Hatha yoga is a set of physical exercises developed to align the skin, muscles and bones. Yoga devotees also claim that the postures in hatha yoga open the channels of the body so that energy can flow freely.
Hatha is a portmanteau - "ha" means "sun" and "tha" means moon. An article in Yoga Journal says the name refers to the balance of masculine (active, hot, sun) and feminine (receptive, cool, moon) aspects:
"Hatha yoga is a path toward creating balance and uniting opposites. In our physical bodies we develop a balance of strength and flexibility. We also learn to balance our effort and surrender in each pose."
Previous studies have found that yoga may be beneficial at reducing anxiety, depression and stress. In 2013, Medical News Today reported on a study by the University of Illinois team that found a 20-minute session of hatha yoga improves brain function more than aerobic exercises.
Does practicing yoga result in 'an improved ability to sustain attention'?
Neha Gothe, University of Illinois graduate student and lead author on both the 2013 study and the new study, explains that "hatha yoga requires focused effort in moving through the poses, controlling the body and breathing at a steady rate."
She says that "it is possible that this focus on one's body, mind and breath during yoga practice may have generalized to situations outside of the yoga classes, resulting in an improved ability to sustain attention."
Participants in the yoga group "showed significant improvements in working memory capacity," according to the researchers.
For the study, 108 participants aged 55-79 were recruited. A group of 61 participants were assigned to attend hatha yoga classes, while the others took part in non-yoga stretching and toning exercises.
Gothe and her colleagues found that at the end of the 8-week study period, the yoga participants were reporting more accurate scores on tests of information recall, mental flexibility and task-switching than they had reported before the yoga classes.
However, the participants who took part in stretching and toning showed no cognitive improvements.
The researchers say that the differences between the two groups were not the result of discrepancies in age, gender, social status or other demographic factors.
"Participants in the yoga intervention group showed significant improvements in working memory capacity, which involves continually updating and manipulating information," says co-author and kinesiology and community health professor Edward McAuley.
"They were also able to perform the task at hand quickly and accurately, without getting distracted. These mental functions are relevant to our everyday functioning, as we multitask and plan our day-to-day activities."
"These studies suggest that yoga has an immediate quieting effect on the sympathetic nervous system and on the body's response to stress. Since we know that stress and anxiety can affect cognitive performance, the 8-week yoga intervention may have boosted participants' performance by reducing their stress."
However, the results reported by the team - which are published in The Journals of Gerontology Series A: Biological Sciences and Medical Sciences - are only preliminary findings and involve a short study period and relatively small group of participants. Therefore, further research is needed to confirm the results.