should the concentric part always be done explosively?

[cytrix]

i am a little confused, as to the speed of the concentric part of a movement. should it be always done explosively, no matter if you are using lite, moderate or heavy weights? what about the saying to take 2 sec to eliminate momentum? somebody, please explain!

 

[Blood&Iron]

Some people will tell you that using an 'explosive' concentric lifting speed will help preferentially recruit fast-twitch muscle fibers, which have more potential for hypertrophy. Muscle fibers, however, are recruited according to the 'size principle' and not by speed of movement. This means slow-twitch fibers are recruited first, then as they are fatigued fast-twitch fibers are recruited. Excessive momentum will both take tension off the muscle and expose your joints to significantly greater internal forces. Some people can get away with lifting explosively for years. This doesn't mean it's a good idea. I'd generally suggest a concentric speed of 2 seconds or more. Just make sure you're in control of the weights at all times. If your interested in an interesting take on lifting speed, although a rather dogmatic one, go to:

http://www.superslow.com

They advocate a concentric speed of 10 seconds, and a negative speed of 5 seconds. I've used this to good success, but a 2 second speed is probably fairly safe in the long-term.

 

[bignate73]

just read a study by NSCA....

superslow actually yielded poor results compared to 4 second eccentric, 2 second concentric with no isometric. NASM also advocates a 4/0/2 rep tempo for hypertrophy as well. 2 of the better science backed certs, my money is on them.

 

[cytrix]

does 2 sec on the concentric part mean training explosively? i guess as long as the weight used is heavy, but what about moderate weights? wouldn't it be more like 1 sec concentric? or should you train more rhythmic and take 2 sec also?

 

[DaCypher]

I would consider "explosive" training to be less than 1 second on the concentric movement (this would depend on the exercise though). I would NEVER do train explosively unless you really know what you are doing (like if you are training for a specific sport and have been taught how to do it properly). You can easily injur yourself by using explosive movements while weight training. If you are looking to gain size/strength explosive movements are definetly not for you.