A question of speed

The two most common reasons people lift weights are to gain muscle size and to gain strength. The relationship between these two is often misunderstood. We are going to focus on strength.

While muscle size may look impressive and could perhaps help burn more calories, strength has a more direct relationship with overall health. It is strength that can help move objects, lift heavy boxes or push the stalled car down the road. It is also strength that is responsible for helping brace against an unexpected fall.

It is possible to gain strength without gaining muscle size. To understand this, you must understand how your muscles work. Muscles are filled with groups of workers called motor units. Motor units are strands of muscle fiber that all are attached to the same nerve.

This means all of those units must contract at the same time. There is a principle called the 'all-or-nothing principle' that states a motor unit can either be fully contracted or fully relaxed. There is no 'partially contracted' or 'in between.'

So how, then, do you control your strength? It is the coordinated effort of motor units that determines how much strength you exert at any given moment. If you are lifting a pen, only a few motor units contract. If you are lifting a heavy box, many more motor units come into play.

The coordination of these motor units is more neurological than physiological. This means that when you train for strength, you can actually improve the efficiency of your motor units. You can 'recruit' more of these to work for you in a given moment. Training to increase strength, however, is about more than simply pushing the heaviest weight. It also means training for speed.

To understand why this is important, consider the equation for force:

Force = mass x acceleration

Simply put, force has two components: the mass of the object being moved, and the rate of acceleration. In the weight room, this has an interesting consequence. It turns out that moving a light object quickly (low mass, high acceleration) may take the same force as moving a heavy object slowly (high mass, low acceleration). In both cases, you are generating a force.

While lifting heavy weights burns a lot of calories, it is also very taxing and damaging to the muscles. Having a lighter workout that focuses on speed can help balance these heavier workouts. In fact, for beginners, I always suggest you pick the lighter weights and train for speed rather than risking injury from heavier loads. Remember that speed doesn't mean thrusting the weights out of control, but accelerating as fast as possible while retaining control.

An example workout, then, might involve doing heavier lifts - bench press and squat - during one part of the week. Then, a few days later, you would lighten the load and do push-ups and squat jumps (squats without weight or just holding a medicine ball). This second workout may involve less weight, but focusing on acceleration will still increase the force you are generating and help build your overall strength and speed.

As you can see, strength is, in a sense, a question of speed. This is why martial artist Bruce Lee was incredibly strong and fast despite not having a large amount of muscle mass. If you are training for health, knowing this can help you create more effective workouts by focusing on speed and not just lifting the heaviest weight in the gym.