsion Test and peak oxygen consumption.

DESIGN

Twenty manual wheelchair users with a spinal cord injury completed both tests. Aerobic parameters were measured before, during, and after the tests. Main outcome measures were peak oxygen consumption and total distance traveled.

RESULTS

Progressive cardiorespiratory responses, consistent with guidelines for exercise testing, were observed during both tests. Similar peak oxygen consumption values were obtained during both tests (6-Min Manual Wheelchair Propulsion Test: 20.2 ± 4.9 ml/kg·min; Maximal Arm Crank Ergometer Test: 20.4 ± 5.0 ml/kg·min), were highly correlated (r = 0.92, P < 0.001), and had a good agreement (mean absolute difference = 0.21, 95% confidence interval = -0.70 to 1.11, P = 0.639). The peak oxygen consumption and total distance traveled (mean = 636.6 ± 56.9 m) during the 6-Min Manual Wheelchair Propulsion Test were highly correlated (r = 0.74, P < 0.001).

CONCLUSIONS

The 6-Min Manual Wheelchair Propulsion Test induces progressive aerobic responses consistent with guidelines for exercise testing and can be used to efficiently estimate aerobic fitness in manual wheelchair users with a spinal cord injury.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Explain how to administer the Six-Minute Manual Wheelchair Propulsion Test in long-term manual wheelchair users with a spinal cord injury; (2) Contrast how the workload is developed between the Six-Minute Manual Wheelchair Propulsion Test and the Maximal Arm Crank Ergometry Test and recognize how these differences may affect physiological responses; and (3) Explain why caution is advised regarding the use of the Six-Minute Manual Wheelchair Propulsion Test if aiming to estimate aerobic fitness.

LEVEL

Advanced ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Peak oxygen uptake measured during a perceptually-regulated exercise test is reliable in community-based manual wheelchair users

This study compares test-retest reliability and peak exercise responses from ramp-incremented (RAMP) and maximal perceptually-regulated (PRET_max) exercise tests during arm crank exercise in individuals reliant on manual wheelchair propulsion (MWP). Ten untrained participants completed four trials over 2-weeks (two RAMP (0-40 W + 5-10 W · min^-1) trials and two PRET_max. PRET_max consisted of five, 2-min stages performed at Ratings of Perceived Exertion (RPE) 11, 13, 15, 17 and 20). Participants freely changed the power output to match the required RPE. Gas exchange variables, heart rate, power output, RPE and affect were determined throughout trials. The V̇O_2peak from RAMP (14.8 ± 5.5 ml · kg^-1 · min^-1) and PRET_max (13.9 ± 5.2 ml · kg^-1 · min^-1) trials were not different (P = 0.08). Measurement error was 1.7 and 2.2 ml · kg^-1 · min^-1 and coefficient of variation 5.9% and 8.1% for measuring V̇O_2peak from RAMP and PRET_max, respectively. Affect was more positive at RPE 13 (P = 0.02), 15 (P = 0.01) and 17 (P = 0.01) during PRET_max. Findings suggest that PRET_max can be used to measure V̇O_2peak in participants reliant on MWP and leads to a more positive affective response compared to RAMP.

Energy Expenditure as a Function of Activity Level After Spinal Cord Injury: The Need for Tetraplegia-Specific Energy Balance Guidelines

The World Health Organization recognizes obesity as a global and increasing problem for the general population. Because of their reduced physical functioning, people with spinal cord injury (SCI) face additional challenges for maintaining an appropriate whole body energy balance, and the majority with SCI are overweight or obese. SCI also reduces exercise capacity, particularly in those with higher-level injury (tetraplegia). Tetraplegia-specific caloric energy expenditure (EE) data is scarce. Therefore, we measured resting and exercise-based energy expenditure in participants with tetraplegia and explored the accuracy of general population-based energy use predictors. Body composition and resting energy expenditure (REE) were measured in 25 adults with tetraplegia (C4/5 to C8) and in a sex-age-height matched group. Oxygen uptake, carbon dioxide production, heart rate, perceived exertion, and exercise intensity were also measured in 125 steady state exercise trials. Those with motor-complete tetraplegia, but not controls, had measured REE lower than predicted (mean = 22% less, p < 0.0001). REE was also lower than controls when expressed per kilogram of lean mass. Nine had REE below 1200 kcal/day. We developed a graphic compendium of steady state EE during arm ergometry, wheeling, and hand-cycling. This compendium is in a format that can be used by persons with tetraplegia for exercise prescription (calories, at known absolute intensities). EE was low (55–450 kcal/h) at the intensities participants with tetraplegia were capable of maintaining. If people with tetraplegia followed SCI-specific activity guidelines (220 min/week) at the median intensities we measured, they would expend 563–1031 kcal/week. Participants with tetraplegia would therefore require significant time (4 to over 20 h) to meet a weekly 2000 kcal exercise target. We estimated total daily EE for a range of activity levels in tetraplegia and compared them to predicted values for the general population. Our analysis indicated that the EE values for sedentary through moderate levels of activity in tetraplegia fall well below predicted sedentary levels of activity for the general population. These findings help explain sub-optimal responses to exercise interventions after tetraplegia, and support the need to develop tetraplegia-specific energy-balance guidelines that reflects their unique EE situation.