Your brain does send an electrical impulse along nerves that enter muscles to cause them to contract. The electrical impulses generated by ab machines are so weak that they can't possibly cause contractions that strengthen muscles significantly. If they did give you enough electricity to strengthen your muscles, they would give you a very painful shock.
When I look at today's baseball players, I just can't believe how big they are. They are larger and stronger than the best players of the 1930s to 1970s. Babe Ruth, arguably the greatest hitter who ever lived, was a fat elephant with relatively small muscles and a huge belly compared to the average player today.
If you want to become fit and use exercise to help prevent a heart attack, first check with your doctor to make sure that you do not have anything wrong with your heart or blood vessels. Intense exercise can increase your risk for a heart attack if you already have a damaged heart.
Should you exercise when you have a cold or the flu? Most doctors allow their patients to exercise when they have a cold, as long as they don't have a fever and their muscles don't hurt when they exercise.
A 28-year-old woman collapsed and died after finishing the Boston Marathon. Her blood salt levels were extremely low and she died from a condition called hyponatremia. A few weeks ago, a policeman training for bicycle duty died of the same condition. On July 26, 2005, sports medicine experts issued a warning to all athletes from the First International Exercise-Associated Hyponatremia Consensus Development Conference.
The ends of bones are soft, so they must be covered with a thick white gristle called cartilage. Once damaged, cartilage can never heal. When knee cartilage is damaged, the person spends the rest of his life losing more cartilage until it is completely gone and the knee hurts 24 hours a day.
Many marathon runners think that they have to run 100 miles a week to compete successfully, but most will be able to run a marathon faster if they run fewer than 50 miles a week. Top marathon runners can run 100 miles a week and not be injured because of their superior genes.