The primary muscles worked in the Lunge are the quadriceps and gluteals, including the gluteals maximus and most of the muscles in the hips and butt.
Many people consider the Lunge, and their many variations a CORE or Functional exercise, since the Lunge activates your CORE muscles.
The other muscles activated by the Lunge involve all your abdominal muscles, including the transverse abdominus (especially if you are sucking-your-gut-in”), lower back muscles (primarily acting as stabilizers), hamstrings and calf muscles.
Don’t forget the gastrocnemius in your calf and has it’s origin above the knee and outside the hamstrings, so it is typically aiding all knee extension action by 19%.
There are two primary forms of the Lunge. The first is the Forward Lunge.
When performing this exercise, you lift one foot and step forward within your functional range of motion (FROM). Then, you bend your knee, lowering your body until the knee of the back leg (the support leg that did not step forward) nearly touches or just barely touches the ground.
Remember your IFPA Knee safety Guidelines and DO NOT put weight on the knee.
In the second form of the Lunge, the Reverse Lunge, you take one step backward.
The leg that stepped backward will lower your body until the backward knee just barely touches the ground.
Both Forward and Reverse Lunges target the same muscle groups.
The primary benefit of doing both, is to improve your agility, balance, and coordination by adding stimulus to your neurophysiology.
The more variation you perform in your movements, the greater the adaptation will occur in your neurophysiology and therefore, the greater the improvement in your agility, balance, and coordination.
Once your neurophysiology has adapted to Front and Reverse Lunges, you can provide additional adaptation and improvements to your neurophysiology with Crossover Front Lunges (also known as the Curtsy Lunge).
Instead of stepping directly forward, you step forward and to your “left” crossing over your “right” foot at first approximately 30 degrees, and then gradually increasing the angle as your neurophysiology adapts and your agility, balance, and coordination improves.
On the next Repetition, you perform the exercise on the opposite side: stepping forward with your left foot and “crossing it over your right,” again at 30 degrees to start.
Once Forward Crossover Lunges get easy, you can add neurophysiology adaptation by now trying Reverse Crossover Lunge, where… you guessed it… you “crossover while stepping backwards”.
Most people find the Reverse Crossover Lunge more of a challenge, so I suggest you start with a 10-15 degree crossover instead of starting at 30 degrees.
Here are important safety tips to keep in mind. These are a refresher from the IFPA Knee Safety Guidelines, you learned in the IFPA Text: The Book on Personal Training
Do not exceed: “Knee Toe-Line”
Do not exceed: “Knee Hip-Line
No hard contact with the knee to the ground
Do not put pressure on the kneecap (Patella)
Keep the knee directly over the toes
Do not twist the tibia (shin bone) in relationship to the femur (thigh bone)
Do not allow the angle of the ankle on the” Stepping Leg,” to become less than 90 degrees Note: Less than 90 degrees at the angle means you are exceeding” Knee Toe Line”
Stay within your FROM. Exceeding FROM will probably lead to sore muscles, especially your hamstrings and gluteals, not from over-loading them, but from over-stretching them
If you violate these IFPA Knee Safety Guidelines, it will most likely lead to knee damage and pain. Not because the Lunge is a bad exercise, but because you performed it badly
I also recommend you learn each Lunge exercise UNLOADED.
Get your form and technique perfect before you add weight.
In the beginning, I recommend you use dumbbells held at your sides, arms hanging down. This will allow you to Drop the dumbbells safely at your side should you lose your balance.
If you use a barbell on your back and lose your balance, you are going to come down hard on your knee with all your weight and the weight you are carrying with the barbell.
This is a lot of potential damage to your knee that can be completely avoided with dumbbells.
Keep your lower back and all the Erector Spinae muscle group tight and activated, along with the Rhomboids and Trapezius to keep your back upright and scapula (shoulder blades) retracted.
Rounding the shoulders or back can cause back damage as is the cause in most strength training exercises.
Remember IFPA Personal Trainer Rule Number One: DO NO HARM!
If you or your personal training client feels knee or back pain, or any PAIN. STOP Immediately!!!!!!!!!
If pain occurs, check to see if you have violated any IFPA Personal Trainer Guidelines. If not, your client may have an imbalance between hypertonic (overly strong/overly weak) muscle groups which will require you to stretch the overly tight muscles and strengthen the overly weak group.
The 11th, IFPA Component of Fitness is Symmetry. You must always look to develop your client’s body in perfect symmetry to avoid injury and pain.
You may have to consider more “Stabile” leg exercises like the Squat, Deadlift, Leg Press and Leg Extension/Curls until the symmetry issues of your personal training clients are corrected, before you can safely use Lunge exercises.
In concluding this article, I am reminded of the argument of which way do the toes point on the back leg. Without going into a lengthy dissertation, the toes of the back-foot point 90 degrees away from the stepping direction if your client requires stability. The toes point in the direction of the stepping foot if your personal training client has improved their agility, balance, and coordination and are looking to improve the neurophysiology with a more challenging foot position.