Tag: exercise limits

Long COVID and chronic fatigue syndrome/myalgic encephalitis share similar pathophysiologic mechanisms of exercise limitation

Abstract:

Post-acute sequelae of SARS-CoV-2 (PASC or “long COVID”) and chronic fatigue syndrome/myalgic encephalitis (CFS/ME) share symptoms such as exertional dyspnea. We used exercise oxygen pathway analysis, comprising six parameters of oxygen transport and utilization, to identify limiting mechanisms in both conditions. Invasive cardiopulmonary exercise testing was performed on 15 PASC patients, 11 CFS/ME patients, and 11 controls.

We evaluated the contributions of alveolar ventilation (V̇a), lung diffusion capacity (DL ), cardiac output (Q̇), skeletal muscle diffusion capacity (DM ), hemoglobin (Hb), and mitochondrial oxidative phosphorylation (Vmax) to peak oxygen consumption (V̇O2peak). To simulate targeted interventions, each variable was sequentially normalized to assess its impact on V̇O2peak. V̇O2peak was significantly reduced in both PASC and CFS/ME compared to controls.

Skeletal muscle O2 diffusion (DM ) was the most impaired parameter in both patient groups (p = 0.01). Correcting DM alone improved V̇O2 by 66% in PASC (p = 0.008) and 34.7% in CFS/ME (p = 0.06), suggesting a dominant role for peripheral O2 extraction in exercise limitation. Impaired skeletal muscle oxygen diffusion (DM ) is a shared mechanism of exercise intolerance in PASC and CFS/ME and may represent a therapeutic target. However, our findings are limited by small sample size.

Source: Jothi S, Insel M, Claessen G, Kubba S, Howden EJ, Ruiz-Carmona S, Levine T, Rischard FP. Long COVID and chronic fatigue syndrome/myalgic encephalitis share similar pathophysiologic mechanisms of exercise limitation. Physiol Rep. 2025 Sep;13(17):e70535. doi: 10.14814/phy2.70535. PMID: 40892700. https://physoc.onlinelibrary.wiley.com/doi/10.14814/phy2.70535 (Full text)

Can exercise limits prevent post-exertional malaise in chronic fatigue syndrome? An uncontrolled clinical trial

Abstract:

OBJECTIVE: It was hypothesized that the use of exercise limits prevents symptom increases and worsening of their health status following a walking exercise in people with chronic fatigue syndrome.

DESIGN: An uncontrolled clinical trial (semi-experimental design).

SETTING: Outpatient clinic of a university department.

SUBJECTS: Twenty-four patients with chronic fatigue syndrome.

INTERVENTIONS: Subjects undertook a walking test with the two concurrent exercise limits. Each subject walked at an intensity where the maximum heart rate was determined by heart rate corresponding to the respiratory exchange ratio = 1.0 derived from a previous submaximal exercise test and for a duration calculated from how long each patient felt they were able to walk.

MAIN OUTCOME MEASURES: The Short Form 36 Health Survey or SF-36, the Chronic Fatigue Syndrome Symptom List, and the Chronic Fatigue Syndrome -Activities and Participation Questionnaire were filled in prior to, immediately after and 24 hours after exercise.

RESULTS: The fatigue increase observed immediately post-exercise (P= 0.006) returned to pre-exercise levels 24 hours post-exercise. The increase in pain observed immediately post-exercise was retained at 24 hours post-exercise (P=0.03). Fourteen of the 24 subjects experienced a clinically meaningful change in bodily pain (change of SF-36 bodily pain score > or =10); 6 indicated that the exercise bout had slightly worsened their health status, and 2 had a clinically meaningful decrease in vitality (change of SF-36 vitality score > or =20). There was no change in activity limitations/participation restrictions.

CONCLUSION: It was shown that the use of exercise limits (limiting both the intensity and duration of exercise) prevents important health status changes following a walking exercise in people with chronic fatigue syndrome, but was unable to prevent short-term symptom increases.

 

Source: Nijs J, Almond F, De Becker P, Truijen S, Paul L. Can exercise limits prevent post-exertional malaise in chronic fatigue syndrome? An uncontrolled clinical trial. Clin Rehabil. 2008 May;22(5):426-35. Doi: 10.1177/0269215507084410. https://www.ncbi.nlm.nih.gov/pubmed/18441039