As the name suggests, isolation exercises work one muscle group hard, while compound exercises (such as a squat) target multiple muscles and joints together. In the single vs multi-joint resistance exercises (opens in new tab) debate, any strength and conditioning program worth its salt will use progressive overload techniques with a combination of the two, focusing on connection and adding isolation exercises as supplemental moves to the big lifts.
But before we go any further, doing an isolation exercise every day isn’t the best way to build strength and muscle throughout your body. Over time, training in this way can put undue stress on the muscles and associated joints. You should always allow at least 24 hours of recovery between leg day workouts to allow muscles to recover. But for this challenge, I only wanted to test higher reps for one week.
Grab a set of the best adjustable dumbbells to keep on standby for a variation on the leg extension exercise, and read on to see how my legs fared.
How to do leg extensions
Like hamstring curls, leg extensions are usually done on a machine at the gym, but that makes the exercise less accessible to those with limited equipment. The dumbbell leg extension can build size and definition in your quads and can be done anywhere with one dumbbell. Using free weights also helps overcome muscle imbalances and improve body-to-research coordination (opens in new tab) suggests that resistance band training could provide similar benefits.
How to do machine leg extensions
This method is accessible to beginners and teaches you how to move correctly with more support for your back. However, your stronger side (we all have one) has the potential to take the brunt, which can cause imbalances.
How to do dumbbell leg extensions
Leg extensions using a barbell require more balance, core activation and better posture. Either method can be added to the end of a strength training program when the muscles are already tired from squats, deadlifts and other compound exercises. You can use drop sets (drop the weight or reps for extra rounds) or aim for maximum reps to achieve burnout.
- Sit up straight with your core engaged and grip the sides of your bench
- Place a dumbbell between your feet and keep your legs at a 90-degree angle
- Stay tall as you lift your legs and straighten your knees
- Pause and squeeze your quads and avoid arching or bending your back
Never swing your legs or throw the weight. Always move with control. If you can’t straighten your knees, lower the weight to achieve a greater range of motion.
I Did 60 Leg Extensions Every Day For A Week – Here’s What Happened To My Legs
My quads were in pieces
Leg extensions strengthen the quadriceps muscles and attachments at the knee joint. This move allows you to focus on one muscle group as you work your knee through full flexion and extension to build strength and muscle.
I used dumbbells for this fitness challenge and did six sets of 10 reps – this is more than I would program for clients, but it’s not outrageous either, as I didn’t want to risk injury. I focused on squeezing my quads hard at the top with a short pause, then slowly lowered the weight. Honestly, I had to squeeze every last drop out of the last few reps of each set, and my quads were on fire for days. Reminder – isolation exercises are full.
My knees hurt
If you have a knee injury, experience joint pain, or have limited mobility, always consult a medical professional before doing leg extensions and stop if you experience pain.
Leg extensions have a bad reputation for damaging the knees, but there are two ways to look at it. For many people, it’s a great exercise to strengthen the muscles around the knee joint and can protect you from injury. The strength exercise can also help develop muscles needed for sports like soccer (think of how you kick a ball) and sprinting.
Knee pain is usually the result of stress on the ankles, which puts stress on the knee. Overloading your muscles and tendons can be another cause and can sometimes be remedied by lifting lighter weights. The high reps and daily reps were definitely too much for me, so I dropped the weight to a lighter load than I would normally use. It helped me focus on my full range of motion without straining my knees, and this felt much more comfortable while still working my quads hard.
These are the best knee strengthening exercises and a yoga for knee pain workout to try.
My core worked hard
Machine leg extensions allow you to rest your back, which can help improve posture, but performing dumbbell leg extensions using only a flat bench requires more work from your core muscles to sit upright. I found myself leaning forward too much, so I spent the remaining days in front of the mirror checking my form.
At first I felt pressure to my lower back and noticed that I had curled my pelvis towards my spine. After a quick adjustment and regular check-ins, my core felt engaged and surprisingly sore. And while progressive overload (the gradual adjustment of reps, weights, or other variables over time) doesn’t set in after a week, I started to feel more comfortable as the week progressed.
I overloaded my quads
Hardly a shock, but my quadriceps felt significantly weaker during CrossFit workouts all week and my legs felt overstretched. The Journal of Physiology (opens in new tab)explains that micro-tears of the muscle during exercise are a major cause of muscle soreness, known as DOMS (delayed-onset muscle soreness).
I can’t stress enough the importance of rest and recovery in helping your muscles repair, recover and grow. Always wait at least 24 hours after a lower or upper body strength training program, and focus on alternating muscle groups throughout the week to avoid overtraining.
Next one: These are the core 5 dumbbell exercises And core 5 dumbbell exercises to build strength, muscle and power. Add these compound movements to your workout routine alongside a mix of isolation exercises to work your entire body.