The 5,000-year-old discipline of yoga is widely recognized for helping to build strength and flexibility in healthy people via a combination of meditation, controlled breathing and specific stretches. Claims that the practice has therapeutic value, however, are more controversial.

Extensive research has explored yoga's potential value as an adjunct treatment for such health problems as anxiety, hypertension, heart disease, depression, low-back pain, headaches and cancer -- and that's a partial list. But while much of this research suggests yoga produces benefits, many of the studies are poorly designed, say experts, and are small, highly specialized or contradicted by other findings.

In a thumbnail review of the scientific literature on yoga, Harvard Medical School researchers found that virtually every study indicated that further research was needed before yoga could be recommended for any of the health conditions being investigated. However, they also noted that proven benefits for yoga include reduced heart rate and blood pressure, increased lung capacity and improved physical endurance.

Here are some recent findings on yoga's impact on various conditions:

* Chronic low-back pain In a randomized, controlled study published in May in the journal Pain, researchers found significant reductions in pain intensity, functional disability and reliance on pain medication for patients complaining of chronic low-back pain after 16 weeks of Iyengar yoga therapy. The study, however, was limited to 42 patients, and data were called preliminary.

* Multiple sclerosis. A randomized, controlled study published in June 2004 in the journal Neurology found reduced fatigue levels in MS patients who practiced yoga for six months.

* Stress A small study of transplant recipients who followed an eight-week program involving meditation and gentle yoga postures found significant improvements in the quality and duration of sleep that continued for six months after completion of the course. The study was published in June in Progress in Transplantation.

* Mild to moderate asthma A four-week program of yoga, including postures and breath work, produced no appreciable benefit for patients with mild to moderate asthma, found researchers in a randomized, controlled, double-blind study published in the Annals of Allergy, Asthma and Immunology in May.

-- Rita Zeidner