One of my favorite exercises is squat. It is a great combination of lower body and core strenghthening exercise. It is great for multisport athletes as it reduce overuse injuries. It should always be a part of an balanced triathlon training program but it is also great for everyone as it helps maintain function and integrity durng movement in daily life (work, hobby, gardening, etc).
I do every day 3 x Squat. Beginners can flex their knees until 90 degrees. Hold in the position for 1-5 sec (rest short). Later you can try to perform squat by reaching parallel.