scientists at the university of wisconsin-la crosse have warned that bikram yoga , which involves 26 poses , can raise a person 's body temperature and heart rate to dangerous levels .
a typical session lasts for 90 minutes and is performed in a room heated to 40 °c -lrb- 105 -rrb- , with 40 per cent humidity .
but body temperature was found to steadily increase throughout the 90-minute class , in both men and women .
but body temperature was recorded before the class started , as well as at 10-minute intervals throughout the session .