According to their research, funded by the National Institutes of Health, the optimal length of exercise per week is: minimum of 5 to 10 hours of moderate physical activity (42 minutes to an hour and 25 minutes daily) minimum 2 hours and 30 minutes to 5 hours of vigorous physical activity (21-42 minutes daily)

Best times to attend the gym: 10am: After the typical working day has started. 2pm-4pm: After lunch breaks have ended and before the work day finishes. 8pm: After the crowds attending straight from work have finished their workouts for the day.

One study found that your body's ability to perform peaks in the afternoon. Your body temperature increases throughout the day, optimizing your muscle function and strength, enzyme activity, and endurance for performance. Between 2 p.m. and 6 p.m., your body temperature is at its highest.

When you've been up and moving all day, your body may be better prepared to handle a sweat or strength-training session, physicians say. Plus, you have more fuel in your system from meals and snacks throughout the day to fuel your energy level and keep you going.