Why the Negative Leads to Positive Training Results

Don't skip the opportunity to make $50 an hour to earn $20 an hour. Imagine you ran a business where you offered two services: option A, a flashy service that offers some value and helps you earn $20 an hour; and option B, a less sexy but more valuable service which you earn $50 an hour for.

The downward phase of the dip is more valuable than the upward phase.

Which service would you spend the majority of your time on? I would focus on option B...and I hope you would, too.

However, many strength training enthusiasts focus on option A. Option A is the positive, or lifting portion, of a repetition. The lifting phase of the repetition is sometimes sexy (have you seen an Instagram video of a person lifting a weight, then dropping it?). Option B is the negative, or the lowering phase of the repetition. While it is less sexy, the negative provides the majority of strength and muscle gains.

Unfortunately, many trainees avoid the negative (dropping the weight) or race through the negative. This is the exact opposite of what people should do.

Advantages of the Negative

There are a few ways to test which part of the repetition is more valuable. One way is to compare people who performed the positive AND negative to people who performed twice as many positives but NO negatives. This was tested in two studies (1,2). In both studies, the people who lifted and lowered the weight gained more muscle and strength. In one study, the group performing the full rep gained 25% more muscle than the group who only performed the positives (1). In the other study, the positive and negative group gained 73% more strength than the positive-only group (2).

To maximize your benefits on the leg press, bring the weight down slowly.

Another way to get an answer is to compare negative-only training to positive-only training. A meta-analysis (research combining the results of other studies) of 20 studies comparing the two training types determined that negative-only training leads to more strength and muscle development (3).

While both are valuable, the negative is more important than the positive for building strength and muscle.

Negative-Accentuated Repetitions

The negative offers one additional benefit: people can lower more weight than they can lift. Knowing that, you can perform "negative-accentuated repetitions," which is when extra weight is added on the negative. This can be practiced by adding more weight to the negative on each rep, just before starting to lower the weight. Another method is to use a weight 20-40% heavier than your usual training weight, but have someone help on the lifting phase. The weight would be lowered entirely by yourself.

Negative-accentuated reps, with 40% more weight on the negative, leads to more endurance and muscle growth than traditional training (4,5). Researchers also found accentuated reps increased the production of testosterone, cortisol, and growth hormone (4). Those hormone changes are generally associated with enhanced strength and muscle growth during training (4).

My Recommendations

The negative is more important. With that in mind, we should emphasize it. Here's how:

1. The negative should be as slow, if not slower, than the positive. If you generally lift the weight in two seconds, you should lower the weight in at least two seconds. 
2. Ideally, I recommend you shoot for at least four seconds on the lowering phase. Slow negatives will lead you to perform less overall repetitions, but the goal is to gain strength and muscle, not perform reps. Keep that in mind.
3. If you have a training partner, consider negative accentuated reps. Make sure to perform at least two warm-up sets before doing this! Consider starting with a weight 20% above your usual training weight. Ask your partner to help you lift. Hold at the end of the positive, remove the assistance, and lower as slow as you can.

Don't let the Instagram videos fool you. The lowering phase is where your "gains" are coming from.

References

1. Hather, B.M., Tesch, P.A., Buchanon, P., & Dudley, G.A. (1991). Influence of eccentric actions on skeletal muscle adaptations to resistance training. Acta Physiologica, 143(2), 177-185.
2. Dudley, G.A., Tesch, P.A., Miller, B.J., & Buchanon, P. (1991). Importance of eccentric actions in performance adaptations to resistance training. Aviation, Space, and Environmental Medicine, 62(6), 543-550.
3. Roig, M., O’Brien, K., Kirk, G., Murray, R., McKinnon, P., Shadgan, B., & Reid, W.D. (2008). The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis. British Journal of Sports Medicine, 43, 556-568.
4. Walker, S., Hakkinen, K., Haff, G.G., Blazevich, A.J., & Newton, R.U. (2017). Acute elevations in serum hormones are attenuated after chronic training with traditional isoinertial but not accentuated eccentric loads in strength-trained men. Physiological Reports, 5, e13241, DOI: 10.14814/phy2.13241.
5. Walker, S., Blazevich, A.J., Haff, G.G., Tufano, J.J., Newton, R.U., & Hakkinen, K. (2016). Greater strength gains after training with accentuated eccentric than traditional isoinertial loads in already strength-trained men. Frontiers in Physiology, 7, 149.