With today in mind (being a heavy day) we wanted to discuss the purpose of heavy days, how to approach them, and why it’s important to stick with the programming.

First of all, heavy days are programmed to develop strength and technique. Single movement heavy days are also a vital part of the program. They give the central nervous system (CNS) a rest. 

Conditioning workouts that increase heart rate and add metabolic stressors to the body affect the CNS and leaves it fatigued. We use single movement heavy days, where the heart rate does not get high to give the CNS a break and provide a day to develop the strength and technique stated above.

There is the tendency for new CrossFit athletes to avoid heavy days entirely or execute them incorrectly. However, CrossFit is a strength-and-conditioning program. While people sometimes characterize CrossFit by the mixed-modal workouts for time (“met-cons”), this is a limited view. Days devoted to strength training are an essential variant of CrossFit and are also “CrossFit” workouts.

“For every long distance effort our athletes will do five or six short distance. Why? Because compound or functional movements and high intensity or aerobic cardio is radically more effective at eliciting nearly any desired fitness result.”


Heavy days are necessary to build top-end strength and power or work capacity in the intervals of about 10 seconds or less. Power output decreases with time, meaning that an athlete’s work capacity in very short time domains sets the theoretical limit for his or her entire curve.

It is possible to have high levels of short-duration power and little power elsewhere (e.g., a powerlifter), but it is impossible to have low levels of short-duration power and higher levels of longer duration power. Therefore, heavy days are essential to a general physical preparedness program and should be used at least once a week.

The heavy-day workout consists of small sets, most often in the range of 1-5 repetitions, where the total volume of working repetitions is approximately 7-25. Repetitions significantly outside of this range do not produce the desired response.

If there are too few repetitions (e.g., one repetition of a near-maximum load), the athlete does not produce enough stress on the taxed muscles to drive a new adaptation. Conversely, too many repetitions (e.g., 30 or more repetitions of near-maximum load), produces too much stress for the athlete to recover from in a reasonable time period. The working sets generally occur at or above 80-85 percent of a one-repetition-maximum load, and warm-up sets used to get to this loading do not count toward the total working repetitions.

This is not an exact percentage, but a working set should be heavy enough to require concentrated effort. The working sets also do not produce a significant cardiorespiratory response, although you may notice you are breathing heavy immediately following your working sets. 

Relatively new athletes often set a personal record or best every time they lift heavy. As the lifter becomes more experienced, sessions without a new personal record occur. Setting a personal record is not necessary to reap the benefits from lifting heavy.

Where an experienced lifter will experience the most gains will be from lifts within 70-90% range.  This will move the needle of overall strength.  Athletes must always remember 1 rep maxes are extremely relative.  Relative to current training, stress levels, recovery (sleep, training frequency and volume), nutrition (enough fuel and nutrients) among many things to be considered.  Just because you were able to lift “X” a few months ago or during a competition and weren’t close today is normal.  When it’s hot in the kitchen as we say, enjoy it, celebrate and relish in it and when you have those days where you’re feeling weaker than your best, put in the work, keep your head straight and use it as an opportunity to refine mechanics and potentially re-assess all other factors as stated above.

It is also important to remember that if we program a 5×5 back squat day, we base this upon a 25 rep workout where the athlete aims to increase weight across each set and builds to a heavy set of 5, NOT A 1 rep max (RM). We get this feeling, we feel good through the 5×5 and we haven’t PR’d in a while. But we must understand the programming isn’t structured for that and overtraining/overreaching can result. We would never do 5×10 strict pull-ups and then want to test out our max set. It wouldn’t work and it wouldn’t be accurate. If we approach the 5×5 back squat PROPERLY, focus on good technique, and build to a heavy set of 5, finding a new 1RM afterwards is not possible because you should be totally SPENT from those heavy sets of 5. 

We say this all the time but society values the long slow endurance efforts (more is better). We consider intensity to be way more valuable. But with that we must understand is that there has to be balance. One of the goals of CrossFit is to be well balanced across the 10 Components of Fitness, which means on a strength day that is where our focus should be. The common thought on those days can be that it wasn’t taxing because we didn’t get the heart rate up so I should probably go for a run. This is a fundamental error, and one likely causing no benefit.

We all want to be strong enough to do the things we love, in and out of the gym.

Life will often demand us to provide strength, whether that’s moving something, picking something up or even performing a normal day to day task.  Our bodies need to be strong enough to answer, otherwise we run the risk of injury or eventual decrepitude.

In the end, heavy days are for everyone: the young, old, fit, and unfit.

What’s heavy is different for each individual but the benefits are for everyone.