A Bout of High-Intensity Interval Training (HIIT) in Children and Adolescents during Acute Cancer Treatment-A Pilot Feasibility Study

Abstract

Low- and moderate-intensity exercise is safe and feasible during childhood cancer treatment. The feasibility of a bout of high-intensity interval training (HIIT) in this population has not been analyzed to date. Pediatric cancer patients aged between 6 and 18 years were selected based on clinical conditions to perform ten sets of 15 s HIIT (>90% of estimated maximal heart rate (HRmax)) and 1 min active recovery on a bicycle ergometer within the first three chemotherapy courses. We assessed safety and feasibility criteria and the following parameters: perceived exertion rate, heart rate, and lactate and adrenaline concentrations. Out of 212 eligible patients, 11 patients aged 13.9 ± 3.6 years (n = 7 ♂) with lymphoma, leukemia, rhabdomyosarcoma, nephroblastoma, and synovial sarcoma completed the bout of HIIT without serious adverse events. During exercise, patients reached a BORG value maxima of 16 ± 1.2, and their heart rates rose from 78 ± 17 beats per minute (bpm) at rest to 178 ± 12 bpm after exercise (90 ± 6% estimated HRmax). The power-to-weight ratio was 2 ± 0.5 W/kg (watt per kilogram). Blood lactate concentrations increased from 1.09 ± 0.50 mmol/L (millimole per liter) at rest to 5.05 ± 1.88 mmol/L post-exercise. Our preliminary data suggest that HIIT is applicable only in a small number of childhood cancer patients. Individually adapted exercise protocols for patients with multiple impairments are needed.

Keywords: adrenaline; childhood cancer; exercise intervention; feasibility; heart rate; high-intensity interval training; lactate; safety.

Figure 1

High-intensity interval training (HIIT) intervention protocol, including point of time for blood samples.

Figure 2

Scale for rating of perceived exertion (RPE scale, modified version of the BORG scale) (Borg 1962). The scale shows a range from 6 to 20. Participants were asked to estimate their subjectively perceived rate of exertion. For children and adolescents, the scale was modified by adding faces that visually reflect the level of exertion.

Figure 3

Flowchart of recruitment and study participation. n, number. ^a pre-existing exercise intervention study (ClinicalTrials.gov Identifier NCT03934060). ^b medical reasons for exclusion: severely reduced capacity (n = 13), treatment at intensive care unit (n = 3), osteoporotic vertebral compression fractures (n = 3), inability to sit/walk (n = 2), ventilated (n = 1), and severe comorbidity (n = 1).

Figure 4

High-intensity interval training (HIIT) was performed with 11 childhood cancer patients after completing a two-minute warm-up. Between each interval, there was one minute of active recovery, during which the patients stated their estimated exertion level. (a) Power-to-weight ratio indicates the ratio of body weight to power output for ten intervals for all eleven childhood cancer patients. Average values are presented, excluding active recovery periods, as the mean of the 10 intervals per patient, which range from 1.46 to 3.16 W/kg. The maximum power levels reached range between 65 watts and 300 watts. (b) Patients provided information on their exertion level based on the BORG scale ranging from 6 to 20. After warm-up, BORG values were stated to be between 6 and 7, indicating a very, very low perceived exertion level. Maximum BORG values range from 15 to 19, indicating the perceived exertion level to be high and very high, respectively. (c) Heart rate, evaluated in only seven of eleven patients due to technical difficulties with the chest strap, increased significantly during exercise from 78 ± 17 bpm at rest to a maximum of 178 ± 12 bpm using a paired t-test (p < 0.0001). n, number; W, watt; kg, kilogram; PWR, power-to-weight ratio; bpm, beats per minute; max, maximal.

Figure 5

Lactate and plasma adrenaline concentrations were measured in blood samples obtained prior to and directly after exercise intervention. (a) There was a significant increase in lactate concentrations when comparing resting (1.09 ± 0.50 mmol/L) and post-exercise values (5.05 ± 1.88 mmol/L) using a paired t-test (p < 0.0001). (b) There was no significant change in adrenaline concentrations when comparing resting and post-exercise values, despite adrenaline concentrations showing high variability within the tested group. Low adrenaline concentrations of 0.2 nmol/L (nanomole per liter) are in line with available data in healthy children [42]. mmol/L, millimole per liter; nmol/L, nanomole per liter.