The benefits of yoga are available to anyone, irrespective of flexibility, strength or age. Your body is unique to you so you should simply start where you feel the most comfortable and work from there without worrying about what anyone else can do. A lot of the time you'll get more benefit from practicing simple postures with the right bodily alignment, rather than trying to force your body into a position it's not ready for.
Flexibility: Stretching your tight body in new ways will help it to become more flexible, bringing greater range of motion to muscles and joints. Over time, you can expect to gain flexibility in your hamstrings, back, shoulders, and hips.
Strength: Many yoga poses require you to support the weight of your own body in new ways, including balancing on one leg (such as in Vrksasana - Tree Pose) or supporting yourself with your arms (such as in Adho Mukha Svanasana - Downward Facing Dog). Some exercises require you to move slowly in and out of poses, which also increases strength.
Muscle tone: As a by-product of getting stronger, you can expect to see increased muscle tone. Yoga helps shape long, lean muscles.Pain
Prevention: Increased flexibility and strength can help prevent the causes of some types of back pain. Many people who suffer from back pain spend a lot of time sitting at a computer or driving a car. That can cause tightness and spinal compression, which you can begin to address with yoga. Yoga also improves your alignment, both in and out of class, which helps prevent many other types of pain.
Better Breathing: Most of us breathe very shallowly into the lungs and don't give much thought to how we breathe. Yoga breathing exercises, called Pranayama, focus the attention on the breath and teach us how to better use our lungs, which benefits the entire body. Certain types of breath can also help clear the nasal passages and even calm the central nervous system, which has both physical and mental benefits.
Mental Calmness: Yoga asana practice is intensely physical. Concentrating so intently on what your body is doing has the effect of bringing a calmness to the mind. Yoga also introduces you to meditation techniques, such as watching how you breathe and disengagement from your thoughts, which help calm the mind.
Stress Reduction: Physical activity is good for relieving stress, and this is particularly true of yoga. Because of the concentration required, your daily troubles, both large and small, seem to melt away during the time you are doing yoga. This provides a much-needed break from your stressors, as well as helping put things into perspective. The emphasis yoga places on being in the moment can also help relieve stress, as you learn not to dwell on past events or anticipate the future. You will leave a yoga class feeling less stressed than when you started.Body
Awareness: Doing yoga will give you an increased awareness of your own body. You are often called upon to make small, subtle movements to improve your alignment. Over time, this will increase your level of comfort in your own body. This can lead to improved posture and greater self-confidence.