ATP: Heavy Singles

If you’ve ever done heavy singles, you know how important it is to take a long rest period. Most seasoned lifters have a pretty good internal clock. In other words, they intuitively know when they’re ready to lift again. Unfortunately, that’s not always true. Some lifters look great on the first heavy single. And then they get completely buried on the second one. 

Lifter sitting on a bench, resting in between heavy squats

Why does that happen?

Adenosine triphosphate (ATP) is the body’s primary energy resource for ANY muscle contraction. The body has a limited supply of ATP, and it must be replenished for work to continue. And here’s the important part: the amount of rest taken in between sets is directly related to how much ATP/energy will be available to the muscles for the next set.

Let’s back up a minute. 

There are three energy systems that produce ATP: 

  • ATP/PC (phosphocreatine): high power/short duration: 1-3 reps, 10 seconds of max effort
  • Glycolytic: moderate power/moderate duration: 10 seconds – 2 minutes
  • Oxidative: low power/long duration: 2 minutes or longer

How much rest do you need between heavy singles?

You’ve done a heavy single and your ATP stores are depleted. It takes at least 3 MINUTES of rest for muscles to recover the maximum amount possible of ATP. After a minimum of 3 minutes, your ATP-PC system will be ready for explosive movements again. (However, some lifters require 4-5+ minutes)

What happens if you don’t rest long enough?

If you’ve depleted your ATP-PC system but continue to lift, the glycolytic system kicks in and breaks down glucose to form more ATP. You can produce a lot of force with the glycolytic system, but not as much as you can produce with the ATP/PC system. In other words, you can continue to lift, but the weight will need to be lighter.

Why you should care:

  • If your body hasn’t replenished it’s ATP-CP stores and you get back under the bar to lift heavy weight, form may fail and the risk of injury increases.
  • If you’re doing heavy singles, you obviously want to get stronger, and missing a lift you should make is demoralizing and frustrating!

On a final note, it’s important to remember: all three of these systems contribute to the energy needs of the body during physical activity. These systems do not work independently of each other. The duration and the intensity of the activity will dictate which will be the dominant system.

(If you’re doing heavy singles, you need to know about moment arms!)