On last week’s post, I discussed quadriceps weakness in runners with chronic low back pain.
This week, I’ll be discussing the utility of variations of single-leg mini-squats to strengthen the quadriceps muscle group.
I particularly like these exercises because they strengthens the quads (among other muscles) towards the mid to end-ranges of knee movement. During a running gait, the quadriceps work eccentrically to decelerate the limb upon initial contact. Most runners tend to undergo approximately 35 degrees of knee flexion (bending) during the running gait cycle. A single-leg mini-squat works to focus on quad strength, and eccentric control, during that range of motion (depending on the step height).
The particular study I’ll be discussing was published in the Journal of Orthopedic and Sports Physical Therapy (JOSPT) in 2007. It is open-access and you can download the full-text pdf from JOSPT’s link here.
This study was also discussed in a lesson plan on The Runner’s Zone. This is a fantastic online community that I would highly encourage joining if you work with the rehabilitation of runners.
You can read the abstract below.
Type of Study
This was a prospective repeated measures design. This means that all participants underwent the same experimental conditions. In this case, EMG values were recorded variations of a single-leg mini-squat.
What Did They Look At
The researchers utilized electromyography (EMG) recordings to quantify the muscle activation during various exercises.
Four different muscle groups were recorded during five different unilateral exercises. For the purposes of the blog post, to follow up last week’s post on quad strength, I will focus on quad activation during these exercises.
First, the researchers determined the maximal voluntary isometric contraction (MVIC) of the quadriceps muscle group using a Bio-dex machine during a leg extension exercise. The quadriceps activation would then be expressed as a percentage of the MVIC determined during this test.
The variations of these exercises are described and pictured below. Note: The names listed are what the researchers named each exercise. I would typically label them differently.
A. Unilateral Wall Squat (like a single-leg wall slide)
B. Unilateral Mini-Squat
C. Forward Step-Up
D. Lateral Step-Up
E. Retro Step-Up
All five variations of this single-leg mini-squat produced high levels of quad activation. The percent of MVIC, for each, are listed below.
- Wall squat– 66% MVIC
- Mini-squat– 60% MVIC
- Forward Step-up– 65% MVIC
- Lateral Step-up– 55% MVIC
- Retro Step-up– 57% MVIC
The authors concluded that the wall-squat (and forward step-up) likely demonstrated the highest quad activation due to the anterior position of the foot compared to the hip.
I believe single-leg exercises should be a staple of any well-rounded strength program for runners. The results of this study demonstrate that all five of these variations elicit high quadriceps activation.
If high quadriceps activation is the main goal, the wall-squat (like a single-leg wall slide) and forward step-up may be the most suitable variation.
Although the purpose of this post was about the quads, the wall-squat also demonstrated the highest activation of the gluteus maximus and gluteus medius muscle groups compared to the other four variations.
Questions for Readers
What are some of your favorite ways to strengthen the quadriceps group?
Do you have any other single-leg variations that are part of your strength or rehabilitation exercise selection?