Leg Effort Research Articles

Two-day cardiopulmonary exercise testing in long COVID post-exertional malaise diagnosis

BackgroundLong COVID patients present with a myriad of symptoms that can include fatigue, exercise intolerance and post exertional malaise (PEM). Long COVID has been compared to other post viral syndromes, including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), where a reduction in day 2 cardiopulmonary exercise test (CPET) performance of a two-day CPET protocol is suggested to be a result of PEM. We investigated cardiopulmonary and perceptual responses to a two-day CPET protocol in Long COVID patients. Methods15 Long COVID patients [n=7 females; mean (SD) age: 53(11) yr; BMI = 32.2(8.5) kg/m2] performed a pulmonary function test and two ramp-incremental CPETs separated by 24 hr. CPET variables included gas exchange threshold (GET), peak oxygen uptake (V̇O2peak) and peak work rate (WRpeak). Ratings of perceived dyspnoea and leg effort were recorded at peak exercise using the modified 0–10 Borg Scale. PEM (past six months) was assessed using the modified DePaul Symptom Questionnaire (mDSQ). One-sample t-tests were used to test significance of mean difference between days (p<0.05). Results.mDSQ revealed PEM in 80 % of patients. Lung function was normal. Responses to day 1 CPET were consistent with the presence of aerobic deconditioning in 40 % of patients (V̇O2peak <80 % predicted, in the absence of evidence of cardiovascular and pulmonary limitations). There were no differences between day-1 and day-2 CPET responses (all p>0.05). ConclusionPEM symptoms in Long COVID patients, in the absence of differences in two-day CPET responses separated by 24 hours, suggests that PEM is not due to impaired recovery of exercise capacity between days.

Maximum exercise capacity: Barcroft revisited in a large population

RATIONALE In 1973, the first exercise test was performed at McMaster University Medical Center to provide a standardized approach to clinical exercise testing, based on Barcroft’s maxim that the maximum capacity to exercise is “the essence of the machine,” emphasizing integration between different mechanisms. The test was incremental ergometer exercise to symptom limited maximum. Physiologic and symptom measurements were made before and during exercise. 46,288 tests were collected and entered into a dataset; unique both in terms of the large number and the physiologic variables collected (skeletal muscle strength, gas transfer capacity, symptoms). OBJECTIVES The objective of this study was to understand CO2 production in relation to oxygen uptake when exercising to maximum capacity. MEASUREMENTS AND MAIN RESULTS Physiologic factors contributing to maximum exercise capacity (Wmax) were skeletal muscle strength, FEV1 (ventilatory capacity) and DLCO (gas transfer capacity). The response of VCO2 in relation to VO2 (RER) showed a lag in CO2 production (related to CO2 storage), which was longer in subjects with higher maximum exercise capacity. This lag was followed by a progressive increase toward W max that reached a maximum value independent of W max. The perceived intensity of leg effort and dyspnea increased in a positively accelerating manner in parallel with increases in CO2 output. CONCLUSION Maximum power in incremental cycling was symptom limited, dependent on muscle (strength, oxidative capacity), together with FEV1. Previous emphasis on oxygen delivery as limiting exercise, irrespective of clinical diagnosis, may be augmented by the perceptual limitation that accompanies, remarkably symmetrically, the adaptation to CO2 removal maintaining homeostasis in muscle (muscle buffering capacity).

Reference values for leg effort during incremental cycle ergometry in non-trained healthy men and women, aged 19-85.

Heightened sensation of leg effort contributes importantly to poor exercise tolerance in patient populations. We aim to provide a sex- and age-adjusted frame of reference to judge symptom's normalcy across progressively higher exercise intensities during incremental exercise. Two-hundred and seventy-five non-trained subjects (130 men) aged 19-85 prospectively underwent incremental cycle ergometry. After establishing centiles-based norms for Borg leg effort scores (0-10 category-ratio scale) versus work rate, exponential loss function identified the centile that best quantified the symptom's severity individually. Peak O2 uptake and work rate (% predicted) were used to threshold gradually higher symptom intensity categories. Leg effort-work rate increased as a function of age; women typically reported higher scores at a given age, particularly in the younger groups (p < 0.05). For instance, "heavy" (5) scores at the 95th centile were reported at ~200 W (<40 years) and ~90 W (≥70 years) in men versus ~130 W and ~70 W in women, respectively. The following categories of leg effort severity were associated with progressively lower exercise capacity: ≤50th ("mild"), >50th to <75th ("moderate"), ≥75th to <95th ("severe"), and ≥ 95th ("very severe") (p < 0.05). Although most subjects reporting peak scores <5 were in "mild" range, higher scores were not predictive of the other categories (p > 0.05). This novel frame of reference for 0-10 Borg leg effort, which considers its cumulative burden across increasingly higher exercise intensities, might prove valuable to judging symptom's normalcy, quantifying its severity, and assessing the effects of interventions in clinical populations.

Persistent Contralateral Pain Compromises Exercise Tolerance but Does not Alter Corticomotor Responses During Repeated, Submaximal Isometric Knee Extensions to Task Failure

Muscle pain is an important determinant of exercise tolerance, but its relationship with neurophysiological responses during a submaximal exercise trial is unclear. The purpose of this study was to determine the effect of persistent contralateral pain on neurophysiological function and perceptual responses during ipsilateral isometric knee extensions to task failure. Ten participants performed a single-leg repeated submaximal isometric knee extensions with (PAIN) or without (CTRL) constant pain induced by intermittent blood flow occlusion combined with evoked muscle contraction applied to the contralateral, resting leg. Transcranial magnetic stimulation (TMS) applied over the motor cortex was used to assess corticospinal excitability (quantified as motor evoked potentials), corticospinal inhibition (quantified as silent period duration), and short interval intracortical inhibition. Maximal voluntary contractions (MVCs), coupled with femoral nerve stimulation to the exercising leg, were performed every 12 submaximal contractions to assess neuromuscular function. Perceived leg pain and effort were also assessed throughout the exercise. The experimental pain shortened the time to task failure compared to CTRL (P = 0.019). Although time effects were present, no differences appeared between conditions for MVC force, voluntary activation, or potentiated twitch force across both tasks (all P > 0.05). Additionally, no differences between CTRL and PAIN were demonstrated for any TMS-derived measures assessing corticospinal responses. Exercising leg pain was higher in CTRL (P = 0.018), as was perceived exertion (P = 0.030). Overall, when using a persistent, submaximal experimental pain intervention, it appears that although muscle pain compromises exercise tolerance, this phenomenon occurs independently of potential alterations in corticomotor mechanisms.

Respiratory Muscle Interval Training Improves Exercise Capacity in Obese Adolescents during a 3-Week In-Hospital Multidisciplinary Body Weight Reduction Program.

The purpose of this study was to determine whether a novel approach of interval training targeted to the respiratory muscles (RMIT; normocapnic hyperpnea with resistance) in addition to a multidisciplinary in-hospital body weight reduction program (BWRP) was able to improve the integrative response to exercise in young patients with obesity. Nine male patients (17.9 ± 4.9 (x ± SD) years; 113.8 ± 16.3 kg) underwent 12 sessions of RMIT and eight age-and sex-matched patients underwent 12 sessions of a sham protocol (CTRL) during the same 3-week BWRP. Before and after the interventions the patients performed an incremental and a heavy-intensity constant work-rate (CWR>GET) cycling exercise to voluntary exhaustion. Body mass decreased by ~4.0 kg after both RMIT (p = 0.0001) and CTRL (p = 0.0002). Peak pulmonary O2 uptake (V˙O2) increased after RMIT (p = 0.02) and CTRL (p = 0.0007). During CWR>GET at ISO-time, V˙O2 (p = 0.0007), pulmonary ventilation (p = 0.01), heart rate (p = 0.02), perceived respiratory discomfort (RPER; p = 0.03) and leg effort (p = 0.0003) decreased after RMIT; only RPER (p = 0.03) decreased after CTRL. Time to exhaustion increased after RMIT (p = 0.0003) but not after CTRL. In young patients with obesity, RMIT inserted in a 3-week BWRP reduced the cardiorespiratory burden, the metabolic cost, the perceived effort, and improved exercise tolerance during heavy-intensity cycling.

Longitudinal study of physical activity with various methods in maintenance hemodialysis patients.

The purpose was to make longitudinal measurements of physical activity and study whether physical activity decreases over time in maintenance hemodialysis (MHD) patients. This was an observational study, where MHD patients were considered in a 12-month follow-up. Laboratory variables and physical activity were tested three times over 12-months in 124 hemodialysis patients. Physical activity was measured using the Human Activity Profile (HAP), the Stanford 7-day Physical Activity Recall Questionnaire (PAR), and walking speed. Repeated measure variance analysis was used to analyze changes of physical activity. The Bonferroni method was used to do pairwise comparisons. The proportion of decreased physical activity increased (P < 0.05). The maximal activity score (MAS), adjusted activity score (AAS), HAP dimension scores, and walking speed all decreased at the three time points studied (P < 0.001). At the same time, moderate physical activities and PAR values changed at three time points (P < 0.05). Pairwise comparisons showed that between the baseline and the 6-month follow-up, MAS, AAS, the scores of personal/household work, entertainment/social, independent exercise, leg effort, and back effort, all decreased(P < 0.05). Between the baseline and the 12-month follow-up, and between the 6-month follow-up and the 12-month follow-up, all the scores of HAP and walking speed decreased significantly (P < 0.001). Between the baseline and the 6-month follow-up, moderate physical activities and PAR values increased (P < 0.05). However, between the baseline and the 12-month follow-up, and between the 6-month follow-up and the 12-month follow-up, moderate physical activities and PAR did not change statistically. Physical activity decreased in hemodialysis patients in the 12-month follow-up.

The effects of calf massage in boys with Duchenne muscular dystrophy: a prospective interventional study

Purpose We explored the effects of standardized calf massage in ambulant boys with Duchenne muscular dystrophy (DMD) using a prospective study design. Materials and Methods Twenty boys completed two study visits, 1 week apart. At both visits, each leg received a 10-min calf massage (intervention) and a 10-min control rest period (placebo) in randomized order. Muscle length of calf and hamstrings and gastrocnemius stiffness were measured by a blinded assessor before and after intervention and placebo. Measures of gait function (timed 10-m walk/run and spatio-temporal gait parameters); gastrocnemius muscle ultrasound findings; participant perception of leg pain, stiffness and effort of walking and general psychological well-being were also collected. Results Consistent significant small increases in muscle length of soleus, gastrocnemius and hamstrings were recorded post-massage, and gastrocnemius stiffness decreased. Small changes in gastrocnemius and soleus length only were also recorded following the control rest period. Gait function and general well-being remained stable throughout. Measurement across both study visits suggested that gains in muscle length may be cumulative with repeated massage. Conclusions Calf massage is safe and associated with benefits to muscle length and stiffness for ambulant boys with DMD. Implications for Rehabilitation In a small sample of boys with Duchenne muscular dystrophy, calf massage was found to be safe, well-tolerated and associated with increased muscle length and decreased stiffness. The use of massage may assist in managing muscle length in boys with Duchenne muscular dystrophy.

The contribution of FEV1 and airflow limitation on the intensity of dyspnea and leg effort during exercise. Insights from a real-world cohort.

RationaleThe effort required to cycle and breathe intensify as power increases during incremental exercise. It is currently unclear how changes in FEV1 in the presence or absence of airflow limitation) impacts the intensity of dyspnea and leg effort. This is clinically important as the improvement in FEV1 is often the target for improving dyspnea.ObjectivesTo investigate the relationship between dyspnea (D), leg effort, power (P), and FEV1 with and without airflow limitation using direct psychophysical scaling performed during incremental exercise testing to symptom limited capacity.MethodsRetrospective analysis of consecutive patients over the age of 35 referred for cardio‐pulmonary exercise testing at McMaster University Medical Centre from 1988–2012.The modified Borg scale was used to measure dyspnea throughout incremental exercise testing.Measurements and results38,788 patients were included in the analysis [Mean Age 58.6 years (SD ±11.8), Males 61%, BMI 28.1 kg/m2 (SD ±5.1), FEV1 was 2.7 L (SD ±0.85), 95% predicted (SD ±20.4), FVC 3.4 L (SD ± 1.0), 94% predicted (SD ±17.0)], and 10.9% had airflow limitation (AL, FEV1/FVC < 70%). In a nonlinear regression analysis, the intensity of dyspnea increased in a positively accelerating manner with power and as the FEV1% predicted decreased: Dyspnea = 0.06 * Power1.03 * FEV1%Pred−0.66(r = .63). The intensity of leg effort increased with power and declining quadricep strength and FEV1% predicted: Leg Effort = 0.06 * Power1.22 * Quad−0.56*FEV1%Pred−0.39(r = .73). There was no independent effect of AL on dyspnea of leg effort.ConclusionPower, quadriceps strength and FEV1 are the dominant factors contributing to dyspnea and leg effort, irrespective of the degree of airflow limitation.

Preoperative high-intensity interval training is effective and safe in deconditioned patients with lung cancer: A randomized clinical trial.

The outcome of surgery in deconditioned patients can be improved through prehabilitation. This study examined the effect of prehabilitation in patients diagnosed with lung cancer. Candidates for lung cancer resection were assigned to high-intensity interval training (n = 74) or usual care (n = 77). Cardiopulmonary exercise testing and 6-min walk test were performed before and after training. High-intensity interval training consisted of 2-3-weekly, 2 × 10-min series of cycling at peak power, measured with cardiopulmonary exercise testing prior to training, with a 15-s on-off duty cycle, preceded by a 5-min warm-up and followed by a 5-min cool-down. Work-rate, heart-rate, saturation, dyspnoea and leg effort were monitored. Waiting time (median 25 days) allowed a median of 8 high-intensity interval training sessions to be performed. Adherence to mean high-intensity interval training was 87% (18% standard deviation; SD). High-intensity interval training power increased (23 watt, 95% confidence interval (95% CI): 20-26 watt), as did heart rate (14 bpm, 95% CI 11-16 bpm). Resting heart rate (-6 bpm, 95% CI -4 to -7 bpm) and heart rate 1 min post-cool-down decreased (-5 bpm, 95% CI -4 to -7 bpm). Aerobic capacity increased after high-intensity interval training (14%, 95% CI 3-26%), as did peak power output (median 7%, 95% CI 2-13%), but not after usual care. Six-min walk test score increased after high-intensity interval training (median 20%, 95% CI 14-26%), but not after usual care. Short-term high-intensity interval training is feasible in deconditioned patients and increases cardio-respiratory fitness and walking capacity.

Thoracoabdominal Asynchrony Contributes to Exercise Limitation in Mild Asthmatic Subjects

This study aimed to better understand how subjects with stable asthma and without exercise-induced bronchoconstriction respond to mild exercise. Breathing pattern, chest wall compartmental and operational volumes, and thoracoabdominal asynchrony were assessed in 11 stable asthmatic subjects and 10 healthy subjects at rest and during exercise in a cycle-ergometer through optoelectronic plethysmography. Dyspnea and sensation of leg effort were assessed through Borg scale. During exercise, with similar minute ventilation, a significant lower chest wall tidal volume (p = 0.003) as well as a higher respiratory rate (p < 0.05) and rapid shallow breathing (p < 0.05) were observed in asthmatic when compared to healthy subjects. Asthmatic subjects exhibited a significantly lower inspiratory (p < 0.05) and expiratory times (p < 0.05). Intergroup analysis found a significant higher end-expiratory chest wall volume in asthmatic subjects, mainly due to a significant increase in volume of the pulmonary ribcage (RCp; 170 ml, p = 0.002), indicating dynamic hyperinflation (DH). Dyspnea and sensation of leg effort were both significantly greater (p < 0.0001) in asthmatic when compared to healthy subjects. In addition to a higher thoracoabdominal asynchrony found between RCp and abdominal (AB) (p < 0.005) compartments in asthmatic subjects, post-inspiratory action of the inspiratory ribcage and diaphragm muscles were observed through the higher expiratory paradox time of both RCp (p < 0.0001) and AB (p = 0.0002), respectively. Our data suggest that a different breathing pattern is adopted by asthmatic subjects without exercise-induced bronchoconstriction during mild exercise and that this feature, associated with DH and thoracoabdominal asynchrony, contributes significantly to exercise limitation.

Excess ventilation in COPD: Implications for dyspnoea and tolerance to interval exercise

Interval exercise delays critical mechanical-ventilatory constraints with positive consequences on Dyspnoea and exercise tolerance in COPD. We hypothesized that those advantages of interval exercise would be partially off-set in patients showing excessive ventilation (V˙E) to metabolic demand (V˙CO2). Sixteen men (FEV1 = 42.3 ± 8.9%) performed, on different days, 30 s and 60 s bouts at 100% peak (on) interspersed by moderate exercise at 40% (off). Nine patients did not sustain exercise for 30 min irrespective of on duration. They presented with higher V˙E/V˙CO2 nadir (35 ± 3 vs. 30 ± 5) and dead space/tidal volume (0.39 ± 0.05 vs. 0.34 ± 0.06) compared to their counterparts (p < 0.05). [Lactate], operating lung volumes and symptom burden (dyspnoea and leg effort) were also higher (p < 0.05). Unloading off decreased the metabolic-ventilatory demands, thereby allowing 7/9 patients to exercise for 30 min. Increased wasted ventilation accelerates the rate at which critical mechanical constraints and limiting dyspnoea are reached during interval exercise in patients with COPD.

Caffeine effects on VO2max test outcomes investigated by a placebo perceived-as-caffeine design.

Ergogenic effects of caffeine (CAF) ingestion have been observed in different cycling exercise modes, and have been associated with alterations in ratings of perceived exertion (RPE). However, there has been little investigation of maximal oxygen uptake (VO2MAX) test outcomes. This study aimed to verify whether CAF may reduce RPE, thereby improving maximal incremental test (MIT) outcomes such as VO2MAX, time to exhaustion and peak power output (WPEAK). Nine healthy individuals performed three MITs (25 W/min until exhaustion) in a random, counterbalanced fashion after ingestion of CAF, placebo perceived as caffeine (PLA), and no supplementation (baseline control). VO2 was measured throughout the test, while RPE was rated according to overall and leg effort sensations. The power output corresponding to submaximal (RPE = 14 according to the 6-20 Borg scale) and maximal RPE was recorded for both overall (O-RPE14 and O-RPEMAX) and leg RPE (L-RPE14 and L-RPEMAX). VO2MAX did not change significantly between MITs; however, CAF and PLA increased time to exhaustion (↑ ∼18.7% and ∼17.1%, respectively; p < .05) and WPEAK (↑ ∼13.0% and ∼11.8%, respectively; p < .05) when compared with control. When compared with control, CAF ingestion reduced submaximal and maximal overall and leg RPEs, the effect being greater in maximal (likely beneficial in O-RPEMAX and L-RPEMAX) than submaximal RPE (possibly beneficial in O-RPE14 and L-RPE14). Similar results were found when participants ingested PLA. Compared with control, CAF and PLA improved MIT performance outcomes such as time to exhaustion and WPEAK, without altering VO2MAX values. CAF effects were attributed to placebo.

Effects of non-fatiguing respiratory muscle loading induced by expiratory flow limitation during strenuous incremental cycle exercise on metabolic stress and circulating natural killer cells.

Exercise induces release of cytokines and increase of circulating natural killers (NK) lymphocyte during strong activation of respiratory muscles. We hypothesised that non-fatiguing respiratory muscle loading during exercise causes an increase in NK cells and in metabolic stress indices. Heart rate (HR), ventilation (VE), oesophageal pressure (Pes), oxygen consumption (VO2), dyspnoea and leg effort were measured in eight healthy humans (five men and three women, average age of 31±4years and body weight of 68±10kg), performing an incremental exercise testing on a cycle ergometer under control condition and expiratory flow limitation (FL) achieved by putting a Starling resistor. Blood samples were obtained at baseline, at peak of exercise and at iso-workload corresponding to that reached at the peak of FL exercise during control exercise. Diaphragmatic fatigue was evaluated by measuring the tension time index of the diaphragm. Respiratory muscle overloading caused an earlier interruption of exercise. Diaphragmatic fatigue did not occur in the two conditions. At peak of flow-limited exercise compared to iso-workload, HR, peak inspiratory and expiratory Pes, NK cells and norepinephrine were significantly higher. The number of NK cells was significantly related to ΔPes (i.e. difference between the most and the less negative Pes) and plasmatic catecholamines. Loading of respiratory muscles is able to cause an increase of NK cells provided that activation of respiratory muscles is intense enough to induce a significant metabolic stress.

Respiratory muscle endurance training reduces the O2 cost of cycling and perceived exertion in obese adolescents.

In obesity, the increased O2 cost of breathing negatively affects the O2 cost of exercise and exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, the addition of respiratory muscle endurance training (RMET) (isocapnic hyperpnea) to a standard body mass reduction program decreases the O2 cost of exercise and perceived exertion. Nine male obese adolescents [16.0 ± 1.4 yr (x ± SD), body mass 114.4 ± 22.3 kg] underwent 3 wk of RMET (5 days/week) in addition to a standard body mass reduction program. Eight age- and sex-matched obese adolescents underwent only the standard program (CTRL). Before and after interventions, patients performed on a cycle ergometer: incremental exercise; 12-min exercises at a constant work rate (CWR) of 65% and 120% at the gas exchange threshold (GET) determined before the intervention. Breath-by-breath pulmonary ventilation (V̇e) and O2 uptake (V̇o2), heart rate (HR), and ratings of perceived exertion for dyspnea/respiratory discomfort (RPER) and leg effort (RPEL) were determined. Body mass decreased (by ~3.0 kg) after both RMET (P = 0.003) and CTRL (P = 0.002). Peak V̇o2 was not affected by both interventions. Peak work rate was slightly, but significantly (P = 0.04), greater after RMET but not after CTRL. During CWR < GET, no changes were observed after both interventions. During CWR > GET, the O2 cost of cycling at the end of exercise (P = 0.02), the slope of V̇o2 vs. time (3-12 min) (P = 0.01), RPER (P = 0.01), and RPEL (P = 0.01) decreased following RMET, but not following CTRL. HR decreased after both RMET (P = 0.02) and CTRL (P = 0.03), whereas V̇e did not change. In obese adolescents RMET, superimposed on a standard body mass reduction program, lowered the O2 cost of cycling and perceived exertion during constant heavy-intensity exercise.

Imposed expiratory resistance, hyperinflation, and dyspnea are dissociated from locomotor fatigue during moderate exercise

Expiratory flow resistance (e.g. asthma, chronic obstructive pulmonary disease) results in dyspnea, dynamic hyperinflation, and premature exercise intolerance during heavy intensity exercise. This cascade seems to be primarily precipitated by abnormal lung mechanics that result in exacerbated symptoms and reduced maximal evocable limb motor activity. We do not know whether this cascade behaves in the same way during moderate exercise where only modest locomotor fatigue is expected to develop.We hypothesized that expiratory flow resistance would result in dynamic hyperinflation, dyspnea, and exacerbated locomotor fatigue during moderate intensity exercise in a similar manner to that during heavy intensity exercise.Volunteers (N=10, 27±6 yr) completed constant power moderate exercise (50% peak ramp power) with 3 levels of imposed expiratory flow resistance (7, 9, 11 cm H2O·L·s−1) or control (no imposed flow resistance). We measured operating lung volumes during exercise with inspiratory capacity maneuvers. Participants reported dyspnea and leg effort using a Borg 10‐point scale. At the termination of exercise we used a rapid switch from hyperbolic to isokinetic cycling to measure the decline in peak isokinetic power (Piso).Decline in Piso was not different when expiratory flow resistance was imposed (p&gt;0.05). Inspiratory capacity was smaller at the end of exercise in the most severe resistance (11 cm H2O·L·s−1) as compared to control (2.31±1.52 vs. 3.15±0.71 L; p&lt;0.05). Similarly, inspiratory reserve volume was smaller at the end of exercise in the most severe resistance as compared to control (−0.07±1.28 vs. 0.82±0.43 L; p&lt;0.05). Dyspnea was greater at the end of exercise in both mild and severe resistance (7 and 11 cm H2O·L·s−1) as compared to control (5.7±2.5 and 5.2±1.9 vs. 3.7±1.6; p&lt;0.05). Piso was not related to inspiratory reserve volume, inspiratory capacity, or dyspnea (p&gt;0.05).Imposed severe expiratory flow resistance results in hyperinflation and exacerbated dyspnea in healthy volunteers. Unlike what we have found during heavy exercise, however, abnormal lung mechanics and dyspnea were not related to maximal locomotor power during moderate exercise.

Acute respiratory muscle unloading by normoxic helium-O₂ breathing reduces the O₂ cost of cycling and perceived exertion in obese adolescents.

In obesity, an increased work of breathing contributes to a higher O2 cost of exercise and negatively affects exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, acute respiratory muscle unloading via normoxic helium-O2 breathing reduces the O2 cost of cycling and perceived exertion. Nine males [age 16.8 ± 1.6 (x ± SD) years, body mass 109.9 ± 15.0 kg] performed on a cycle ergometer, breathing room air (AIR) or a 21 % O2-79 % helium mixture (He-O2): an incremental exercise, for determination of [Formula: see text]O2 peak and gas exchange threshold (GET); 12 min constant work rate (CWR) exercises at 70 % of GET (<GET) and 120 % of GET (>GET) determined in AIR. [Formula: see text]O2 peak was not different in the two conditions. From the 3rd to the 12th minute of exercise (both during CWR < GET and CWR > GET), [Formula: see text]O2 was lower in He-O2 vs. AIR (end-exercise values: 1.40 ± 0.14 vs. 1.57 ± 0.22 L min(-1) <GET, and 2.23 ± 0.31 vs. 2.54 ± 0.27 L min(-1) >GET). During CWR > GET in AIR, [Formula: see text]O2 linearly increased from the 3rd to the 12th minute of exercise, whereas no substantial increase was observed in He-O2. The O2 cost of cycling was ~10 % (<GET) and ~15 % (>GET) lower in He-O2 vs. AIR. Heart rate and ratings of perceived exertion for dyspnea/respiratory discomfort and leg effort were lower in He-O2. In obese adolescents, acute respiratory muscle unloading via He-O2 breathing lowered the O2 cost of cycling and perceived exertion during submaximal moderate- and heavy-intensity exercise.

Work-rate-guided exercise testing in patients with incomplete spinal cord injury using a robotics-assisted tilt-table

Purpose: Robotics-assisted tilt-table (RTT) technology allows neurological rehabilitation therapy to be started early thus alleviating some secondary complications of prolonged bed rest. This study assessed the feasibility of a novel work-rate-guided RTT approach for cardiopulmonary training and assessment in patients with incomplete spinal cord injury (iSCI). Methods: Three representative subjects with iSCI at three distinct stages of primary rehabilitation completed an incremental exercise test (IET) and a constant load test (CLT) on a RTT augmented with integrated leg-force and position measurement and visual work rate feedback. Feasibility assessment focused on: (i) implementation, (ii) limited efficacy testing, (iii) acceptability. Results: (i) All subjects were able follow the work rate target profile by adapting their volitional leg effort. (ii) During the IETs, peak oxygen uptake above rest was 304, 467 and 1378 ml/min and peak heart rate (HR) was 46, 32 and 65 beats/min above rest (subjects A, B and C, respectively). During the CLTs, steady-state oxygen uptake increased by 42%, 38% and 162% and HR by 12%, 20% and 29%. (iii) All exercise tests were tolerated well. Conclusion: The novel work-rate guided RTT intervention is deemed feasible for cardiopulmonary training and assessment in patients with iSCI: substantial cardiopulmonary responses were observed and the approach was found to be tolerable and implementable.Implications for RehabilitationWork-rate guided robotics-assisted tilt-table technology is deemed feasible for cardiopulmonary assessment and training in patients with incomplete spinal cord injury.Robotics-assisted tilt-tables might be a good way to start with an active rehabilitation as early as possible after a spinal cord injury.During training with robotics-assisted devices the active participation of the patients is crucial to strain the cardiopulmonary system and hence gain from the training.

Obstructive sleep apnea (OSA) does not affect ventilatory and perceptual responses to exercise in morbidly obese subjects

We have tested the hypothesis that high mass loading effects and obstructive sleep apnea (OSA) constrain the ventilatory response to exercise in morbidly obese subjects as compared to their counterparts without OSA. Fifteen obese patients with (8) and without OSA and 12 lean healthy subjects performed incremental cycle exercise. The functional evaluation included ventilation, oxygen uptake, carbon dioxide production, end-expiratory-lung-volumes (EELV), inspiratory capacity, heart rate, dyspnea and leg effort (by a modified Borg scale). Changes in ventilation and dyspnea per unit changes in work rate and metabolic variables were similar in the three groups. Breathing pattern and heart rate increased from rest to peak exercise similarly in the three groups. Leg effort was the prevailing symptom for stopping exercise in most subjects. In conclusion, OSA does not limit exercise capacity in morbidly obese subjects. Ventilation contributes to exertional dyspnea similarly as in lean subjects and in obese patients regardless of OSA.

ESRD patients using permanent vascular access report greater physical activity compared with catheter users

Low levels of physical activity among end-stage renal disease (ESRD) patients are associated with increased risk of hospitalization and mortality, and contributors to low activity levels are important to identify. Among hemodialysis (HD) patients, use of a central venous catheter (CVC) might impede physical activity due to factors such as infection or patient fear of catheter dislodgement. This Comprehensive Dialysis Study surveyed patients who had recently started regular dialysis. Physical activity level was ascertained using responses to the Human Activity Profile (HAP) provided by 1,458 HD participants. We examined the association of vascular access type with patients' scores on HAP subscales measuring self-care and leg effort, two dimensions that are especially important for daily living. 32.6% of patients used an arteriovenous fistula (AVF), 11.5% used an arteriovenous graft, 51.8% used a CVC, and 4.1% used a CVC with another maturing access. Patients' self-care and leg effort scores differed by vascular access type and receipt of early nephrology care, and the mean self-care score of AVF users who received early care was similar to the mean score reported for healthy adults. Reported levels of self-care and leg effort activity were higher among incident HD patients using an AVF compared to those using a CVC. Future research should examine whether reinforcing the importance of regular physical activity in the pre-dialysis period, as well as wider early use of AVF in the HD population, may improve physical activity levels among ESRD patients.

Inflammation in Peripheral Artery Disease

Peripheral artery disease (PAD), which consists of partial or complete obstruction of the arteries in the lower limbs, is one of the most common manifestations of atherosclerosis, affecting ≈27 million individuals in Europe and North America.1 Its main symptomatic expression, intermittent claudication, was first described by the French veterinarian Bouley2 in a horse affected by progressive limping and lameness consequent to a fibrous clot that occluded the femoral arteries of the posterior limbs. In humans, this condition was noted by Brodie3 in 1846, but it was Charcot4 who in 1858 clearly defined and described the syndrome (and used the term “intermittent claudication”).3,4 Reproducibly elicited by walking-induced muscle ischemia and consistently relieved by rest that allows reperfusion of the affected limb, intermittent claudication may be considered “leg effort angina.” Indeed, for a long time, treatment was aimed exclusively at relieving leg symptoms and improving the functional status of affected individuals. However, in the 1950s, Stammers5 and Allen et al6 independently observed that patients with claudication were at high mortality risk. Subsequent prospective studies confirmed that patients with PAD rarely progress to limb loss but that the presence of PAD is a powerful and independent predictor of cardiac and cerebral ischemic events.7,–,11 However, this increased risk appears to be poorly related to classic risk factors, suggesting that once PAD is established, subsequent cardiovascular risk is related to the severity and extent of the underlying atherosclerotic disease and possibly other factors.7,–,11 It is well established that hypertension, smoking, diabetes mellitus, and hypercholesterolemia play a major role in the initiation and development of atherosclerosis and its clinical manifestations, although the prognostic potency of each of these factors in atherogenesis differs in the …