Deduced Respiratory Scores on COVID-19 Patients Learning from Exertion-Induced Dyspnea.

Dyspnea is one of the most common symptoms of many respiratory diseases, including COVID-19. Clinical assessment of dyspnea relies mainly on self-reporting, which contains subjective biases and is problematic for frequent inquiries. This study aims to determine if a respiratory score in COVID-19 patients can be assessed using a wearable sensor and if this score can be deduced from a learning model based on physiologically induced dyspnea in healthy subjects. Noninvasive wearable respiratory sensors were employed to retrieve continuous respiratory characteristics with user comfort and convenience. Overnight respiratory waveforms were collected on 12 COVID-19 patients, and a benchmark on 13 healthy subjects with exertion-induced dyspnea was also performed for blind comparison. The learning model was built from the self-reported respiratory features of 32 healthy subjects under exertion and airway blockage. A high similarity between respiratory features in COVID-19 patients and physiologically induced dyspnea in healthy subjects was observed. Learning from our previous dyspnea model of healthy subjects, we deduced that COVID-19 patients have consistently highly correlated respiratory scores in comparison with normal breathing of healthy subjects. We also performed a continuous assessment of the patient's respiratory scores for 12-16 h. This study offers a useful system for the symptomatic evaluation of patients with active or chronic respiratory disorders, especially the patient population that refuses to cooperate or cannot communicate due to deterioration or loss of cognitive functions. The proposed system can help identify dyspneic exacerbation, leading to early intervention and possible outcome improvement. Our approach can be potentially applied to other pulmonary disorders, such as asthma, emphysema, and other types of pneumonia.

Does the Number of Substitutions Used during the Matches Affect the Recovery Status and the Physical and Technical Performance of Elite Women's Soccer?

The aim of this study was to compare the effect of a new rule for substitutions (four and five) with the rule before the COVID-19 pandemic (up to three) on recovery status, physical and technical performance, internal workload, and recovery process in elite women soccer players. Thirty-eight matches from 2019 to 2020 from the Brazilian Championships were analyzed. All data for the two conditions (≤3 and 4-5 substitutions) were compared using an independent t-test. The physical demands measured by a global positioning system (GPS) and the technical (obtained from Instat) and internal workload (rating of perceived exertion [RPE]) were assessed. The recovery process was measured by the total quality recovery (TQR) 24 h after each match. No differences were observed in any physical and technical parameters between 4-5 and ≤3 substitutions (p > 0.05). Moreover, 4-5 substitutions demonstrated lower RPE (p < 0.001) and workload-RPE (p < 0.001), higher TQR (p = 0.008), and lower time played by the player (p < 0.001), compared to ≤3. Thus, the new provisory rule for substitutions improved the balance between stress and recovery.

A tele-health primary care rehabilitation program improves self-perceived exertion in COVID-19 survivors experiencing Post-COVID fatigue and dyspnea: A quasi-experimental study.

BACKGROUND: Current evidence suggests that up to 70% of COVID-19 survivors develop post-COVID symptoms during the following months after infection. Fatigue and dyspnea seem to be the most prevalent post-COVID symptoms. OBJECTIVE: To analyze whether a tele-rehabilitation exercise program is able to improve self-perceived physical exertion in patients with post-COVID fatigue and dyspnea. METHODS: Sixty-eight COVID-19 survivors exhibiting post-COVID fatigue and dyspnea derived to four Primary Health Care centers located in Madrid were enrolled in this quasi-experimental study. A tele-rehabilitation program based on patient education, physical activity, airway clearing, and breathing exercise interventions was structured on eighteen sessions (3 sessions/week). Self-perceived physical exertion during daily living activities, dyspnea severity, health-related quality of life and distance walked and changes in oxygen saturation and heart rate during the 6-Minute walking test were assessed at baseline, after the program and at 1- and 3-months follow-up periods. RESULTS: Daily living activities, dyspnea severity and quality of life improved significantly at all follow-ups (p<0.001). Additionally, a significant increase in oxygen saturation before and after the 6-Minute Walking test was found when compared with baseline (P<0.001). Heart rate adaptations at rest were found during the follow-up periods (P = 0.012). Lower perceived exertion before and after the 6-Minute Walking test were also observed, even if larger distance were walked (P<0.001). CONCLUSION: Tele-rehabilitation programs could be an effective strategy to reduce post-COVID fatigue and dyspnea in COVID-19 survivors. In addition, it could also reduce the economic burden of acute COVID-19, reaching a greater number of patients and releasing Intensive Unit Care beds for prioritized patients with a severe disease. STUDY REGISTRATION: The international OSF Registry registration link is https://doi.org/10.17605/OSF.IO/T8SYB.

Perceived Exertion during Moderate and Vigorous Physical Activity While Mask Wearing: A Quantitative and Qualitative Pilot Study.

There is limited research examining the perception of exertion during exercise while wearing a facemask. The current study examined if mask usage during moderate or vigorous physical activity (MVPA) changed the self-reported perception of exertion. Seventy-two adults (18 years and older) who were physically active before the COVID-19 pandemic completed a questionnaire that assessed exercise habits and perceptions of mask wearing during MVPA. Participants reported their ratings of perceived exertion (RPE, on a scale of 1-10) while exercising. Wearing a mask resulted in higher RPE vs. no mask during both vigorous (8.4 ± 0.2 vs. 7.4 ± 0.1; p < 0.001) and moderate PA (6.6 ± 0.2 vs. 5.6 ± 0.2; p < 0.001). Qualitative analysis revealed mostly negative perceptions of exercising while wearing a mask, including respiratory issues, detriments to cardiovascular endurance, and general discomfort. A total of 40% of participants reported that they stopped exercising in an indoor/public setting because of a mask mandate in their region. Participants reported participating in less vigorous PA (4.7 ± 0.4 vs. 4.0 ± 0.4 h/week; p = 0.046), but not less moderate PA (3.3 ± 0.3 vs. 3.0 ± 0.3 h/week; p = 0.443) pre vs. during the pandemic. Our study suggests that facemask usage during MVPA causes an increase in RPE and may be one reason for a decrease in vigorous PA during the COVID-19 pandemic.

Diaphragm dysfunction as a potential determinant of dyspnea on exertion in patients 1 year after COVID-19-related ARDS.

Some COVID-19 patients experience dyspnea without objective impairment of pulmonary or cardiac function. This study determined diaphragm function and its central voluntary activation as a potential correlate with exertional dyspnea after COVID-19 acute respiratory distress syndrome (ARDS) in ten patients and matched controls. One year post discharge, both pulmonary function tests and echocardiography were normal. However, six patients with persisting dyspnea on exertion showed impaired volitional diaphragm function and control based on ultrasound, magnetic stimulation and balloon catheter-based recordings. Diaphragm dysfunction with impaired voluntary activation can be present 1 year after severe COVID-19 ARDS and may relate to exertional dyspnea.This prospective case-control study was registered under the trial registration number NCT04854863 April, 22 2021.

The Effects of Face Coverings on Perceived Exertion and Attention Allocation during a Stepping Task.

The COVID-19 pandemic has impacted the entire world from lockdowns to various recommended restrictions including social distancing and wearing face coverings. In a safe environment, cardiovascular exercise is important for both physical health and mental health. The current study examined the effects of face coverings on rating of perceived exertion and attention allocation during an exertive stepping task. Participants completed a stepping task with a weighted vest at 20% of their bodyweight until volitional fatigue with a face covering (n = 23) or without a face covering (n = 31). Results revealed a non-significant difference (p = 0.25) in the duration of the stepping task (in seconds) between the no face covering (M = 455.81, SD = 289.77) and face covering (M = 547.83, SD = 285.93) conditions. Results indicated increases in perceived exertion (p < 0.001) and heart rate (p < 0.001) as time progressed across the four time points (i.e., 30 s, 1/3 time to exhaustion, 2/3 time to exhaustion, and exhaustion) in both conditions. No significant differences were found between the conditions for RPE (p = 0.09) and heart rate (p = 0.50). Participants wearing a face covering were more internally focused across the duration of the stepping task (p = 0.05). This study has relevance for applied practitioners implementing physical activity interventions that require face coverings.

Effects of surgical facemasks on perceived exertion during submaximal exercise test in healthy children.

Only a few data associated to wearability of facemask during exercise are available in children. The aim of the study was to evaluate the effect of wearing a facemask on perceived exertion (primary aim), dyspnea, physical performance, and cardiorespiratory response during a submaximal exercise test in children aged between 8 and 12 years. This study was performed in 2021 in healthy volunteer children from 8 to 12 years. They performed prospectively two 1-min sit-to-stand tests (STST), with or without a surgical facemask. The perceived exertion (modified Borg scale), dyspnea (Dalhousie scale), heart rate, and pulsed oxygen saturation were recorded before and after STST. The STST measured the submaximal performance. Thirty-eight healthy children were recruited (8-9 years: n = 19 and 10-11 years: n = 19). After the STST, the perceived exertion increased with or without a facemask (8-9 years group: + 1 [0.6; 1.4] and + 1.6 [1.0; 2.1] - 10-11 years group: + 1.3 [0.7; 1.8] and + 1.9 [1.3; 2.6]) and it was higher with the facemask. The difference between the two conditions in perceived exertion was not clinically relevant in any group (mBorgf: 0.56 pts and 0.68 pts, respectively). The different domains of dyspnea assessed with Dalhousie scale were not influenced by the facemask. The submaximal performance measured by the STST was not changed by the mask whatever the age group. The cardio-respiratory demand was not clinically modified.Conclusion: The surgical facemask had no impact on dyspnea, cardiorespiratory parameters, and exercise performance during a short submaximal exercise in healthy children.

Comparison of Ratings of Perceived Exertion and Target Heart Rate-Based Exercise Prescription in Cardiac Rehabilitation: A RANDOMIZED CONTROLLED PILOT STUDY.

PURPOSE: Although ratings of perceived exertion (RPE) are widely used to guide exercise intensity in cardiac rehabilitation (CR), it is unclear whether target heart rate ranges (THRRs) can be implemented in CR programs that predominantly use RPE and what impact this has on changes in exercise capacity. METHODS: We conducted a three-group pilot randomized control trial (#NCT03925493) comparing RPE of 3-4 on the 10-point modified Borg scale, 60-80% of heart rate reserve (HRR) with heart rate (HR) monitored by telemetry, or 60-80% of HRR with a personal HR monitor (HRM) for high-fidelity adherence to THRR. Primary outcomes were protocol fidelity and feasibility. Secondary outcomes included exercise HR, RPE, and changes in functional exercise capacity. RESULTS: Of 48 participants randomized, four patients dropped out, 20 stopped prematurely (COVID-19 pandemic), and 24 completed the protocol. Adherence to THRR was high regardless of HRM, and patients attended a median (IQR) of 33 (23, 36) sessions with no difference between groups. After randomization, HR increased by 1 ± 6, 6 ± 5, and 10 ± 9 bpm ( P = .02); RPE (average score 3.0 ± 0.05) was unchanged, and functional exercise capacity increased by 1.0 ± 1.0, 1.9 ± 1.5, 2.0 ± 1.3 workload METs (effect size between groups, ηp2 = 0.11, P = .20) for the RPE, THRR, and THRR + HRM groups, respectively. CONCLUSIONS: We successfully implemented THRR in an all-RPE CR program without needing an HRM. Patients randomized to THRR had higher exercise HR but similar RPE ratings. The THRR may be preferable to RPE in CR populations for cardiorespiratory fitness gains, but this needs confirmation in an adequately powered trial.

[Effects of surgical face masks on exercise performance and perceived exertion of exercise in well-trained healthy boys]. / Einfluss einer Mund-Nase-Maske auf die objektive körperliche Leistungsfähigkeit sowie das subjektive Belastungsempfinden bei gut-trainierten, gesunden Jungen.

This study investigated the effects of surgical "everday" face masks on the physical performance and perceived exertion in trained eleven-year-old boys.No decrease in objective performance parameters was found in the aerobic and aerobic-anaerobic transition zones. However, at the maximum performance level with surgical face mask, there was a significant reduction in running time as well as a significant increase in the subjective perception of exertion with otherwise unchanged performance parameters. In summary, the use of surgical face masks in trained children does not affect athletic activities as long as the loads are performed primarily in the aerobic intensity range.

Ain't Just Imagination! Effects of Motor Imagery Training on Strength and Power Performance of Athletes during Detraining.

PURPOSE: This study aimed to investigate the effects of motor imagery (MI) training on strength and power performances of professional athletes during a period of detraining caused by the COVID-19 outbreak. METHODS: Thirty male professional basketball players (age, 26.1 ± 6.2 yr) were randomly assigned to three counterbalanced groups: two MI training groups, who completed imagery training by mentally rehearsing upper and lower limb resistance training exercises loaded with either 85% of one repetition maximum (85%1RM) or optimum power loads (OPL), or a control group. For six consecutive weeks, although all groups completed two weekly sessions of high-intensity running, only the MI groups performed three additional MI sessions a week. Maximal strength and power output were measured through 1RM and OPL assessments in the back squat and bench press exercises with a linear positioning transducer. Vertical jump and throwing capabilities were assessed with the countermovement jump and the seated medicine ball throw tests, respectively. Kinesthetic and visual imagery questionnaires, and chronometry and rating of perceived effort scores were collected to evaluate MI vividness, MI ability, and perceived effort. RESULTS: Physical performances improved significantly following both MI protocols (range, ~2% to ~9%), but were reduced in the control group, compared with preintervention (P ≤ 0.016). Moreover, interactions (time-protocol) were identified between the two MI groups (P ≤ 0.001). Whereas the 85%1RM led to greater effects on maximal strength measures than the OPL, the latter induced superior responses on measures of lower limb power. These findings were mirrored by corresponding cognitive and psychophysiological responses. CONCLUSIONS: During periods of forced detraining, MI practice seems to be a viable tool to maintain and increase physical performance capacity among professional athletes.

Exertional intolerance and dyspnea with preserved lung function: an emerging long COVID phenotype?

The COVID-19 pandemic has resulted in significant acute morbidity and mortality worldwide. There is now a growing recognition of the longer-term sequelae of this infection, termed "long COVID". However, little is known about this condition. Here, we describe a distinct phenotype seen in a subset of patients with long COVID who have reduced exercise tolerance as measured by the 6 min walk test. They are associated with significant exertional dyspnea, reduced health-related quality of life and poor functional status. However, surprisingly, they do not appear to have any major pulmonary function abnormalities or increased burden of neurologic, musculoskeletal or fatigue symptoms.

Effects of surgical and cloth facemasks during a submaximal exercise test in healthy adults.

BACKGROUND: Surgical (SM) or cloth facemasks (CM) has become mandatory in many public spaces during the COVID-19 pandemic. They may interfere with the participation in physical activities. OBJECTIVE: To evaluate how these masks influence dyspnoea (primary outcome), exercise performance and cardiorespiratory response during a 1-min sit-to-stand test (1STST), and to assess masks discomfort sensations. METHODS: A randomized crossover trial was conducted in healthy adults. They performed 3 1STST (with either no mask (NM), a SM, or a CM) separated from each other by 24-72 h. The number of 1STST repetitions and leg rate of perceived exertion (RPE) were measured. Dyspnoea (Borg scale), hearth rate, respiratory rate and SpO2 were recorded before and at the end of 1STST, as well as after a short resting period. Several domains of subjective discomfort perceptions with masks were assessed. RESULTS: Twenty adults aged 22 ± 2y (11 males) were recruited. Wearing the CM generated significantly higher dyspnoea than NM at all time points, but it only became clinically relevant after the 1STST (median difference, 1 [95%CI 0 to 1]). The SM generated a small but significant higher leg RPE than NM (median difference, 1 [95%CI 0 to 1]). The masks had no impact on 1STST performance nor cardiorespiratory parameters. Both masks were rated similarly for discomfort perceptions except for breathing resistance where CM was rated higher. CONCLUSIONS: In healthy adults, the CM and SM had minimal to no impact on dyspnoea, cardiorespiratory parameters, and exercise performance during a short submaximal exercise test.

Effects of Face Mask Use on Objective and Subjective Measures of Thermoregulation During Exercise in the Heat.

BACKGROUND: While increased face mask use has helped reduce COVID-19 transmission, there have been concerns about its influence on thermoregulation during exercise in the heat, but consistent, evidence-based recommendations are lacking. HYPOTHESIS: No physiological differences would exist during low-to-moderate exercise intensity in the heat between trials with and without face masks, but perceptual sensations could vary. STUDY DESIGN: Crossover study. LEVEL OF EVIDENCE: Level 2. METHODS: Twelve physically active participants (8 male, 4 female; age = 24 ± 3 years) completed 4 face mask trials and 1 control trial (no mask) in the heat (32.3°C ± 0.04°C; 54.4% ± 0.7% relative humidity [RH]). The protocol was 60 minutes of walking and jogging between 35% and 60% of relative VO2max. Rectal temperature (Trec), heart rate (HR), temperature and humidity inside and outside of the face mask (Tmicro_in, Tmicro_out, RHmicro_in, RHmicro_out) and perceptual variables (rating of perceived exertion (RPE), thermal sensation, thirst sensation, fatigue level, and overall breathing discomfort) were monitored throughout all trials. RESULTS: Mean Trec and HR increased at 30- and 60-minute time points compared with 0-minute time points, but no difference existed between face mask trials and control trials (P > 0.05). Mean Tmicro_in, RHmicro_in, and humidity difference inside and outside of the face mask (ΔRHmicro) were significantly different between face mask trials (P < 0.05). There was no significant difference in perceptual variables between face mask trials and control trials (P > 0.05), except overall breathing discomfort (P < 0.01). Higher RHmicro_in, RPE, and thermal sensation significantly predicted higher overall breathing discomfort (r2 = 0.418; P < 0.01). CONCLUSION: Face mask use during 60 minutes of low-to-moderate exercise intensity in the heat did not significantly affect Trec or HR. Although face mask use may affect overall breathing discomfort due to the changes in the face mask microenvironment, face mask use itself did not cause an increase in whole body thermal stress. CLINICAL RELEVANCE: Face mask use is feasible and safe during exercise in the heat, at low-to-moderate exercise intensities, for physically active, healthy individuals.

Persistent Poor Health after COVID-19 Is Not Associated with Respiratory Complications or Initial Disease Severity.

Rationale: Much is known about the acute infective process of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus of the coronavirus disease (COVID-19) pandemic. The marked inflammatory response and coagulopathic state in acute SARS-CoV-2 infection may promote pulmonary fibrosis. However, little is known about the incidence and seriousness of post-COVID-19 pulmonary pathology. Objectives: To describe the respiratory recovery and self-reported health after infection at the time of outpatient attendance. Methods: Infection severity was graded into three groups: 1) not requiring admission, 2) requiring hospital admission, and 3) requiring intensive care unit care. Participants underwent chest radiography and a 6-minute walk test (6MWT). Fatigue and subjective return to health were assessed, and concentrations of CRP (C-reactive protein), IL-6 (interleukin-6), sCD25 (soluble CD25), and D-dimer were measured. The associations between initial illness and abnormal chest X-ray findings, 6MWT distance, and perception of maximal exertion were investigated. Results: A total of 487 patients were offered an outpatient appointment, of whom 153 (31%) attended for assessment at a median of 75 days after diagnosis. A total of 74 (48%) had required hospital admission during acute infection. Persistently abnormal chest X-ray findings were seen in 4%. The median 6MWT distance covered was 460 m. A reduced distance covered was associated with frailty and length of inpatient stay. A total of 95 (62%) patients believed that they had not returned to full health, whereas 47% met the case definition for fatigue. Ongoing ill health and fatigue were associated with an increased perception of exertion. None of the measures of persistent respiratory disease were associated with initial disease severity. Conclusions: This study highlights the rates of objective respiratory disease and subjective respiratory symptoms after COVID-19 and the complex multifactorial nature of post-COVID-19 ill health.

Physiological demands of singing for lung health compared with treadmill walking.

INTRODUCTION: Participating in singing is considered to have a range of social and psychological benefits. However, the physiological demands of singing and its intensity as a physical activity are not well understood. METHODS: We compared cardiorespiratory parameters while completing components of Singing for Lung Health sessions, with treadmill walking at differing speeds (2, 4 and 6 km/hour). RESULTS: Eight healthy adults were included, none of whom reported regular participation in formal singing activities. Singing induced acute physiological responses that were consistent with moderate intensity activity (metabolic equivalents: median 4.12, IQR 2.72-4.78), with oxygen consumption, heart rate and volume per breath above those seen walking at 4 km/hour. Minute ventilation was higher during singing (median 22.42 L/min, IQR 16.83-30.54) than at rest (11 L/min, 9-13), lower than 6 km/hour walking (30.35 L/min, 26.94-41.11), but not statistically different from 2 km/hour (18.77 L/min, 16.89-21.35) or 4 km/hour (23.27 L/min, 20.09-26.37) walking. CONCLUSIONS: Our findings suggest the acute metabolic demands of singing are comparable with walking at a moderately brisk pace, hence, physical effects may contribute to the health and well-being benefits attributed to singing participation. However, if physical training benefits result remains uncertain. Further research including different singing styles, singers and physical performance impacts when used as a training modality is encouraged. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov registry (NCT04121351).

Home-based training program during the SARS-CoV-2 quarantine: training load, motivation, and wellbeing in professional elite female basketball players.

BACKGROUND: Due to the quarantine caused by the Coronavirus disease 2019 (COVID-19), professional team-sports adapted their training routine to maintain the athletes' performance and minimize the negative emotional effects. The aim of the present study was to describe a home-based training program and extra-activities applied during the quarantine in elite professional female basketball players, and to compare the internal training load (ITL), session rating of perceived exertion (s-RPE), motivation, and wellbeing responses before and during the quarantine. METHODS: Nine female elite players (25.7±7.0 years; 180.0±8.0 cm; 79.0±11.0 kg) belonging to a professional basketball team performed a home-based training program during the quarantine. ITL, s-RPE, training motivation, and wellbeing were examined before (phase 1), at the beginning (phase 2), and during (phase 3) the quarantine. RESULTS: ITL was higher (main effect) in phase 1 (449.5±62.8 a.u.) compared to phase 2 (265.5±39.0 a.u.) and phase 3 (423.1±18.7 a.u.); s-RPE was higher in phase 1 (4.50±0.63 a.u.) compared to phase 2 (3.8±0.6 a.u.), but not to phase 3 (4.37±0.79 a.u.). Motivation was higher in phase 1 (3.6±0.3 a.u.) compared to phase 2 (2.3±0.6 a.u.) and phase 3 (2.4±0.5 a.u.). CONCLUSIONS: The results of the study demonstrated that extra-activities involving online athletes' socialization were implemented to rouse the motivation, but the quarantine period induced a reduction in ITL and influenced the player's training motivation.

Exertional hypoxia in patients without resting hypoxia is an early predictor of moderate to severe COVID-19.

The importance of exertional hypoxia without resting hypoxia in COVID-19 is unknown and may help objectively identify high-risk patients. Interventions may be initiated earlier with sufficient lead-time between development of exertional hypoxia and other outcome measures. We performed a retrospective study of adult patients hospitalized with COVID-19 from March 1, 2020 to October 30, 2020 in an integrated academic medical system in the Chicagoland area. We analyzed patients who had daily exertional oximetry measurements taken. We defined exertional hypoxia as SpO2 < 90% with ambulation. We excluded patients who had first exertional oximetry measurements or first exertional hypoxia after the use of oxygen therapies. We determined the association of exertional hypoxia without resting hypoxia with the eventual need for nasal cannula or advanced oxygen therapies (defined as high flow nasal cannula, Bi-PAP, ventilator, or extracorporeal membrane oxygenation). We also calculated the time between development of exertional hypoxia and the need for oxygen therapies. Of 531 patients included, 132 (24.9%) had exertional hypoxia. Presence of exertional hypoxia was strongly associated with eventual use of nasal cannula (OR 4.8, 95% CI 2.8-8.4) and advanced oxygen therapy (IRR 7.7, 95% CI 3.4-17.5). Exertional hypoxia preceded nasal cannula use by a median 12.5 h [IQR 3.25, 29.25] and advanced oxygenation by 54 h [IQR 25, 82]. Exertional hypoxia without resting hypoxia may serve as an early, non-invasive physiologic marker for the likelihood of developing moderate to severe COVID-19. It may help clinicians triage patients and initiate earlier interventions.

Direct and indirect evidence of efficacy and safety of rapid exercise tests for exertional desaturation in Covid-19: a rapid systematic review.

BACKGROUND: Even when resting pulse oximetry is normal in the patient with acute Covid-19, hypoxia can manifest on exertion. We summarise the literature on the performance of different rapid tests for exertional desaturation and draw on this evidence base to provide guidance in the context of acute Covid-19. MAIN RESEARCH QUESTIONS: 1. What exercise tests have been used to assess exertional hypoxia at home or in an ambulatory setting in the context of Covid-19 and to what extent have they been validated? 2. What exercise tests have been used to assess exertional hypoxia in other lung conditions, to what extent have they been validated and what is the applicability of these studies to acute Covid-19? METHOD: AMED, CINAHL, EMBASE MEDLINE, Cochrane and PubMed using LitCovid, Scholar and Google databases were searched to September 2020. Studies where participants had Covid-19 or another lung disease and underwent any form of exercise test which was compared to a reference standard were eligible. Risk of bias was assessed using QUADAS 2. A protocol for the review was published on the Medrxiv database. RESULTS: Of 47 relevant papers, 15 were empirical studies, of which 11 described an attempt to validate one or more exercise desaturation tests in lung diseases other than Covid-19. In all but one of these, methodological quality was poor or impossible to fully assess. None had been designed as a formal validation study (most used simple tests of correlation). Only one validation study (comparing a 1-min sit-to-stand test [1MSTST] with reference to the 6-min walk test [6MWT] in 107 patients with interstitial lung disease) contained sufficient raw data for us to calculate the sensitivity (88%), specificity (81%) and positive and negative predictive value (79% and 89% respectively) of the 1MSTST. The other 4 empirical studies included two predictive studies on patients with Covid-19, and two on HIV-positive patients with suspected pneumocystis pneumonia. We found no studies on the 40-step walk test (a less demanding test that is widely used in clinical practice to assess Covid-19 patients). Heterogeneity of study design precluded meta-analysis. DISCUSSION: Exertional desaturation tests have not yet been validated in patients with (or suspected of having) Covid-19. A stronger evidence base exists for the diagnostic accuracy of the 1MSTST in chronic long-term pulmonary disease; the relative intensity of this test may raise safety concerns in remote consultations or unstable patients. The less strenuous 40-step walk test should be urgently evaluated.