In Fitness, How Hard Are You Actually Working?

When we exercise, there are a few major variables we typically change for any movement.  We’ll change the number of reps that we perform, the number of sets we do of those reps, or the weight that we lift.

These are the three most common variables, but there’s one more that can drastically change the effectiveness of your training program.

One of the focal points that our training team at MFF has recently has been manipulating is the duration of rest periods during workouts.

That’s right, the amount of time that you spend not working can be just as important as the duration or intensity of the set that you do.

Today we’re going to talk about the energy systems involved in several popular styles of exercise, and how finding a well-balanced diet of all of them can lead us to better health and hotness.

You’ll find suggestions for when to work hard then rest a lot, when to keep things casual but not stop, and why classes at MFF are focused on blending the best of both worlds.

Call Me Bill Nye

First, a return to 8th grade biology. Why are we going back to the days of Trapper Keepers and decorated lockers? To provide a better understanding of why your body feels a certain way while exercising, and why we program workouts to provide that sensation.

On a physiological level, exercise is about dosed measures of stress that lead to desirable adaptations. That might not sound sexy, but here’s a sexy chart that breaks down five types of energy systems and how long we can work within them before needing to recover.

Notice that at the starting point of this graph, all of these energy systems are working at the same time. Your body regularly switches between combinations of these energy systems to allow you to do the intended work.

There are systems that give you lots of power for a few seconds (think powerlifting or Olympic weightlifting), and systems that can last for hours at a time if the intensity is lower (like a marathon or triathalon). You can think of it as the original hybrid engine, although it’s far more complicated than a Prius.

During most interval-based workouts like classes at MFF, a timer is used to delineate between work and rest periods. In our minds, there is a clear beginning and end to any work or rest period.

But in our bodies, those clean transitions are grey, meaning that our rest periods have a massive influence on how hard we’re able to work, how much we’re able to recover between sets, and which energy system is being used.

At this point, you may be thinking, “We get it Harold, you like science. What does this have to do with the rest periods of my workout?”

Here’s Why It Matters

Learning about these bioenergetics can change everything. Well, not like the meaning of life, but if you’re considering the duration of work sets and rest sets, it’s pretty important.

Let’s look at the extreme ends of the spectrum with a personal anecdote:

5 years ago I competed in two powerlifting meets, and the most I squatted in a meet was 400 lbs. That rep lasted less than 10 seconds, but required maximal effort to complete. I could barely walk after that, let alone squat anything else.

Last week, I went for my first 30+ mile bike ride, and it lasted about 3 hours. I used some fancy math to predict that I pedalled about 12,600 times in that workout.

1 rep in 10 seconds vs. 12,600 reps in 3 hours

The demands on the body are massively different between these two activities, and I use this example because it’s such a clear example of the difference between strength and endurance.

These are two extremes, so let’s look at the style of classes that we use at MFF.

In fitness parlance, we call our classes metabolic resistance training because we’re challenging our strength and conditioning at the same time.

Using the names from our fancy chart, in almost all group exercise classes that use the same “cardio with weights” idea, we spend most of our time focusing on glycolytic pathways, both with oxygen (aerobic) and without oxygen (anaerobic) in the reaction.

Let’s put that on a spectrum with some other types of exercise:

  • Semi-Private Training (strength and power focused): ATP-CP
  • Superhero Strength, Ninja Essentials: Anaerobic Glycolysis
  • Kick-Ass Conditioning, Circuit Party: Aerobic Glycolysis
  • Endurance Exercise (90+ minutes): Aerobic Lipolysis

The decade that you grew up in changes your appreciation for different types of exercise. In the 70s and 80s, cardio was considered the ultimate form of exercise. In the 90s and 00s, strength training was considered to be extremely efficient. In the last 10 years, the fitness industry has learned that in fact, a little bit of everything in moderation is good for you.

So what does this mean for my workouts?

I’m always excited when I learn about how Ninjas balance out their classes and semi-privates at MFF with other types of activities. Ultimately, we’re getting a little bit of everything; strength training, interval-based classes and lower intensity, endurance activity.

For Strength Seekers

If you’re only doing strength training, where you’re resting 2+ minutes between sets, it would be beneficial to incorporate more exercises that focus on the cardiovascular system, feature shorter rest breaks, and challenge the ability of your heart and lungs to get oxygenated blood to your muscles.

If you feel strong but lose your breath walking up a flight of stairs, you could be missing aerobic exercise from your life, which can help with recovery between training sessions, as well as being vital for health and longevity.

It’s not necessary to do 90+ minutes at a time, but at least 20-30 minutes of brisk walking or low-impact activity can be great for the benefits of a consistently elevated heart rate.

This could be a quick walk around town, a bike ride, or a swim, but it doesn’t have to be “formal” in that way. One of my favorite ways to get in my lower-intensity exercise is to go for a walk or a hike with my fiancée. We get to explore nature, and it’s great for our health, too!

Taking the time to focus on low intensity work can better prepare you for your challenging sets of 3-8 reps. You’ll likely notice that those 2+ minute rest periods start to feel shorter, meaning you’re recovering faster and able to spend more time focusing on the lifting than the recovery.

For Class Addicts

If you only take a single type of class at MFF, or only use interval-based training elsewhere, it will be harder for you to build maximal strength or muscle in that setting. At the same time, your body’s ability to recover won’t improve as much as it could if you included lower intensity, continuous effort work.

For you classaholics, I want you to plan on finding the more extreme rep ranges during class. If sets of 8-12 is your norm, you’re used to sending your heart rate sky high during a set before recovering 60 seconds later. Try playing around with reps of 4-6 and then 12-14 during the work sets, and noticing how your body responds differently to those differing volumes of work…

Understanding the range of these energy systems, we write classes at MFF to include as many of these energy systems as possible, while finding the middle ground as often as possible. Ninja Essentials and Superhero Strength typically focus more on the power and strength side of things while being an interval-based class, and Kick-Ass Conditioning and Circuit Party focus more on the endurance side of things while still being an interval-based class.

You’ll notice that it’s important to lift different weights depending on the duration of the work set or the rest period, and that your body responds pretty differently if the set is 4-6 reps long followed by longer rest, or 12-14 reps long followed by more exercises.

That being said, there’s room for even more adaptation with dedicated strength and endurance workouts. It’s also important to spend 1-2 days per week focusing on strength training and 1-2 days per week focusing on endurance or aerobic work, to really allow for the best training effect with a variety of modalities.

For Endurance Junkies

If you only do endurance exercise, it will be a game changer for you to get stronger. Spending a day or two each week off of GPS and focusing on strength will build a dimension of your fitness life that didn’t exist before.

I’d suggest spending a few workouts that feel slow and lifting a weight that’s challenging for about 5 reps. Having 1-2 days per week that focus exclusively on strength will ensure that you’re as powerful as possible when you need to be.

When endurance training is your passion, the biggest challenge with proper strength training is that it often doesn’t feel like a workout.  We’ve trained a ton of runners, cyclists, and swimmers at MFF, and countless times we’ve focused on slowing down a given workout to make it as effective as possible.

When it comes to getting stronger, it’s important to lift a challenging weight for 3-8 reps, and then rest for 2+ minutes before repeating for 3-5 sets total. The duration of rest time may feel unproductive, but when your stride or stroke gets faster, you’ll be thankful that you slowed down to get stronger, so in the end you can speed up.

A Recipe for Success

When it comes to strength and conditioning, it isn’t as much about how you feel doing the exercise, but about what the actual exercise consists of. It’s totally normal to feel strong after a long run, or be out of breath after heavy squats. That doesn’t mean that it’s making you stronger, or counts as cardio. We’re all guided by personal preference, but don’t let it leave you less healthy or successful than you could be.

Creating a weekly plan that includes 1-2 days each week of strength training, interval training, and aerobic training can be what’s missing to take your health or hotness to the next level. The focused balance of all energy systems means you can nail all aspects of fitness, while having a ton more fun in the process!


Harold Gibbons is the Steward of Strength at MFF, where he teaches classes & semi-privates, manages the program design team for semi-private training, is the director of the Trainer-in-Residence program, and the founder of our Motivation and Movement LAB. When not teaching, he loves cuddling up on the couch with his fiancée Katie, sliding through the woods on his mountain bike, and considering why Thestrals are the best.


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