If you’ve lifted weights for a while, you know that building strength means challenging your muscles more than they’re accustomed to – but in a controlled manner. We call this concept progressive overload. As you increase the load or volume you place on a muscle, it’s forced to adapt and become stronger. By becoming stronger, it’s better equipped to handle the additional stress you place on it.
Using Progressive Overload to Build Strength
As you know, there are a variety of ways to create progressive overload for strength development. As mentioned, you can increase the resistance you use or the exercise volume. To increase the volume, you can do more sets, add more reps, train more frequently, or increase the number of exercises you do during a given workout. You can also decrease the rest period between sets or change the type of exercises you do. Finally, you can change the tempo of the reps you do, the speed at which you move the weight.
In terms of changing the tempo of a rep, you can slow the speed of each rep so that the muscle spends more time under tension. Some fitness trainers reduce the speed of each movement to keep the muscle under tension longer and increase the amount of microscopic injury to muscle fibers. With controlled stress and damage to muscle fibers come growth. So-called “slow training” comes in different varieties. Super slow training, using a 10-second lifting and 10-second lowering speed, was developed by Dr. Vincent Bocchicchio. More common is a form that uses a 3 seconds up and 3 seconds downtempo.
At the other end of the spectrum, you can increase the tempo to the point that a rep becomes explosive. This, too, has benefits. Both approaches can lead to strength gains – but does one lead to better strength gains than the other? That’s what researchers at the Human Performance and Neuromuscular Physiology Lab at Loughborough University wanted to know. Does explosive training lead to greater increases in strength?
What a Study Showed
The goal of the study was to look at the impact of different contraction speeds on quadriceps strength. In the study, 43 healthy, young males were assigned to one of three groups. One did slow, but not super-slow, leg contractions – 3 seconds up and 3 seconds down. Another group did explosive leg contractions – 1 second up and 1 second down. A control group did neither. Each group did 40 contractions three times a week for 12 weeks. The guys they selected for the study were untrained and had done no structured lower body training prior to the study.
The results? At the end of 12 weeks of training, the researchers concluded that explosive contractions are a more efficient way of building strength. Explosive contractions, 1 second up and 1 second down, effectively build strength without causing as much muscle fatigue as doing slow, more sustained contractions. As they point out, this is an advantage for people who might fatigue more quickly such as older folks and those with injuries or conditions like osteoarthritis.
On the other hand, slower contractions – 3 seconds up and 3 seconds down – are an efficient way to increase muscle size. So, if your main goal is to build strength without regard for muscle size, explosive contractions might be the way to go.
The Neural Component of Strength Training
Why could explosive training be a more efficient way to build strength? Strength development has a neural component to it, meaning your brain and nervous system play a role, not just your muscles. What happens is your brain becomes better at communicating with your muscles and synchronizing the firing of motor units. As a result of synchronization, you can generate the maximum amount of force with each contraction, generating the maximal force with the muscle fibers you have.
When you first start building strength, you may notice you’re a bit stronger during the first month or two of training. Your muscles haven’t had time to grow. The additional force you can generate comes from better motor unit synchronization. This may explain the more efficient strength gains you get with explosive training – explosive contractions cause greater neural adaptations than slow contractions. Also, you’re still recruiting fast-twitch muscle fibers with each explosive rep. These are the ones optimized for strength and power.
Variety is Key
So, there’s more than one way to build strength. You can get stronger by lifting heavy weights or by using lighter weights and making the contractions more explosive. When you use the latter approach, you also develop power. That can help you perform better in certain sports. You can also make explosive training a part of your workout, as a way to add variety and train your muscles differently. Plyometrics and kettlebell swings offer similar benefits as well since they recruit fast, explosive moves.
If you’re trying to build muscle size, this study suggests that your focus should be more on slower contractions so that you keep the muscles under tension longer. Time under tension, in and of itself, is important for muscle growth, but it also boosts the release of hormones, like growth hormone and testosterone, that help you build muscle size.
The Bottom Line
You can build strength, based on this study, using explosive contractions and this may be a more efficient way to do it since you get less muscle fatigue. Such movements also improve functional strength and can help you perform better in sports. However, if you want to build muscle size, stick more with standard rep speeds and slow training to increase the time under tension. You can also periodize your workouts to include both forms of training. Doing this may help you continue to make strength gains without reaching a plateau.
Science Daily. “Best Ways to Improve Strength”
Journal of Applied Physiology Published 7 April 2016 Vol. no. DOI: 10.1152/japplphysiol.00091.2016.
Resistance Training: Adaptations and Health Implications By Len Kravitz, Ph.D.
Int. J. Exerc. Sci 2(2): 131-151, 2009.
FitnessRX. June 2015. “Explosive Plyometric Training”
Experimental Psychology. “Volume 97, Issue 5. May 2012 Pages 630-641.
Related Articles By Cathe: