Factors Associated with Fatigue in COVID-19 ICU Survivors.

PURPOSE: Approximately 30% of people infected with COVID-19 require hospitalization and 20% of them are admitted to an intensive care unit (ICU). Most of these patients experience symptoms of fatigue weeks post-ICU, so understanding the factors associated with fatigue in this population is crucial. METHODS: Fifty-nine patients [38-78 yr] hospitalized in ICU for COVID-19 infection for 32 [6-80] days including 23 [3-57] days of mechanical ventilation, visited the laboratory on two separate occasions. The first visit occurred 52 ± 15 days after discharge and was dedicated to questionnaires, blood sampling and cardiopulmonary exercise testing, while measurements of the knee extensors neuromuscular function and performance fatigability were performed in the second visit 7 ± 2 days later. RESULTS: Using the FACIT-F questionnaire, 56% of patients were classified as fatigued. Fatigued patients had worse lung function score than non- fatigued (i.e. 2.9 ± 0.8 L vs 3.6 ± 0.8 L; 2.4 ± 0.7 l vs 3.0 ± 0.7 L for forced vital capacity and forced expiratory volume in one second, respectively) and forced vital capacity was identified as a predictor of being fatigued. Maximal voluntary activation was lower in fatigued patients than non-fatigued patients (82 ± 14% vs 91 ± 3%) and was the only neuromuscular variable that discriminated between fatigued and non-fatigued patients. Patient-reported outcomes also showed differences between fatigued and non-fatigued patients for sleep, physical activity, depression and quality of life (p < 0.05). CONCLUSIONS: COVID-19 survivors showed altered respiratory function 4 to 8 weeks after discharge, that was further deteriorated in fatigued patients. Fatigue was also associated with lower voluntary activation and patient-reported impairments (i.e. sleep satisfaction, quality of life or depressive state). The present study reinforces the importance of exercise intervention and rehabilitation to counteract cardiorespiratory and neuromuscular impairments of COVID-19 patients admitted in ICU, especially individuals experiencing fatigue.

Cardiorespiratory Fitness and Neuromuscular Function of Mechanically Ventilated ICU COVID-19 Patients.

OBJECTIVES: The aim of the current study was to investigate the level of cardiorespiratory fitness and neuromuscular function of ICU survivors after COVID-19 and to examine whether these outcomes are related to ICU stay/mechanical ventilation duration. DESIGN: Prospective nonrandomized study. SETTING: Patients hospitalized in ICU for COVID-19 infection. PATIENTS: Sixty patients hospitalized in ICU (mean duration: 31.9 ± 18.2 d) were recruited 4-8 weeks post discharge from ICU. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients visited the laboratory on two separate occasions. The first visit was dedicated to quality of life questionnaire, cardiopulmonary exercise testing, whereas measurements of the knee extensors neuromuscular function were performed in the second visit. Maximal oxygen uptake (V o2 max) was 18.3 ± 4.5 mL·min -1 ·kg -1 , representing 49% ± 12% of predicted value, and was significantly correlated with ICU stay/mechanical ventilation (MV) duration ( R = -0.337 to -0.446; p < 0.01 to 0.001), as were maximal voluntary contraction and electrically evoked peak twitch. V o2 max (either predicted or in mL· min -1 ·kg -1 ) was also significantly correlated with key indices of pulmonary function such as predicted forced vital capacity or predicted forced expiratory volume in 1 second ( R = 0.430-0.465; p ≤ 0.001) and neuromuscular function. Both cardiorespiratory fitness and neuromuscular function were correlated with self-reported physical functioning and general health status. CONCLUSIONS: V o2 max was on average only slightly above the 18 mL·min -1 ·kg -1 , that is, the cut-off value known to induce difficulty in performing daily tasks. Overall, although low physical capacities at admission in ICU COVID-19 patients cannot be ruled out to explain the association between V o2 max or neuromuscular function and ICU stay/MV duration, altered cardiorespiratory fitness and neuromuscular function observed in the present study may not be specific to COVID-19 disease but seem applicable to all ICU/MV patients of similar duration.

Fatigue, physical activity, and quality of life in people self-reporting symptoms of chronic venous disease.

OBJECTIVE: The aim of this study was to quantify fatigue and quality of life (QoL) in people self-reporting chronic venous disease (CVD) symptoms or at risk of CVD within a large cohort representative of the French population. The relationship between self-reported physical activity and both fatigue and QoL was also investigated. We hypothesized that a greater fatigue and impaired QoL would exist in participants self-reporting CVD symptoms, with the impairments being attenuated in those with greater level of physical activity. METHODS: Using a web-based, custom and adaptive survey, 3008 participants were asked to self-report the presence of common symptoms and risk factors of CVD. Fatigue, QoL, and physical activity were assessed using the Functional Assessment of Chronic Illness Therapy-Fatigue scale, the Chronic Venous Insufficiency Quality of Life Questionnaire, and the Godin-Shepard Leisure-Time Physical Activity Questionnaire, respectively. RESULTS: Thirty-two percent of participants were categorized as having CVD symptoms, whereas 50% were categorized as at risk of CVD. Fatigue was greater in participants with CVD symptoms than non-CVD participants (P < .001), with the score of participants at risk of CVD being intermediate (P ≤ .001). QoL was more impaired in participants with CVD symptoms compared with participants at risk of CVD (P < .001). In participants with CVD symptoms, there were relationships between fatigue and QoL (P < .001) and between physical activity and fatigue (P < .001). Despite the relationship between physical activity and QoL not reaching significance (P = .067), a lower QoL was found in insufficiently active as compared with active (P < .001) and moderately active (P < .001) participants with CVD symptoms. CONCLUSIONS: Participants self-reporting CVD symptoms suffer from greater fatigue and impaired QoL. In this population, a higher level of physical activity is associated with less fatigue and a tendency toward improved QoL.

Performance Determinants in Trail-Running Races of Different Distances.

PURPOSE: While the physiological determinants of road running have been widely studied, there is a lack of research in trail-running racing performance. The aim of our study was to determine the physiological predictors of trail-running performance in races of different distances in similar terrain and weather conditions. METHODS: Seventy-five trail runners participating in one of the races of the Ultra-Trail du Mont-Blanc were recruited. Previous to the race, each runner was evaluated with (1) an incremental treadmill test to determine maximal oxygen uptake, ventilatory thresholds, cost of running, and substrate utilization; (2) a power-force-velocity profile on a cycle ergometer; (3) maximal voluntary contractions of the knee extensors and plantar flexors; and (4) anthropometric characteristics. Neuromuscular fatigue was evaluated after the races. Twenty-four runners finished a SHORT (<55 km), 16 finished a MEDIUM (101 km), and 14 finished a LONG (>145 km) race. Correlations and multiple linear regressions were used to find the determinants of performance in each race distance. RESULTS: Performance in SHORT was explained by maximal oxygen uptake and lipid utilization at 10 km/h (r2 = .825, P < .001). Performance in MEDIUM was determined by maximal oxygen uptake, maximal isometric strength, and body fat percentage (r2 = .917, P < .001). A linear model could not be applied in LONG, but performance was correlated to peak velocity during the incremental test. CONCLUSIONS: Performance in trail running is mainly predicted by aerobic capacity, while lipid utilization also influences performance in races <60 km and performance in approximately 100 km is influenced by muscle strength and body composition.

Effect of race distance on performance fatigability in male trail and ultra-trail runners.

The etiology of changes in lower-limb neuromuscular function, especially to the central nervous system, may be affected by exercise duration. Direct evidence is lacking as few studies have directly compared different race distances. This study aimed to investigate the etiology of deficits in neuromuscular function following short versus long trail-running races. Thirty-two male trail runners completed one of five trail-running races as LONG (>100 km) or SHORT (<60 km). Pre- and post-race, maximal voluntary contraction (MVC) torque and evoked responses to electrical nerve stimulation during MVCs and at rest were used to assess voluntary activation and muscle contractile properties of knee-extensor (KE) and plantar-flexor (PF) muscles. Transcranial magnetic stimulation (TMS) was used to assess evoked responses and corticospinal excitability in maximal and submaximal KE contractions. Race distance correlated with KE MVC (ρ = -0.556) and twitch (ρ = -0.521) torque decreases (p ≤ .003). KE twitch torque decreased more in LONG (-28 ± 14%) than SHORT (-14 ± 10%, p = .005); however, KE MVC time × distance interaction was not significant (p = .073). No differences between LONG and SHORT for PF MVC or twitch torque were observed. Maximal voluntary activation decreased similarly in LONG and SHORT in both muscle groups (p ≥ .637). TMS-elicited silent period decreased in LONG (p = .021) but not SHORT (p = .912). Greater muscle contractile property impairment in longer races, not central perturbations, contributed to the correlation between KE MVC loss and race distance. Conversely, PF fatigability was unaffected by race distance.

Sex Differences in Neuromuscular Fatigue and Changes in Cost of Running after Mountain Trail Races of Various Distances.

INTRODUCTION: Women have been shown to experience less neuromuscular fatigue than men in knee extensors (KE) and less peripheral fatigue in plantar flexors (PF) after ultratrail running, but it is unknown if these differences exist for shorter trail running races and whether this may impact running economy. The purpose of this study was to characterize sex differences in fatigability over a range of running distances and to examine possible differences in the postrace alteration of the cost of running (Cr). METHODS: Eighteen pairs of men and women were matched by performance after completing different races ranging from 40 to 171 km, divided into SHORT versus LONG races (<60 and >100 km, respectively). Neuromuscular function and Cr were tested before and after each race. Neuromuscular function was evaluated on both KE and PF with voluntary and evoked contractions using electrical nerve (KE and PF) and transcranial magnetic (KE) stimulation. Oxygen uptake, respiratory exchange ratio, and ventilation were measured on a treadmill and used to calculate Cr. RESULTS: Compared with men, women displayed a smaller decrease in maximal strength in KE (-36% vs -27%, respectively, P < 0.01), independent of race distance. In SHORT only, women displayed less peripheral fatigue in PF compared with men (Δ peak twitch: -10% vs -24%, respectively, P < 0.05). Cr increased similarly in men and women. CONCLUSIONS: Women experience less neuromuscular fatigue than men after both "classic" and "extreme" prolonged running exercises but this does not impact the degradation of the energy Cr.

French Translation and Validation of the Rating-of-Fatigue Scale.

BACKGROUND: The Rating of Fatigue (ROF) scale can measure changes in perceived fatigue in a variety of contexts. OBJECTIVE: The aim of the present study was to translate and subsequently validate the ROF scale in the French language. METHODS: The study was composed of three phases. Phase 1 involved a comprehensive translation, back-translation, and consolidation process in order to produce the French ROF scale. During phase 2, the face validity of the French ROF scale was assessed. A cohort of 60 native French speaking participants responded to a range of Likert scale items which probed the purposes of the ROF scale and what it is intended to measure. During phase 3, the convergent and divergent validity of the ROF scale was assessed during ramped cycling to exhaustion and 10 min of resting recovery. RESULTS: The results from phase 1 demonstrated comparability and interpretability between the original and back-translated ROF scale. In phase 2, participants reported a high face validity, with a score of 3.48 ± 0.70 out of 4 when given the item probing whether the scale "measures fatigue". This score further improved (3.67 ± 0.57, P = 0.01) after participants read the accompanying instructions. Participants were able to distinguish the purposes of the scale for measuring fatigue rather than exertion. In phase 3, strong correlations were found between ROF and heart rate (HR) both during exercise (r = 0.91, P < 0.01) and recovery (r = 0.92, P < 0.01), while discriminant validity between ROF and rating of perceived exertion (RPE) was found during recovery. CONCLUSION: The present study permits the applications of the ROF scale in the French language.

The Effects of Anodal Transcranial Direct Current Stimulation on the Walking Performance of Chronic Hemiplegic Patients.

OBJECTIVE: To evaluate the effect of a single session of tDCS over the primary motor cortex of the lower limb (M1-LL) vs. placebo on the walking performance in chronic hemiplegic patients. PATIENTS AND METHODS: Randomized, cross-over, double-blinded study. Eighteen patients with initially complete hemiplegia and poststroke delay >6 months were included. Each patient received a single session of anodal stimulation (2 mA, 20 min) over M1-LL (a-tDCS condition) and a pseudostimulation session (SHAM condition). The order of the two sessions was randomly assigned, with an 11-day interval between the two sessions. The anodal electrode was centered on the hotspot identified with Transcranial magnetic stimulation. The cathode was placed above the contralesional orbitofrontal cortex. Walking performance was evaluated with the Wade test and the 6-minute walk test (6MWT), gait parameters with GAITRite, and balance with posturography. These tests were performed during and 1 hour after the stimulation. Baseline assessments were performed the day before and 10 days after each session. RESULTS: The comparison between the 6MWT under a-tDCS vs. SHAM conditions demonstrated a nonsignificant positive effect of the stimulation by 15% during stimulation (p = 0.360) and a significant positive effect of 25% 1 hour after stimulation (p = 0.038). No significant differences were observed for the other evaluations. DISCUSSION: These results showed a significant positive effect of a single session of anodal tDCS of the M1-LL in chronic hemiplegic patients. This proof-of-concept study supports the conduct of clinical studies evaluating the effectiveness of a walking training program associated with iterative tDCS stimulation. CONFLICT OF INTEREST: The authors reported no conflict of interest.

Effects of compression stockings on sympathetic activity and heart rate variability in individuals with spinal cord injury.

OBJECTIVE: To investigate whether wearing graduated compression stockings (GCS) could affect the sympatho-adrenergic and heart rate variability (HRV) responses at rest and after a strenuous wheelchair exercise in individuals with spinal cord injury (SCI). DESIGN: Crossover trial. SETTING: Department of Physical Medicine and Rehabilitation, Saint Etienne, France. PARTICIPANTS: Nine men with SCI (five with low paraplegia: LP, four with high paraplegia: HP). INTERVENTIONS: Two maximal wheelchair exercise tests: with and without GCS (21 mmHg). MAIN OUTCOME MEASURES: HRV measurements: high frequency (HF), low frequency (LF), and LF/HF ratio. Norepinephrine (NOR) and epinephrine (EPI), at rest and post-exercise. Secondary measures were: blood pressure, heart rate, maximal power output, oxygen uptake, stroke volume, cardiac output, at rest, during and after exercise. RESULTS: When wearing GCS: LFnu(wavelet-post) significantly increased and HFnu(wavelet-post) significantly decreased (P < 0.05) in SCI subjects, leading to an enhance ratio of LF(wavelet)/HF(wavelet) and a significantly increased in NOR(rest) (P < 0.05). CONCLUSIONS: GCS induces an enhanced sympathetic activity in individuals with paraplegia, regardless of the level of the injury. Enhanced post-exercise sympathetic activity with GCS may help prevent orthostatic hypotension or post-exercise hypotension.

Effects of compression stockings during exercise and recovery on blood lactate kinetics.

This study aimed to investigate if wearing compression stockings (CS) during exercise and recovery could affect lactate profile in sportsmen. Eight young healthy trained male subjects performed two maximal exercise tests on a cycle ergometer on two different occasions performed randomly: CS during both exercise and recovery, and no CS. Blood lactate concentration was taken during exercise and at 0, 3, 5, 10, 15, 30 and 60 min post-exercise. The individual blood lactate recovery curves were fitted to a biexponential time function: La(t) = La(0) + A1(1 - e(-gamma1t)) + A2(1 - e(-gamma2t)), where gamma(1) and gamma(2) denote the abilities to exchange lactate between the previously active muscles and the blood and to remove lactate from the organism, respectively. A significantly higher blood lactate value at the end of the maximal exercise was found (12.1 +/- 0.5 vs. 10.8 +/- 0.5 mmol l(-1)) wearing CS as compared to no CS (P < 0.05). Lower gamma(1) and higher gamma(2) values were observed with CS during recovery, as compared to no CS. It was concluded that CS during graded exercise leads to a significant higher blood lactate value at exhaustion. Since lactate exchanges were expected to be decreased during exercise due to CS, this result was likely attributable to a higher lactate accumulation related to a greater overall contribution of anaerobic glycolysis. Although the lactate removal ability was significantly improved when wearing CS during recovery, its efficacy in promoting blood lactate clearance after high-intensity exercise is limited.

Evaluation of the effects of compression stockings using venous plethysmography in persons with spinal cord injury.

BACKGROUND/OBJECTIVE: To examine the effect of graduated compression stockings (GCS) on the properties of the venous vascular system, as characterized by venous capacitance (VC) and venous outflow (VO), in the lower extremities of individuals with spinal cord injury (SCI), according to injury level. METHODS: Nine male subjects with SCI (5 with low paraplegia [LP], 4 with high paraplegia [HP]) performed 2 plethysmography tests: with and without graduated compression knee-length stockings (pressure of 21 mm/Hg). The VC, VO, and cardiovascular parameters (heart rate and blood pressure) were evaluated with and without GCS. RESULTS: The VC and VO were lower in patients with HP than in those with LP. For all subjects, VC was significantly lower (-14%) with GCS than without (1.77 +/- 1.18 vs 1.53 +/- 1.09 vol%, P < 0.01). On the contrary, VO did not differ significantly when wearing or not wearing GCS. CONCLUSIONS: This study demonstrated that 21-mm/Hg knee-length GCS are sufficient to prevent venous distension in individuals with SCI, even those with longstanding paraplegia, by significantly decreasing venous capacitance. This intervention may help to prevent deep vein thrombosis.

Effects of graduated compression stockings on cardiovascular and metabolic responses to exercise and exercise recovery in persons with spinal cord injury.

OBJECTIVE: To investigate whether reporting blood redistribution by means of graduated elastic stockings affects exercise and postexercise responses in people with spinal cord injury (SCI). DESIGN: Crossover trial. SETTING: Physical medicine and rehabilitation department in France. PARTICIPANTS: Fourteen men with traumatic SCI, grouped according to their level of injury. INTERVENTIONS: Subjects performed 2 maximal wheelchair exercise tests 1 week apart, in random order and under a counter-balanced design. One test was done with and the other without graduated elastic stockings (21 mmHg). MAIN OUTCOME MEASURES: Blood lactate, blood pressure, heart rate, maximal power output, and oxygen consumption (Vo2). RESULTS: Postexercise venous lactate concentration was reduced in SCI subjects with lesion levels below T6 while wearing graduated elastic stockings during both exercise and recovery (10.9+/-3.9 mmol/L vs 12.5+/-4.6 mmol/L, P<.05). There were no significant differences in submaximal and maximal values (heart rate, Vo2, power output) between subjects tested with and without graduated elastic stockings. CONCLUSIONS: Wearing elastic stockings affects postexercise responses by decreasing lactate concentration in well-trained, low-level paraplegic patients after a maximal exercise. The relatively low pressure generated by the stockings may not, however, influence the venous system enough to produce improved performance and cardiovascular responses.

Relationship between maximal exercise capacity and walking capacity in adult hemiplegic stroke patients.

OBJECTIVE: To evaluate the relationship between maximal exercise capacity and walking capacity in hemiplegic stroke patients. DESIGN: An uncontrolled observational study was conducted in the physical medicine and rehabilitation unit in an academic hospital. Participants were 21 hemiplegic stroke patients (18 men, 3 women; age, 18-70 yrs) whose stroke occurred >3 mos before the study and who could walk independently with or without walking aids. Main outcome measures were peak oxygen uptake, workload, walking capacity, and motor impairment. RESULTS: There was a significant correlation between walking capacity (6-min-walk test) and both peak oxygen uptake (r=0.602, P=0.0032) and maximal power output (r=0.867, P<0.0001). CONCLUSIONS: Aerobic capacity and walking capacity are decreased in hemiplegic stroke patients and are correlated with each other. These results underscore the need for future studies, to confirm the role of fitness in relation to walking capacity, and to evaluate the benefit of integrating aerobic training into more traditional rehabilitation programs after stroke.