Stamina
Stamina is the energy we need to keep our bodies active. if you got good stamina, you will be able to to keep going at an activity for a long time.
All sports and physical activity require some good degree of stamina.

Tennis
How stamina can benefit your health?
Feeling physically tired can harm your focus, concentration and many other psychological factors. A physically fit person will generally find it easier to maintain focus during studies, and day-to-day tasks.
Stamina based activities help lower heart rate and blood pressure and help us to burn fat.
Stamina is also important for performance; mental fitness benefits from physical fitness.
We will tell you how to improve your stamina in 5 steps
1 Walking or running

Running boosts your stamina
You can start walking for around 10 to 15 minutes and increase your time gradually by five minutes every week or every time you feel your walking or running sessions feel easy or short. Keep adding 5 minutes until you are consistently walking or running for 30 to 45 minutes per session.
2 Plan a circuit
Try planning 8 to 10 different activities and dedicate 4 to 8 minutes to each one before moving to the next. Perform cardio activities, like running on the spot or jumping jacks between activities that require equipment. No resting between exercises, your heart rate should stay elevated so you can improve your stamina and cardiovascular health.
3 Switch up your routine
Switching up your workout is essential to building stamina. if you’re always running, start doing jumping jacks instead. You need to move your muscles in different directions.
4 Combine moves

Set your dumbbells as part of your circuit
The more muscles you move, the better you will boost your endurance. Combine squats + jumping pull-ups+ press. Try different combinations.
5 Add short and highly challenging moves
Movements that take a lot of energy challenge your strength and endurance simultaneously. Once you get started, you will notice that you will get faster. Try adding things like burpees, box jumps, jumping knee tucks and power push-ups to your workout routine.
Read more:
http://news.bbc.co.uk/sportacademy/hi/sa/in_the_gym/workouts/newsid_3168000/3168089.stm
http://www.livestrong.com/article/184665-how-to-increase-cardio-stamina/