The following is a list of tentative definitions of Yoga Therapy by the International Association of Yoga Therapy: 
Yoga therapy, derived from the Yoga tradition of Patanjali and the
Ayurvedic system of health care refers to the adaptation and application
of Yoga techniques and practices to help individuals facing health
challenges at any level manage their condition, reduce symptoms, restore
balance, increase vitality, and improve attitude.
-American Viniyoga Institute
Gary Kraftsow
Yoga therapy is that facet of the ancient science of Yoga that focuses
on health and wellness at all levels of the person: physical,
psychological, and spiritual. Yoga therapy focuses on the path of Yoga
as a healing journey that brings balance to the body and mind through an
experiential understanding of the primary intention of Yoga: awakening
of Spirit, our essential nature.
-Integrative Yoga Therapy (U.S.A.)
Joseph LePage, M.A.
Yoga therapy adapts the practice of Yoga to the needs of people with
specific or persistent health problems not usually addressed in a group
class.
-Samata Yoga Center (U.S.A.)
Larry Payne, Ph.D.
Yoga therapy is the adaptation of yoga practices for people with health
challenges. Yoga therapists prescribe specific regimens of postures,
breathing exercises, and relaxation techniques to suit individual needs.
Medical research shows that Yoga therapy is among the most effective complementary therapies for several common aliments.
The challenges may be an illness, a temporary condition like pregnancy
or childbirth, or a chronic condition associated with old age or
infirmity.
-Yoga Biomedical Trust (England)
Robin Monro, Ph.D.
Yoga comprises a wide range of mind/body practices, from postural and
breathing exercises to deep relaxation and meditation. Yoga therapy
tailors these to the health needs of the individual. It helps to promote
all-round positive health, as well as assisting particular medical
conditions. The therapy is particularly appropriate for many chronic conditions that persist despite conventional medical treatment.
-Yoga Therapy and Training Center (Ireland)
Marie Quail
(Yoga
therapy is) the use of the techniques of Yoga to create, stimulate, and
maintain an optimum state of physical, emotional, mental, and spiritual
health.
-Judith Hanson Lasater, Ph.D.
Yoga
therapy consists of the application of yogic principles, methods, and
techniques to specific human ailments. In its ideal application, Yoga
therapy is preventive in nature, as is Yoga itself, but it is also
restorative in many instances, palliative in others, and curative in
many others.
-Art Brownstein, M.D.
Yoga
therapy is of modern coinage and represents a first effort to integrate
traditional yogic concepts and techniques with Western medical and
psychological knowledge. Whereas traditional Yoga is primarily concerned
with personal transcendence on the part of a "normal" or healthy
individual, Yoga therapy aims at the holistic treatment of various kinds
of psychological or somatic dysfunctions ranging from back problems to
emotional distress. Both approaches, however, share an understanding
of the human being as an integrated body-mind system, which can function
optimally only when there is a state of dynamic balance.
--Georg Feuerstein, Ph.D.
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