Purpose: Chemotherapy and/or radiation are the most often delivered treatments to cancer patients. Usually during the adjuvant treatment, patients complain about fatigue. In addition, physical exercise during adjuvant treatment of cancer seems to have beneficial effects. The aim of this investigation was to assess the effects of multimodal aerobic and strength exercises programs on muscle deoxygenation of patients with breast cancer undergoing adjuvant chemotherapy treatment. Methods: Thirty-two women with breast cancer (20 patients as the training group and 12 patients as the control group) undergoing adjuvant chemotherapy participated in the study. The training group took part in 6 weeks of supervised intermittent aerobic cycling, home-based walking, isometric and electrical muscle stimulation (EMS) exercise training programs. The Outcome measures were muscle deoxygenation (ÄHHb), Maximal Voluntary isometric Contraction (MViC) and Endurance Time (ET) before and after the training period. Results: Compared to the control group, a significant increase in ÄHHb (P < 0.01) accompanied with an increase in ET (P < 0.01) and MViC (P < 0.01) of the quadriceps was obtained in the training group. However, no significant differences of MViC, ET and ÄHHb were observed in the control group. Conclusion: Multimodal aerobic and strength exercise programs enhance muscle oxygen utilization, which may partly explain the improvement in muscular strength and endurance, and the reduction of muscle fatigue in patients with breast cancer during an adjuvant chemotherapy period.  Kulcsszavak: multimodal training, breast cancer, muscle deoxygenation, muscle fatigue, strength exercise