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Eighty-five per cent of the subjects (41 of 48) met either a plateau or a blood lactate criterion for . A plateau or change in oxygen uptake () of 8 mm was found in two adult and five elderly subjects not showing a plateau. The remaining 15% of the subjects who did not achieve the standard criteria nonetheless had an RERmax >1.15 and accumulated lactate during the test ([Lactatemax-rest]=��3.7 to ��6.2 mm; no lactate sample in one adult subject). Four of five elderly subjects in this group had a HRmax at the age-predicted value (i.e. 220 minus age), and the final subject not meeting the HRmax criterion had a final lactate of 7.6 mm. In a separate experiment, Osimertinib clinical trial we activated the quadriceps muscles by transcutaneous electrical stimulation of the femoral nerve, with the subject in a General Electric Signa 1.5 T imager/spectrometer, as previously described (Blei et al. 1993; Conley et al. 1997, 1998). Magnetic resonance spectra were acquired using a standard one-pulse experiment with partially saturated nuclear spins (1.5 s interpulse delay). The free-induction decays were Fourier transformed into spectra and analysed as previously described (Blei et al. 1993; Conley et al. 1997). GPX4 The area corresponding to each spectral peak was expressed relative to the ATP peak, which was calibrated using the ATP concentration measured in biopsies of the vastus lateralis muscle. The chemical shift (��) of the inorganic phosphate (Pi) Alectinib peak relative to phosphocreatine (PCr; ?2.54 p.p.m.) referenced to phosphoric acid (0 p.p.m.) was used to calculate pH (Taylor et al. 1983). Imaging muscle area and volume A standard T1-weighted magnetic resonance sequence was used to image the thigh and obtain cross-sectional areas of the quadriceps, as previously described (Jubrias et al. 1997; Fig. S1). We activated the quadriceps muscles by transcutaneous electrical stimulation of the femoral nerve, as previously described (Blei et al. 1993; Conley et al. 1997, 1998). Briefly, a 3 cm �� 4 cm cathode was placed over the femoral nerve immediately below the inguinal ligament in the femoral triangle, and a 7.5 cm �� 12.5 cm anode was placed on the posterolateral hip. We used the EMG to monitor muscle activation and establish the maximal stimulating voltage. The active electrode was placed over the belly of the vastus lateralis muscle and the reference electrode at the tendon immediately above the patella. The application of a series of single stimulations (150�C350 ��s) of increasing intensity allowed us to determine the intensity that evoked the maximal EMG response for each subject. During the experiment, stimulations of supramaximal intensity (1.3�C1.5 times maximal) were delivered for 2 min at 3 Hz. ATP supply Electrical stimulation was used to decrease [PCr].
