Do you really need a knee replacement?

Joint replacement surgery is a booming industry as our ageing population faces the degenerative processes that come with getting older.  Surgical techniques and hardware continue to improve, but wait times continue to worsen.  In the Calgary Health Region alone there are thousands of patients on the waiting list for hip or knee replacement, with wait times for a mere consult often over one year.  The reality is that only a small proportion of these people actually NEED a joint replacement.

Medicine is not immune to the powers of marketing, and joint replacement surgery is no exception.  Knee and hip replacements are BIG business in the developed world, and family doctors are indoctrinated early on to refer directly to a surgeon whenever a patient presents with some knee or hip osteoarthritis.  The reality is that only some joints require replacement; the rest can be managed very well with conservative measures.  Reason would suggest that a patient with an osteoarthritic joint should start with the most conservative treatment options first, progressing on to more and more invasive options as needed, with total joint replacement as the final intervention once all others have failed.  Outlined below is a sample continuum that a patient can take on their journey through hip or knee osteoarthritis.

Get a weight bearing X-ray.

Proper positioning and select views in a weight bearing position can help to clarify exactly how much degenerative change has occurred to the joint in question.  Ask your doctor for weight bearing (standing) views to best ascertain the extent of wear.

Get a diagnostic ultrasound or and MRI.

An MRI is not always required, but it behooves the doctor and patient to get a clear picture not only of the boney deterioration of the joint but also the soft tissue and cartilage damage.  Remember that osteoarthritis (OA) is a degenerative joint process involving the soft tissues of the joint as well as the bone.  One does not exist in isolation from the other.

Correlate imaging findings with a thorough, hands-on clinical exam.

Too often I hear stories of doctors conducting a physical examination of a patient without ever putting their hands on the patient.  There is often a poor correlation between imaging findings and clinical symptoms, so it is vitally important to have a thorough, hands on examination of the joint in question to help complete the clinical picture.

Follow the clinical triad:

  1. Treat the actual problem
  2. Strengthen the area
  3. Avoid making it worse

Get stronger.

With increased strength comes increased stability, and instability within an arthritic joint is very often a considerable pain generator.  Beginning a strength program in an already painful joint can be agonizing, but there really is no alternative. Pushing through the first month of exercise-exacerbated pain will be worth it, and study after study suggest that resistance training and loading of an arthritic joint does not cause the joint to wear down faster, but rather helps to prolong the viability of that joint.

Get a custom unloader knee brace

One of the most effective, least invasive interventions that can be done is the use of a truly custom, unloading brace.  Made for both knee and hip osteoarthritis, a custom brace is often the single most effective intervention, and represents ‘the most bang for your buck’.  Custom knee braces in particular can offload the exact region of the knee that is most painful, allowing you to carry on with the activities that you are passionate about with considerably less discomfort.  By reducing the magnitude of impact on the arthritic joint with each step these braces also help to slow the rate of further progression.  They are lightweight, slim and can be worn under ‘most’ day to day clothing.  Custom unloader braces are often covered 100% by your private health insurance with a doctor’s prescription.

Consider a guided lubricant injection.

Viscosupplementation is the name for a type of hyaluronic acid injection that can serve to lubricate the internals of an osteoarthritic joint.  Brand names include Synvisc, Monovisc, Durolane, Cingal, Neovisc, Orthovisc, Synolis and others. Any of them can be beneficial in creating some hydraulic cushioning with the joint and defraying mechanical compressive load on to worn down cartilage.  These injections typically take about one month to begin working and can last for 10 – 12 months.  Some research suggests that repeating these injections once per year for three years (think of it as an annual oil change) can further slow the rate of wear of the joint.  These injections should be done under image guidance (ultrasound or fluoroscopy) to improve the accuracy of the injecting doctor.  Contraindications for viscosupplementation include very severe arthritis (it works best in mild to moderate OA), significant leg deformity (bow legged or knock kneed) and morbid obesity.

Consider Platelet Rich Plasma (PRP) injections

Platelet Rich Plasma is derived from a small fraction of your blood.  Drawn from your arm in the same fashion as having regular blood work done, the blood is spun in a special centrifuge to separate out the growth factors of your blood.  Reinjected into an arthritic joint twice over a six-week span, PRP can help to stimulate the development of new blood vessels and consequently allow for some new tissue regeneration.  With the exclusion of stem cell injections, PRP is the primary regenerative medicine that we have available to us in the management of joint osteoarthritis.  The benefits of PRP can often be felt after about six weeks, and can continue to have a positive effect on joint health for several years thereafter.  The injected joint is often sore for two to three days post injection, and it is important to know that you are not allowed to take anti-inflammatory medication for one week leading up to the procedure

Stay away from repeated cortisone injections

Cortisone (corticosteroid) injections are a very effective way to diminish inflammation within a joint.  The problem is that osteoarthritis, despite its name, is not truly an inflammatory process.  Rather, osteoarthritis is degenerative joint disease, and while you may get some symptom relief from a single cortisone injection as it wipes out any residual inflammation that is present in the joint, it is not a clinically appropriate intervention to repeat.  Why put an anti-inflammatory into something that isn’t truly inflamed?

With any combination of the measures outlined above, patients can expect to have at least some improvement in their symptoms.  Sticking to the clinical triad (treat it, strengthen it, don’t make it worse) helps to keep patients focused on what’s important in the management of an arthritic joint, and will reduce the likelihood of truly needing a knee replacement.  In our clinic we hedge our bets by making the surgical referral on the assumption that it will take about one year to get to the surgeon.  During that year we work diligently with the patient using the interventions listed above.  Most of the time we are able to improve the patient’s symptoms and quality of life so much that they take themselves off the surgical list.  Check out our testimonials page to read some of the success stories.

Repetitive strain injuries: getting back to your activity

If you live an active lifestyle, chances are you’ve dealt with an injury at some point. You may have even heard this expression: repetitive strain injury.

Often, for athletes or those who enjoy leisure sports, the thing that keeps them out of the game is not a sudden injury. It’s an injury caused by consistent, repeated stress to the body’s muscles, tendons, nerves and other soft tissues.

“Repetitive strain injuries are among the most common problems we see,” says Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary.
“People have a hard time not doing that physical activity they love.”

Macdonald understands that way of thinking. He and his colleagues in the clinic are all dedicated to their activities. He admits they can be a bit over-zealous at times, too. He notes, though, that doing something too long or too hard without adequate rest can easily sideline you from your favorite activity.

Here are the four most common repetitive strain injuries to watch out for. In each case, Elite Sport Performance Clinic can help.

Plantar fasciitis: “It hurts on the bottom of my foot and/or my heel.”

The plantar fascia is the thick connective tissue that supports the arch of the foot. It’s exposed to incredible impact every time we take a step, whether walking or running. Plantar fasciitis occurs when microscopic damage to the tissue causes inflammation of the plantar fascia and overlaying connective tissue sheath. Prolonged or repeated injury can create scar tissue as the body tries to ‘repair’ the injured area.

Achilles tendonitis: “It hurts at the back of my foot and just above my heel.”

The Achilles tendon connects the calf muscle to your heel. During the first stage of overuse, the Achilles tendon becomes inflamed. With prolonged, repeated stress, scar tissue can form, the tendon structure can change and the tendon can tear or rupture.

Patellar tendonitis: “It hurts below my knee.”

The patella is the kneecap covering the knee joint. Patellar tendonitis is an injury to the tendon that connects the kneecap to the shinbone. Symptoms include pain or aching in the front of the knee, and/or weakness or swelling in the area (during or after exercise). With Osgood-Schlatter’s disease, pain is closer to the shinbone. It’s not actually a disease, but an overuse injury and it’s very common in adolescents experiencing growth spurts. With Sinding-Larsen-Johannson syndrome, the pain or swelling is closer to the knee area.

IT band friction syndrome: “It hurts on the side of my knee or my outer thigh.”

The iliotibial (IT) band is the ligament that runs down the outside of the thigh from the hip to the shinbone. It primarily provides stabilization when running. IT band friction syndrome (sometimes called runner’s or jumper’s knee) occurs when the IT band rubs across the bony protuberance where it attaches to the knee. This friction causes irritation and swelling. The IT band can also be aggravated by muscle imbalance elsewhere in the body (weakness or tightness in other muscle groups) and poor pelvic muscle strength.

When to seek help

If a repetitive strain injury is caught early, healing can occur by avoiding or modifying an activity for a time. The problem, as Macdonald sees it, is that people may not stop their activity until the pain becomes unmanageable. That’s when they need to see a specialist.

“As a runner, when I am hurting, I just want to get going again,” Macdonald says. “But, pushing through an injury is not smart. If you want to return to an activity as quickly and safely as possible, you may need help getting there.”

Macdonald notes that repetitive strain injuries respond well to a number of different treatments.

For injuries in the early stages, treatment options include:

manual therapies such as Graston techniques or myofascial release techniques to break down scar tissue or overcome fascial restrictions and restore movement
active-release therapy, where soft tissues and muscles are massaged or put through a series of controlled movements
eccentric loading exercises, where a muscle is contracted and simultaneously lengthened

For stubborn or advanced injuries, treatment options may include:

shock wave therapy to reduce the size of the scar tissue
corticosteroid injection therapy to help minimize inflammation of connective tissue (but not scar tissue)
injection of platelet-rich plasma to encourage new tissue regeneration

In some cases, injury-specific treatments will be recommended, such as:

a custom orthotic that helps counter the pain of plantar fasciitis
exercises that focus on strengthening underlying muscle weakness or imbalances, like pelvis, hip flexor and abductor muscle strengthening when managing IT band friction syndrome

For active people – from runners to cyclists to golfers to yoga enthusiasts – Macdonald says there is always something that can be done for repetitive strain injuries. It’s a matter of seeing a specialist who can build a custom treatment plan that is matched to the patient’s body, the length of time they’ve had the injury and the type of activity they want to get back to.

The truth about stretching: it might not be doing what you think

For years, stretching has been promoted as beneficial for those with an active lifestyle. The trouble is, the touted benefits of stretching – lengthening and strengthening your muscles, and improving performance – aren’t supported by current research.

“As an avid runner, I was raised on the concept of stretching,” says Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary. “Today, studies increasingly show that stretching is not beneficial in the ways we thought. In fact, stretching can actually cause harm.”

Macdonald points to three myths about stretching that may have you re-evaluating your fitness routine.

Myth #1: Stretching makes your muscles longer

One study tested muscle fibers before and after an eight- and 10-week intensive stretching program. Using biopsy tests measured under a scanning electron microscope, the result showed no gain in muscle length. The resting muscle fibers did not lengthen even a nanometer.

So why does it feel you ‘go further’ after stretching for weeks or months at a time? Macdonald says it’s not because the muscle is longer, but because the muscle is becoming numb.

Stretching desensitizes the nerve endings where the skin, muscle and connective tissues are being stretched. Over a period of time, pushing a stretch further makes it seem like you have a greater range of motion. In reality, you’re reaching the same end-range of motion but without that same sensation of pain.

Myth #2: Stretching muscles makes them stronger

Stretching can create miniscule amounts of strength. In laboratory tests, a muscle put on a jig and stretched for weeks at a time gained 2% to 3% in strength.

However, this is an incredibly small gain for the effort that goes into stretching. Couple that with the fact that stretching also desensitizes nerves and it’s clear: stretching isn’t worth it.

“That’s why I often disappoint my patients when I tell them yoga is not, in fact, a strength-building exercise,” Macdonald says. “Yoga has its benefits, but greatly improved muscle strength is not one of them.”

If it’s strength you are after, Macdonald suggests trying weight-bearing or resistance exercises instead.

Myth #3: stretching improves athletic performance

The purpose of muscles is to stabilize and move our joints. If you stretch the muscles around a joint, you essentially make that joint less stable and less sensitive to stresses placed on it. This, in turn, dramatically increases the risk of injury to the joint and the surrounding connective tissues and muscles.

Suppose a runner stretches right before a run, and therefore reduces the nerve sensitivity in that area. The runner’s nervous system could be slower to catch an injury – like a rolled ankle – before significant harm occurs.

The bottom line? Stretching muscles desensitizes them, leaving athletes at increased risk of injury. Studies continue to show that stretching before an event actually decreases overall performance.

How can I improve my flexibility?

If stretching doesn’t improve flexibility, what will? Macdonald states that the #1 way to become more flexible is simply to become stronger.

Stronger tissue is healthier, and healthier tissue is naturally more pliable. This pliability, in turn, gives a person better range of motion while creating a stronger and more stable environment for the joints.

Is it still OK for me to stretch?

If you really enjoy the sensation of stretching, Macdonald’s advice is to wait until after your activity to do so. Even so, he believes stretching is only truly beneficial if you’re hurting, since the desensitizing quality may help reduce pain.

Alternately, Macdonald recommends a dynamic stretch to kick off your workout. This takes your muscles through the full range of motion and warms up the nervous system in the specific firing pattern that’s required for that activity. Google-search ‘dynamic warm up drills for runners’ or any other exercise for better pre-activity results.

Hurt vs. harm: why pushing through pain hurts in the long run

Every year, up to 85% of runners are forced to take time off because of injury.

We all experience some discomfort during training, and it’s okay to have some degree of achiness and soreness. It’s also important not to ignore your body’s pain signals when returning to your activity.

“Pain is our body’s way of telling us that something is wrong,” says Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary. “The tricky thing can be discerning whether it’s something small, or something that truly needs attention.”

One of the most common questions patients ask Macdonald when they’re returning to an activity is, how to tell if they are re-injuring themselves. His simple answer is: be aware of sharp pain and avoid modifications to technique.

For example, if you are forced to limp or change your gait while running – or you feel a stab of pain – you should stop right away. On the flip side, if a run simply causes achiness and soreness, you are most likely fine to continue.

“Pushing through real pain is not okay,” says Macdonald. “That just increases the risk of a more serious injury that may stop you from enjoying that activity altogether.”

Macdonald, an avid runner himself, understands the joy of running, but also the disappointment of not running because you’re hurt. Still, he says, it’s a fine line between hurt and harm.

Macdonald teaches a yearly Smart Runner Workshop series to educate runners about running better and faster, while reducing the risk of pain or injury. Along with his colleagues, he presents the latest in running-related research in an engaging, informative manner.

Runners can apply this knowledge immediately to their own running and come closer to their true potential as a runner.

Five signs that it’s time to replace your running shoes

If you think knee pain indicates your body isn’t up to the task of running, think again. It’s quite possible it’s your running shoes that are to blame.

“Many runners tend to think the worst when they come into my clinic with knee pain,” says Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary. “Although there can be a variety of causes of knee pain, one overlooked cause is worn-out shoes.”

It’s common for runners to use shoes for between one and three years. Macdonald notes that today’s running shoes are simply not built for that kind of longevity.

To give your body the best chance at a long running career, follow Macdonald’s five shoe tests to make sure your shoes are still capable of doing their job.

1. Count your mileage

Research suggests a typical running shoe loses about 45% of its midsole shock absorption by 450 kilometers. A moderate runner might reach that milestone in four to six months. How many miles have you put on your current pair of running shoes? If you are close – or over – 450 kilometers, don’t push it. Buy new shoes.

2. Look at the wear pattern

The black rubber on the sole of the running shoe is a higher-density carbon rubber, which is difficult to wear out. Many shoes have a detailed pattern over this carbon rubber. When you see signs of wear on the patterned overlay, harmful wear has begun. If you see wear through to the black carbon that exposes the colors underneath, replace your shoe.

3. Check mid-section wrinkles

Although many runners think the shoe’s heel gets the highest impact, Macdonald says that’s just not true. A runner’s major force is caught in the mid-section of the shoe, and it’s natural for the foam in this area to compress over time. Turn your shoe on its side and look at the sole. If you see wrinkles at the mid-section of the sole, it’s an indication that compression is negatively impacting the shoe’s support. You know what to do: buy new.

4. Do the twist test

With two hands, grab the toe and heel of the shoe. Now, twist the shoe in opposite directions at the mid-section. If you see a worsening of the sole’s wrinkles or the shoe folds over and creates creases in the middle of the shoe, the mid-section is no longer doing the job it was designed to do. Go shoe-shopping before your next run.

5. Do the fold test

Grab the heel and toe of the shoe and try to fold the toe back towards the heel. If it folds in half, the mid-section has collapsed and your toeing-off support will be compromised. Throw the shoes out, and treat yourself to new ones.

Who said running was an inexpensive sport?

These five tests will tell you whether or not your shoes are sound enough for running. Make no mistake: a steady runner will probably go through two or three pairs of shoes each year. Although that can be a hit to the pocketbook, it does have an upside. Fresh shoes are a simple fix that will decrease your chance of pain and injury. That may help you avoid costly treatment expenses in the long run.

Exercise is good for bones and joints, but listen to your pain

While it’s true that weight-bearing exercises can keep your bones and joints healthy, your body’s infrastructure can be susceptible to injuries from overuse.

“Muscles are not the only structures that can be injured through overuse,” says Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary. “Nothing happens in isolation in the body. When impact is absorbed, numerous tissues disperse the impact throughout the body, and this can affect our joints and bones.”

When we run or play sports, the body’s mechanical system works overtime. It’s not uncommon for our body to absorb from three- to seven-times our body weight with every stride. This impact – and the resulting vibration – can have a harmful effect on the body’s bones and joints, especially when overuse comes into play.

Bone injuries – easy to miss

Like many injuries, bone injury occurs on a continuum. Injuries can start as simple irritation, then progress to tears where the muscles attach to the bone, right through to stress fractures.

People often ignore early-warning signs with bone injuries (like shin splints) because fracture pain can lessen once the tissue is warmed up. This lets a person continue their activity, but increases the aggravation and damage to the injured area over time.

Once a stress fracture occurs, though, the pain will be significant. Since stress fractures don’t often show up on x-rays, Macdonald suggests you may need a bone scan or a highly accurate SPECT/ CT scan to uncover the issue.

Management for a stress fracture includes rest, avoiding high-impact activities and wearing an air cast. Macdonald’s clinic has also seen great results from using ultrasound or a Graston tool to stimulate bone-forming cells where the stress fracture occurred.

Lower back and joint pain – high-stress areas

Another common injury Macdonald sees in the clinic is mechanical lower back pain. The lower back is the area where the majority of the force is absorbed from the legs. It’s no surprise, then, that lower back pain affects up to 85% of adults during their lifetime.

Distance runners are particularly susceptible to low back issues. The small of the back or the area around the back of the pelvis (the lumbosacral junction) is the first area of the body to absorb impact from the legs. It’s also one area where too much sitting can contribute to injury.

“The stresses of running, combined with a typical athlete’s sitting requirements during their workday, all adds up to enormous stress on the lower back area,” Macdonald says. “Treatment needs to take a whole-life approach.”

Macdonald notes that lower back pain is actively helped by chiropractic manipulation. He also stresses that with back pain, patients must be partners in their own healing.

“At Elite Sport Performance we successfully treat back pain,” Macdonald says. “To make sure the symptoms continue to improve, though, the patient must also make modifications to their lifestyle. We feel strongly about education. A customized program of strengthening exercises and advice about the best way to sit, lift and exercise with lower back symptoms is the best prevention there is.”

Encouraging results from platelet-rich plasma (PRP) therapy

When it comes to healing procedures, Dr. Dale Macdonald likes to harness the body’s own natural response to injury.

“We’ve been using platelet-rich plasma therapy in our clinic with very good success for some time now,” says Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary. “We see this as a way of repairing damage by enhancing the body’s natural healing properties.”

Macdonald explains that with many injuries, the body’s natural healing defense is inflammation. This brings an increased supply of blood to the injured area. This blood contains important healing platelets that stimulate reparative action and tissue regrowth.

Sometimes, though, injuries occur in areas where tissues have relatively low blood supplies to begin with. This is where the body is less capable of healing on its own. For a little help in those areas, Macdonald says that platelet-rich plasma (PRP) therapy is often a viable solution.

During PRP therapy, blood is drawn from a person’s arm, similar to when a blood test is done. A special centrifuge then spins this blood at high speeds and separates the platelets and other beneficial blood components. The layer rich in concentrated platelets and growth factors is sometimes five to 10 times what would normally occur in the body. This platelet-rich plasma is then injected in and around the injury to stimulate the development of new blood vessels and regenerate new tissue.

Since a patient’s own blood is used, this is a safe method that minimizes the risk of transmittable infections and allergic reactions. This treatment can easily be done in an examination room in less than an hour.

Macdonald says PRP therapy is best used to treat two types of injuries:

Soft tissue injuries. Injuries that fall under this category could include knee injuries where the tendons or muscles are torn (like jumper’s knee), or even tears to the meniscus cartilage that cushions the knee. Some of these areas don’t have an ample blood supply available, so PRP therapy can result in faster healing times.

PRP therapy can also be successful in helping to regrow tissue with flexor or extensor injuries (like golfer’s elbow or tennis elbow) when damage exists at the point where the muscle changes into tendon, or where the tendon attaches to the bone.

Early-stage or moderate joint deterioration. Joints take a lot of impact, and can wear out over time. PRP therapy can bring healing platelets to the joints and can help the body resolve certain inflammatory conditions or help to heal worn-down tissues.

For Macdonald, this leading-edge approach to treating injuries is showing encouraging results in the Elite Sport Performance clinic. Consider PRP as one more option for patients in the treatment toolbox.

“We offer this safe and easy management alternative for patients to try, before moving to more invasive treatments like surgery,” Macdonald says.

Does my knee need surgery?

One of the most common knee injuries is damage to the meniscus — the cartilage that stabilizes and cushions the knee. Often, people assume surgery is required to improve this condition.

“Some kind of treatment is often needed for a meniscal tear,” says Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary. “However, a lot can be done without resorting to surgery.”

Macdonald believes that surgery is sometimes recommended too quickly for this injury. Current research indicates that meniscal surgery may provide some short-term benefits, but in the long run, the benefits provided by surgery lessen. In some instances, meniscal surgery can also create new problems.

For example, when surgery is used to remove damaged bone or cartilage, the remaining parts of the meniscus can endure larger-than-normal mechanical loads. This can cause accelerated deterioration in the knee.

Macdonald adds that the meniscus naturally dehydrates as we age. In fact, it’s normal for adults who have no symptoms to have tiny tears in the meniscus. No treatment is required because this small degeneration creates no problem or pain.

Treatment is required, according to Macdonald, when a person’s knee is painful, swollen, catching, clicking, popping, locking or feels unstable and/or gives way. The treatment depends on the type of tear or damage, and will take into account a patient’s age, health and activity level.

Physiotherapy can be a great option for meniscus injuries. Strengthening your leg muscles provides improved stability and shock-absorption for the knee. Exercises targeted to this area can also reduce swelling, improve kneecap alignment and build strength and flexibility around the knee so the chance of re-injury is minimized.

Beyond physiotherapy, Macdonald is encouraged by new research for non-surgical management of meniscal tears. Some promising early results show that injections of platelet-rich plasma (PRP) can help certain areas of the meniscus with tissue regeneration. Stem cell injections – just now being introduced in Canada – may also prove beneficial for meniscal injuries.

“In my mind, surgery is a last resort after other methods have been tried without success,” Macdonald says. “The body has amazing self-healing properties. With a little guidance from a professional and the support of non-invasive treatments, patients can often get back to their activity in pretty short order.”

Can running too intensely make you sick?

If a little of something is good, then a lot of it must be even better. Right? For runners, this is definitely not the case. Excessive running – or any exercise beyond the body’s ability to cope – could make you sick.

According to Dr. Dale Macdonald, Sport Specialist and Clinic Director at Elite Sport Performance in Calgary, if you run moderately, you’ll probably be just fine. Overdo it, however, and the opposite could be your experience.

“Running is one of the healthiest things we can do,” says Macdonald. “Countless studies show a broad range of health benefits attributed to moderate distance running. It’s important to know, however, that there are stresses associated with too much running that can impact your health.”

For example, Macdonald points out that many elite endurance runners experience increased upper respiratory tract infections around the time of competitive events or during periods of high-intensity training.

In Macdonald’s experience, when a runner trains too intensively without letting the body recover, he or she runs the risk of three potentially harmful physiological results.

1. Free radicals may weaken the body

When we exercise hard, oxygen consumption increases along with certain chemical reactions in the body created by this oxygen. For example, intense exercise can produce inflammation in the body’s tissues. Oxygen also creates a byproduct called a free radical, and production of free radicals over a sustained period can be harmful.

2. Immune system suppression may put you at risk of illness

Moderate exercise of about an hour in length can actually stimulate your immune system. On the other hand, intense or prolonged exercise can cause immune cells to drop below their normal level. While these cells generally bounce back within 24 hours, intense exercise may lower a runner’s resistance until the immune system returns to normal. Having too many consecutive training sessions without a break may increase your risk of illness.

3. A constant supply of stress hormones may undermine body strength

Stress releases epinephrine, norepinephrine and cortisol into the body. When cortisol is released, our blood sugar increases to supply more energy to our muscles. Sustained cortisol release over time can contribute to bone density loss and increased risk of skeletal stress fractures.

So what’s the best approach when running? Moderation is key, in Macdonald’s view.

“Our immune system is well-designed to deal with running in moderate amounts,” he says. “Moderate intensity would include five or more days a week of aerobic exercise, with each session lasting about 45 to 60 minutes each.”

The other key to optimal running health is giving the body adequate rest and recovery time, to let the immune system bounce back. Macdonald also recommends eating foods high in antioxidants, which naturally counter free radicals. While antioxidant supplements are available, he cites research that indicates antioxidants are most easily absorbed through food.

What if you do get sick? Macdonald offers this advice for runners.

You’re good to go, if: you have a cold with no fever and only mildly depressed energy levels. Take it easy, though. Exercise at 60% or less of your VO2 max. In other words, go for a very easy run of no longer than one hour.

Skip your run, if: you have a fever, moderate-to-severe energy depletion, muscle aches or pains not related to training, or diarrhea or vomiting, or your resting heart rate is higher than normal.