Can You Really Build Strength Lifting Lighter Weights?

 

To get stronger, you need to lift heavy, or at least that’s the conventional approach to strength training. Yet, a new study from McMaster University calls this idea into question. According to the results of a new study they recently carried out, lifting lighter weights may be as effective as lifting heavy for building strength.

Lifting Lighter to Build Strength?

Researchers at McMaster’s divided a group of trained, male weightlifters into two groups. One group took a traditional approach to weight training. These guys lifted heavy weights, up to 90% of their one rep, max and did between 8 and 12 reps per set. The second group used lighter weights, about 50% of their one rep max and performed 20 to 25 reps for each set. Both groups did upper and lower body exercises using these protocols for a total of 12 weeks and trained to the point of muscle failure.

At the end of 12 weeks, the researchers analyzed their muscle tissue and took blood samples. Based on the results of muscle biopsy, both groups of men experienced a similar increase in muscle size and muscle fiber size. The results were identical, despite their different training protocols. The researchers used gains in muscle size and fiber size as a marker for strength.

What Do Other Studies Show about Lifting Lighter Weights to Build Strength or Size?

The McMaster study suggests that you can increase strength by lifting lighter weights but, in reality, it mainly shows you can increase muscle size and fiber size using lighter weights. In the study, they documented that the men experienced an increase in muscle size and fiber size but didn’t actually test whether their strength changed as a result of their training.  This study also doesn’t necessarily show that, if you get stronger, you will continue to do so using a high rep, lower weight protocol. To keep getting stronger, you need progressive overload. To keep making gains, you have to increase the challenge. Plus, at some point, your muscles will likely adapt to a high-rep routine and stop growing stronger.

Still, this isn’t the first study to show you can increase muscle SIZE working using lighter weights. In a study published in the Journal of Applied Physiology, researchers divided men into three distinct training groups. One group did three sets of leg exercises to fatigue using 80% of their one-rep max. A second group did one set of exercises using 80% of one-rep max to muscle failure. A third group did three sets using 30% of one-rep max to fatigue. The guys trained in this manner three times a week.

At the end of the 10-week study, researchers used MRI imaging to look for gains in muscle volume. They also measured the degree of muscle protein synthesis in each group. The results? All three groups experienced gains in muscle volume and the gains were similar. One thing to be aware of, in a previous assessment, researchers found doing three sets increased muscle protein synthesis more than doing a single set.

Lifting to Fatigue or Failure

It might seem counterintuitive that you’d make significant gains in strength or size lifting lighter weights. We traditionally think that using lighter weights and high reps is effective for building muscle endurance but not necessarily strength or size. You need to recruit as many muscle fibers as possible to build maximal strength, especially the powerful fast-twitch muscles. Lifting heavy weight forces you to recruit more muscle fibers and more fast-twitch fibers to move that weight.

Yet, if you lift a lighter weight long enough, your muscles are forced to activate more total fibers to take over for the fibers that are fatiguing. When lifting light weights (less than 50% of your one-rep max), you recruit mostly slow-twitch fibers initially but as your muscles fatigue, fast-twitch fibers are called in to take up the slack. This was confirmed in a study published in the Journal of Neurophysiology. So, don’t underestimate the power of your slow-twitch fibers. Some muscles, like your glutes, have a high proportion of slow-twitch fibers and respond well to lighter weights and higher reps. Plus, there’s growing evidence that slow-twitch fibers hypertrophy too, especially when you train them to failure.

In terms of building muscle size (but not strength), using a weight that’s 90% of your one-rep-max is not the best approach because you can’t do as many repetitions. That’s because your muscles fatigue quickly under such a heavy load. As a result, the time your muscles are under tension is reduced and time under tension is a factor in muscle growth.

Simply put, keeping your muscles under tension longer is conducive to muscle hypertrophy. You can make up for this, to some degree, by doing a greater number of sets. Still, lifting at 90% of your one-rep max works for strength building but isn’t optimal for increasing muscle size. That’s why powerlifters who lift super-heavy don’t have the muscle definition that bodybuilders do. Bodybuilders usually use moderate weight and reps and do three or more sets of each exercise. Such an approach keeps the muscles under tension longer.

The Bottom Line

This is one of the first studies to show that training with lighter weights and higher reps is an effective way to build strength. Yet, this study really demonstrated that this type of training increases muscle volume and muscle fiber size. This is consistent with other studies showing that lighter weights, high reps are effective for hypertrophy when you train to failure or near-failure. Don’t count on building muscle if your muscles aren’t thoroughly fatigued by the end of each set. To maximize muscle protein synthesis, three sets may be better than a single set even if you go to failure.

If your main goal is to build strength rather than size, you should still include heavy lifts and lower reps in your routine. It’s a “tried and true” way to build strength. But regardless of your goals, varying the resistance and reps you use will help you best reach your goals. You don’t want your body to adapt to a repetitive training routine.

 

References:

Eurekalert.org. “Lighter Weight Just as Effective as Heavier Weights to Gain Muscle, Build Strength”

J. Neurophysiol. 90, 2919-2927 (2003).

Brett Contreras. The Glute Guy. “March Research Round-Up: the Muscle Fiber Types Edition

 

Related Articles By Cathe:

4 Principles of Resistance Training and How Some People Get Them Wrong

Can You Build Strength Lifting Lighter Weights?

Do You Have to Lift Heavy Weights to Build Muscle?

Beyond Progressive Overload: 5 Strategies for Maximizing Strength

Do Women Have Greater Muscle Endurance Than Men?

Is There a Threshold Intensity at Which You Need to Train for Muscle Growth?

Advanced Strength Training Using a Rest-Pause Approach

 

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