Many cancer survivors are inactive, putting them at risk of developing additional diseases
such as cardiovascular disease (CVD). Even though general physical activity guidelines exist,
cancer survivors commonly do not meet them and engage in too much sedentary behaviour.
The optimal level of physical activity and/or exercise for reducing CVD risk in cancer
survivors remains unclear. High-intensity interval training (HIIT) is being used by some
individuals (including those with a chronic condition such as Diabetes and CVD) as a method
of achieving additional physiological benefits compared to traditional exercise modes. It
remains unclear if HIIT is effective, achievable or safe for cancer survivors and if the same
benefits would be seen. The studies combined in this thesis aimed to investigate the efficacy
of HIIT within cancer survivors for reducing risk factors for CVD.
High-intensity exercise interventions elicited significant improvements (p < 0.05) in
VO2 max, strength, body mass, body fat and hip and waist circumference compared with
CMIT and/or control groups. The studies reviewed showed low risk in participating in
supervised high-intensity exercise interventions. A self-reported questionnaire was used to
determine the changes in physical activity (PA) patterns and body weight (BW) throughout
the first 12 months after a cancer diagnosis. In the 12 months post-diagnosis, cancer survivors
increased their sleep time and reduced their levels of both vigorous and light PA, this may or
may not be related to the increases in BW, which was observed for 60% of the
participants. These negative changes in PA puts this population at risk of additional diseases
such as CVD.
Cancer survivors (16) within 24 months post diagnosis, were randomly assigned into
the LVHIIT or CLMIT group for 36 sessions (12 weeks) of supervised exercise.
The LVHIIT group performed 7 x 30 second intervals (≥ 85% maximal heart rate) and
the CLMIT group performed continuous aerobic training for 20 minutes (≤ 55% maximal
heart rate) on a stationary bike or treadmill. Significant improvements (time) were observed
for 13 of the 23 dependent variables (ES 0.05-0.61, p=<0.05). An interaction effect was
observed for six-minute walk test (18.53% [32.43-4.63] ES 0.50, p = <0.01) with the LVHIIT
group demonstrating greater improvements. The study that followed incorporated a lager
sample size (75) of sedentary cancer survivors (n = 75, aged 51 ± 12 y) within 24 months of
diagnosis using the same exercise protocol. Significant improvements from baseline were
observed for seven of the 22 variables (ES 0.35 – 0.97, p ≤ 0.05). There was an interaction
effect (p < 0.01) after 12 weeks in the LVHIIT group for six-minute walk test (p < 0.01; d =
0.97; 95% CI = 0.36, 1.56; large), sit to stand test (p <0.01; d = - 0.83; 95% CI = -1.40, -
0.22; large) and waist circumference reduction (p = 0.01; d = - 0.48; CI = -1.10, 0.10;
medium). An interaction effect (p < 0.01) was also observed for quality of life in both the
LVHIIT (d = 1.11; 95% CI = 0.50, 1.72; large) and CLMIT (d = 0.57; 95% CI = -0.00, 1.20;
moderate) compared with the control group (d = -0.15; 95% CI = -0.95, 0.65; trivial). Lowvolume
high-intensity training showed promise as an effective exercise prescription within
the cancer population, showing greater improvements in cardio-respiratory fitness, lower
body strength and waist circumference compared with traditional CLMIT and control groups.
Both LVHIIT and CLMIT improved quality of life.
The impact of exercise intensity on autonomic nervous system (ANS) and immune function
in breast cancer survivors is not known. The final intervention included 17 participants
using the same protocol except for the rest between intervals which was increased to two
minutes. A significant improvement (p ≤ 0.05) in VO2peak from pre to post intervention in
both exercise groups were observed. Non-significant changes were observed in ANS function
and mucosal immunity in individuals with outlying baseline levels. Both HIIT and CMIT
improved cardiorespiratory fitness.
CVD remains one of the highest diagnosed comorbidities in the cancer population. Cancer
survivors continue to be inactive, increasing the negative impact on their health profile,
increasing CVD risk factors. Traditional and generic exercise guidelines are commonly used
by clinicians to assist in prescribing recommendations for increased amounts
of PA in the cancer population. In this thesis the “novel” exercise
modality (supervised LVHIIT) showed increased improvements in some of the health
outcomes measured, when compared with traditional CMIT however CMIT still showed
significant improvements, something that we were not expecting after the short amount of
exercise used. In summary, LVHIIT could be considered for use as an alternative to
traditional CMIT within the cancer population for improved fitness, quality of life and
compliance in those who are time poor. As shown in the final study cancer survivors who
had reduced measures of HPA axis and immune functions at baseline benefited most from
exercise. The studies within the thesis contributed to understanding HIIT within the cancer
population. HIIT could assist in the optimisation of individualised exercise prescription to
reduce risk factors for CVD in cancer.
|Date of Award||2018|
|Supervisor||Stuart Semple (Supervisor), Kate Pumpa (Supervisor) & Julie Cooke (Supervisor)|