A reader recently sent me a link to a post on a HIT blog recommending fast repetition speeds and claiming they were necessary to recruit the high threshold, fast twitch motor units. Although I just posted a Q&A on repetition speed, motor unit recruitment and stimulation last week and am probably just repeating myself I figured I would post my responses here for those interested.
The specific statements in his post I responded to were:
Type II muscles fibers are responsible for explosive/ballistic movements and stimulating muscle growth.
and
Every rep you should aim to accelerate it at the greatest velocity possible while still maintaining control of it.
and
You can use moderate weight as long as you keep in mind that acceleration is key. It won’t be until the last few reps, near failing, that those high threshold motor units are really fatigued which will lead to your gains.
Normally I would ignore this since the internet is full of bad training advice and if I tried to address all of it I wouldn’t have time for anything else. However, since this was on a HIT web site I felt compelled to respond. The following was my initial response to the above comments:
I’m surprised and disappointed to see such bad advice on a HIT site.
High levels of acceleration are not necessary to recruit the high threshold IIB fibers. Even with loads as low as 60% of 1RM all the motor units in the primary muscles in an exercise will be recruited within a few reps after which force is maintained despite fatigue by increased rate coding.
Whether you move slowly or quickly, as long as you use at least a moderately heavy weight ALL of the motor units will be recruited.
Also, the type II fibers are not responsible for explosive movements. The “fast” and “slow” in “fast twitch” and “slow twitch” refers to the time in ms it takes a fiber to reach it’s maximum tension, not the speed of movement the fiber is capable of producing. The difference in twitch speed between slow and fast twitch is less than 1/10th of a second. Slow twitch fibers can produce rapid movements and fast twitch fibers will be involved in even extremely slow or isometric movements as long as there is adequate resistance.
He replied,
Drew,
I was advocating higher levels of acceleration when using submaximal weights for the sole reason of generating more total force which would result in the greatest recruitment of type 2 fibers. Type 2 being responsible for the most hypertrophy. Moving more slowly, even though utilizing all fiber types, would create far less total force than a faster concentric pace not fatiguing those HI motor units optimally.
The point of calling them fast twitch is because they contract quicker than do slow twitch. I looked in 2 sources and they say fast contract up to 10x quicker than do slow.
During your entire rant, you neglect to mention anything about the size principle. Making your argument about how slow and fast twitch fibers don’t really differ that much flawed. When talking about weight lifting and producing relatively large forces, we are mainly talking about fast twitch even though slow twitch are still active.
I honestly don’t care if you agree with me or not. Yuri Verkhoshansky, Im sure you know who that is cuz you seem to know everything sees shit the same way I do. Here’s a exerpt from Supertraining:
“Further research reveals that this high intensity is not necessarily dependent on the use of 1RM or near 1RM loads, but the degree to which the relevant muscle fibres are recruited during the effort. In this respect, the terms fast twitch and slow twitch do not necessarily mean that fast movements recruit exclusively FT fibres and slow movements ST fibres. To analyze the involvement of the different fibre types, it is vital to determine the forece that needs to be produced. If large acceleration of the load is involved, Newtown’s Second Law of Motion decrees that the resulting force will be large. This, the maximal force generated during the rapid acceleration of a 100kg bench press easily can exceed the maximal force produced during a slowly accelerated 150kg bench press. Both a small load accelerated rapidly and a heavy load accelerated slowly strongly involve the FT fibres….”
I responded,
A higher rate of acceleration would result in a greater peak (momentary) force, followed by a proportional decrease in force as result of kinetic energy imparted to the moving bar or weights. The average force would be approximately the same – the difference is, with a slower movement the force is more consistent over the full range of motion.
Additionally, due to greater cross-bridging a muscle is capable of contracting with more force at slower velocities (force/velocity curve) during concentric contraction.
The best way to increase force is not to rapidly accelerate, but to simply use a heavier weight. Doing so increases the tension over the full range of the exercise and not just during the initial acceleration.
The reason they’re called fast “twitch” is because the twitch speed, or time it takes the fiber to reach maximum tension is faster – not the resulting speed of movement. If your sources say otherwise, they’re wrong. In Karla Punkt’s Fibre Types in Skeletal Muscles, on page 10 there is a table which includes the twitch times in ms: 40-90 for fast, 90-140 for slow. On average, this is a difference of about 50 ms, or 0.05 seconds.
Fast twitch motor units within a muscle are larger and as a result capable of producing greater force thus greater acceleration, but this is because of their size not necessarily their physiology. It is not necessary to move quickly to recruit them, however, only to use an adequately heavy weight.
I didn’t mention anything about the size principle because it wasn’t necessary for the point I was making, nor did I say the fibers don’t really differ. I said the speed of movement they are capable of producing does not differ and the average difference in twitch speed or rate of force development is less than most make it out to be (when they make a distinction at all).
As for the quote from Verkhoshansky, while the maximum force generated during a rapid acceleration of a 100kg bench press can exceed the maximum force producing during a slow 150kg bench press, it will only do so briefly and will be followed by a significant reduction in force. The average force over the full range of motion would be higher for the 150.
With the exception of practicing competitive lifts there is no reason to recommend moving quickly during exercise. Fast reps are not necessary to recruit the type IIB fibers, provide no advantage slow reps with adequate resistance, and have the disadvantage of producing an inconsistent level of tension over the range of motion, not to mention an increased risk of injury.
I give him partial credit for qualifying his recommendation to accelerate at the greatest velocity possible with the words “… while still maintaining control of it. ” Although, technically, this is not bad advice if the emphasis is on control, in practice it tends to result in sloppy and relatively ineffective performance. There is no benefit to moving faster during exercise and no disadvantage to moving more slowly so it is best to err on the slow side.
During the first few repetitions of an exercise the attempted speed of movement should be at least moderately slow. Specifically, slow enough that you are able to:
- Maintain strict body positioning and alignment.
- Reverse direction smoothly with no bouncing, yanking, jerking or heaving.
- Focus on intensely contracting the target muscles over the full range of the exercise.
As you fatigue the reps will become progressively slower. At this point you should attempt to gradually increase acceleration, trying to move faster but without altering body positioning and without jerking or heaving the weight. By this point it will be impossible for you to move faster if you maintain proper form and attempting to do so in a controlled manner will increase the intensity of contraction.
You should not, however, attempt to accelerate as much as possible at the beginning of an exercise or when using a weight that would allow you to move very rapidly.
I have not returned to the site after posting my second comment and have no interest in continuing the discussion there. I have too many other projects to work on to be writing on other people’s web sites at the moment. For now I’ll be taking Nautilus inventor Arthur Jones advice:
“The next time somebody suggests that you move suddenly during any form of exercise or testing, smile and walk away, because you are talking to a fool.”
Comments on this entry are closed.
Not to mention that velocity and acceleration are different. To increase the F(net)=MA equation the lift would need to be accelerating (that is gaining speed as it gets higher) for it to count in the equation. Doing a rep at 10mph versus 40mph makes no difference to the net force applied. In almost all lifts (irrelevant of speed) the only A you’re going to get is gravity. Makes more sense to add to the M…
Plus, like Drew says, it’s safer. Not to mention cheating the muscles later in the range of motion.
If you’re really into increasing the acceleration component of the force equation, equipment like elastic bands or a BowFlex will do that for you safely. And again, like Drew mentions, slow and even isometric exercises with this equipment has the same A as a fast movement.
Not nice to imply that I am a fool. Also your first sentence is misleading not stating anything about training with submaximal weights or stimulating the HT MUs maximally.
Jason,
Recommending fast rep speeds is foolish.
Also, you were the one that stated, “I was advocating higher levels of acceleration when using submaximal weights for the sole reason of generating more total force which would result in the greatest recruitment of type 2 fibers.”
It simply is not necessary to accelerate rapidly during exercise to recruit the high threshold motor units and doing so provides no advantage over slower repetition speeds but does increase the risk of injury. It isn’t necessary to move extremely slowly either, but repetitions should be performed at least slowly enough to meet the criteria mentioned above for body positioning and alignment, smooth turnarounds and contraction of target muscles.
We can agree to disagree then. I have mentioned several sources that disagree with you on my blog including a quote from Arthur Jones.
“A higher rate of acceleration would result in a greater peak (momentary) force, followed by a proportional decrease in force as result of kinetic energy imparted to the moving bar or weights.”
I assume this could also be called “momentum”. It seems intuitive that the more momentum the weights have during the movement the less force there would be on the muscles. But judging from the response you got from the HIT guy (and what I see from the “bodybuilders” at my gym)it’s far from obvious for most people.
Technically, it would be kinetic energy rather than momentum. Momentum is mass x velocity, kinetic energy is mass x velocity squared, divided by two. Where force is concernd it is an important difference.
A 2 ton truck traveling 80 mph has the same momentum as a 40 ton semi trailer traveling 4 mph but several thousand times more kinetic energy. The difference in kinetic energy is the difference in the force transferred to your body if you get hit by one or the other.
Thanks, Drew. I appreciate you taking the time to explain that to me.
Whenever a weight starts and ends at rest the average acceleration is zero and the average force equal with the weight.
Everyone who claims that explosive lifting “generates more total force” is clueless.
Also…since different muscles are engaged at different parts of ROM…the deceleration phase due to expolsive lifting leaves many muscles not stimulated enough.(Deceleration means less force applied).
The deceleration phase is much longer than most think:
“Elliot et al. revealed that at 81% of 1-RM, the bar deceleration occurs during the final 52% of the range of motion. The accompanying deceleration phases results in significantly decreased motor unit recruitment, velocity of movement, power production and compromises the effectiveness of the exercise.”
Wow. This compeletely flies in the face of everything I’ve learned about athletecism. I have a question about how worth it is it to perform plyometrics. I have always been taught to not lift that heavy so you don’t become slow and to perform plyometrics to increase your athletecism. I am a basketball player so I am trying not only to increase strength but more specifically to increase my vertical jump and explosiveness. Thanks for your help.
Chris,
Lifting heavy will not make you slow; the stronger your muscles the more force they can produce the faster they can accelerate your body in the performance of any movement. Proper strength training will do far more to improve your running speed and vertical jump than plyometrics and will do so with much lower risk of injury.
I strongly discourage people from performing plyometrics. The highest priority of a strength and conditioning program for athletes is the prevention of injury, and the risk of injury with plyometrics is much higher than with strength training at controlled speeds, but plyometrics are not nearly as productive for improving strength or explosiveness as strength training.
Drew,
I recently came across your post while researching repetition speed. I found it very interesting, as everything I had read prior advocated the use of increased rep speed (such as plyometrics) to improve force and explosive strength. That’s not to say you’re wrong or that there is not an equal amount of information in support of your opinion; only that I have not come across it.
Something I had recently incorporated into my workouts was “dynamic effort reps”, as outlined in this pdf (http://westside-barbell.com/westside-articles/PDF.Files/04PDF/Training%20Methods%20Part-1.pdf). Do you feel that this type of movement is an unnecessary component to successful workout program? Thanks for the help.
Adam,
I do not recommend the Westside Barbell dynamic effort method. Fast movement during exercise is not necessary to improve rate of force development, speed or explosiveness in other activities and does nothing to improve muscular strength or size gains, but does increase the risk of injury. If you use a heavy enough weight and strict form eventually you will be contracting as intensely as possible just to keep the weight moving at a controlled pace, and the intended speed and associated max effort during these later reps will improve rate of force development just as effectively and far more safely.
Whenever I mention this train of thought on forums people immediately hit me with ” If this is so they why are all the top athletes training explosively and working out on HIT routines ?”……..That is one question I’m always unable to answer.
Justin,
There are many professional and collegiate teams with high intensity training programs, so not all the top athletes are training explosively. Those who do, do so mostly because of tradition. When athletes first started to strength train decades ago they looked to competitive weight lifters for advice, who taught them how they trained. Unfortunately, the Olympic lifts are a very poor choice for other athletes, being highly technical and having a very high risk to benefit ratio for anyone other than competitive Olympic lifters. While there is no good, scientific rationale for athletes other than Olympic lifters to perform those exercises or to lift explosively in general, it is very difficult to change tradition. As Mark Twain wrote, “It’s easier to fool people than to convince them that they have been fooled.”
Hello Drew
For people that want to use weight lifting to accelerate their sport performance like me for example. I play soccer and i really want to become more explosive so i can accelerate faster and run faster. In terms of weight training what would you have me focus on ? like what do you think is important in terms of wich exersices, also what other stuff then just weight training?
Thanx
Karl,
If you want to become as explosive as possible for soccer you have to focus on becoming as strong as possible and practicing the skills you want to improve in soccer. You don’t need to train differently for strength, speed, power, stamina, explosiveness, etc. Getting stronger improves all of those things.