Impact is a force at which a body part contacts the ground during exercise. If you have joint problems or are obese, high-impact exercise can be contraindicated, putting you at risk of doing more harm than good.

Soccer is a physically demanding game that requires a great level of physical fitness. Soccer requires you to walk, sprint and jog for a range of distance over a prolonged period of time. A high level of stamina is required to be a successful soccer player.

An exercise bike may be perfect for your fitness needs if you want something that is convenient and easy to use. An exercise bike does not take up too much room and it can be used indoors, rain or shine.

If you have ever begun a new weight-training program, then found it difficult to walk down stairs for the following few days, you are familiar with the uncomfortable side effects of muscle strengthening. Your muscles swell after weight training.

Any irregularity in a woman's period can be disturbing and cause alarm. Spotting after strenuous exercise is usually not a signal of anything serious. For the most part, health professionals do not worry about an occasional missed period or breakthrough bleeding.

If you experience a poor supply of oxygen to your body--a medical condition referred to as hypoxia--you may develop lasting damage to the tissues of your body or brain. Poor oxygen supply is of crucial concern to pilots, hikers and other people who are frequently exposed to high altitudes.

A rowing machine offers an excellent all-around workout. Not only does it provide an excellent cardiovascular exercise, but it also involves strength and resistance training in your arms, shoulders, legs, hips and core as you go through the rowing motion.

If you cannot do a standard pushup, do not do knee pushups. Elevate your upper body on a chair or bench, but practice standard pushup form. In this position, you are pressing or pushing up about 50 percent of your body weight. A standard pushup utilizes around 65 percent of your body weight as resistance.

Marathon running is an endurance event. Training to run 26.2 miles requires putting in enough hours of running for your body to be ready to handle the entire marathon distance.

Fuel your body before exercise and get the most out of your workout. Types of food and timing of meals affect energy levels during exercise. Heavy, high-fat foods can cause indigestion, sluggishness, fatigue and diarrhea during a workout.

If you play sports, you know an athlete's mantra is hydrate, hydrate, hydrate. While dehydration is common, overhydration can cause a rare, but sometimes fatal, condition called hyponatremia. When you drink a lot of water, the ratio of sodium and fluid in your body becomes skewed. The imbalance causes cells to swell.

Whether on the ground or in the air, a variety of forces contribute to the motion of a ball. Focusing on spherical balls -- such as those used in golf, baseball and basketball -- their size and mass help determine how they travel.