Abstract:
Post-exertional malaise and delayed recovery are hallmark symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Studies on repeated cardiopulmonary exercise testing (CPET) show that previous exercise negatively affects oxygen uptake (VO2 ) and power output (PO) in ME/CFS. Whether this affects arterial lactate concentrations ([Laa ]) is unknown.
We studied 18 female patients (18-50 years) fulfilling the Canadian Consensus Criteria for ME/CFS and 15 healthy females (18-50 years) who underwent repeated CPETs 24 h apart (CPET1 and CPET2 ) with [Laa ] measured every 30th second. VO2 at peak exercise (VO2 peak) was lower in patients than in controls on CPET1 (P < 0.001) and decreased in patients on CPET2 (P < 0.001).
However, the difference in VO2peak between CPETs did not differ significantly between groups. [Laa ] per PO was higher in patients during both CPETs (Pinteraction < 0.001), but increased in patients and decreased in controls from CPET1 to CPET2 (Pinteraction < 0.001). Patients had lower VO2 (P = 0.02) and PO (P = 0.002) at the gas exchange threshold (GET, the point where CO2 production increases relative to VO2 ), but relative intensity (%VO2peak ) and [Laa ] at GET did not differ significantly from controls on CPET1 .
Patients had a reduction in VO2 (P = 0.02) and PO (P = 0.01) at GET on CPET2 , but no significant differences in %VO2peak and [Laa ] at GET between CPETs. Controls had no significant differences in VO2 , PO or %VO2peak at GET between CPETs, but [Laa ] at GET was reduced on CPET2 (P = 0.008).
In conclusion, previous exercise deteriorates physical performance and increases [Laa ] during exercise in patients with ME/CFS while it lowers [Laa ] in healthy subjects.
© 2019 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
Source: Lien K, Johansen B, Veierød MB, Haslestad AS, Bøhn SK, Melsom MN, Kardel KR, Iversen PO. Abnormal blood lactate accumulation during repeated exercise testing in myalgic encephalomyelitis/chronic fatigue syndrome. Physiol Rep. 2019 Jun;7(11):e14138. doi: 10.14814/phy2.14138. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6546966/ (Full article)