In terms of fitness, there are two main sources that the majority of people think of. One is cardiorespiratory fitness and heart health and the other is muscle strength to move the body. Runners seem to prioritize the cardio factor because getting oxygen to the lungs allows you to run faster and longer with training. But the strength factor is just as important. Strength is especially important as a person ages. Falls are one of the leading causes of injury and even death among seniors. Maintaining leg strength to regain balance after tripping is very essential. It is also important to have enough strength in the arms to catch the body and avoid a sudden fall.

There are four common sources of exercise to use to increase strength. One uses your body weight for resistance, a second uses weights as resistance, a third uses rubber or steel cables to provide resistance, and a fourth is an isokinetic exercise machine. Each has a positive effect and each has a negative factor when using one method over the others.

Bodyweight exercises (calisthenics) are the cheapest and are always available. By adjusting the angle of the body, a person can change the resistance. For example, when doing push-ups on the floor, if the head is higher than the feet (like putting your hands on a stair), the resistance is lighter. And having your feet higher than your head (feet on a chair) will increase resistance. If you are doing a squat movement for leg strength, a person can hold a pole for balance and try squatting with one leg up for more resistance. One limitation is that resistance is limited by body weight.

Weights are the most well-known form of exercise and can be free weights or weights on a machine. Using dumbbells, a person can vary the resistance from very light to very heavy and move through a wide range of motion. The most common exercise routine consists of three sets of 8 to 12 repetitions. If you can’t lift the weight for at least six repetitions, the weight is too heavy. If you can lift the weight for 15 reps, the weight is too light. The problem is with the range of motion of an exercise. The resistance changes with the range of motion. If the range of motion is 180 degrees, the first 60 degrees is light, the range of 60 to 120 degrees (the 90 degree angle is the greatest resistance) has the resistance at its maximum, and 120 to 180 degrees, the weight is lighter again. Even the angle of the arm can change the level of resistance when lifting a weight. If the weight is too heavy, the person can strain a muscle and cause an injury. If the weight is too light, the benefit of gaining strength is limited.

A resistance system using cables is good in that as the person goes through the full range of motion (arms bent to be straight for example), the resistance increases as the cable is stretched. The key is finding the right size cable to use so that a full range of motion can be maintained. Cable systems are easy to store and do not take up much space. The negative part of the cables has two factors. The first is that if the end of the anchor comes off, the result is a very hard blow to the body if the angle is incorrect. The other is that when the cable is at its maximum stretch, the resistance is greatest and if the person loses control, the cable will quickly pull the arm holding it down and can lead to injury.

The fourth resistance method is an isokinetic machine. Resistance is measured in foot-pounds (the force multiplied by the distance traveled) and the resistance is equal throughout the entire range of motion. The movement is set at a constant speed and whether you pull hard or soft, the speed of the movement is the same. The advantage is that you don’t have to adjust weights, change stations for different exercises and anyone can use it. Husband, wife and children can all use the same machine without changing any parts. The negative (although some say it’s a positive thing) is that there is no eccentric resistance. You do not need to return the weight to the starting position. It is the eccentric movement that causes muscle soreness, so you can exercise for the first time and not have muscle soreness. But we live in a quirky world where most lifted objects have to be put down. Machines can be expensive but will last a long time and won’t take up much space.

All forms of resistance exercise will increase strength and be beneficial. It may be worth trying them all for some variety in your workout. Strong muscles will help you run further and faster.