Firestormm, 'exercise', 'activity', and 'exertion' can sometimes be used interchangeably. For example, all three apply to 'running' or 'swimming'.
The word 'exertion' would apply to
any activity in which you had to 'exert'
any effort, so it does apply to energetic pursuits that we think of as 'exercise', but it can also apply to far less demanding activities. For example, just to lift my arm, or to nod my head, requires exertion.
'Exercise'
usually applies to physical routines that are used to increase fitness and health.
The dictionary defines exercise as: "Activity requiring physical effort, carried out esp. to sustain or improve health and fitness."
So it's a flexible word, and could be used to describe various activities that help improve health.
It would describe different activities depending on the context, and the state of your health or level of fitness.
For example, physiotherapy can involve totally different exercises than what a top-level athlete would consider 'exercise' to mean.
In relation to GET, the word 'exercise' is unhelpful because it is suggestive of repetitive energetic athletic pursuits, such as running or swimming. But GET
should be a program that aims to gently increase levels of activity, if/when safe to do so. Perhaps GET has caused so many problems for ME/CFS patients partly because doctors assume that GET simply involves 'exercise' routines with steady increases in intensity. (Both assumptions are incorrect.)
I don't support the NICE guidelines but with regards to GET, they give an example of the sort of 'activity' or 'exercise' that can be focused on in GET programs:
1.6.2.14 GET should be based on the person’s current level of activities
(such as physical activity, daily routines, sleep patterns and frequency of
setbacks/relapses) and emotional factors, vocational or educational factors and
individual goals (details of these may be obtained from an activity diary). The
programme should also include sleep and relaxation strategies (see
recommendations 1.4.2.1–6).
1.6.2.15 When planning GET, the healthcare professional should:
• Undertake an activity analysis to ensure that the person with CFS/ME is
not in a ‘boom and bust’ cycle before they increase the time spent in exercise.
• Discuss with the person the ultimate goals that are important and relevant
to them.
This might be, for example, a twice-daily short walk to the shops, a
return to a previous active hobby such as cycling or gardening, or, for people with
severe CFS/ME, sitting up in bed to eat a meal.
• Recognise that it can take weeks, months or even years to achieve goals,
and ensure that this is taken into account in the therapy structure (for example,
by setting short- and medium-term goals).
• Explain symptoms and the benefits of exercise in a physiological context. Full guidelines August 2007
NCC-PC
Page 51 of 317
1.6.2.16 When starting GET, the healthcare professional should:
• Assess the person’s current daily activities to determine their baseline.
• Agree with them a level of additional low-intensity exercise that is
sustainable, independent of daily fluctuations in symptoms, and does not lead to
‘boom and bust’ cycles.
This may be sitting up in bed or brushing hair, for
example, for people with severe CFS/ME, or gentle stretches or a slow walk.
http://www.nice.org.uk/nicemedia/live/11824/36191/36191.pdf