Accuracy and feasibility of wearable devides - implications for assessing autonomic control

Question 1

What is direct calorimetry?

Answer 1

Measures heat exchange between the human body and the environment.

Question 2

What is indirect calorimetry?

Answer 2

Measures the type and rate of substrate utilization, whereby energy metabolism is estimated from respiratory gas exchange measurements.

Question 3

What does ‘doubly labelled water’ do?

Answer 3

Drink a solution with isotopes in it, this measures total carbon dioxide production by observing the differential rates of elimination of a bolus dose of the stable isotope tracers [hydrogen(H2) and oxygen (O18)].

Question 4

What do cost, complexity and practicality issues do?

Answer 4

limit the use of criterion methods to measure free-living TDEE in this
population.

Question 5

ANS maintains homeostasis at
rest and in response to changes
in physiological state, how is this achieved?

Answer 5

Through changes in activity of the parasympathetic and sympathetic nervous system branches.

Question 6

What is the criterion measure/’gold standard’ way of measuring HR/HRV?

Answer 6

ECG - During each heartbeat, the heart
depolarizes and repolarizes, resulting
in measurable electrical charges on
the skin

Question 7

Most smart watches etc use PPG (reliable and valid), how does this work?

Answer 7

The optical properties in skin and tissue are periodically changing due to the blood flow driven by the heartbeat. By using a light emitter toward the skin surface, the photosensor can detect the variations in
light absorption, normally from wrist or finger.

Question 8

What is the premise behind HRV?

Answer 8

Beat-to-beat variation in the length of the cardiac cycles

Question 9

How to interpret HRV?

Answer 9

The greater the HRV, the greater the modulatory influence of the cardiac vagus on HR.

Question 10

Why might my HRV be lower
than yours right now?

Answer 10

Increased activation of the SNS & suppressed PNS activity

Question 11

How can we apply HRV in an applied sports science setting?

Answer 11

By measuring the impact of various stressors (e.g. training or lifestyle) on our resting physiology (HR and HRV), we can make meaningful adjustments that can lead to better health and performance.

Question 12

What are ‘acute stressors’?

Answer 12

e.g. a hard workout, intercontinental travel, too many alcoholic drinks, high caffeine intake etc. anything that has an effect on your physiology that lasts from a few minutes up to 24–48 hours.

Question 13

What are ‘chronic stressors’?

Answer 13

e.g. work or study-related worries, infection, illness