A toned, sleek and well-defined physique is on most women’s fitness wish list, but for many there is still fear that strength (or resistance) training will build bulging bulky muscles. How strength training affects your muscles depends on a number of factors – most importantly, the way you train (in terms of frequency, weight, number of reps and sets) and your genes, but also what other physical activity you do, you diet and even your technique.
This is part 1 of our women’s guide to shaping muscle where we present the vital information you need to meet your strength and toning goals.
So what exactly are muscles, and how do they work?
To find out, let’s pick a muscle, say the biceps on the front of the upper arm, and take a closer look.
A muscle is made up of thousands of long, thin fibers which contract to pull on bones and enable the skeleton to move. The signal to contract comes from a special type of nerve cell, called a motor neuron, and each one of these acts as the ‘governor’ to a set group of fibers. These fibers could number anything from several thousand to just a few.
A motor neuron and the muscle fiber it activates are collectively called a motor unit. When the motor neuron receives a message from the central nervous system (base control) saying, ‘Move!’ it, in turn, tells all its muscle fibers to contract.
The muscle consists of scores of motor units, and not all them contribute to any given movement. The number that gets activated depends on the effort required by the muscle. If you were to try lifting an iron bar, for example, most of the motor units in the biceps would be recruited, whereas if it were just a piece of paper, only a small number of motor units would be called into play.
Whatever the movement, the motor units involved are not continuously active. Instead, they switch on and off at different times, but they do this so fast that you get a smooth contraction (think of a Mexican wave). The question of how many are firing at any one time is determined by your training experience and efficiency, not to mention your genes.
As you become used to training, you are capable of handling a greater load because you are stronger; but for any given load fewer motor units are required, as those activated are more efficient. However, whether it is just a couple of motor units or a few hundred that take part, the order in which they are recruited is always the same. This sequential order is related to the types of muscle fiber.
Fast & Slow Twitch Fibers
Muscle fiber types come in different varieties. There are two principles types and we all have some of both, but the type that predominates varies from person to person and muscle to muscle, and that will influence – to some extent – the kind of activity you are best suited to.
Endurance athletes tend to have a lot of Type 1 or ‘slow twitch’ fibers (muscle biopsies 9on endurance athletes have revealed as much as 99 percent slow twitch fibers in the calf muscles). These fibers are highly resistant to fatigue because if their ability to process lots of oxygen but they tend to be recruited mainly as low intensities of effort (such as picking up a piece of paper).
Type 2 or ‘fast-twitch’ fibers, on the other hand, are associated with muscle power, strength and speed – and kick in only when the intensity of effort required increases.
An important thing to know as far as strength training is concerned is this . . .
Since the motor units are recruited in sequential order from Type 1 to Type 2, it follows that the only way to train a muscle in its entirety (getting the maximum number of motor units involved) is to expose it to increasingly challenging loads, to ensure they all get a ‘piece of the action.’
That is why doing lots of reps with a light weight is pretty much a waste of time!
Just to confuse things, there are two types of Type 2 fibers – imaginatively known as Type 2a and Type 2b. While 2b are the true power rangers, the Type 2a fibers are more ‘middle of the road’ and, depending on the type of training you do, can be made to act either more like endurance-based Type-1 or power based Type 2b fibers. In other words, they can be trained to boost stamina or aid brute strength. This is very important when it comes to program planning, as you can’t have you cake and eat it – at least, not within one particular muscle.
How Muscles Get Stronger and Firmer
Muscle will only be as strong as it needs to be. If you spend most of your time sprawled out on the sofa, your muscles will have adapted to that level of o demand and consequently will find more taxing activities a challenge. To make a muscle stronger, you need to overload it. That is, you need to put it under more stress that it is accustomed to. Just as importantly, you need to increase the overload progressively. Otherwise, the muscle has no incentive to improve and strength or muscle development will plateau.
So what builds strength?
It comes down to two things.
First, the muscle’s ‘pulling power’, which is dependent on the number of cross-bridges (protein-based structures that facilitate the pulling action of fibers in a muscle) per fiber. If you want to pull harder, you need more cross-bridges.
So, how do you get them?
Tiny amounts of damage, caused by training, initiate their creation, by way of increasing the number of myofibrils in the fiber (myofibrils are basically packages of contracting protein, that are arranged in bundles lengthways along the muscle fiber). More myofibrils means the fiber gets physically bigger, as it has more bundles packed along its length. But this doesn’t necessarily mean the muscle itself gets bigger.
It is worth knowing that, while you can make the fibers bigger, it is not believed that you can change the number of fibers within a muscle – that is determined by your genes. Nor can you change the number of fibers per protein unit. This varies between individuals, and is one of the reasons why some people can increase muscle size and improve strength far more easily than others. Research shows that men tend to have more fibers per motor unit than women do.
The second thing that changes in order to increase strength is to do with the communication between the nervous system and the muscles (neuromuscular pathways). The central nervous system recruits the number of motor units it thinks best fits the job in hand. In an untrained person, this mechanism is very crude – and the nervous system will tend to underestimate. But when you train regularly, you become more effective and fire up more motor units every time, so you get more ‘hands on deck,’ and consequently greater strength. It is thought that for the first few weeks of training, strength gains are mostly to do with improved neuromuscular pathways, rather than the physiological changes in the muscles, which set in after.
We all use the word ‘tone’ as though it is a specific goal, but really what tone means is a ‘state of slight tension’ – in other words, the muscle is slightly active, rather than totally passive. If muscles are accustomed to being active, they tend to have a higher level of tone than in people who are inactive and don’t use their muscles much.
Tone is related to shape, or definition, in a muscle because when a muscle contracts, it shortens and bulges as the fibers overlap one another, giving more shape. So, yes, strength training will improve your muscle tone.
However, definition -or lack of it – is very often more to do with too much body fat covering the muscle than with a lack of muscle shape.
So, Is it possible to get firmer and stronger without getting bigger muscles?
The answer is yes. If you were to look at a muscle in a cross-section, you’d see that there are spaces between the fibers. In an untrained muscle there is lots of space. As you know, when you train a muscle, the fibers get bigger. Initially, however, this won’t show, aas the muscle fibers merely take up more of the free space in the muscle by becoming more tightly packed, rather than actually increasing the volume of the muscle. This is one reason why muscles firm up when you train them.
If you don’t want to increase the overall size of the muscle, you can stop increasing the overload once the muscle has firmed up to maintain this new level of tone, without adding volume.
Continue to overload the muscle, though, and it will increase in size. This takes place through a process called ‘myofibril splitting,’ which is when the existing myofibrils actually split into two (rather than continue to increase in size), hiking up the overall number within the muscle fiber and, therefore, increasing its cross-sectional area. This increase in muscle fiber size is called hypertrophy, and it is the basis of every bodybuilder’s regime.
It bears repeating that even if you don’t want to have larger muscles, performing endless sets of repetitions with very little weight isn’t the answer. This will not actually instigate the adaptations that allows the fiber to get thicker, so will not achieve either definition or firmness.
In Part 2 of our Women’s Guide to Shaping Muscle, we put the theory from this article into practice as we discover the training factors that influence how you should exercise to maximally shape your body.