Category: Exercise

Mechanisms underlying exercise intolerance in long COVID: An accumulation of multisystem dysfunction

Abstract:

The pathogenesis of exercise intolerance and persistent fatigue which can follow an infection with the SARS-CoV-2 virus (“long COVID”) is not fully understood. Cases were recruited from a long COVID clinic (N = 32; 44 ± 12 years; 10 (31%) men), and age-/sex-matched healthy controls (HC) (N = 19; 40 ± 13 years; 6 (32%) men) from University College London staff and students.

We assessed exercise performance, lung and cardiac function, vascular health, skeletal muscle oxidative capacity, and autonomic nervous system (ANS) function. Key outcome measures for each physiological system were compared between groups using potential outcome means (95% confidence intervals) adjusted for potential confounders. Long COVID participant outcomes were compared to normative values.

When compared to HC, cases exhibited reduced oxygen uptake efficiency slope (1847 (1679, 2016) vs. 2176 (1978, 2373) mL/min, p = 0.002) and anaerobic threshold (13.2 (12.2, 14.3) vs. 15.6 (14.4, 17.2) mL/kg/min, p < 0.001), and lower oxidative capacity, measured using near infrared spectroscopy (τ: 38.7 (31.9, 45.6) vs. 24.6 (19.1, 30.1) s, p = 0.001). In cases, ANS measures fell below normal limits in 39%.

Long COVID is associated with reduced measures of exercise performance and skeletal muscle oxidative capacity in the absence of evidence of microvascular dysfunction, suggesting mitochondrial pathology. There was evidence of attendant ANS dysregulation in a significant proportion. These multisystem factors might contribute to impaired exercise tolerance in long COVID sufferers.

Source: Jamieson A, Al Saikhan L, Alghamdi L, Hamill Howes L, Purcell H, Hillman T, Heightman M, Treibel T, Orini M, Bell R, Scully M, Hamer M, Chaturvedi N, Montgomery H, Hughes AD, Astin R, Jones S. Mechanisms underlying exercise intolerance in long COVID: An accumulation of multisystem dysfunction. Physiol Rep. 2024 Feb;12(3):e15940. doi: 10.14814/phy2.15940. PMID: 38346773; PMCID: PMC10861355. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10861355/ (Full text)

Exploring the neurocognitive consequences of post-exertional malaise in myalgic encephalomyelitis

Background and aims:

Myalgic encephalomyelitis (ME) is a complex, debilitating and heterogeneous disorder. It affects over 500,000 people in Canada but remains poorly understood. People are affected with multi-systemic symptoms such as fatigue that is not alleviated by rest, pain, cognitive impairment and post-exertional malaise (PEM), which is considered as the hallmark symptom of ME. PEM is triggered by minimal mental or physical effort and exacerbates other symptoms. Our aim was to measure how individuals’ cognition can be impacted by the induction of PEM, and investigate the difference in cognitive response.

Section snippets:

Methods
A prospective cohort of people with ME (n = 42) and matched healthy controls (n = 15) was recruited and subjected to PEM induction through a 90-minutes mechanical arm stimulation. BrainCheck test (BrainCheck, Inc., TX, USA) was used at baseline (T0) and after 90 minutes of stimulation to evaluate six cognitive domains for which each participant received a score and a population percentile based on their performance.

Results
Comparison between both groups was significant (p < 0.05) at T90, but not at T0, in four out of six cognitive domains. We then classified our ME cohort in three clusters by k-means method based on the Δ percentile (T90-T0) for each cognitive task. This stratification allowed us to notice how some cognitive domains seem more affected depending on the cluster, namely memory and attention.

Conclusions
These results showed the impact of PEM on the disturbance of cognition in the context of ME as well as the variability of cognitive domains affected in people with ME.

Source: Corinne Leveau, Iurie Caraus, Anita Franco, Alain Moreau. Exploring the neurocognitive consequences of post-exertional malaise in myalgic encephalomyelitis. Journal of the Neurological Sciences, Volume 455, Supplement, December 2023, 122590. https://www.sciencedirect.com/science/article/abs/pii/S0022510X23020518

 

Central 5-HTergic hyperactivity induces myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like pathophysiology

Abstract:

Objectives: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a significant medical challenge, with no indisputable pathophysiological mechanism identified to date.

Methods: Based on clinical clues, we hypothesized that 5-hydroxytryptamine (5-HT) hyperactivation is implicated in the pathogenic causes of ME/CFS and the associated symptoms. We experimentally evaluated this hypothesis in a series of mouse models.

Results: High-dose selective serotonin reuptake inhibitor (SSRI) treatment induced intra- and extracellular serotonin spillover in the dorsal raphe nuclei of mice. This condition resulted in severe fatigue (rota-rod, fatigue rotating wheel and home-cage activity tests) and ME/CFS-associated symptoms (nest building, plantar and open field test), along with dysfunction in the hypothalamic-pituitary-adrenal (HPA) axis response to exercise challenge. These ME/CFS-like features induced by excess serotonin were additionally verified using both a 5-HT synthesis inhibitor and viral vector for Htr1a (5-HT1A receptor) gene knockdown.

Conclusions: Our findings support the involvement of 5-HTergic hyperactivity in the pathophysiology of ME/CFS. This ME/CFS-mimicking animal model would be useful for understanding ME/CFS biology and its therapeutic approaches.

Source: Lee JS, Kang JY, Park SY, Hwang SJ, Bae SJ, Son CG. Central 5-HTergic hyperactivity induces myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like pathophysiology. J Transl Med. 2024 Jan 8;22(1):34. doi: 10.1186/s12967-023-04808-x. PMID: 38191373. https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-023-04808-x (Full text)

Muscle abnormalities worsen after post-exertional malaise in long COVID

Abstract:

A subgroup of patients infected with SARS-CoV-2 remain symptomatic over three months after infection. A distinctive symptom of patients with long COVID is post-exertional malaise, which is associated with a worsening of fatigue- and pain-related symptoms after acute mental or physical exercise, but its underlying pathophysiology is unclear.

With this longitudinal case-control study (NCT05225688), we provide new insights into the pathophysiology of post-exertional malaise in patients with long COVID. We show that skeletal muscle structure is associated with a lower exercise capacity in patients, and local and systemic metabolic disturbances, severe exercise-induced myopathy and tissue infiltration of amyloid-containing deposits in skeletal muscles of patients with long COVID worsen after induction of post-exertional malaise. This study highlights novel pathways that help to understand the pathophysiology of post-exertional malaise in patients suffering from long COVID and other post-infectious diseases.

Source: Appelman, B., Charlton, B.T., Goulding, R.P. et al. Muscle abnormalities worsen after post-exertional malaise in long COVID. Nat Commun 15, 17 (2024). https://doi.org/10.1038/s41467-023-44432-3 https://www.nature.com/articles/s41467-023-44432-3 (Full text)

Differential Cardiopulmonary Hemodynamic Phenotypes in PASC Related Exercise Intolerance

Abstract:

Background Post-acute sequelae of COVID-19 (PASC) affects a significant portion of patients who have previously contracted SARS-CoV-2, with exertional intolerance being a prominent symptom.

Study Objective This study aimed to characterize the invasive hemodynamic abnormalities of PASC-related exertional intolerance using a larger data set from invasive cardiopulmonary exercise testing (iCPET).

Study Design & Intervention Fifty-five patients were recruited from the Yale Post-COVID-19-Recovery-Program, with most experiencing mild acute illness. Supine right heart catheterization (RHC) and iCPET were performed on all participants.

Main results The majority (75%) of PASC patients exhibited impaired peak systemic oxygen extraction (pEO2) during iCPET in conjunction with supranormal cardiac output (CO) (i.e., PASC alone group), On average, the PASC alone group exhibited a “normal” peak exercise capacity, VO2 (89±18% predicted). Approximately 25% of patients had evidence of central cardiopulmonary pathology (i.e., 12 with resting and exercise HFpEF and 2 with exercise PH). PASC patient with HFpEF (i.e., PASC HFpEF group) exhibited similarly impaired pEO2 with well compensated PH (i.e., peak VO2 and cardiac output >80% respectively) despite aberrant central cardiopulmonary exercise hemodynamics. PASC patients with HFpEF also exhibited increased body mass index of 39±7 kg·m−2. To examine the relative contribution of obesity to exertional impairment in PASC HFpEF, a control group compromising of obese non-PASC group (n=61) derived from historical iCPET cohort was used. The non-PASC obese patients with preserved peak VO2 (>80% predicted) exhibited a normal peak pulmonary artery wedge pressure (17±14 versus 25±6 mmHg; p=0.03) with similar maximal voluntary ventilation (90±12 versus 86±10%predicted; p=0.53) compared to PASC HFpEF patients. Impaired pEO2 was not significantly different between PASC patients who underwent supervised rehabilitation and those who did not (p=0.19).

Conclusions This study highlights the importance of considering impaired pEO2 in PASC patients with persistent exertional intolerance unexplained by conventional investigative testing. Results of current study also highlights the prevalence of a distinct high output failure HFpEF phenotype in PASC with a primary peripheral limitation to exercise.

Source: Peter A. Kahn, Phillip Joseph, Paul M. Heerdt, Inderjit Singh. Differential Cardiopulmonary Hemodynamic Phenotypes in PASC Related Exercise Intolerance. ERJ Open Research Jan 2023, 00714-2023; DOI: 10.1183/23120541.00714-2023 https://openres.ersjournals.com/content/early/2023/12/07/23120541.00714-2023 (Full text available as PDF file)

Post-COVID exercise intolerance is associated with capillary alterations and immune dysregulations in skeletal muscles

Abstract:

The SARS-CoV-2 pandemic not only resulted in millions of acute infections worldwide, but also in many cases of post-infectious syndromes, colloquially referred to as “long COVID”. Due to the heterogeneous nature of symptoms and scarcity of available tissue samples, little is known about the underlying mechanisms.

We present an in-depth analysis of skeletal muscle biopsies obtained from eleven patients suffering from enduring fatigue and post-exertional malaise after an infection with SARS-CoV-2. Compared to two independent historical control cohorts, patients with post-COVID exertion intolerance had fewer capillaries, thicker capillary basement membranes and increased numbers of CD169+ macrophages. SARS-CoV-2 RNA could not be detected in the muscle tissues.

In addition, complement system related proteins were more abundant in the serum of patients with PCS, matching observations on the transcriptomic level in the muscle tissue. We hypothesize that the initial viral infection may have caused immune-mediated structural changes of the microvasculature, potentially explaining the exercise-dependent fatigue and muscle pain.

Source: Aschman, T., Wyler, E., Baum, O. et al. Post-COVID exercise intolerance is associated with capillary alterations and immune dysregulations in skeletal muscles. acta neuropathol commun 11, 193 (2023). https://doi.org/10.1186/s40478-023-01662-2 https://actaneurocomms.biomedcentral.com/articles/10.1186/s40478-023-01662-2 (Full text)

Post-exertional malaise in daily life and experimental exercise models in patients with myalgic encephalomyelitis/chronic fatigue syndrome

Abstract:

Post-exertional malaise (PEM) is commonly recognized as a hallmark of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is often used as one of several criteria for diagnosing ME/CFS.

In this perspective paper we want to reflect on how PEM is understood, assessed, and evaluated in scientific literature, and to identify topics to be addressed in future research.

Studies show that patients use a wide variety of words and concepts to label their experience of PEM in everyday life, and they report physical or mental exertions as triggers of PEM. They also report that PEM may have an immediate or delayed onset and may last from a few days to several months.

When standardized exercise tests are used to trigger PEM experimentally, the exacerbation of symptoms has a more immediate onset but still shows a wide variability in duration.

There are indications of altered muscular metabolism and autonomic nervous responses if exercise is repeated on successive days in patients with ME/CFS. The decreased muscular capacity appears to be maintained over several days following such controlled exercise bouts. These responses may correspond to patients’ experiences of increased exertion.

Based on this background we argue that there is a need to look more closely into the processes occurring in the restitution period following exercise, as PEM reaches the peak in this phase.

Source: Nina K. Vøllestad, Anne Marit Mengshoel. Post-exertional malaise in daily life and experimental exercise models in patients with myalgic encephalomyelitis/chronic fatigue syndrome. Frontiers in Physiology, Volume 14- 2023. https://www.frontiersin.org/articles/10.3389/fphys.2023.1257557/abstract

Exercise capacity in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) treated with long-term pyridostigmine

Abstract:

Background: The pathophysiology underlying exertional intolerance in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) remains poorly understood. Previously, a single-dose of 60 mg pyridostigmine, a reversible acetylcholinesterase inhibitor, was found to acutely improve aerobic capacity (Joseph, P. et al. Chest 2022; 162:1116–26).

Aims: To build upon these prior findings, this study aimed to evaluate the long-term effect (>1 month) of pyridostigmine treatment on exercise intolerance in ME/CFS.

Methods: Between 2017-2022, patients who met the National Academy of Medicine criteria for ME/CFS, and had a minimum of two clinical, constant load, submaximal exercise tests (Shape Medical System, MN) were evaluated. Patients who began pyridostigmine after their baseline test were considered the treatment group. Measurements were taken at baseline (T0) and most recent follow-up (T1).

Results: At the follow-up evaluation (690 ± 547 days), the treatment group (n=37, dose range: 24-360mg/d) demonstrated a significant increase in oxygen uptake efficiency slope (OUES) (T0: 1.82 ± 0.56, T1: 1.98 ± 0.53; p=0.044) and pulmonary vascular capacitance (PVCAP) (T0: 486.19 ± 169.89 ml*mmHg, T1: 540.03 ± 170.59 ml*mmHg; p=0.040). These differences were not observed in the control group (n=16) OUES (T0: 1.62 ± 0.40, T1: 1.77 ± 0.47; p=0.268) and PVCAP (T0: 446.94 ± 144.80 ml*mmHg, T1: 465.81 ± 124.34 ml*mmHg; p=0.590).

Conclusion: Long-term treatment with pyridostigmine improved aerobic capacity in ME/CFS as demonstrated by an increase in OUES, mediated by improvements in central hemodynamics (PVCAP).

Source: Johanna Squires, Sarra Al-Zayer, David Systrom. Exercise capacity in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) treated with long-term pyridostigmine. European Respiratory Journal Sep 2023, 62 (suppl 67) PA4639; DOI: 10.1183/13993003.congress-2023.PA4639 https://erj.ersjournals.com/content/62/suppl_67/PA4639

Maximal Oxidative Capacity During Exercise is Associated with Muscle Power Output in Patients with Long coronavirus disease 2019 (COVID-19) Syndrome. A Moderation Analysis

Abstract:

Background & Aims: Long COVID syndrome (LCS) involves persistent symptoms experienced by many patients after recovering from coronavirus disease 2019 (COVID-19). We aimed to assess skeletal muscle energy metabolism, which is closely related to peak fat oxidation rates during exercise, in patients with LCS compared with healthy controls. We also examined whether muscle power output mediates the relationship between COVID-19 and skeletal muscle energy metabolism.

Methods: In this cross-sectional study, we enrolled 71 patients with LCS and 63 healthy controls. We assessed clinical characteristics such as body composition, physical activity, and muscle strength. We used cardiopulmonary exercise testing to evaluate substrate oxidation rates during graded exercise. We performed statistical analyses to compare group characteristics and peak fat oxidation differences based on power output.

Results: The two-way analysis of covariance (ANCOVA) results, adjusted for covariates, showed that the patients with LCS had lower absolute maximal fatty acid oxidation (MFO), relative MFO/fat-free mass (FFM), absolute carbohydrates oxidation (CHox), relative CHox/FFM, and oxygen uptake (VO2) at maximum fat oxidation (mL∙min−1) than the healthy controls (P < 0.05). Moderation analysis indicated that muscle power output significantly influenced the relationship between LCS and reduced peak fat oxidation (interaction β = −0.105 [95% confidence interval −0.174; −0.036]; P = 0.026). Therefore, when muscle power output was below 388 W, the effect of the LCS on MFO was significant (62% in our study sample P = 0.010). These findings suggest compromised mitochondrial bioenergetics and muscle function, represented by lower peak fat oxidation rates, in the patients with LCS compared with the healthy controls.

Conclusion: The patients with LCS had lower peak fat oxidation during exercise compared with the healthy controls, potentially indicating impairment in skeletal muscle function. The relationship between peak fat oxidation and LCS appears to be mediated predominantly by muscle power output. Additional research should continue investigating LCS pathogenesis and the functional role of mitochondria.

Source: Robinson Ramírez-Vélez, Sergio Oscoz-Ochandorena, Yesenia García-Alonso, Nora García-Alonso, Gaizka Legarra-Gorgoñon, Julio Oteiza, Ander Ernaga Lorea, Mikel Izquierdo, María Correa-Rodríguez. Maximal Oxidative Capacity During Exercise is Associated with Muscle Power Output in Patients with Long coronavirus disease 2019 (COVID-19) Syndrome. A Moderation Analysis. Clinical Nutrition ESPEN, 2023, ISSN 2405-4577, https://doi.org/10.1016/j.clnesp.2023.10.009. https://www.sciencedirect.com/science/article/pii/S2405457723021666 (Full text)

Decreased physical performance despite objective and subjective maximal exhaustion in post-COVID-19 individuals with fatigue

Abstract:

Introduction: Fatigue is a common symptom in post-COVID-19 patients. Individuals with fatigue often perform less well compared to healthy peers or without fatigue. It is not yet clear to what extent fatigue is related to the inability to reach maximum exhaustion during physical exercise.

Methods: A symptom-based questionnaire based on the Carruthers guidelines (2003) was used for reporting the presence of fatigue and further symptoms related to COVID-19 from 85 participants (60.0% male, 33.5 ± 11.9 years). Cardiopulmonary exercise testing (CPET) and lactate measurement at the end of the test were conducted. Objective and subjective exhaustion criteria according to Wasserman of physically active individuals with fatigue (FS) were compared to those without fatigue (NFS).

Results: Differences between FS and NFS were found in Peak V̇O2/BM (p < 0.001) and Max Power/BM (p < 0.001). FS were more likely to suffer from further persistent symptoms (p < 0.05). The exhaustion criterion Max. lactate was reached significantly more often by NFS individuals.

Conclusion: Although the aerobic performance (Max Power/BM) and the metabolic rate (Peak V̇O2/BM and Max. lactate) of FS were lower compared to NFS, they were equally able to reach objective exhaustion criteria. The decreased number of FS who reached the lactate criteria and the decreased V̇O2 peak indicates a change in metabolism. Other persistent post-COVID-19 symptoms besides fatigue may also impair performance, trainability and the ability to reach objective exhaustion.

Trial registration: Trial registration: DRKS00023717; date of registration: 15.06.2021 (retrospectively registered).

Source: Vollrath S, Matits L, Schellenberg J, Kirsten J, Steinacker JM, Bizjak DA. Decreased physical performance despite objective and subjective maximal exhaustion in post-COVID-19 individuals with fatigue. Eur J Med Res. 2023 Aug 26;28(1):298. doi: 10.1186/s40001-023-01274-5. PMID: 37633931; PMCID: PMC10464445. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10464445/ (Full text)