Modeling Perceived Exertion during Graded Arm Cycling Exercise in Spinal Cord Injury

Myoelectric, Myo-Oxygenation, and Myotonometry Changes during Robot-Assisted Bilateral Arm Exercises with Varying Resistances

Robot-assisted bilateral arm training has demonstrated its effectiveness in improving motor function in individuals post-stroke, showing significant enhancements with increased repetitions. However, prolonged training sessions may lead to both mental and muscle fatigue. We conducted two types of robot-assisted bimanual wrist exercises on 16 healthy adults, separated by one week: long-duration, low-resistance workouts and short-duration, high-resistance exercises. Various measures, including surface electromyograms, near-infrared spectroscopy, heart rate, and the Borg Rating of Perceived Exertion scale, were employed to assess fatigue levels and the impacts of exercise intensity. High-resistance exercise resulted in a more pronounced decline in electromyogram median frequency and recruited a greater amount of hemoglobin, indicating increased muscle fatigue and a higher metabolic demand to cope with the intensified workload. Additionally, high-resistance exercise led to increased sympathetic activation and a greater sense of exertion. Conversely, engaging in low-resistance exercises proved beneficial for reducing post-exercise muscle stiffness and enhancing muscle elasticity. Choosing a low-resistance setting for robot-assisted wrist movements offers advantages by alleviating mental and physiological loads. The reduced training intensity can be further optimized by enabling extended exercise periods while maintaining an approximate dosage compared to high-resistance exercises.

Multidimensionality of leisure-time physical activity behaviour in adults with spinal cord injury: implications for measurement

The Physical Activity Recall Assessment for People with SCI (PARA-SCI) has demonstrated the best test-retest reliability and validity of self-report measures of leisure-time physical activity (LTPA) for adults with SCI. However, the absence of internal consistency reliability data has been raised as a concern. Internal consistency is relevant only for unidimensional measures. In other populations, LTPA is known to be a multidimensional construct, evaluated with multidimensional measures. We tested for unidimensionality through secondary analysis of PARA-SCI data (n = 703). Cronbach's α was 0.227. Principal components analysis showed two components/dimensions ('Moderate and Heavy Intensity LTPA' and 'Mild Intensity LTPA') explained 73% of the variance. Binary logic crosstabulation produced no discernible patterns of behavioural interrelatedness across LTPA intensities. Together, these data demonstrate the multidimensionality of LTPA and the PARA-SCI is not unidimensional. Internal consistency should not be a criterion for evaluating LTPA questionnaires for use in studies of people with SCI.

A Physiological Anchor for the Perception of Effort

This is a two-part study to determine one or more reliable physiological anchors for perception of effort. The purpose of Study 1 was to compare ratings of perceived exertion (RPE) at the ventilatory threshold (VT) in running, cycling, and upper body exercise with the premise that if RPE at VT did not differ across exercise modes, VT might provide a unique set of physiological inputs for perception of effort. For 27 participants, values for VT and for RPE at VT (Borg 6 to 20 scale) averaged 9.4 km⋅h^-1 (SD = 0.7) and 11.9 km⋅h^-1 (SD = 1.4) respectively in running, 135 W (SD = 24) and 12.1 W (SD = 1.6) in cycling, and 46 W (SD = 5) and 12.0 W (SD = 1.7) in upper body exercise. RPE did not differ, suggesting that VT may anchor effort perception. In Study 2, 10 participants performed cycle ergometer exercise for 30 minutes at their VT (M = 101 W, SD = 21), at their maximal lactate steady state (M = 143 W, SD = 22), and at their critical power (CP; M = 167 W, SD = 23). Mean end-exercise RPE were 12.1 (SD = 2.1), 15.0 (SD = 1.9), and 19.0 (SD = 0.5), respectively. The very close clustering of RPE during exercise at CP hints that the confluence of physiological responses at CP may (also) serve as a determinant in perception of effort.

Perception of effort and the allocation of physical resources: A generalization to upper-limb motor tasks

Purpose

The perception of effort (PE) is widely used to prescribe and monitor exercise during locomotor and resistance tasks. The present study examines the validity of PE to prescribe and monitor exercise during upper-limb motor tasks under various loads and speed requirements.

Methods

Forty participants volunteered in two experiments. In experiment 1, we used four PE intensities to prescribe exercise on a modified version of the box and block test (BBT) and a pointing task. We investigated the possibility of monitoring the exercise intensity by tracking changes in PE rating in response to three different tempos or additional weights. Experiment 2 replicated the possibility of prescribing the exercise with the PE intensity during the BBT and explored the impact of additional weights on performance and PE during the standardized version of the BBT. Muscle activation, heart rate, and respiratory frequencies were recorded.

Results

In experiment 1, increasing the PE intensity to prescribe exercise induced an increased performance between each intensity. Increasing task difficulty with faster movement tempo and adding weight on the forearm increased the rating of PE. Experiment 2 replicated the possibility to use PE intensity for exercise prescription during the BBT. When completing the BBT with an additional weight on the forearm, participants maintained performance at the cost of a higher PE. In both experiments, changes in PE were associated with changes in muscle activation.

Conclusion

Our results suggest that PE is a valid tool to prescribe and monitor exercise during upper-limb motor tasks.

Applying ubiquitous sensing to estimate perceived exertion based on cardiorespiratory features

Reliable monitoring of one’s response to exercise intensity is imperative to effectively plan and manage training, but not always practical in impact sports settings. This study aimed to evaluate if an inexpensive mobile cardio-respiratory monitoring system can achieve similar performance to a metabolic cart in estimating rated perceived exertion. Eight adult men volunteered to perform treadmill tests under different conditions. Cardiorespiratory data were collected using a metabolic cart and an instrumented oral-cavity device, as well as their ratings of perceived exertion. Pearson correlation corrected for repeated measurements and stepwise regression analysis were used to observe the relationship between the cardiorespiratory features and the ratings of perceived exertion and determine the proportion of the variance of exertion that could be explained by the measurements. Minute ventilation was found to be the most associated variable to perceived exertion, closely followed by a novel metric called the audio minute volume, which can be collected by the oral-cavity device. A generalised linear model combining minute ventilation, audio minute volume, heart rate and respiration rate accounted for 64% of the variance in perceived exertion, whilst a model with only audio minute volume accounted for 56%. Our study indicates that minute ventilation is key to estimating perceived exertion during indoor running exercises. Audio minute volume was also observed to perform comparably to a lab-based metabolic cart in estimating perceived exertion. This research indicates that mobile techniques offer the potential for real-world data collection of an athlete’s physiological load and estimation of perceived exertion.

Changes to Biceps and Supraspinatus Tendons in Response to a Progressive Maximal Treadmill-Based Propulsion Aerobic Fitness Test in Manual Wheelchair Users: A Quantitative Musculoskeletal Ultrasound Study

Objective

To investigate if the completion of a recently developed treadmill-based wheelchair propulsion maximal progressive workload incremental test alters the integrity of the long head of the biceps and supraspinatus tendons using musculoskeletal ultrasound imaging biomarkers.

Method

Fifteen manual wheelchair users completed the incremental test. Ultrasound images of the long head of the biceps and supraspinatus tendons were recorded before, immediately after, and 48 hours after the completion of the test using a standardized protocol. Geometric, composition, and texture-related ultrasound biomarkers characterized tendon integrity.

Results

Participants propelled during 10.2 ± 2.9 minutes with the majority (N = 13/15) having reached at least the eighth stage of the test (speed = 0.8 m/s; slope = 3.6°). All ultrasound biomarkers characterizing tendon integrity, measured in the longitudinal and transversal planes for both tendons, were similar (p = 0.063 to 1.000) across measurement times.

Conclusion

The performance of the motorized treadmill wheelchair propulsion test to assess aerobic fitness produced no changes to ultrasound biomarkers of the biceps or supraspinatus tendons. Hence, there was no ultrasound imaging evidence of a maladaptive response due to overstimulation in these tendons immediately after and 48 hours after the performance of the test.

Intensity of usual care physical therapy during inpatient rehabilitation for people with neurologic diagnoses

BACKGROUND

Early, intense rehabilitation is essential to promote recovery after stroke, spinal cord injury (SCI), and traumatic brain injury (TBI). However, intensity of usual care rehabilitation interventions during inpatient rehabilitation are poorly characterized.

OBJECTIVE

To describe the intensity of usual care rehabilitation interventions completed during the subacute phase of recovery from neurologic injury.

DESIGN

Observational.

SETTING

Inpatient rehabilitation facility.

INTERVENTIONS

Twenty-two usual care physical therapy interventions were grouped into six categories: gait (four activities), functional (two), strengthening (four), aerobic (six), balance (four), and wheelchair (two).

PATIENTS

Patients admitted to inpatient rehabilitation with a primary diagnosis of stroke, SCI or TBI within 6 months of injury.

MAIN OUTCOME MEASURE(S)

Cardiovascular intensity (physiological and perceived) was recorded during rehabilitation activity sessions. Physiological intensity was assessed by heart rate reserve (HRR) via a Polar A370 Fitness Watch and characterized as very light (<30%), light (30-39%), moderate (40-59%), vigorous (60-89%), and near maximal (≥90%). Perceived intensity was assessed using the Rating of Perceived Exertion scale.

RESULTS

Patients (stroke n = 16 [number of activity sessions = 388/average session duration = 15.1 min]; SCI n = 15 [299/27.3 min]; TBI n = 15 [340/13.4 min]) participated. For patients with stroke, moderate-to-vigorous HRR was attained between 42% (aerobic exercise) to 55% (wheelchair propulsion) of activity sessions. For patients with SCI, moderate-to-vigorous HRR was attained between 29% (strength training) to 46% (gait training) of activity sessions. For patients with TBI, moderate-to-vigorous HRR was attained between 29% (balance activities) to 47% (gait training) of activity sessions. Associations between HRR and rate of perceived exertion were very weak across stroke (r = 0.12), SCI (r = 0.18), and TBI (r = 0.27).

CONCLUSIONS

Patients with stroke, SCI, and TBI undergoing inpatient rehabilitation achieve moderate-to-vigorous intensity during some usual care activities such as gait training. Patient perception of intensity was dissimilar to physiological response.

Comparison of two Borg exertion scales for monitoring exercise intensity in able-bodied participants, and those with paraplegia and tetraplegia

STUDY DESIGN

Cross-sectional cohort study.

OBJECTIVES

To compare ratings of perceived exertion (RPE) on Borg's 6-20 RPE scale and Category Ratio 10 (CR10) in able-bodied (AB) participants during upper and lower body exercise, and recreationally active participants with paraplegia (PARA) and athletes with tetraplegia (TETRA) during upper body exercise only.

SETTING

University and rehabilitation centre-based laboratories in UK and Netherlands.

METHODS

Twenty-four participants were equally split between AB, PARA, and TETRA. AB performed maximal tests using cycle (AB-CYC) and handcycle (AB-HC) ergometry. PARA and TETRA performed maximal handcycle and wheelchair propulsion tests, respectively. Oxygen uptake (V̇O₂) and blood lactate concentration were monitored throughout. RPE was rated each stage on Borg's RPE scale and CR10. Thresholds were identified according to log-V̇O₂ plotted against log-blood lactate (LT₁), and 1.5 mmol L^-1 greater than LT₁ (LT₂).

RESULTS

RPE from both scales were best fit against each other using a quadratic model, with high goodness of fit between scales that was independent of exercise mode and participant group (range R²: 0.965-0.970, P < 0.005). Though percentage peak V̇O₂ was significantly greater in TETRA (P < 0.005), there was no difference in RPE at LT₁ or LT₂ between groups on Borg's RPE scale or CR10.

CONCLUSION

Strong association between Borg's RPE scale and CR10 suggests they can be used interchangeably. RPE at lactate thresholds were independent of mode of exercise and level of spinal cord injury. However, inter-individual variation precludes from making firm recommendations about using RPE for prescribing homogenous exercise intensity.

Effect of wheelchair-modified rowing exercise on cardiometabolic risk factors in spinal cord injured wheelchair users: protocol for a randomised controlled trial

INTRODUCTION

Cardiovascular and metabolic diseases are a growing concern for individuals with spinal cord injury (SCI). Physical inactivity contributes to cardiometabolic morbidity and mortality in the SCI population. However, previous studies have shown mixed results regarding the effects of exercise on cardiometabolic risk factors in individuals with SCI. This discrepancy could be influenced by insufficient exercise stimuli. Recent guidelines recommend 30 min of moderate-to-vigorous intensity aerobic exercise, three times per week, for improvement in cardiometabolic health in individuals with SCI. However, to date, no studies have implemented an exercise intervention matching the new recommendations to examine the effects on cardiometabolic risk factors. Therefore, the primary objective of this study is to determine the effects of 12 weeks of wheelchair user-modified upper-body rowing exercise on both traditional (constituents of the metabolic syndrome) and novel (eg, vascular structure and function) cardiometabolic risk factors in manual wheelchair users with SCI.

METHODS AND ANALYSIS

A randomised controlled trial will compare 12 weeks of upper-body rowing exercise, 30 min three times per week, with a control group continuing their normal lifestyle. Outcome measurements will be performed immediately before (baseline), after 6 weeks (halfway), 12 weeks of training (post) and 6 months after the termination of the intervention period (follow-up). Outcomes will include inflammatory (eg, C reactive protein) and metabolic biomarkers determined from venous blood (with serum fasting insulin as primary outcome), body composition, arterial blood pressure, cardiorespiratory fitness level, brachial artery vascular structure and function and autonomic nervous system function.

ETHICS AND DISSEMINATION

This trial is reported to the Danish Data Protection Agency (J.nr. 2019-899/10-0406) and approved by the Committees on Health Research Ethics in The North Denmark Region on 12 December 2019 (J.nr. N-20190053). The principal investigator will collect written informed consent from all participants prior to inclusion. Irrespective of study outcomes, the results will be submitted to peer-reviewed scientific journals for publication.

TRIAL REGISTRATION NUMBER

NCT04390087.

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.

Intensity of physical activity as a percentage of peak oxygen uptake, heart rate and Borg RPE in motor-complete para- and tetraplegia

Objective

The aims were to describe VO_2peak, explore the potential influence of anthropometrics, demographics and level of physical activity within each cohort; b) to define common, standardized activities as percentages of VO_2peak and categorize these as light, moderate and vigorous intensity levels according to present classification systems, and c) to explore how clinically accessible methods such as heart-rate monitoring and Borg rating of perceived exertion (RPE) correlate or can describe light, moderate and vigorous intensity levels.

Design

Cross sectional.

Setting

Rehabilitation facility and laboratory environment.

Subjects

Sixty-three individuals, thirty-seven (10 women) with motor-complete paraplegia (MCP), T7-T12, and twenty-six (7 women) with motor-complete tetraplegia (MCT), C5-C8.

Interventions

VO_2peak was obtained during a graded peak test until exhaustion, and oxygen uptake during eleven different activities was assessed and categorized using indirect calorimetry.

Main outcome measures

VO_2peak, Absolute and relative oxygen consumption, Borg RPE.

Results

Absolute VO_2peak was significantly higher in men than in women for both groups, with fairly small differences in relative VO_2peak. For MCP sex, weight and time spent in vigorous-intensity activity explained 63% of VO_2peak variance. For MCT sex and time in vigorous-intensity activity explained 55% of the variance. Moderate intensity corresponds to 61–72% HR_peak and RPE 10–13 for MCP vs. 71–79% HR_peak, RPE 13–14 for MCT.

Conclusion

Using current classification systems, eleven commonly performed activities were categorized in relative intensity terms, (light, moderate and vigorous) based on percent of VO_2peak, HR_peak and Borg RPE. This categorization enables clinicians to better guide persons with SCI to meet required physical activity levels.

Perceived exertion responses to wheelchair propulsion differ between novice able-bodied and trained wheelchair sportspeople

OBJECTIVES

To investigate peripheral (RPE_P) and central (RPE_C) Ratings of Perceived Exertion during wheelchair propulsion in untrained able-bodied (AB) participants, and trained wheelchair rugby athletes with and without cervical spinal cord injury (CSCI).

DESIGN

Cross-sectional study.

METHODS

38 participants (AB: n=20; wheelchair rugby athletes with CSCI: n=9; without CSCI: n=9) completed an incremental wheelchair propulsion test to exhaustion on a motorised treadmill. Gas exchange measures and heart rate (HR) were collected throughout. RPE_P and RPE_C on the Category Ratio-10 were verbally recorded each minute. Blood lactate concentration ([BLa]) was determined post-test.

RESULTS

Between 50-100% peak oxygen uptake (V̇O_2peak), RPE_P was greater than RPE_C in AB (p<0.05), but not in athletes with (p=0.07) or without (p=0.16) CSCI. RPE_P was greater in AB compared to players with CSCI (Effect sizes: 1.24-1.62), as were respiratory exchange ratio (1.02±0.10 vs 0.82±0.11, p<0.05) and [BLa]_peak (7.98±2.53 vs 4.66±1.57mmol·L^-1). RPE_C was greater in athletes without CSCI compared to those with CSCI (Effect sizes: 0.70-1.38), as were HR (166±20 vs 104±15 beats·min^-1, p<0.05) and ventilation (59.2±28.8 vs 35.1±16.6L·min^-1, p=0.01).

CONCLUSIONS

RPE_P was dominant over RPE_C during wheelchair propulsion for untrained AB participants. For athletes with CSCI, lower RPE_P and RPE_C were reported at the same %V̇O_2peak compared to those without CSCI. The mechanism for this remains to be fully elucidated.

Perceptually regulated training does not influence the differentiated RPE response following 16-weeks of aerobic exercise in adults with spinal cord injury

This study investigated the effect of prolonged familiarisation with ratings of perceived exertion (RPE) on the peripheral (RPE_P) and central (RPE_C) RPE responses to moderate-vigorous exercise in adults with spinal cord injury (SCI). RPE_P and RPE_C characterise the exertion of the working musculature and cardiorespiratory systems, respectively. Nineteen participants (age, 41.4 ± 11.4 years; peak oxygen uptake, 19.2 ± 7.2 mL·kg^-1·min^-1) with chronic SCI were randomly assigned to RPE-guided (n = 11; EXP) or active control (n = 8; CON) groups. EXP performed 16-weeks of RPE-guided, supervised aerobic training for 20 min, twice weekly, at RPE 3-6 (Category-Ratio 10 scale). CON had access to the same exercise equipment but received no specific advice on their exercise-training regime. Participants completed a graded exercise test, using an arm crank ergometer at pre- and post-training to determine peak oxygen uptake, with RPE_P and RPE_C recorded every minute throughout tests. Sixteen weeks training did not improve peak oxygen uptake. RPE decreased post-training at 50% (p = 0.02) and 70% peak oxygen uptake (p = 0.03), though there was no effect of group at either intensity (p = 0.54, 0.42, respectively). At 70% peak oxygen uptake, RPE_P was greater than RPE_C (4.2 ± 1.7 vs 3.4 ± 1.8, p < 0.005). Training with RPE-guidance for 16 weeks had no additional effect on the differentiated RPE responses to moderate-vigorous exercise in adults with SCI. Novelty In adults with SCI, differentiated RPE responses were not different between those who did, and did not, perform 16 weeks of RPE-guided training. This challenges whether familiarisation with RPE is necessary to be an effective regulator of exercise intensity in this population.

Fatigability during volitional walking in incomplete spinal cord injury: cardiorespiratory and motor performance considerations

Fatigability describes the decline in force production (i.e., performance fatigability) and/or changes in sensations regulating performance (i.e., perceived fatigability) during whole-body activity and poses a major challenge to those living with spinal cord injuries (SCI). After SCI, the inability to overcome disruptions to metabolic homeostasis due to cardiorespiratory limitations and physical deconditioning may contribute to increased fatigability severity. The increased susceptibility to fatigability may have implications for motor control strategies and motor learning. Locomotor training approaches designed to reduce fatigability and enhance aerobic capacity in combination with motor learning may be advantageous for promoting functional recovery after SCI. Future research is required to advance the understanding of the relationship between fatigability, cardiorespiratory function and motor performance following SCI.

Assessment of Whole Body and Local Muscle Fatigue Using Electromyography and a Perceived Exertion Scale for Squat Lifting

This research study aims at addressing the paradigm of whole body fatigue and local muscle fatigue detection for squat lifting. For this purpose, a comparison was made between perceived exertion with the heart rate and normalized mean power frequency (NMPF) of eight major muscles. The sample consisted of 25 healthy males (age: 30 ± 2.2 years). Borg’s CR-10 scale was used for perceived exertion for two segments of the body (lower and upper) and the whole body. The lower extremity of the body was observed to be dominant compared to the upper and whole body in perceived response. First mode of principal component analysis (PCA) was obtained through the covariance matrix for the eight muscles for 25 subjects for NMPF of eight muscles. The diagonal entries in the covariance matrix were observed for each muscle. The muscle with the highest absolute magnitude was observed across all the 25 subjects. The medial deltoid and the rectus femoris muscles were observed to have the highest frequency for each PCA across 25 subjects. The rectus femoris, having the highest counts in all subjects, validated that the lower extremity dominates the sense of whole body fatigue during squat lifting. The findings revealed that it is significant to take into account the relation between perceived and measured effort that can help prevent musculoskeletal disorders in repetitive occupational tasks.