Abstract
OBJECTIVE: In this feasibility study, firstly, we aimed to assess whether intramuscular pH (IMpH) could be measured with a glass-tipped electrode. Secondly, we aimed to explore whether we could monitor changes in skeletal muscle pH before and throughout static (isometric) and after dynamic (treadmill) exercise, comparing individuals with intermittent claudication (IC) to a group of healthy controls. METHODS: Forty participants with IC (mean age ± SD) 68 ± 8) and 40 healthy volunteers (63 ± 10) were recruited. Participants in the IC group had an ankle brachial pressure index of <0.7 (mean: 0.62 ± 0.13). The first 20 participants in each group underwent isometric ankle dorsiflexion for 120 s at 30% of maximum voluntary contraction and the remainder underwent treadmill exercise (3.6 km/h, 5° incline) to maximal walking distance. A sterilised reusable 1.5 mm shatterproof, heat strengthened glass tipped pH probe inserted using a peripheral venous cannula and in combination with a pH meter was used to measure IMpH of the tibialis anterior muscle prior to, during and continuously for 1 h after exercise. RESULTS: Resting IMpH was similar between the groups (median 6.8 (interquartile range (IQR) 6.7-6.9)) for IC individuals and 6.7 (6.6 to 6.8) for controls). Following isometric exercise, the magnitude of the decrease in IMpH was greatest in the IC group (median ΔpH max. in patients -0.2 (IQR: -0.2 to -0.1) versus -0.1 (IQR: -0.2 to -0.1) in the control group (p = 0.002). After treadmill exercise, the magnitude of the decrease in IMpH (ΔpH max) was greatest in individuals with IC (median ΔpH max. in patients -0.3 (IQR: -0.3 to -0.3) versus 0 (IQR: -0.2 to 0) in the control group, p = 0.04. CONCLUSIONS: IMpH monitoring with a flexible glass probe inserted into the tibialis anterior muscle is viable and changes in IMpH during static and dynamic exercises are detected.