Other safety precautions are that you should never massage a dog that is suffering from fever, shock or cancer. Also, as you massage, avoid any areas of unexplained swelling. Also, remember that massage is not a substitute for proper veterinary care, it is a compliment to it, and it has many benefits for their health.
Some studies have shown that your deep sleep should at least be 20% of your overall sleep. It means that since most adults need 8-9 hours of sleep, they will need about 1.6-1.8 hours of deep sleep to feel fully functional next day. However, the time of deep sleep is changed and that's mainly due to the change in the sleep need of different group of people. For instance: Age Group.
In adults, total sleep time, sleep efficiency, percentage of slow-wave sleep, and percentage of REM sleep significantly decrease with age, while light sleep and wake after sleep onset increased with age. The decline in deep sleep begins around age 36-50. However, it is important to note that these changes are less prominent among women and in the healthiest older adults. In summary, sleep duration as well as structure changes with age and reflects alterations in physiology and health.