Editing Exercise intensity (section)

==Measures of Intensity==
[[Heart Rate]] is typically used as a measure of exercise intensity.<ref>VO<sub>2</sub>max: what do we know, and what do we still need to know. Levine, B.D. Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, TX 75231. The Journal of Physiology, 2008 Jan 1;586(1):25-34. Epub 2007 Nov 15.</ref> Heart rate can be an indicator of the challenge to the [[cardiovascular system]] that the exercise represents.

The most precise measure of intensity is oxygen consumption (VO<sub>2</sub>). VO<sub>2</sub> represents the overall metabolic challenge that an exercise imposes. There is a direct linear relationship between intensity of aerobic exercise and VO<sub>2</sub>. Our maximum intensity is a reflection of our maximal oxygen consumption ([[VO2 max|VO<sub>2</sub> max]]). Such a measurement represents a cardiovascular fitness level.<ref name="vehrs"/>

VO<sub>2</sub> is measured in [[Metabolic equivalent of task|METs]] (mL/kg/min). One MET, which is equal to 3.5 mL/kg per minute, is considered to be the average resting energy expenditure of a typical human being. Intensity of exercise can be expressed as multiples of resting energy expenditure. An intensity of exercise equivalent to 6 METs means that the energy expenditure of the exercise is six times the resting energy expenditure.<ref name="vehrs">Vehrs, P., Ph.D. (2011). Physical activity guidelines. In Physiology of exercise: An
incremental approach (pp. 351-393). Provo, UT: BYU Academic Publishing.</ref> 
 
Intensity of exercise can be expressed in absolute or relative terms. For example, two individuals with different measures of VO<sub>2</sub> max, running at 7&nbsp;mph are running at the same absolute intensity (miles/hour) but a different relative intensity (% of VO<sub>2</sub> max expended). The individual with the higher VO<sub>2</sub> max is running at a lower intensity at this pace than the individual with the lower VO<sub>2</sub> max is.<ref name="vehrs"/>

Some studies measure exercise intensity by having subjects perform exercise trials to determine [[peak power output]],<ref>{{cite journal|last1=Di Donato|first1=Danielle|last2=West|first2=Daniel|last3=Churchward-Venne|first3=Tyler|last4=Breen|first4=Leigh|last5=Baker|first5=Steven|last6=Phillips|first6=Stuart|display-authors=3|title=Influence of aerobic exercise intensity on myofibrillar and mitochondrial protein synthesis in young men during early and late postexercise recovery|journal=American Journal of Physiology. Endocrinology and Metabolism|date=2014|volume=306|issue=9|pages=E1025–E1032|doi=10.1152/ajpendo.00487.2013|url=http://ajpendo.physiology.org/content/306/9/E1025|access-date=14 June 2015|pmc=4010655|pmid=24595306}}</ref> which may be measured in [[watt]]s, heart rate, or average [[cadence (cycling)]]. This approach attempts to gauge overall workload.

An informal method to determine optimal exercise intensity is the talk test. It states that exercise intensity is “just about right”, when the subject can “just respond to conversation.”<ref>{{Cite journal |last1=Persinger |first1=Rachel |last2=Foster |first2=Carl |last3=Gibson |first3=Mark |last4=Fater |first4=Dennis C. W. |last5=Porcari |first5=John P. |date=2004 |title=Consistency of the talk test for exercise prescription |url=https://pubmed.ncbi.nlm.nih.gov/15354048 |journal=Medicine and Science in Sports and Exercise |volume=36 |issue=9 |pages=1632–1636 |issn=0195-9131 |pmid=15354048}}</ref> The talk test results in similar exercise intensity as the [[ventilatory threshold]] and is suitable for exercise prescription.<ref>{{Cite journal |last1=Foster |first1=Carl |last2=Porcari |first2=John P. |last3=Anderson |first3=Jennifer |last4=Paulson |first4=Melissa |last5=Smaczny |first5=Denise |last6=Webber |first6=Holly |last7=Doberstein |first7=Scott T. |last8=Udermann |first8=Brian |date=2008 |title=The Talk Test as a Marker of Exercise Training Intensity |url=https://journals.lww.com/01273116-200801000-00005 |journal=Journal of Cardiopulmonary Rehabilitation and Prevention |language=en |volume=28 |issue=1 |pages=24–30 |doi=10.1097/01.HCR.0000311504.41775.78 |pmid=18277826 |issn=1932-7501|url-access=subscription }}</ref>