e13002 Background: The neuropsychological impact of malignant glioma is well documented; the physiological and functional effects are not known. We conducted a pilot study to quantitatively assess cardiorespiratiory fitness, skeletal muscle function, and body composition of patients with primary malignant glioma. Methods: Using a cross-sectional design, patients with clinically stable postsurgical (10 ± 7 days post surgery) high-grade glioma (HGG; n=25) and low-grade glioma (LGG) were studied. Participants performed a cardiopulmonary exercise test (CPET) with expired gas analysis to assess peak exercise capacity (VO_2peak) and other parameters of cardiovascular function. Other physiological outcomes included skeletal muscle cross-sectional area (CSA; magnetic resonance imaging), isokinetic muscle strength (isokinetic dynamometer), and body composition (air displacement plethysmography). QOL was assessed by the Functional Assessment of Cancer Therapy-Brain scale (FACT-BR). Results: CPET was a feasible and safe procedure for malignant glioma patients with no serious adverse events. Peak VO₂ indexed to total body weight and lean body mass for both groups was 13.0 mL.min^-1 and 19 mL.min^-1; the equivalent to 59% and 38% below age and sex-predicted normative values, respectively. Skeletal muscle isokinetic strength was significantly lower in HGG relative to LGG patients (83 vs. 125 Nm, p=.025) and predicted peak VO₂ (r = 0.44, p<0.05). In patients with HGG, only self-reported exercise behavior was correlated with QOL (r = 0.42; p=.046) while sex (male) (r = 0.44; p=.037), lean mass (r = -0.41; p=.049), and VO_2peak (r = -0.40; p=.052) were associated with fatigue. Conclusions: CPET is a safe and feasible tool to evaluate physical functioning in select patients with malignant glioma. Postsurgical glioma patients have markedly reduced exercise capacity, isokinetic strength and CSA. Muscle strength is an important contributor to poor VO_2peak in this population. Prospective studies are now required to determine whether such abnormalities influence prognosis as well as test the effect of appropriately selected interventions to prevent and/or mitigate dysfunction. No significant financial relationships to disclose.