Let’s start by thinking about all the MetCons you’ve done over the past months/years… How many of them had rest intervals programmed within? No, we’re not talking about having to break up 20 Shoulder-To-Overheads in to smaller chunks because you can’t go unbroken, we’re talking actual, defined rest intervals within your workout such as “rest 1:00 between rounds” or “rest 1:3”. There’s a very common misconception in the functional fitness world that continuous efforts lead to the best work capacity adaptations. However, I’m going to show you that breaking your workout up into meaningful, defined, and justified rest intervals will truly maximise your physiological adaptations and ultimately your athletic potential. We’ll talk about the preservation of intensity within MetCons, the use of cluster sets for strength and power, and rest intervals for conditioning.
At the most basic level, we implement rest intervals in order to preserve intensity. Coach Glassman in 2011 told us that intensity is equal to power output, or F.d/t (force multiplied by distance, divided by time). In other words, how heavy the object is, how far it moved, and how fast it was done. For the purposes of this article, this is the definition we’ll work from. In your typical “Rounds For Time” (RFT) MetCon, force and distance will likely stay consistent because weights and range of motion won’t change. What will change, and is therefore the most important factor in determining the overall intensity of your workout is time, specifically, the split time to complete an exercise or a round of exercises.
Let’s look at an example workout - 3RFT of 20 Wall Balls, 15 Burpees, and 10 Pullups.
Assuming you’re not pacing, your split times might look something like this - 1:35, 1:55, and 2:30. What we can see is that as each round takes longer to complete, overall power output and therefore intensity decreases significantly. Why is this bad? Because, and I’m quoting Glassman again, “intensity is the independent variable that will always be associated with optimising the rate of return on your efforts”. In other words, if your intensity drops, so too will your fitness adaptations. Now, if we add in a 1:00 rest interval between each round, we’d probably notice that our split times stay a lot closer together, maybe 1:35, 1:42, 1:50, which means that intensity remains higher allowing us to become fitter faster.
The amount of rest in between sets can vastly alter the physiological adaptations related to strength training, and it’s important that coaches understand and implement the right rest intervals for optimal results. One of the best tools we can use to vary rest periods is Cluster training, or, as it is more commonly known, “Every Minute on the Minute” (EMOM). Defined as rest between repetitions within a set, or inter-repetition rest (IRR), the rationale behind Cluster training is actually quite simple. A study completed by Hardee in 2012 used 6 Power Cleans to demonstrate changes in peak power and peak force across each repetition of a Cluster set.
Figure 1 – Summary of Peak Power and Peak Force changes across repetition 1 and 6 during a set with 0s, 20s, and 40s IRR.
As you can see in Figure 1, a traditional working set can reduce peak power output by 14.94% and peak force by 7.16%. Compare this to the much smaller decrements (and even a small increase) by using 20s and 40s IRR and we can see that rest periods improve the quality of individual repetitions by minimising the manifestation of fatigue across the training set. Essentially, Cluster training will allow you to maintain power and force output across every repetition, creating a higher quality training environment that facilitates greater adaptations to your athletic development. There are a number of ways you can implement Clusters (standard, wave, ascending, and undulating), but the current guidelines suggest 5-15s IRR for strength endurance, 15-30s for power development, and 30-45s for maximal power.
When a Coach writes up a conditioning workout, they should have in mind which of the three energetic systems they’re aiming to train – ATP-PC, glycolytic, or oxidative – and what rest intervals are required in order to target those systems. Bompa & Haff (2009) recommend avoiding low intensity (oxidative) exercise as much as possible due to its associations with reduced performance capacity such as decreased power generation, peak force, rate of force development, and hypertrophy. They also suggest that high intensity intervals can be used to develop low intensity endurance without impairing strength and power capacity.
Figure 2 – Summary of the relationship between work:rest ratio and energetic pathways
As seen in Figure 2, the use of work:rest ratios determine the energy systems used and intensity of your workout. For short, maximal effort bouts of exercise targeting the ATP-PC system, a ratio of 1:10 is generally required to adequately recover and replenish energy stores. An example session would be 6 x 50m sprints with 1-minute rest between sets. For slightly longer, high intensity bouts that target the glycolytic system, a ratio of 1:3-5 is used - for example, 4 x 400m run with 3-minutes rest between sets. Finally, longer, low intensity oxidative bouts of exercise typically use a 1:1-2 ratio such as row 1-minute on, 1-minute off for 5 rounds. Remember that if your work:rest ratios are out, your intensity will drop and reduce the physiological adaptations to your workout.
The next time you’re in the gym having a crack at an RFT MetCon, play around with some rest intervals between exercises, or sets, or rounds, and see how the overall intensity of your efforts is affected. The goal of your workout should always be to perform with higher intensities so you can continue to develop your strength, speed, power, work capacity, and endurance. Use Cluster sets to maintain high quality reps that maintain and improve force and power output. Finally, utilize the correct work:rest ratios to target specific energetic pathways and avoid falling in to the trap of lower intensity efforts that will ultimately prevent you from reaching your true potential.
The purpose of CrossFit: Part 1, 2011 (video file), Available from: <https://www.youtube.com/watch?v=xwK4cPNL19I>, accessed 27 January 2015.
Bompa, TO & Haff, GG 2009, Periodization: theory and methodology of training, Human Kinetics, USA.
Hardee, JP, Triplett, NT, Utter, AC, Zwetsloot, KA & McBride JM 2012, ‘Effect of interrepetition rest on power output in the power clean’, J Strength Cond Res, vol. 26, no. 4, pp. 883-889.