Patanjali gives a list of obstacles to yogic practices. They are sickness, lack of mental disposition, doubt about ones practices, insensibility, laziness, sensuality or rousing of desire when sensory objects posses the mind, false or invalid knowledge, failure to attain continuity of thought or concentration, inability to continue the practice due to slackness and failure, pain or sadness, despire, unsteadiness of body and breathing problems.
These either originate in man or due to natural calamities and accidents. Their cures are laid down in yoga sutras.

It may be noted that out of 13 obstacles to yogic practices mentioned by Patanjali only 4 deals with body, namely, sickness, laziness, unsteadiness of the body and respiration.

Yoga asanas improve the blood circulation throughout the body including the head, trunk and limbs. It will also activate the ductless glands. Thus asanas or postures make the blood circulation of the body in effective way and keep the body energy or bio energy in a full circle.

The practitioner of yoga asanas will thereby enable to get rid of the obstacles affecting the physical body before he is ready to tackle the mental obstacles by the practice of pranayama or breathing exercises.