I know this has come up before and has been debated over the years, but I am wondering what the updated current thinking is on this question. If you do a long run of longer than 2 hours or something, even at a slow pace, do you start using fast twitch muscle fibers? Or at what intensity does it happen?
Also, does weight training or stregnth training generally use fast twitch fibers?
The general thinking is that once the slow twitch fibers are adequately fatigued, the fast twitch fibers begin to fire as a means of making up the difference. Along those lines and for this purpose, the pace doesn't matter as much as the duration (although pace will somewhat determine the ceiling of duration). Run long enough and eventually you'll train fast & slow twitch as well as become more efficient at utilizing available fuels.
Maybe that is why ultra runners are so muscular. OR why ironman triathletes have more muscle on them then the typical od triathletes. In pure cycling though i don't seem to see many big guys.
Long distance runner wrote:
The general thinking is that once the slow twitch fibers are adequately fatigued, the fast twitch fibers begin to fire as a means of making up the difference. Along those lines and for this purpose, the pace doesn't matter as much as the duration (although pace will somewhat determine the ceiling of duration). Run long enough and eventually you'll train fast & slow twitch as well as become more efficient at utilizing available fuels.
This.
That is why volume is important.
In well-trained runners, the fast-twitch fibers appear to be quite responsive to changes in training volume and intensity, more so even than slow-twitch fibers. The performance improvements with tapering (reduced volume) are associated with improvements in fast-twitch myofiber size and function.
To more directly answer your questions: you will recruit your fast-twitch fibers during long runs. The intensity issue is dependent on too many factors to provide an answer. With regards to weight-training and fast-twitch fiber recruitment: the same logic applies to running intensity. If you lift with adequate intensity, you will use fast-twitch fibers.
Tike wrote:
Maybe that is why ultra runners are so muscular. OR why ironman triathletes have more muscle on them then the typical od triathletes. In pure cycling though i don't seem to see many big guys.
In cycling, Climbers are the small ones- super high power/weight ratio. None of them are fatties, but TT specialists and sprinters can get pretty beefy.
Fabian Cancellara- 4X World Champion in Time Trial, has won Flanders and Paris-Roubaix 6'1"/180lbs
Lance- You know 5'9"/165lbs
Thor Hushovd- Front Rank sprinter/Classics Rider 6'0"/180lbs
Cycling is much more balanced between power and efficiency compared to running.
This is why ultra runners can sometimes bust out a sub 50 400m without doing any sprint work.
(sarcasm)
If you EAT enough then according to your phenotype you will put on MUSCLE.
Cyclists, tri guys, and runners don't want to gain weight because WEIGHT IS EVERYTHING in endurance sports.
Run a couple hours a day and eat 500 plus calories every two hours, including waking up to eat (like Salazar made his son do) and you will put on muscle.
Muscle alone will not help you bust out a sub 50 400m anymore than doing 100 reps of 225 will help you bench 600 pounds.
You recruit fast-twitch fibers when running at any pace, just fewer of them when running at a slower pace vs. a faster one.
junk master wrote:
If you EAT enough then according to your phenotype you will put on MUSCLE.
Cyclists, tri guys, and runners don't want to gain weight because WEIGHT IS EVERYTHING in endurance sports.
Run a couple hours a day and eat 500 plus calories every two hours, including waking up to eat (like Salazar made his son do) and you will put on muscle.
Muscle alone will not help you bust out a sub 50 400m anymore than doing 100 reps of 225 will help you bench 600 pounds.
a person that benches 600lbs would not be able to do 100 reps of 225
Rational Exercise wrote:
You recruit fast-twitch fibers when running at any pace, just fewer of them when running at a slower pace vs. a faster one.
This.
Since reading the information below, I have always believed it to be true, and have tried to incorporate this theory into my training...
"It has been hypothesized by many athletes and physiologists (triple Olympic gold medalist Dr. Peter Snell among them) that slow or moderate-paced running, if done long enough, would actually necessitate recruitment of "fast twitch" (FT) muscle fibers (motor units) as "slow twitch" (ST) units become depleted. However, this is almost certainly not true in runners unless the speed is increased near the end of a long run or unless strides or drills are used at the conclusion of the run."
Thanks for all the good responses! Sounds good since I love a good long run and need to work my FT fibers.