Strength training, one of the most important components of physical conditioning, keeps joints and ligaments healthy and reduces the risk of bone fractures and osteoporosis. Having a regular physical yoga practice that involves bodyweight-bearing poses will build strength as well as flexibility. For the sole purpose of strength training, yoga may be a good tool depending on advancement of poses and frequency of practice. Yoga, an integrative practice, has much more to offer than simply muscle strength, and building strength is not the only focus or goal.
A Fine Balance
Yoga poses involve stretching, and flexibility is usually the first thing most people think of when they think of yoga. Yoga also involves balancing that flexibility with strength. You achieve positions using your muscles holding your own body weight against gravity. Supporting your own body weight develops muscles that are strong and in proportion to one another. The heavier you are, the stronger you will get doing bodyweight exercises. As with any form of exercise, perform weight-bearing yoga poses and exercises with proper form and alignment to prevent injuries.
Length and Strength
Strength training using weights or other resistance is a good way to build muscle strength and size. You can increase weights progressively as muscle strength increases. Concentric contractions of the muscle, when the muscle shortens, are emphasized with weight training. In yoga, many poses are held statically or isometrically, and when transitioning between poses many of the contractions are eccentric or lengthening in nature. This means that you lengthen as well as contract the muscles. This may give the appearance of less bulky muscles than weight resistance training.
On the Whole
The poses in yoga involve using the body as a whole, as opposed to isolating certain muscles in strength training for bodybuilding or physical therapy. Physically, yoga offers much more than strength in terms of awareness, mindfulness, flexibility, kinesthetic awareness, balance and the ability to use different muscle groups at the same time. Because of the amount of muscular control required to stabilize and transition between poses, many muscle groups work at the same time.
A Fine Balance
Because it uses many muscles at a time, the body becomes strong in ways you may really use them as opposed to isolated positions that do not necessarily simulate a real movement that one would do in daily life. For example, many yoga poses require use of functional abdominal muscles. This is different from crunches, because your body gets used to actually using the muscles to stabilize and support the body as a whole. The strength of the muscles is balanced by their flexibility. Strength without flexibility creates rigidity. Flexibility without strength creates weakness and instability. A regular, consistent yoga practice provides this balance to create a strong, flexible, proportional musculature.
The most weight-bearing yoga poses are standing poses for the legs and balancing for the arms. Standing poses include warrior poses, tree pose and half-moon pose. Arm-balancing poses include handstand, crow and plank. Some poses incorporate core muscles to hold the body up against gravity. These poses include headstand, wheel and side plank.
Whether yoga can replace resistance training depends on your goals. A regular, consistent physical yoga practice would be ideal if you are seeking overall body strength and flexibility. Yoga can increase muscle strength when done regularly and with good alignment. However, you may need to isolate specific muscles while strengthening in certain situations, such as in physical therapy. Whether yoga would be a good option for therapeutic strengthening depends on each situation.