Bodybuilding is all about muscle – finding ways to exhaust it, then finding ways to relax it; figuring out how to feed it, and finally trying to find any use for it. To complete this cycle repeatedly, you must constantly seek new ways to train, explore the latest recommendations, keep your eyes and ears wide open to all the new research and advice to distinguish fact from fiction. Though you need to keep your long-term goals in sight, equally important is periodically zeroing in on the essentials that will carry you forward. None of these elements is more basic than the contraction of a muscle, a repetition (also known as a rep), the single motion within each exercise. No workout goes without repetitions. No simple physical task can be accomplished without them. You perform hundreds, perhaps thousands of reps each day, but how often do you stop to consider what’s actually happening each time you complete one?
You don’t need to understand every single little aspect of muscle physiology each time you simply hit the weights, but a basic understanding of what happens when you complete a repetition may serve you well. The more you know about what makes and influences a repetition, the better you’ll understand how your muscles work and what you can do to help them do their job better. If your reps are sleazy and sloppy, the underlying physiology will not allow you to build any more muscle than you already have. On the other hand, if you put the wisdom of your system to use and polish each repetition with precision based on good form, your training sessions will quickly peak, as will your muscles, you will be able to grow more effectively and efficiently.
So, what’s a rep? In short, it is a muscle contraction. Now, what’s a contraction? For starters, I bet most ignorant sources tell you that a muscle contraction occurs only when you “make a bicep”. Not at all. You don’t even have to physically move to make a muscle contraction. Let’s explore how it all happens.
Muscle Work: Pushing, Pulling, Squeezing and Relaxing
At the most rudimentary level, contraction only means that tension has been generated. For any movement to occur, whether the contraction is involuntary (such as your heart beating), or voluntary (such as consciously lifting your arm or taking a step forward), your muscle fibers need to receive an electrical signal from your brain, initiated by impulses sent via nerves from the brain and spinal column to muscle cells. While you don’t have mind control over your heart beating, you have to make a conscious decision to make physical movement possible. First, you have to think about wanting to lift your arm, for example. A single nerve, or neuron, is connected to several muscle cells, or fibers. Collectively, the neuron and the fibers it innervates constitute a motor unit. When a nerve fires, all muscle fibers constituting the unit contract. Each muscle comprises many such motor units, of course, but only during maximal contraction do they all fire simultaneously. In a less-than-maximal movement only a certain number of motor units respond at one time, depending upon the force and motor skills required.
Each repetition of a muscle contraction comprises three phases:
- The concentric contraction (lifting the weight)
- The transition (holding the weight at the top of concentric contraction)
- The eccentric contraction (lowering the weight).
Let The Rep Begin
Picture yourself getting ready to do your favorite exercise – be it a squat, a bench press, a tricep extension, or a bicep curl, doesn’t matter. Focus on the muscle to be worked. The initial motion flexes the muscle and is called a concentric contraction. Here the working muscle shortens by pulling the bones on either side of the joint being used closer together. To initiate a concentric muscle contraction, the brain sends an electrical impulse, a signal through the Nervous System to your muscle fibers. This causes them to release Calcium which initiates the movement of the contractile protein inside the muscle fiber known as Myosin to pull on the other protein Actin. The end result – muscle contracts and pulls on the bone it is attached to in order to create movement. (A more thorough description of this mechanism is described in chapter “Flexing Muscles”). So, when you curl a dumbbell, picture your forearm and upper arm coming together – the bicep muscle gets shorter and thicker.
At the start of this concentric contraction, only a small number of motor units are activated, generating minimal force. As more force is required, additional motor units are called upon. If the weight being lifted is relatively light, many motor units will remain inactive; only a fraction of the total muscle contracts. However, if the weight is heavy, the muscle is fatigued, or both, the muscle must recruit as many motor units (and fibers) as possible to accommodate the demands being placed upon it. The amount of force that a muscle is able to generate increases with the number of motor units that are utilized. For most exercises, the concentric phase comes first, although on exercises such as the squat and bench press, you actually descend through the eccentric half to assume the real start position.
Reaching Your Peak
At the end of the concentric contraction, a muscle is in its shortest position. Some exercise physiologists, sports coaches and many bodybuilders recommend that you pause here for a second or two to contract the working muscle as intensely as possible, a technique called Peak Contraction. For example, holding something like a triceps extension at the bottom, as opposed to just lightly ‘tapping’ there, adds to the total Time Under Tension (TUT) which has a lot of physiological benefits in terms of activating hard-to-hit muscle fibers, establishing new neural pathways and so forth. (There is a lot more to be said about TUT, and you can find it all out by going to chapter “Muscle Power – Time Under Tension”.)
Others question the need to stop at any point during the rep. Steven Fleck, PhD, CSCS, former head of the physical conditioning program for the U.S. Olympic Committee, believes that using the appropriate resistance is more important than generating a peak contraction. “If the weight is light, you can never reach maximal contraction,” he says. “But if you manage the resistance right, you’ll get near-maximal contraction at some point during the range of motion.” Your best bet is probably to include Peak Contraction as a tool without relying on it entirely to produce maximum growth stimulation. Heavy weights are better known to promote the highest levels of stimuli, activate the more motor units and hence fatigue your muscles to a much greater extent than ‘peaking’ while going light.
What Goes Up Must Come Down
Before another concentric contraction can be made again, the muscle has to relax and lengthen. This happens in eccentric contraction. As you lower a dumbbell during a curl, for example, the bicep lengthens, even though it’s still contracted to some degree. A common misconception is that a muscle contracts during the first half of the movement and then relaxes as you return the weight to the start position. In fact, a muscle contracts during both phases. The difference is that the muscle shortens during the concentric half and lengthens during the eccentric half. During the eccentric phase, nerve impulses continue to signal motor units to fire, even though fewer motor units are used here than during the concentric contraction. As a result, more stress is placed upon each of the activated muscle fibers.
Unfortunately, this eccentric half of the repetition many bodybuilders mistakenly treat as an afterthought. Research confirms that the eccentric component of a lift may be just as important, or even more important than the concentric phase for promoting muscle growth. What not too many are aware of is that this “negative” portion of a rep causes more tissue breakdown and has important implications for muscle soreness – key issues in muscle-building. Since during an eccentric contraction you lower the same weight with fewer muscle fibers, each fiber involved has to sustain greater force. Therefore, a higher percentage is damaged which could lead to increased growth.
Muscle Contraction Types
So, muscles can contract in the following ways:
Isometric – a contraction where force is applied, but there is no movement or change in length of the muscle, even though the tissues are tensed. This happens because the load on the muscle exceeds the tension generated by the contracting muscle and occurs when a muscle attempts to push or pull an immovable object. (When I said that you actually don’t even need to move to contract a muscle I was referring to the Isometric contraction).
Isotonic – a contraction in which movement does take place, because the tension generated by the contracting muscle exceeds the load on the muscle. This occurs when you use your muscles to successfully push or pull an object.
Isotonic contractions are further divided into two types:
- Concentric – a contraction in which the muscle decreases in length (shortens) against an opposing load, such as lifting a weight up. During a concentric contraction, the muscles that are shortening serve as the agonists and hence do all of the work.
- Eccentric – a contraction in which the muscle increases in length (lengthens) as it resists a load, such as preventing the weight from dropping down by the force of gravity. During an eccentric contraction the muscles that are lengthening serve as the agonists (and do all of the work).
Full Range of Motion
Combining the concentric and eccentric phases of the rep produces an exercise’s range of motion. For maximal contraction and muscle fiber recruitment, you want to fully utilize this. Exercising through a full range of motion is safe as long as the rep is slow and under control. Also, taking the weight through the full Range Of Motion (ROM) will promote joint flexibility. Movements that fall short at either end will limit the number of muscle fibers involved, and may actually lead to decreased flexibility. Limiting factors can include individual joint mobility and structure as well as body composition, both of which will serve as a natural “stopper” letting you know when you’ve taken a movement far enough. Maintain tension (contraction) in the working muscle during the entire movement. While you don’t have to stop at the midpoint of the rep to accentuate the contraction, don’t hesitate to do it if it feels good.
During each repetition the brain sends signals down through the Nervous System to the muscles necessary to make the motion which requires actions by more than one muscle. In this very complex and well-orchestrated event some muscles must shorten (contract) and pull, others must relax to allow the movement to happen, and still others work to stabilise the primary movement. When muscles cause a limb to move through the joint’s Range Of Motion, they usually act in the following cooperating groups:
- Agonists create the normal range of movement in a joint by contracting. Agonists are also referred to as prime movers since they are the muscles that are primarily responsible for generating the movement.
- Antagonists act in opposition to the movement generated by the agonists and are responsible for returning a limb to its initial position.
- Synergists assist in performing the movement executed by agonists and make sure that the force generated works within the desired plane of motion. Synergists are sometimes referred to as neutralizers because they help ‘neutralize’ or cancel out the extra motion from the agonists.
- Fixators or stabilizers, provide the necessary support to assist in holding the rest of the body in place while the movement occurs. Fixators are also
Agonists and antagonists are usually located on opposite sides of the affected joint (like your hamstrings and quadriceps, or your triceps and biceps), while synergists are usually located on the same side of the joint near the agonists. Larger muscles often call upon their smaller neighbors to function as synergists.
When an agonist contracts, in order to cause the desired motion, it usually forces the antagonists to relax. This phenomenon is called reciprocal inhibition because the antagonists are inhibited from contracting. As an example, when you flex your knee, your hamstring serves as the agonist, or prime mover which contracts. Meanwhile, the antagonist quadricep is relaxed and lengthened somewhat. The calf and lower buttocks serve as the synergists.
Interestingly enough, reciprocal inhibition of the antagonistic muscles does not always happen and is not necessary to produce contraction. In fact, co-contraction can occur. For example, when you sit down or perform a squat, or do a set of lunges, you could assume that the agonists (hamstrings and glutes) of the back upper thigh inhibit the contraction of the muscles in the front (your quads). Not so. In this particular instance the antagonists also contract, except they contract eccentrically. Similar situation is seen in performing sit-ups for abs – all muscles around your waist, including the abdominals and spinal erectors co-contract. This is one reason why sit-ups are good for strengthening the back as well as the stomach.
The following is a list of commonly used agonist/antagonist muscle pairs:
- Chest/pectorals and Back/latissimus dorsi (pecs and lats)
- Front/anterior shoulder, Back/posterior shoulder (front & back deltoids)
- Upper-mid back/trapezius and Shoulder/deltoids
- Stomach/abdominals and Spinal erectors/lower-back
- Left and Right external obliques (sides of the waist)
- Front thigh/quadriceps and Back thigh/hamstrings
- Front-lower leg/shins and Back-lower leg/calves
- Front-upper arm/biceps and Back-upper arm/triceps
- Forearm flexors and extensors
The High Quality Repetition
A quality rep is performed by raising and lowering the weight in a deliberate, controlled manner. When you perform a typical weight-bearing repetition, use a speed at which the movement is completely controlled with no swinging. If you let momentum do some of the work for you, you won’t use as many muscle fibers to lift the weight which makes the exercise less productive and less efficient. Lifting a weight in a rapid, explosive fashion also exposes your muscles, joint structures and connective tissue to potentially dangerous forces which magnify the likelihood of an injury.
In most cases it should take about 2 seconds to lift the weight in the concentric phase and 4 seconds to lower the weight back to the starting/stretched position during the eccentric portion. This speed will guarantee that you’re exercising in a safe, efficient manner. But don’t take this as a gospel – changing the speed of repetitions has astonishing muscle-building potential. (I dedicated a chapter called “Repetition Speed” with over 10 pages of information on the subject to barely cover the basics… and you’ll love reading it.)
Breathing is another important aspect of any rep.
“Listen, are you breathing just a little and calling it a life?” (Mary Oliver)
Remember to breathe naturally and execute movements through a full ROM in a slow, controlled manner. Now you are thinking – weight plate goes up, weight plate goes down, when do you inhale and exhale throughout all this?
“Learn how to exhale, the inhale will take care of itself” (Carla Melucci Ardito).
As a rule of thumb, exhale during the concentric contraction, the period of greatest exertion, and take deep breaths in during the eccentric or relaxing phase. I like to think about it as “exhaling the effort” as if pushing the air out of the lungs helps to push or pull the weight from its original position. For example, when you are training your chest on a bench press, exhale as you bring the bar up from the chest, then inhale as the bar is lowered down.
Concentrate on your breathing as you do each rep and try to make each breath steady, smooth, deep and calm. Breathing too fast or too slow can make you hyperventilate or dizzy. Always control the intake of breath, keeping it smooth and deep. This will prevent gulping air which in turn regulates the oxygen levels in your blood.
Breathe from your belly or diaphragm, not your chest. Drawing the belly out brings the diaphragm down, inflating the lungs. Next, the ribcage is expanded to draw in more air. Finally, the shoulders and clavicles are drawn back to bring in the final small increase in lung volume. The reverse action takes place during exhalation. Pay attention to your breath not only when you train, but during any time of the day. Many people keep their stomachs sucked in and tight continuously, thereby depriving themselves of the belly expanding major portion of each breath. This very shallow breath using only the shoulders/clavicles and the ribcage for inhalation and exhalation will keep you alive, but may deprive you of energy-giving oxygen. When you breathe through your chest, only a small volume of air is drawn in which results in your energy levels plummeting. At the end of a training session, do a few slow controlled breathing exercises – this will help to move the metabolic wastes and even speed up healing. A very effective strategy is to use slow deep breaths during the cool-down and stretching.