The Hustle in Your Muscle

Do you know all of the major muscles in your legs? More importantly, what's the best way to keep those muscles powering you? iRun went to the experts to bring you this unofficial 'Owner's Guide' for your legs.

By Sonia Mendes and Lora Shinn

Muscle Power: How does the magic happen?

You may already know that muscles consist of fibers, but how do these fibers work in tandem to power a major appendage – like a leg under pressure to move as fast as it can?

“Muscle fibers are complex arrangements of muscle cells and proteins with connecting tissues that ‘bind’ them together and attach them to bones via tendons,” explains Dr. Bruce Minnes, Associate Medical Director in the Division of Paediatric Emergency Medicine at The Hospital for Sick Children in Toronto.

The basic contracting unit of the muscle fibre is called the sarcomere. A muscle is made up of a large collection of these fibers, arranged in different orientations and with different cell types. Muscle fibers rarely extend the whole length of the muscle. A number of uniquely-arranged proteins in the muscle unit allow for contraction and relaxation to occur at a rapid rate.

Calcium also has a central role in triggering muscle contractions. When a nerve impulse “triggers” a muscle contraction, calcium is released from storage areas and allows for the contraction of muscle proteins. As the impulse passes, calcium is returned to the storage areas, and the muscle then relaxes.

Control and coordination of muscle contractions begins with nerve impulses, which are themselves coordinated by both conscious and automatic parts of our nervous system. The movement centres in our brain control conscious movement and coordination, but the feedback loops between spinal cord and muscle unit also control the more reflexive and kinaesthetic, or “position sense” aspects of muscle movement. This is important as much of our limb positioning and “step-to-step” adjustments for surface, incline and terrain occur ultra-quickly and without any thought.

When it all goes wrong: Muscle irritation & injury

Despite our best efforts, no runner is immune to injury. At some point in every running career, most of us will experience some type of an injury.

“Muscle irritation, injury or damage can occur for a variety of reasons,” says Dr. Minnes. “Muscle soreness and cramps are common and can relate to local electrolyte or fluid or acid imbalances and are typically self-limited.

“Cramps may occur as a result of a transient ‘hyper-excitable’ state of the nerve cells controlling a particular muscle, and can sometimes be stopped by a slow and firm stretching of affected muscle or by activating the antagonistic muscles – those muscles that would move the joint affected by the cramping muscle in the opposite direction.”

What is less common – and more serious – is muscle haematoma or contusion (bleeding or bruising of the muscle), which can result from direct impact or severe strain. The result can be severe pain, swelling, tenderness and hardness at the affected site.

According to Dr. Minnes, initial care is pain control, icing and rest with an initial short period of immobilization. An early return to gentle motion and careful increases in both passive and active movement, while avoiding re-injury in therapy, result in a shorter period of disability.

Why does it happen?

Muscle strains represent about 50 per cent of athletic injuries, says Minnes, and typically result from a forced or overstretched activated muscle. Muscles that cross two or more joints and that can be subject to stretch at more than one site, such as the hamstrings, are at higher risk for this type of injury.

Strains can range from mild and partial to severe, with complete tears of the muscle or tendon units. In its most severe form, the disability is immediate and significant and does not settle quickly. Bleeding into the muscle and localized inflammation are the sources of pain and swelling, and the muscle is at a high risk of re-injury until these have resolved – sometimes up to 10 or 12 weeks from the initial injury. Minnes suggests rest, application of cold or ice-packs and pain management with a non-steroidal anti-inflammatory medication (such as ibuprofen).

Light activity with stretching and muscle activation can be resumed as soon as there is no great discomfort, with a slow and controlled return to sport so as to avoid re-injury during this healing phase. A return to higher-level or competitive activity can happen only when the range of movement and strength of the injured area is complete and equal to that on the other side, and training occurs with only mild or no pain. More serious tears require a complete athletic or medical assessment and some may even require surgical repair.

No pain, no gain?

We’ve all heard the old adage, “No pain, no gain.” While today this is generally considered to be an antiquated notion, there is a happy medium to be struck between athletic complacency and totally overdoing it.

“Pain is a part of training and ‘listening’ to your body – much like you listen to those noises from your car – is very important,” says Dr. Minnes.


He advises that while mild and symmetric discomfort that resolves with easing up a bit or settles following a run is common and not a cause for concern, severe and debilitating pain from a major muscle tear will stop you and there’s little to do but get assistance. In between the two, pain which is worsening rather than decreasing as you “ease up” a bit, and particularly asymmetric pain (only on one side) may herald a more significant injury and should cause you to slow down a lot or stop the activity altogether.

“Each individual has their own ‘threshold’ that can be affected by experience, conditioning, age, medical conditions, individual biomechanics and previous injury,” says Minnes. “With experience, each runner should learn what pain is ‘normal’ for them.”

Pain that is more severe, as well as pain that persists beyond the usual recovery period for the particular type of running event, should be assessed by a qualified athletic or physical therapist or a physician.

Bruce Minnes (BSc, MD, FRCPC, ABPEM) is Associate Medical Director, Division of Paediatric Emergency Medicine, at The Hospital for Sick Children. He is also Assistant Professor of Paediatrics, University of Toronto and Medical Director for The Scotia Bank Toronto Waterfront Marathon. Most importantly, he is a father, a runner (including a bunch of marathons) and a self-described “generally engaged guy” as well as a VIP (Variably Injured Person).

Lactate vs. lactic acid

Around the runner’s water cooler, you may have heard fellow runners discussing lactate or lactic acid in the muscles. The two terms seem to be often confused.

“Lactic acid and lactate are not the same substance,” explains Dr. Minnes, “although many use the two terms interchangeably. Lactic acid is the end product of one of the energy-producing cycles and is converted into lactate very quickly; lactate is the ‘fuel source.’”

Our lactate levels can be measured in our blood. Blood lactate accumulation represents the balance between lactate production and removal, and can be affected by many factors. Oxygen availability at the cellular level does not appear to be among the main factors.

Accumulation of lactic acid in muscle cells may contribute to muscle fatigue and soreness, but the body’s efficiency at converting and moving lactic acid along can be improved by conditioning. Lactic acid does not generally accumulate in sustained endurance activity. It is converted to lactate and used as an energy source.

Lactic acid only builds up in muscle during relatively short and high-intensity activity, such as sprinting. This is one rationale as to why “going out quickly” may cause more fatigue and soreness later in a run.

The effect of local “acidosis” at the cellular level has been challenged in its effects on muscle fatigue and soreness. Some researchers have suggested that accumulation of other substances – such as potassium ions or inorganic phosphate (from the breakdown of ATP) are to blame, but the definitive answer has not been determined.

Runners depend on some of the strongest muscles in the human body to move forward fast. These are the muscles that keep us upright on a daily basis. “Without these muscles, we’d crumble in a heap,” says Dr. Tim Rindlisbacher, MD and Director of Sports Health at the Cleveland Clinic Canada. On a run, muscles, ligaments and joints work together to help you reach the finish line.

Your Legs: a Quick Guide

Quadriceps
Located on the front of the thigh, the quadricep extends the knee joint, allowing the leg to swing forward.

Knee
The joint that flexes, extends and rotates leg bones and ligaments, ensuring a smooth run. The knee is actually made of four bones: femur; tibia; fibula; and patella (or knee cap).

The Hamstrings
A group of muscles located behind the thigh and knee – counterbalance the quadriceps and decelerate knee extension.

Illiotibial band
Located in the outer thigh, the iliotibial band joins the pelvis, hip and knee. The illiotibial band is prone to injury – often referred to as Illiotibial Band Syndrome or ITBS – due to poor shoes, running on embankments or sudden increases in speed or distance. “The illiotibial band is a unique, non-elastic structure since it connects bone to bone like a ligament but also has muscles attached to it, allowing it to function as a tendon,” says Rindlisbacher.

Calf
The largest part of this group is known as the gastrocnemius; this muscle flexes the ankle and stabilizes the knee. Without proper warming up and stretching, the calf is prone to spasms and cramping – more so than other muscles.

Piriformis
This muscle rotates the thigh outward, and connects the sacrum to the femur. The piriformis can irritate the sciatic nerve, causing piriformis syndrome – a neuromuscular disorder that causes pain, tingling and numbness in the buttocks and along the path of the sciatic nerve descending down the lower thigh and into the leg. Stretching helps to head off piriformis syndrome.

Glutes
A cluster of muscles in the upper leg. The gluteal maximus is one of the strongest muscles in the human body; it extends the hip and supports the pelvis during a run. Located beside the gluteus maximus, the gluteal medius abducts the hip upon leg extension. This powerhouse supports the body when gravity is located over one leg, and the other leg is extended off-ground behind the torso.