Near infrared spectroscopy (NIRS) provides a non invasive method of analysing muscle metabolism and response to stress in human muscle, normally under ischaemic conditions (1,2). The aim of this study was to examine the feasibility of using NIRS during muscle fatigue in non-ischaemic state as a basis for future exploration of tissue oxygenation and muscle performance in humans with metabolic problems. A convenient sample of 10 healthy adults (5M, 5F) mean age 36 (SD 7) years with no known metabolic, neurological or musculoskeletal diseases participated in this ethically approved study. Participants were seated in isometric torque chair and NIRS optodes (NIRO-200, Hamamatsu Photonics Deutschland GMBH) were placed over both quadriceps femoris muscles. Responses of the right limb to (A) proximal limb occlusion with a thigh cuff pressure of 100 mmHg greater than systolic pressure for 15 minutes, (B) percutaneous stimulation at 40Hz for 250 ms every second for 3 minutes (modified Burke fatigue protocol) and (C) proximal limb occlusion for 5 minutes applied immediately after muscle fatigue were recorded. Anthropometric details including skinfold thickness were also recorded. Changes in oxyhaemoglobin (ΔO2Hb) and deoxyhaemoglobin (ΔHHb) during the first 3 minutes of each condition was measured. Repeated measures ANOVA was performed to determine possible significant differences between conditions A, B, and C and post-hoc t-tests were conducted as appropriate. The relationship with anthropometric characteristics was examined using Pearson’s correlation coefficients. As expected, measures ΔO2Hb and ΔHHb were related to skin fold thickness (r = -0.677 to -0.783, p<0.05). For conditions A, B and C, absolute values (mean ± SEM) for ΔO2Hb were 133 ± 50 μM, 194 ± 67 μM and 214 ± 60 μM respectively and for ΔHHb were 158 ± 40 μM, 260 ± 39 μM and 154 ± 65 μM respectively. Significant differences were observed in ΔO2Hb (ANOVA: F2 = 8.975, p<0.01) and ΔHHb (ANOVA: F2 = 7.448, p<0.05). Post hoc analysis confirmed that change in ΔO2Hb levels was significantly less in condition A (p<0.05) whereas change in ΔHHb levels was significantly greater during condition B (p<0.05). Differences in the response of ΔO2Hb and ΔHHb during ischaemia in a fresh and fatigued state and during fatiguing muscle contraction support the feasibility of the procedure but unresolved issues include the effectiveness of lower limb occlusion and potential localised volume changes in the lower limb distal to the cuff. The negative correlation between skinfold thickness and measures of ΔO2Hb and ΔHHb suggests that skinfold thickness may account for the large observed variability.