The number of RCTs investigating the role of exercise in oncology is rising, but do studies adhere to the principles of training?
When trials don’t adhere to the principles of training or transparently explain how they prescribed exercises to participants it makes it almost impossible to use their results in clinical practice. It also becomes difficult to avoid mistakingly drawing conclusions that are due to methodological limitations.
This is also true for clinical practice. Without clear and transparent exercise prescription how do you know it is your exercises having the desired effect but also how can you hand over to a colleague and they pick up where you left off?
A new and updated systematic review published in BMC Cancer has sought out to investigate the adherence of the principles of training in cancer trials involving exercise.
What Are The Principles of Training?
The principles of training can be thought of as the golden rules of exercise prescription. When the rules are followed progression and improvement in strength and fitness are pretty much guaranteed. A detailed understanding of these rules is essential if you’re prescribing exercises to your patients.
- Specificity – training adaptations are specific to the muscles being trained
- Progression – over time the body adapts to exercise and for this to continue the volume or intensity must be increased
- Overload – for an intervention to improve fitness, the training volume must exceed current habitual levels of training
- Initial Values – improvements in the outcome of interest will be greatest in those with lower initial values
- Reversibility – once a training stimulus has been removed fitness levels will return to baseline
- Diminishing returns – the rate and size of improvement in fitness decreases as the individual becomes more fit. Also known as the ceiling effect.
FITT, or frequency, intensity, time (duration) and type of exercise are all essentials to communicate and prescribe the exercise itself. when exercises are communicated this way patients understand how long and how hard they should exercises and these are derived from the principles of training.
This is an updated systematic review which follows the same protocol as the two previous reviews which took place in 2012 and 2014.
The search terms, as previously used, included cancer (neoplasm, carcin- oma) and exercise (physical activity, aerobic, resistance, walking) specified for each database, in combination with the AND term.
Four databases were searched for relevant research and to be included articles has to meet the following criteria:
- RCTs involving 1 or more arms involving at least 4 weeks of aerobic and/or resistance exercise
- Report one physiological outcome related to exercise
- Include patients with a cancer diagnosis other than only breast or prostate
- Be published between 01/01/2021 to 23/09/2020 and published in English
Articles were excluded if alternative forms of exercise were performed, if only patients with metastatic or incurable cancers were included or if studies focussed on rehabilitation, physical activity or nutrition.
Four reviewers screened, reviewed and judged the eligibility of the articles for inclusion with disagreements resolved by a fifth reviewer.
Data extracted included: cancer type, sample size, timing of intervention delivery, treatment type, intervention duration, mode of delivery, timing of follow up, primary outcomes and secondary outcomes. FITT was used to summarise the exercise prescription.
The primary aim being to evaluate the use of the principles of training in the design of exercise prescription and secondary aims being to assess whether reporting had improved since the last review was performed.
In total 107 studies were included within the review with 58 studies conducted among adults with solid tumours, 25 with haematological cancer and 24 with mixed cancers. The majority of interventions were delivered during cancer treatment as opposed to afterwards.
In terms of application of principles of training only 2 studies fully reported all six training principles. Full application and reporting of at least half of the principles was found in 53% of studies. 5 studies did not report using the principles at all.
Of the 6 principles of training, specificity was the most frequently applied and was reported in 91% of studies and this is consistent with the two previous systematic reviews performed on the topic. Initial values was the next most commonly reported principle (72%) followed by overload (46%), progression (32%), reversibility (7%) and diminishing returns (5%).
All four FITT prescription components were reported in 58% of studies with 91% reporting at least half. Frequency was the most commonly reported prescription component (93%) and this hasn’t changed over time. Intensity was reported in 72% of studies, Time, or duration, was reported in 84% of studies and Type was reported in 80% of studies. However there has been marginal improvement in the past decade.
Without the principles of training being clearly reported during trials it is very challenging to replicate their results clinically. This is the same for the FITT prescription too. It appears there is improvement to be made in exercise reporting in oncology research however, some improvement has been made over the past decade.
It does ask the question, when you prescribe exercises in your clinical practice do you transparently adhere to the principles of training and FITT prescription?