Bodyweight leg exercises are a great way to build up lower limb strength, prevent injuries and improve your overall physical fitness. A common question I get as a physio is: "Are squats or lunges more beneficial to do regularly?"
Firstly to answer this question, it is important to understand that both squats and lunges can be adjusted to preferentially activate certain muscle groups.
Squats and lunges both use your gluteals, hamstrings and quadriceps muscle groups. However, lunges involve leaning the body forward which activates more hamstrings and gluteals, while if you keep the body upright, you will activate the quadriceps more - for instance, when you perform a classic style squat. However, going lower down will activate more gluteals and hamstrings.
It is also interesting to note that single leg exercises such as lunges also preferentially activate the gluteal mininus, medius and core muscles specifically to assist with hip stabilisation. Lunges also changes your dynamic balance, compared to a squat which has a large stable base of support.
A 2018 research study demonstrated that 6 sets of 6-12 rep weighted squats can produce an endocrine system response, which may play a role in stimulating muscle growth and tissue regeneration.
I would recommend that you incorporate both lunges and squats in your exercise regime for more health benefits.
Here is a useful reference article explaining the common fitness mistakes associated with squatting, lunging and planking, written by a leading expert physiotherapy lecturer from the University of South Australia, Dr Steve Milanese. It provides some simple tips on correcting your technique.