What the Hell Does Work Capacity Mean & How We Train It


The term Work Capacity in the strength and conditioning world is broad, vague, and generally poorly defined. You'll find plenty of similar terms - the Crossfit world calls it Metabolic Conditioning (METCON), some may call it Circuit Training, High-Intensity Interval Training (HIIT), Anaerobic Training, and others may use it in the general context of conditioning. 

The most common definition stems from Mel Siff, author of "Supertraining."

"Work capacity refers to the general ability of the body as a machine to produce work of different intensity and duration using the appropriate energy systems of the body"

If you've read previous articles here, the energy systems are broken into Phosphagen (Powers you for 0-30 seconds), Glycolytic (0-3 Minutes), and Oxidative (0-3+ minutes). Phosphagen and Glycolytic are grouped into Anaerobic energy pathway, while oxidative falls into the Aerobic pathway. 

These time zones are rough - each individual varies slightly due to genetics and training history. To make it more complicated, you are never truly using just one energy system... it's more of a mix of all three until you enter a steady state aerobic zone. Unless we're doing a sport specific program where the coach programs to focus on a particular energy system, our body will determine the appropriate system to fuel us. 

Rob Shaul, owner of Mountain Tactical Institute (and my former employer) has two of my favourite definition. 

"Work Capacity is where it all comes together – aerobic base, sprint cardio, raw strength, strength endurance and mental fitness."

"Combine more horsepower, increased strength endurance, and greater mental fitness and the athlete can do more in less time. Work Capacity is increased"

In other words, building the all-around engine known as our body to perform a challenging task(s), recover quickly, and stand ready to perform again.

Work capacity is the sum game - we don't care how much you can lift if you can't also move quickly or for long distances, and we don't care if you can run a marathon but crumple beneath a light external load. The combination and application of the various fitness attributes is what I would call general fitness. 

How We Train Work Capacity

  • Use of Planes of Motion

We utilize exercises which work through all planes of motion (Saggital, Frontal, & Transverse) during an individual training session. This develops a degree of athleticism employed during high threshold efforts by moving in all directions. Constant use of a single plane of motion can risk overuse injury, and may establish poor movement patterns out in the real world when you have to apply your fitness (sport, profession, chasing your toddler around the house). 

  • Focused Time Domains

While in a Work Capacity or Strength focused cycle, we will focus on one of three different time domain efforts. This includes:

5 Min + 5 Min + 5 Min: Short but high intensity efforts with 2-3 minutes of rest between.

10 Min + 10 Min: Slightly longer in total time volume, but able to still maintain a high intensity of work. 3-5 Minutes of rest between efforts.

20 - 25 Min: The longest duration efforts. I personally find these to be the most mentally challenging and requires strong intrinsic motivation to keep pushing hard through out the training. 

  • Assessment & Movement Driven Focus

Our Work Capacity cycles will have a total of four assessments. A assessment in week one and a re-assessment at the beginning of Week 4, followed by a second assessment at the end of Week 4 and re-assessment at the end of the cycle (Week 7). The exercises assessed are embedded into follow on training sessions. This allows us to see verifiable results. We could use specific progressions based on the exercise, but I've found those to get very boring, very fast. This is a nice middle ground. 

  • Varied Round/Reps/Rest Constructs

Work/Rest interval based training, EMOM density style, ascending and descending ladders, and AMRAP's - we use them all. This keeps the training fresh and challenging. 

  • Focus on Perfect Movement Patterns

This one is unnegotiable. All movements must be perfect to ensure athlete safety. If I see an athlete losing form, I'll have them stop and rest. The gym is the dumbest place you could possibly get hurt. Form is primary, intensity is secondary. 

  • Safe, Simple Movements

We don't use anything overly technical in work capacity training. No gymnastics, no snatch's, no kipping pull ups, no rapid-rebounding box jumps. 


Work Capacity is the sum game, but training it everyday can lead to serious burnout. I've experienced this first hand. During a work capacity cycle, we'll train it no more than 3x/week. This allows us to properly recover - both physically and mentally. Smart training extends our ability to do this over a long lifetime, not burn out like a shooting star through atmosphere. 



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