You go to the gym, get on the treadmill. Far across the room are people lifting weights (isotonic exercises). A guy grunts while bench-pressing and a woman 3 feet from him has turned red trying to raise that bar with those big round weights from the ground. Boy does it seem these people are working hard!
Not far from the weight folks is an older woman holding the plank (an isometric exercise.) You can’t see her face but it definitely looks like she’s not working as hard as the weight lifting folks – even though she has a round weight resting on her back. But is that really true? Are the weight lifters really working harder?
The right answer here is – it depends. Let’s discuss.
The plank is a common isometric exercise, while the weight lifters were focusing on isotonic ones.
Huh? You’re probably wondering what that even means.
What is the difference between isometric exercises and isotonic exercises?
- Isometric exercises are strength exercises where you hold a position to keep a muscle contracted without moving the joint. Isometric comes from the Greek “iso-“, equal + “metron”, measure = maintaining the same measure, dimension or length (MedicineNet.)
- Isotonic exercises involve movement at the joint at a full range of motion to contract the muscle. Then, you eccentrically move it back to the starting position. Isotonic comes from the Greek “iso-“, equal + “tonos”, tone = maintaining equal (muscle) tone (MedicineNet.)
Let’s use bicep curls, a common isotonic exercise, to better explain this. You can use a dumbbell as I’m showing you, but using a can of soup from your pantry is a great alternative if you don’t have any equipment.
Start with your hand at your side, and lift your hand up towards your shoulder for a full range bicep curl. Then, return your hand back to starting position by straightening your arm. That completes one full repetition. Repeat with a total of 8-12 repetitions.
Now say you didn’t want to do an isotonic exercise, but wanted to do an isometric one. No prob. Instead of moving your arm up and down, you’d first get into position by lifting your hand at 90 degrees, and then hold that position for 30 seconds or so.
Both isometric and isotonic exercises can be performed to build muscle strength and have their own advantages.
Do isometric exercises really work?
It’s only natural to get the perception that isometrics are just not as good as isotonic exercises. After all, just the fact that someone is moving makes it look like harder work. While in isometric exercises, you’re not moving at all, you’re standing still and it looks like nothing is happening.
But that’s only a perception; in fact a lot is happening while you’re holding that pose in an isometric exercise.
What are the benefits of isometric exercises?
Isometric exercises are part of resistance training, just like the isotonic ones. So they get to provide the common resistance training benefits, like:
- Building strength (Folland et al.),
- Helping with osteoarthritis (Alghadir et al.),
- Reducing pain and improving range of motion (Khan et al.),
- Improving blood pressure (Carlson et al.)
The main benefits of isometric exercises in particular are:
- In rehabilitation. Many physical therapists start their patients with isometrics before proceeding to the use of isotonic exercises.
- Slower workout pace (albeit not easier.) If you’ve ever done yoga (start here) you know what I mean. Many people find the slower pace of holding the same pose for a long time boring; others thrive in it.
- They engage your muscles in a slightly different way than their isotonic counterparts.
So unless you have specific training goals that focus on isotonic exercises only, your training generally get better when you include both isometrics and isotonics in your programming.
What are some isometric exercises?
Here are some examples of isometrics along with how to convert isometric exercises to isotonic and vice versa: for each isotonic exercise I present to you, I will alternatively show you the isometric version of that option.
Let’s do this!
1. Isotonic Plank vs. Isometric Plank
There are several plank variations, both isotonic and isometric ones. For this example, let’s take the isotonic open and close plank.
Lay stomach down on the floor and feet together. Place your palms under your shoulders and lift your body up into a plank. Keep it straight. Then jump and open your legs more than hip width apart. Quickly jump again, and bring your feet together to starting position.
If jumping is hard, then just step to the sides to open your legs and then step again, one leg at a time, to bring them back together. Repeat 8-12 times.
The isometric plank is simple! Just contract your abs and hold the plank position for 20-30 seconds.
2. Isotonic Squat vs. Isometric Wall Squat
Before you try this out, make sure you’re not making any of those squat form mistakes.
For the isotonic squat, start with feet hip-width apart. Keep back straight and arms extended in front of you.
Lower down as if you were sitting on a chair behind you. Make sure your knees do not go in front of your toes. Press through your heels to return to the starting position. Repeat 8-12 times.
To start your isometric wall squat, meet the Wall Sit. Stand back to a wall with your legs hip-width apart. Slide down until your knees are in 90 degree angle.
Keep your back flat against the wall while you keep this position for 20-30 seconds.
3. Isotonic Wall Pushup vs. Isometric Wall Pushup
To begin your isotonic wall push up, stand across from a wall, and extend your arms in front of you so that your fingertips are almost touching the wall. Lean towards the wall, keeping your back straight.
Now, lower until your nose is almost touching the wall, and then push back. Repeat for a total of 8-12 repetitions.
To make this push up isometric, just hold the lowered position for 20-30 seconds.
4. Isotonic Tricep Press vs. Isometric Tricep Press
For the isotonic tricep press, sit on the floor with your knees bent, your feet flat on the floor, and your arms a few inches behind you, palms on the floor pointing forward. Now contract your triceps, the muscles at the back of your arms, to extend your arms and push your hips above the floor.
Then bend your elbows without touching the floor with your seat. Repeat, bending and straightening your elbows for 8-12 repetitions. Keep your shoulders back and your chest lifted at all times.
To make the tricep press isometric, follow the instructions above until you bend your elbows without touching the floor with your seat. This is your isometric position. Hold this for 20-30 seconds.
5. Isotonic Shoulder Bridge vs. Isometric Shoulder Bridge
Begin with the isotonic shoulder bridge first. Lie on your back with legs bent and feet hip-width apart.
Contract your abs and glutes to roll your body off the floor. Then lower down. Repeat 8-12 times.
To make this isometric, simply hold your position at the top for 20-30 seconds.
Getting stronger? How to make both isotonic and isometric exercises more difficult.
Progression with isotonics is easy:
- Do more repetitions, say 10 squats rather than 8.
- Increase the weight you’re lifting. Goodbye 10-pound dumbbells, welcome 12-pounds ones!
- Do your reps faster. This is a common theme in HIIT where you give it your all fitting in as many reps as possible for, say, 30 seconds, and then rest.
With isometrics, here’s what you’d do to progress and make them more difficult:
- Hold the pose for longer. A 10-second plank sounds like a piece of cake. But try a 20 min one. What? A 20-min one? Am I nuts? This marine did it for almost 8 hours!
- Add weight. Many people have connected isometric exercises in their minds as bodyweight ones. While you can certainly only use your bodyweight, you can also add weight. E.g., add a weight bar on your hip bones when you’re performing the isometric shoulder bridge.
Personally I do both isometrics and isotonics.
I like most exercise styles – from yoga to weight lifting to HIIT (and as a result get the benefits of cross-training.) Just don’t make me get on the treadmill – I hate running!
Yoga workouts focus more on isometrics, weight lifting is more about isotonics, HIIT depends heavily on how you structure it (it can be just cardio if that’s what you want!)
Take my HIIT home workout program Flat Belly Firm Butt in 16 Minutes as an example (start here). I’ve included both isometrics and isotonics (and cardio) – to get the benefit of all types of exercise.
I may even do both isotonics and isometrics in the same set! E.g., take the shoulder bridge. I sometimes do 10 reps (isotonic) but then hold the last rep for 10 seconds (isometric.)
Now that doesn’t mean that you should always be doing both types of exercise. At the end of the day it all comes down to the specific goals you have at each point in time. Specific physique goals may make you focus 100% on isotonic ones for example, and that is fine.
Back to the gym example: Who was working harder?
Remember the weight lifters and the older woman I started this article with? I hope you see by now that just because the old woman holding the plank was not moving, that doesn’t mean she working any less hard than the weight lifting folks.
That would actually depend on:
- Her fitness level.
- How long she holds the plank for.
- The size of the weight on her back.
If you want to “cheat” with exercise then you can do that pretty easily regardless of the type of exercise you’re doing. So if performing an isotonic one, you can easily use less weight than what would actually challenge your muscles to grow. With isometrics, you can hold them for less time than what would take you to the next level.
At the end of the day, your results will depend less on the type of exercise (isometric vs. isotonic) and more on the effort you put in it. Makes sense?