Optimizing accelerometer data analysis to assess physical activity and sedentary behavior among breast cancer survivors: a laboratory study

Survival after cancer has substantially improved due to advances in early
detection and treatment. In the Netherlands, 14.631 patients were diagnosed
with breast cancer in 2014 and the current 5-year survival rate of patients
diagnosed with breast cancer is 87%.

Currently, (neo-) adjuvant systemic therapy is one of the standard cancer
treatments. (Neo-) adjuvant systemic therapy includes chemotherapy, hormonal
therapy or a combined treatment of both types of therapy, and aims to delay or
even prevent relapses and death. Although great improvements in disease free
and overall survival rates are achieved after (neo-) adjuvant systemic therapy,
cancer survivors (defined as patients following first diagnosis, until the end
of life) often experience negative side effects of cancer and cancer treatment,
with fatigue and a decrease in Quality of Life (QoL) as the most common and
distressing symptoms.

Physical activity during and after cancer treatment has beneficial effects on a
number of physical and psychosocial outcomes. Several reviews and meta-analyses
demonstrate beneficial effects of physical activity (PA) and exercise (i.e.
form of PA that is planned, structured and repetitive and aims to improve
fitness, performance or health) in cancer survivors during and after treatment
on physical and psychosocial outcomes, including increased aerobic fitness,
reduced fatigue and depression, and improved health-related quality of life
(HRQoL). Observational studies showed higher levels of moderate-to-vigorous PA
to be associated with lower mortality risk in survivors of breast, colon, and
prostate cancer.

Physical activity guidelines for cancer survivors suggest that physical
activity should be an integral and continuous part of care for all cancer
survivors. In 2010, the American College of Sports Medicine (ACSM) organized a
roundtable and formulated exercise guidelines for cancer survivors. The ACSM
recommends avoiding inactivity and being as physically active as abilities and
conditions allow. If possible, adult cancer survivors are recommended to engage
in at least 150 minutes per week of moderate intensity or 75 min per week of
vigorous intensity aerobic physical activity or an equivalent combination of
moderate and vigorous intensity aerobic physical activity, for at least 10 min
per session. In addition, muscle-strengthening activities involving all major
muscle groups are recommended at least 2 days per week. The ACSM acknowledges
that some activity is better than nothing and exceeding the guideline is likely
to provide additional health benefits. At present, the guidelines are rather
generic and resemble the age-appropriate physical activity guidelines for the
general population.

Physical activity levels of cancer survivors are lower than in the general
population, and they tend to decline during cancer treatment and remain lower
for years after cancer treatment. In addition, breast cancer survivors are more
sedentary and participate in less low intensity physical activity than matched
non-cancer controls. Sedentary behavior is characterized by a low energy
expenditure (i.e. * 1.5 metabolic equivalent multiple of rest (METs)). Similar
to findings in the general population, excessive sedentary behavior, as
distinct from insufficient physical activity, may be linked to negative health
effects. Recent experimental studies have indicated the importance of breaking
up prolonged sedentary time for improving health. Thus far, studies on the
pattern in which both sedentary behavior and physical activity is accumulated
and the effects of such patterns on health outcomes (e.g. fatigue and HRQoL)
are lacking in cancer survivors. Objective measurement of both physical
activity and sedentary behavior are obtained using accelerometers. Following
data reduction procedures (e.g. non-wear time, valid day definition), time
spent in sedentary, light, moderate or vigorous physical activity behavior are
subsequently assessed by applying cut-points. As these cut-points are validated
in the general population, which generally have a higher fitness level, they
may not be appropriate for cancer survivors. Therefore, alternative cut-points
or innovative predictions of accelerometer-based physical activity and
sedentary behavior may be required to capture the pattern of both physical
activity and sedentary behaviour in cancer patients. This information can be
used to better tailor exercise prescriptions to patients which may lead to
faster physical recovery and an increase in quality of life.

1. To validate accelerometer cut-points to asses physical activity and
sedentary behavior of breast cancer survivors.
2. To investigate the validity of accelerometers, inclinometers, heart rate and
oxygen consumption to assess time spent in sedentary behavior and light,
moderate-to vigorous intensity physical activity of breast cancer survivors.

Cardiorespiratory fitness will be measured during a maximal exercise test at a
cycle ergometer. The patient will be asked to cycle on a cycle ergometer
according to a ramp protocol which is tailored to the individual. The protocol
aims at achieving peak oxygen consumption (PeakVO2) within 8-12 minutes. In
addition, the following activities will be performed in random order for 6
minutes each, with resting intervals of 2 minutes in between:

1. Lying supine.
2. Sitting naturally in a lounge chair while watching TV.
3. Sitting in a chair behind a desk using a computer.
4. Standing upright while reading a newspaper.
5. Cycling on a cycle ergometer (i.e. 8.9 km/hr).
6. Cycling on a cycle ergometer (i.e. 15.1 km/hr.
7. Walking on a treadmill (i.e. 3.2 km/hr).
8. Walking on a treadmill (i.e. 4.8 km/hr).
9. Walking on a treadmill (i.e. 6.4 km/hr).
10. Stair climbing at a comfortable speed.


A heart rate monitor (Polar; RS800XC) will be used to monitor a participant*s
heart rate during the activities. Participant*s heart rate will be used to
estimate energy expenditure during the activities. Furthermore, oxygen
consumption will be measured continuously (breath-by-breath) using an (mobile)
oxycon. Metabolic equivalents (METs) will be calculated for every activity by
dividing the average oxygen consumption during the different activities by the
resting metabolic rate (determined when the patient is lying supine). In
addition, participants will wear ActiTrainer accelerometers (tri-axial, 51
gram; 86x33x15mm) at their right hip and wrist. ActiTrainer accelerometers
collect data on the amount and frequency of sedentary behaviour and ambulatory
activities. This device provides information on activity counts, vector
magnitude, steps taken and subject position and has a sample rate up to 100Hz.
An ActivPAL inclinometer (15 gram; 53x35x7mm) is worn on their right thigh.
ActivPAL is a single-site instrument to quantify free-living sedentary and
ambulatory activities. Using this device, the pattern of sedentary and
ambulatory activities and the intensity of the participants activities can be
captured and analysed. This device gives an accurate measurement of dynamic
acceleration and inclination.

Minimal risks are associated with the maximal exercise test. In the general
population, serious adverse events requiring hospitalization have been reported
in <1 to 5 times per 10000 tests.