In an effort to save the natural lifter time and energy, I’m going to pick two exercises which have the highest muscle activation in the lower body. Unless you’re a juice up horse with a needle in your butt, you don’t need to spend two hours in the gym to maximize efficiency. Once you trigger muscle protein synthesis, it’s time to leave the gym. The idea that a natural lifter needs 20 sets of 5 different exercises all targeting the same muscle group is misguided time wasting. I will try my best to avoid choosing the same exercise in different muscle categories. Five categories will be considered: the quadriceps, hamstrings, glutes, hip adductors, and hip flexors. Exercises will be evaluated by their electromyographical (EMG) amplitude. EMG is recorded by placing electrodes on muscle groups in an effort to record electrical impulses. EMG can be described as the study of electricity in muscles. More specifically, EMG amplitude is a measure of motor unit activity during muscle action. It’s described as an evaluation of muscle tension or how hard a muscle becomes during exercise. EMG comes with a set of limitations: cross talk, interference, placement error, muscle fatigue, technique, etc. Researchers plan for this and typically make every effort to avoid these limitations.
Colloquially called the thigh, the quadriceps are so named for it’s comprised of four muscles. The vastus medius (VM) lies on the inside of the thigh and connects to the knee joints. The vastus lateralis (VL) runs up the outside of both thighs. The rectus femoris (RF) and vastus intermedius (VI) run up the middle of the thigh on top of the femur connecting the hip to the knee.
For the quadriceps, I picked the lunge and the leg extension. It’s the ultimate blend of closed chain and open chain. All of the weaknesses of the leg extension are addressed with the lunge and vice versa. Multiple studies report the lunge having nearly equal EMG amplitude of the vastus lateralis and medialis, but rectus femoris activation leaves something to be desired.
The barbell lunge outperforms the squat in VL and VM EMG amplitude, yet it’s one of the least common exercise you will see in the gym. Everyone seems to be obsessed with dumbell walking lunges, a gross replacement for the barbell variation. Firstly, the barbell lunge should be a relatively stationary activity. The participant should stand on one leg, kick the other leg back and inhibit its contribution to the activity. In reality, the activity would be better named the unilateral squat, as the rear foot/leg should play only a support or balance role: it’s a one legged squat. It’s an activity that requires the hip, knee, and ankle joints to work simultaneously. Because it’s compound, the lunge activates numerous muscle groups: the quads, glutes, adductors, calves, and low back. The barbell lunge develops the VL and VM greater than any exercise, while activating the RF to lesser degree. Considering the quadriceps muscle group makes up the most mass in the human body, it’s an important choice. The barbell lunge has the capability to be loaded progressively, it is a compound exercise, it challenges the back and abdominals, it requires upper back strength, and it challenges balance. There is an added benefit of having around 50% the weight a barbell squat would. And believe me, I’m not trying to bash the squat. I had originally chosen the squat as my first choice, but the research kept showing the lunge ahead of the squat in EMG activity. As much as I love the squat, I couldn’t deny the multiple studies all recording the lunge ahead of the squat in VM and VL amplitude.
This study conducted by Faith et. al, compared four exercises across multiple lower extremity muscle groups . The researchers data shows that the lunge had the highest degree of VL and VM activity . The lunge, step-up and squat are all great developers of the leg and the goal of looking at the research is to not play favorites.
My second choice for the quadriceps group is the leg extension machine. The constant tension of a machine contrasts the nature of free weights and it’s the best way to develop the RF. These two activities fit together extremely well as they supplement each other’s weakness. The leg extension doesn’t force as much VM and VL activation as the lunge, but develops the rectus femoris unlike any other activity. One study which analysed the leg extension at different knee angles found that the RF is most activated at near full extension, when the exercise is most difficult. This is likely the reason why lunge has less RF activity, considering, during the lunge, the exercise gets progressively easier as the knee nears full extension. The leg extension activity also develops the VI. Understanding VI’s location elucidates the difficulty in finding an appropriate activation, as it sits hidden underneath the rectus femoris and lies atop the femur bone. Nevertheless, some research has been conducted on the muscle . It appears to be activated by the leg extension machine to a greater degree than any of the three other quadriceps muscles at a lower knee angle: 90-115, and dwindles at higher knee angles. Therefore, the leg extension machine may be considered “better” than the lunge for total quadriceps development, if you are a bodybuilder. It certainly activates all four of the quadriceps muscle (no research was found regarding barbell lunges and VI activation) in a relatively even manner, whereas doing lunges will emphasize the VM and VL. The leg extension is absolutely 100% safe for the ACL and will not make it more susceptible to injury; knee pain during the activity it is likely the patellar joint.
The data collected by Ebben et. al, compared five extremely common lower body activities . The data shows the leg extension exercise having the highest peak and average RF emg activity.