Cardiorespiratory fitness in persons with lower limb amputation

The aim of this study is to gain insight in the cardiorespiratory fitness of persons with lower limb amputation (LLA) during rehabilitation, and in potential factors influencing their cardiorespiratory fitness. We performed a retrospective cohort study using data from cardiopulmonary exercise tests. Included participants were adults with LLA. Main outcome was cardiorespiratory fitness expressed as O 2 peak (ml/min/kg) and was directly determined using breath-by-breath gas analysis. O 2 peak was compared to reference values for able-bodied controls. Multivariate regression analysis was performed to investigate potential factors related to O 2 peak in persons with LLA. Potential factors were age, BMI adjusted, gender, level of amputation, aetiology of amputation, unilateral/bilateral, type of ergometry and use of beta blockers. Data of 74 participants with LLA are presented; 84% male (n = 62), mean age 58.9 (SD 11.6), mean BMI 26.7 (SD 5.6), 44 participants have a LLA above the knee, 30 below the knee. Overall O 2 peak was lower in persons with LLA compared to reference values for able-bodied controls, with mean O 2 peak for the total LLA group of 14.6 ± 4.1 ml/kg/min. In the multivariate regression analysis, only age was a significant predictor for lower O 2 peak (regression coefficient: -0.15, 95% CI [0.23-0.069], r 2  = 0.166). These results indicate that the cardiorespiratory fitness in persons with LLA is low, while they actually need more energy to walk and perform other daily activities. Cardiorespiratory fitness is not closely associated with the analysed demographic or clinical factors and will have to be determined on an individual basis for use in daily practice.

Cardiorespiratory Fitness in Individuals Post-stroke: Reference Values and Determinants

OBJECTIVE

To provide reference values of cardiorespiratory fitness for individuals post-stroke in clinical rehabilitation and to gain insight in characteristics related to cardiorespiratory fitness post stroke.

DESIGN

A retrospective cohort study. Reference equations of cardiopulmonary fitness corrected for age and sex for the fifth, 25th, 50th, 75th, and 95th percentile were constructed with quantile regression analysis. The relation between patient characteristics and cardiorespiratory fitness was determined by linear regression analyses adjusted for sex and age. Multivariate regression models of cardiorespiratory fitness were constructed.

SETTING

Clinical rehabilitation center.

PARTICIPANTS

Individuals post-stroke who performed a cardiopulmonary exercise test as part of clinical rehabilitation between July 2015 and May 2021 (N=405).

MAIN OUTCOME MEASURES

Cardiorespiratory fitness in terms of peak oxygen uptake (V˙O2peak) and oxygen uptake at ventilatory threshold (V˙O2-VT).

RESULTS

References equations for cardiorespiratory fitness stratified by sex and age were provided based on 405 individuals post-stroke. Median V˙O2peak was 17.8[range 8.4-39.6] mL/kg/min and median V˙O2-VT was 9.7[range 5.9-26.6] mL/kg/min. Cardiorespiratory fitness was lower in individuals who were older, women, using beta-blocker medication, and in individuals with a higher body mass index and lower motor ability.

CONCLUSIONS

Population specific reference values of cardiorespiratory fitness for individuals post-stroke corrected for age and sex were presented. These can give individuals post-stroke and health care providers insight in their cardiorespiratory fitness compared with their peers. Furthermore, they can be used to determine the potential necessity for cardiorespiratory fitness training as part of the rehabilitation program for an individual post-stroke to enhance their fitness, functioning and health. Especially, individuals post-stroke with more mobility limitations and beta-blocker use are at a higher risk of low cardiorespiratory fitness.

Relative Aerobic Load of Daily Activities After Stroke

OBJECTIVE

Individuals after stroke are less active, experience more fatigue, and perform activities at a slower pace than peers with no impairments. These problems might be caused by an increased aerobic energy expenditure during daily tasks and a decreased aerobic capacity after stroke. The aim of this study was to quantify relative aerobic load (ie, the ratio between aerobic energy expenditure and aerobic capacity) during daily-life activities after stroke.

METHODS

Seventy-nine individuals after stroke (14 in Functional Ambulation Category [FAC] 3, 25 in FAC 4, and 40 in FAC 5) and 22 peers matched for age, sex, and body mass index performed a maximal exercise test and 5 daily-life activities at a preferred pace for 5 minutes. Aerobic energy expenditure (mL O2/kg/min) and economy (mL O2/kg/unit of distance) were derived from oxygen uptake ($\dot{\mathrm{V}}{\mathrm{O}}_2$). Relative aerobic load was defined as aerobic energy expenditure divided by peak aerobic capacity (%$\dot{\mathrm{V}}{\mathrm{O}}_2$peak) and by $\dot{\mathrm{V}}{\mathrm{o}}_2$ at the ventilatory threshold (%$\dot{\mathrm{V}}{\mathrm{o}}_2$-VT) and compared in individuals after stroke and individuals with no impairments.

RESULTS

Individuals after stroke performed activities at a significantly higher relative aerobic load (39%-82% $\dot{\mathrm{V}}{\mathrm{o}}_2$peak) than peers with no impairments (38%-66% $\dot{\mathrm{V}}{\mathrm{o}}_2$peak), despite moving at a significantly slower pace. Aerobic capacity in individuals after stroke was significantly lower than that in peers with no impairments. Movement was less economical in individuals after stroke than in peers with no impairments.

CONCLUSION

Individuals after stroke experience a high relative aerobic load during cyclic daily-life activities, despite adopting a slower movement pace than peers with no impairments. Perhaps individuals after stroke limit their movement pace to operate at sustainable relative aerobic load levels at the expense of pace and economy.

IMPACT

Improving aerobic capacity through structured aerobic training in a rehabilitation program should be further investigated as a potential intervention to improve mobility and functioning after stroke.

Effects of Handrail and Cane Support on Energy Cost of Walking in People With Different Levels and Causes of Lower Limb Amputation

OBJECTIVE

The energy cost of walking with a lower limb prosthesis is higher than able-bodied walking and depends on both cause and level of amputation. This increase might partly be related to problems with balance control. In this study we investigated to what extent energy cost can be reduced by providing support through a handrail or cane and how this depends on level and cause of amputation.

DESIGN

Quasi-experimental study.

SETTING

Rehabilitation gait laboratory.

PARTICIPANTS

Twenty-six people with a lower limb amputation were included: 9 with vascular and 17 with nonvascular causes, 16 at transtibial, and 10 at transfemoral or knee disarticulation level (N=26).

INTERVENTIONS

Participants walked on a treadmill with and without handrail support and overground with and without a cane.

MAIN OUTCOME MEASURES

Energy cost was assessed using respirometry.

RESULTS

On the treadmill, handrail support resulted in a 6% reduction in energy cost on average. This effect was attributed to an 11% reduction in those with an amputation attributable to vascular causes, whereas the nonvascular group did not show a significant difference. No interaction with level of amputation was found. Overground, no main effect of cane support was found, although an interaction effect with cause of amputation demonstrated a small nonsignificant decrease in energy cost (3%) in the vascular group and a significant increase (6%) in the nonvascular group when walking with a cane. The effect of support was positively correlated with self-selected walking speed.

CONCLUSIONS

This study demonstrates that providing external support can contribute to a reduction in energy cost in people with an amputation due to vascular causes with reduced walking ability while walking in the more challenging condition of the treadmill. Although it is speculated that this effect might be related to problems with balance control, this will need further investigation.

[Exercise capacity after mechanical ventilation because of COVID-19: Cardiopulmonary exercise tests in clinical rehabilitation]

OBJECTIVE

To safely and effectively train the exercise capacity of post-COVID-19 patients it is important to test for cardiopulmonary risk factors and to assess exercise limitations. The goal of this study was to describe the exercise capacity and underlying exercise limitations of mechanically ventilated post-COVID-19 patients in clinical rehabilitation.

DESIGN

A retrospective cohort study.

METHOD

Twenty-four post-COVID-19patients that were mechanically ventilated at ICU and thereafter admitted for clinical rehabilitation performed a symptom-limited cardiopulmonary exercise test (CPET) with breath-by-breath gas-exchange monitoring, ECG-registration, blood pressure- and saturation monitoring. In absence of a primary cardiac or ventilatory exercise limitation patients were considered to be limited primarily by decreased peripheral muscle mass.

RESULTS

Twenty-three patients could perform a maximal exercise test and no adverse events occurred. Cardiorespiratory fitness was very poor with a median peak oxygen uptake of 15.0 [10.1-21.4] mlO2/kg/min (57% of predicted values). However, we observed large differences within the group in both exercise capacity and exercise limitations. While 7/23 patients were primarily limited by ventilatory function, the majority (70%) was limited primarily by the decreased peripheral muscle mass.

CONCLUSION

Cardiorespiratory fitness of post-COVID-19 patients in clinical rehabilitation is strongly deteriorated. The majority of patients seemed primarily limited for exercise by the decreased peripheral muscle mass.

Oxygenation Threshold Derived from Near-Infrared Spectroscopy: Reliability and Its Relationship with the First Ventilatory Threshold

BACKGROUND

Near-infrared spectroscopy (NIRS) measurements of oxygenation reflect O2 delivery and utilization in exercising muscle and may improve detection of a critical exercise threshold.

PURPOSE

First, to detect an oxygenation breakpoint (Δ[O2HbMb-HHbMb]-BP) and compare this breakpoint to ventilatory thresholds during a maximal incremental test across sexes and training status. Second, to assess reproducibility of NIRS signals and exercise thresholds and investigate confounding effects of adipose tissue thickness on NIRS measurements.

METHODS

Forty subjects (10 trained male cyclists, 10 trained female cyclists, 11 endurance trained males and 9 recreationally trained males) performed maximal incremental cycling exercise to determine Δ[O2HbMb-HHbMb]-BP and ventilatory thresholds (VT1 and VT2). Muscle haemoglobin and myoglobin O2 oxygenation ([HHbMb], [O2HbMb], SmO2) was determined in m. vastus lateralis. Δ[O2HbMb-HHbMb]-BP was determined by double linear regression. Trained cyclists performed the maximal incremental test twice to assess reproducibility. Adipose tissue thickness (ATT) was determined by skinfold measurements.

RESULTS

Δ[O2HbMb-HHbMb]-BP was not different from VT1, but only moderately related (r = 0.58-0.63, p<0.001). VT1 was different across sexes and training status, whereas Δ[O2HbMb-HHbMb]-BP differed only across sexes. Reproducibility was high for SmO2 (ICC = 0.69-0.97), Δ[O2HbMb-HHbMb]-BP (ICC = 0.80-0.88) and ventilatory thresholds (ICC = 0.96-0.99). SmO2 at peak exercise and at occlusion were strongly related to adipose tissue thickness (r2 = 0.81, p<0.001; r2 = 0.79, p<0.001). Moreover, ATT was related to asymmetric changes in Δ[HHbMb] and Δ[O2HbMb] during incremental exercise (r = -0.64, p<0.001) and during occlusion (r = -0.50, p<0.05).

CONCLUSION

Although the oxygenation threshold is reproducible and potentially a suitable exercise threshold, VT1 discriminates better across sexes and training status during maximal stepwise incremental exercise. Continuous-wave NIRS measurements are reproducible, but strongly affected by adipose tissue thickness.