Building strength doesn't have to be done solely through gym workouts or strength training sessions. In fact, using your own body weight as resistance is a form of resistance training and can be a great (and free) way to build strength across your entire body. For example, Chaturanga (a key flowing transition in yoga) builds strength in your upper body and core whilst Warrior poses works your lower body (hamstrings, quads and glutes). Pick stronger styles of yoga like Vinyasa, Hatha, Power and Rocket to build muscular endurance and strength – just make sure to skew it to your level. Most teachers will give modification advice to make the poses easier, so listen out.