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Understand just what the overall reaction of the body to exercise can be.
* Some people are super responders, some people are super not-responders. Find out where you are and make peace with it.
* There is a tradeoff between tiring yourself out and replenishing your energy. Don't overtrain
* There are two types of muscle short explosive muscle for strength and bulk and lean muscle for duration / marathon
* Muscle training works by tearing the muscles a little bit. This needs to recover and regrow. Segment the muscles you train. Biceps and Triceps one day. Shoulders the next, then legs the following.
* A lot of exercise is boring. Treadmill esp. Consider watching a live sport while treadmilling... that keeps it more interesting. ( Get outside and use communal facilities )
* Exercise releases endorphines, which registers as pleasurable to you brain and body. However they are weak and only slightly addictive. Get to a place where your body craves the endorphin release of exercise. Remove caffeine and sugar from your diet which are much stronger than endorphines and erase the addiction.
* The body adjusts to any exercise and you get diminishing returns often. Switch your routine to incorporate different body parts.
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Understand yourself.
Exercise within reasonable boundaries of what is possible for your body type
I'm 6"2' and 100KG I just can't do rock climbing easily, altough I look at American Ninja Warriors with envy.
Do you need a Personal Trainer to get motivated ?
Are you best in the morning or after work?
Things change with age. I used to be able to exercise in the evening. Now it has to be the morning.
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Ignore The Noise
Fashions, drinks, creatin, powders, straps, gadgets, expensive gyms and personal trainers. Ignore them all.
Exercise can be a mild meditation. Encourage that via having a rythmic routine, yet still including variety.