Whether you are a long time exerciser or just beginning---the "overload" training principle is important to understand to make real progress. We must provide overload to muscles in order for them to adapt and rebuild and become stronger--the key is overload without a severe injury. That is why it is vital to understand the difference between fatigue--the burn---and real pain.
fatigue defined is your muscles momentary inability to repeat the movement(work)--feeling the burn means lactic acid builds up and you'll need to give muscles a chance to get rid of that build up---pain is pure and simple real hurt that can lead to injury which puts you out of commission for a while. The no pain no gain philosophy is definite old school and NO school. The new tag line is: train for gain with no pain!
Learning your body's different feelings for these three(pain, burn, fatigue) can mean the difference between increase predisposition to injury or true gains in muscular strength--safely and effectively! Feel free to contact me if you want specifics or have questions about this in your own exercise regimen--I'm here for ya! Cheers! Dee
