What no one looks like after sheltering in place for two months. Photo: Shutterstock

The most common way to make an exercise harder is simply to add more weight. But adding more weight isn't always an option, particularly if you are working out at home. And sometimes just adding more weight even if you have access to it isn't always the best choice if you have injuries or joint issues.

As many of us continue to shelter in place amid the pandemic, I'm using these five strategic ways to avoid plateaus in strength building with virtual personal training clients to keep them fit, safe and engaged in their workouts. For an even bigger list of ideas check out this MyFitnessPal Blog post by my pal Julia Malacoff.

Increase the range of motion. Every exercise has a "range of motion," which is just a fancy way to measure how far your joints move and thereby how much your muscles work to perform a full and proper repetition. For instance, think of a push-up. From the top of the push-up where your elbows are fully extended all the way down to where your chest touches the floor is the full range of motion for a standard push-up. But, if you elevate your hands on a yoga block like I show in this video, you have increased the range of motion for a greater challenge.

Change the angle. The angle at which you perform a movement will affect which specific muscles or parts of a muscle will predominate. Returning to our push-up example, if you were to elevate your feet on a bench, you would be changing the angle and difficulty of the push-up. It takes more strength to push yourself back up, and it uses the chest, shoulder and arm muscles differently. Or when doing a row or pulling exercise, as I show in this video, you can simply change the direction or "line of pull."

Try 1.5 reps. The principle here is pretty simple. Increase the work done in each repetition so the muscles end up working a lot longer. Take a body-weight or a front-loaded squat, as I show in this video. A traditional rep would be to go down all the way and to come all the way back up. To make it harder and to force the glutes and quads to work longer, we go down, half way up, back down and then all the way up. Multiply that across 12-20 reps and multiple sets and you'll certainly notice a difference.

Perform 21s. I'll admit, these can be deliciously gnarly. As with 1.5 reps, the concept here is to increase the work in a set and focus on now different parts of the muscle predominate at different points along the range of motion. When doing 21s, perform seven reps at the bottom range of motion, seven reps at the top range of motion, and then seven full range of motion reps. A great example of how to do 21s is a bicep curl, which I show in this video.

Slow down the eccentric phase. Every movement can be broken down into a concentric phase (where your muscles are exerting force) and an eccentric phase (where your muscles are working to resist force). There's also an isometric phase where you just hold still like in a plank. Most often we do an exercise with a 1/1 tempo. Using our push-up example, we go down for a beat and up for a beat. Or in a reverse lunge we go down for a beat and up for a beat. As I show in this video, slow down the eccentric phase and you will force your muscles to work harder and you will gain more strength due to how the myosin and actin myofilaments move inside the sarcomeres of the muscle (don't worry about that technical jargon; trust me it works).

So you see, even if you are stranded at home or anywhere you can't simply add more weight, you still have many ways to make your workouts more challenging and effective.

Jonathan Jordan is a personal trainer, nutrition coach and corporate wellness consultant in San Francisco. Check out his blog JJ Fit 24/7.