A pilot study of high-intensity interval training in older adults with treatment naïve chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the USA, affecting predominantly older adults. CLL is characterized by low physical fitness, reduced immunity, and increased risk of secondary malignancies and infections. One approach to improving CLL patients' physical fitness and immune functions may be participation in a structured exercise program. The aims of this pilot study were to examine physical and immunological changes, and feasibility of a 12-week high-intensity interval training (HIIT) combined with muscle endurance-based resistance training on older adults with treatment naïve CLL. We enrolled eighteen participants with CLL aged 64.9 ± 9.1 years and assigned them to groups depending on distance lived from our fitness center. Ten participants (4 M/6F) completed HIIT and six participants (4 M/2F) completed a non-exercising control group (Controls). HIIT consisted of three 30-min treadmill sessions/week plus two concurrent 30-min strength training sessions/week. Physical and immunological outcomes included aerobic capacity, muscle strength and endurance, and natural killer (NK) cell recognition and killing of tumor cells. We confirmed feasibility if > 70% of HIIT participants completed > 75% of prescribed sessions and prescribed minutes, and if > 80% of high-intensity intervals were at a heart rate corresponding to at least 80% of peak aerobic capacity (VO_2peak). Results are presented as Hedge's G effect sizes (g), with 0.2, 0.5 and 0.8 representing small, medium and large effects, respectively. Following HIIT, leg strength (g = 2.52), chest strength (g = 1.15) and seated row strength (g = 3.07) were 35.4%, 56.1% and 39.5% higher than Controls, respectively, while aerobic capacity was 3.8% lower (g = 0.49) than Controls. Similarly, following HIIT, in vitro NK-cell cytolytic activity against the K562 cell line (g = 1.43), OSU-CLL cell line (g = 0.95), and autologous B-cells (g = 1.30) were 20.3%, 3.0% and 14.6% higher than Controls, respectively. Feasibility was achieved, with HIIT completing 5.0 ± 0.2 sessions/week and 99 ± 3.6% of the prescribed minutes/week at heart rates corresponding to 89 ± 2.8% of VO_2peak. We demonstrate that 12-weeks of supervised HIIT combined with muscle endurance-based resistance training is feasible, and that high adherence and compliance are associated with large effects on muscle strength and immune function in older adults with treatment naïve CLL.Trial registration: NCT04950452.