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Information for ME/CFS physicians
Adelaide research 2: lactate threshold during exercise
The following information was supplied as part of a handout at the November 7 talk given by Professor Garry Scroop at the AGM of the ME/Chronic Fatigue Syndrome Society of Victoria Inc:
Normal aerobic capacity and lactate threshold during incremental exercise in patients with chronic fatigue syndrome
Exercise Physiology Research Unit, Department of Physiology, Unversity of Adelaide, SA 5005
November 7, 2004
The metabolic responses during incremental exercise to exhaustion in 5 patients with Chronic Fatigue Syndrome (CFS) were compared with 5 healthy sedentary controls matched for gender (3 female, 2 male), age (CFS 34.80 +/- 4.73; controls, 35.20 +/- 4.59, yr), height (CFS, 170.40 +/- 4.39; controls 171.70 +/- 5.00, cm) and mass (CFS, 72.12 +/- 9.58; controls, 76.58 +/- 9.80, kg).
Control subjects exercised for longer (CFS, 18.80 +/- 0.58; controls, 23.66 +/- 1.01,min p<0.006), reached a higher peak workload (CFS, 125.00 +/- 7.91; controls 165.00 12.75, watts, p<0.04), and consequently did more work (CFS, 67.20 +/- 8.78; controls, 114.45 +/- 16.58, kJ, p<0.05).
Peak VO2 (VO2peak) at exhaustion was not significantly different between these 2 subject groups (CFS, 28.01 +/- 1.93; controls, 35.23 +/- 3.54; ml.kg-1.min-1, NS) or from their predicted VO2max determined during an earlier submaximal cycling test (CFS, 29.87 +/- 1.36; controls, 33.34 +/- 3.76; ml.kg-1.min-1; NS).
VO2peak achieved at peak heart rates (Hrpeak) which were not significantly different from each other (CFS, 177+/- 5; controls, 180 +/- 6; beats.min-1) or from their age-predicted maximum heart rates (Hrmax; CFS, 185 +/- 5; controls, 185 +/- 5; beats.min-1; NS).
The lactate threshold (LT, determined from a log-log plot of absolute VO2 versus blood lactate concentration) occurred at VO2 levels which were not significantly different between the 2 groups whether expressed in relative (CFS, 14.53 +/- 1.26 ml.kg-1.min-1; controls 14.16 +/- 2.05 ml.kg-1.min-1) or percentage (CFS, 52.2 +/- 3.4; controls, +41.9 +/- 7.8; % VO2peak) terms.
Despite doing less work the blood lactate concentration (CFS, 4.54 +/- 0.84; controls, 6.38 +/- 0.36; mmol.l-1) and VO2 at exhaustion in patients with CFS were not different from controls.
It is concluded that while the work capacity of patients with CFS is significantly less than sedentary controls, aerobic capacity and the LT are not, suggesting that factors other than so-called “deconditioning” are responsible for the earlier fatigue during exercise.