&quot;It could go on to show that extreme (exercising at low intensity for 8 hours a day for 5-6 months)&quot;<p>That doesn&#x27;t sound extreme by any definition.  It sounds really hard and is a lot of output over time, but it is not at all what I would characterize as &quot;extreme&quot;.<p>If I were trying to discover what &quot;extreme&quot; exercise did to ones heart (or body, whatever) I would simulate a life or death scare that would enlist adrenaline and then present an insurmountable obstacle (basically a steep hill, or staircase that doesn&#x27;t end) and have them run to muscle failure.<p><i>That</i> sounds like extreme physical output and that would be an interesting scenario to test heart health in.d