EXERCISE INDUCED MUSCLE PAIN, SORENESS, AND CRAMPS

1. concentric muscle contraction - the length of the muscle is shortened as it overcomes resistance. This is the type of contraction that occurs as you use your bicep to do a dumbbell curl and can also be thought of as the muscle actively shortening.

2. eccentric muscle contraction - the muscle works actively (actively lengthens) to slow its lengthening against a force . This is the work done by the bicep as it lowers the dumbbell to the starting position of the curl exercise.

3. isometric muscle contraction - the length of the muscle remains constant as force (weight) is applied. For example when the muscle is pushing against a heavy and immovable object.

If the goal is increasing muscle strength, eccentric contractions are actually more effective than concentric contractions. This is counter-intuitive but is a result of the fact that you can apply a greater force to tensed, but relaxing, muscle fibers than in the concentric phase of active muscle contraction. And the muscle strengthens proportionally to the amount of force (weight) applied. In the dumbbell example you can lower a heavier weight than you can initially curl. Research indicates that when the intensity of training is comparable (dumbbell weight is kept constant) with eccentric and concentric contractions, the gains in muscle strength are not significantly different. In other words, a greater increase in strength with eccentric training is only the case when the load (weight used) is higher during eccentric training than in the concentric training.

When it comes to the development of muscle pain, the result of micro trauma (small tears in the tissue) to the muscle fibers from the stress of the activity, eccentric contractions are more likely to be the culprit. In addition to the fact that you can develop more force (higher weights can be used) on the muscle fibers with an eccentric contraction, the shortened muscle fiber also has more engaged cross striations (than the lengthened muscle fiber that is shortening in a concentric contraction) and it is the cross striations that appear to be the site of the micro tears. Thus actual injury to the muscle is more of a risk with an eccentric exercise program than the traditional concentric work out.

Exercise induced/associated muscle pain includes:

1. soreness during exercise
2. delayed onset muscle pain
3. muscle cramps (which can occur during or post exercise)

I. MUSCLE PAIN DURING EXERCISE

Lactic acid is usually blamed for the discomfort. But recent information suggests that the muscle cell metabolizes lactic acid quickly, and in fact it may be a better fuel to power the muscle than glucose. Thus it is more likely that other acidic metabolites such as pyruvic acid and ammonia are involved. The pain in the actively contracting muscle is almost certainly multifactorial, related to a combination of acidic intermediate metabolites, ionic shifts at the cell membrane level (K, magnesium), and actual changes in the muscle cell proteins themselves. As training increases the level of activity at which discomfort occurs, we know that the muscle cell can adapt to these factors.

It is interesting to note that the body has developed a mechanism to deal with this discomfort. Endorphins, opiate like substances produced internally, are secreted into the central nervous system during endurance exercise and alter the perception of pain during prolonged high intensity exercise. Thus we have a mechanism to warn of muscle overuse (pain) as well as an intrinsic process to help us deal with that pain if we opt to continue.

• What works for treatment/prevention of muscle pain while cycling:
  • Caffeine (even in regular coffee drinkers)
• What doesn't work for treatment/prevention of muscle pain while cycling:
  • Aspirin - Although the conventional wisdom is that taking aspirin before a ride will cut down on muscle pain during exercise, a study at the University of Georgia concluded that even at large doses (20 mg per kg - or 4 standard aspirin for the average rider), aspirin did not modify the perception of muscle discomfort during exercise or reduce the perceived intensity at which it occurred.
  • Ginger - It had been speculated that, based on work in horses, ginger might provide some relief from muscle discomfort with exercise, but this same study proved that wrong as well.

II. DELAYED ONSET MUSCLE SORENESS (DOMS)

Delayed soreness (or stiffness) does not occur immediately after a workout, but 8 to 24 hours after exercise, peaking at 48 to 72 hours. It is more common after "eccentric" muscle activity (actively resisting lengthening of the muscle such as occurs in raising or lowering a weight) as it is possible to develop a high tension on muscle fibers and connective tissues (read above) than in isometric or static tension activity. The soreness is accompanied by a decrease in muscle strength, a reduced range of motion, and leakage of muscle cell proteins (creatine kinase, myoglobin) into the blood where these enzyme and protein levels can be directly measured. As you might expect, those with a higher CPK (creatine phosphokinase) tend to have greater muscle soreness. These three findings indicate that actual muscle damage is the culprit (most likely minute tears) rather than a buildup of metabolic byproducts (lactic acid) of intense muscular activity. Muscle biopsies have confirmed that the pain is from direct muscle fiber trauma with an inflammatory response.

DOMS is most common at the beginning of the training season when athletes are increasing their training after a period of reduced activity, or as a result of exercise at a greater than normal level. It does not appear that a history of soreness earlier in the season increases the odds of further muscle damage. In fact the adaptive process of healing, even from microscopic injury with minimal pain, appears to have a protective effect against the development of additional muscle damage and soreness from subsequent exercise. Theoretically small doses of damage over time will provide cumulative protection - thus the rationale for a gradually progressive exercise training program.

In 1997, a small group of elite athletes with a combination of chronic fatigue and delayed onset muscle soreness were studied. Muscle biopsies were abnormal and the authors speculated that cumulative, low level, chronic injury might interfere with performance. Whether chronic injury is involved in the symptoms we call overtraining is still considered speculative. But it does lend support to the idea that adequate rest in a training program is as important as the actual physical training itself.

Some interesting facts about DOMS:

• There is no sex difference in the degree of pain for a specific level of over exercise.
• Older athletes have less pain than younger athletes for a specific level of over exercise.

• What works for treatment/prevention of delayed onset muscle pain:
  • Introduce exercises or novel activities progressively over a period of 1 or 2 weeks at the beginning of, or during, the season. Have a good mileage base before intensifying training.
  • Warm up (second article)
  • Reduce the intensity and duration of exercise for 1-2 days following intense DOMS-inducing exercise.
    • Exercise will alleviate pain during DOMS, however the analgesic effect is temporary.
  • Emphasize exercises targeting less affected muscle groups to allow the affected muscle groups to recover.
  • There is weak evidence (single study, second tier journal, no confirmatory studies) that watermelon may decrease post exercise muscle soreness. And as we generally need to rehydrate after a ride, adding watermelon to chocolate milk (or other carb/protein) refueling drink makes sense from a rehydration perspective alone. The active agent? The amino acid L-citrulline is suggested in the original article and supported in the single additional study I could find. There are no side effects from excess watermelon ingestion that I am aware of.
• What doesn't work for treatment/prevention of delayed onset muscle pain:
  • Anti inflammatories
    • Topical ibuprofen gel
    • Oral ibuprofen
    • Aspirin (900 mg/day);codeine (60 mg/day); or paracetamol (1000 mg/day) started the day of the over exertion.
  • cold or icing
  • Homeopathy, ultrasound and electrical current modalities
  • Stretching
  • Cooling down - although it has been speculated that cooling down by exercising at a lower level after an intense workout might prevent muscle soreness, that is not the case. Cooling down may accelerate the removal of the byproduct of muscle activity (one of which is lactic acid) from muscles, but it is not the buildup of these byproducts that causes muscle soreness.

    In fact, post exercise icing may prevent the conditioning benefits of training. Many trainers use icing and ice baths as a piece of their intense training recovery to cut down on muscle soreness to increase likelihood of staying on track for a training program. In this study biopsies from one leg iced post exercise with the other, kept in room temp water, showed significantly less protein synthesis in the cooled leg. And "Less muscle protein synthesis very likely translates into less muscle building in the long-term." Over time Cold-water immersion during recovery from resistance-type exercise reduces myofibrillar protein synthesis rates and, as such, likely impairs muscle conditioning.

  • Ginger

ARE FREE RADICALS THE SOURCE OF POST EXERCISE MUSCLE PAIN?

Data suggests a benefit from this dietary approach as measured both by hard numbers (muscle enzymes - CK) as well as less soreness (DOMS) after exercise. (I have often wondered about CK levels as a way to quantify post exercise muscle injury and soreness, and this is the first article I've seen that provides hard numbers.)

Whether the benefit is from less oxidative stress or some other factor, the studies show benefits from

• spinach
• tart cherries
• black currant juice (raisins or grapes)

Medjool Date, Muscle Mending Recovery Smoothie

• 2 Natural Delights Medjool dates, pitted and chopped
• 1/2 cup fresh blueberries
• 1 1/2 - 2 cups unsweetened almond milk
• 1 Tbsp. chia seeds (or flax seeds)
• 1 Tbsp. hemp seeds
• 1 scoop vanilla protein powder
• Large handful of spinach
• Couple cubes of ice (optional)

1. warm up before you push it
2. get a good training base and ramp up slowly
3. if it hurts, listen to your body and take a few days off or exercise a different set of muscles at the gym. In fact, gentle exercise of the injured muscle to the point of discomfort may speed up the healing process by keeping the injured muscles active, but those who push it "to work out the pain" generally have more prolonged soreness than those that give the injured muscle a chance to heal.

MORE ON ANTI-INFLAMMATORIES

The first article, in the 2009 New York Times, references a study of Western States 100 runners. To quote: "Those runners who'd popped over-the-counter ibuprofen pills before and during the race displayed significantly more inflammation and other markers of high immune system response afterward than the runners who hadn't taken anti-inflammatories....and ....We had researchers at water stops during the Western States event, Nieman says, asking the racers how the hours of exertion felt to them. There was no difference between the runners using ibuprofen and those who weren't. So the painkillers were not useful for reducing pain during the long race and afterward the runners using ibuprofen reported having legs that were just as sore as those who hadn't used the drugs."

Not only is it questionnable as to any performance benefits, this article in 2012 points out they may have peripheral harmful effects. "....the men briskly rode stationary bicycles for that same hour. Before one of those rides, though, they again took 400 milligrams of ibuprofen the night before and the morning of their workouts. At the end of each rest or ride, researchers drew blood to check whether the men's small intestines were leaking. Dr. van Wijck found that blood levels of a protein indicating intestinal leakage were, in fact, much higher when the men combined bike riding with ibuprofen than during the other experimental conditions when they rode or took ibuprofen alone."

A recent study provides insight as to how anti-inflammatories may blunt the natural healing process. "Inflammation occurs for a reason, says Mogil, and it looks like it's dangerous to interfere with it. Neutrophils arrive early during inflammation, at the onset of injury - just when many of us reach for pain medication. This research suggests it might be better not to block inflammation, instead letting the neutrophils "do their thing." Taking an analgesic that alleviates pain without blocking neutrophils, like acetaminophen, may be better than taking an anti-inflammatory drug or steroid." Even though more than 50% of elite athletes report taking ibuprofen (vitamin I) before or during an event or race, an editorial in the British Journal of Sports Medicine nicely summarizes the current thinking. "There is no indication or rationale for the current prophylactic use of NSAIDs by athletes, and such ritual use represents misuse."

BOTTOM LINE - Use muscle pain during exercise as well as DOMS to your advantage to help fine tune your training. When you are doing intervals (pushing the muscle into an anaerobic state), exercise right to the point of the muscle burn and then back off and recover. Pick up the pace again. Repeat this cycle until your muscles feel completely drained of are starting to stiffen (usually when the glycogen stores have been depleted). Then it is time to stop the workout. If your muscles are sore the next day, take the next day off or go at a recovery pace. And hold off on further intervals until the soreness is gone completely. Use perceived exertion to gauge your level of exertion and then listen to your body's distress signals to optimize your training program.

If you are tempted to use ice or anti-inflammatories to treat your discomfort, remember that it may actually be harmful. Not only may this approach delay healing, you blunt the pain as a reminder you to back off for a few days, increasing the likelihood you will return to training too soon, increasing the risk of further injury.

III. MUSCLE CRAMPS

"I entered my first mountain bike race (18 miles) and at mile 14, my thighs and right calf cramped up. This has happened before on long rides. I thought I trained enough, hydrated enough, and ate enough bananas, but I still cramped up and had to go real slow for the last 4 miles. It was sooooo frustrating. I have another race coming up next month but its only 12 miles but has steeper hills. What should I do? Do tights help reduce cramps? When I get them (cramps) should I massage the cramped area? Should I train the amount of miles of the race?"

A cramp is an intense, active contraction of the muscle. Cramps are much more common when you use your muscles beyond their accustomed limit either for a longer than normal duration or at a higher than normal level of exertion. This explains why cramps are more common at the end of a long or particularly strenuous ride or after a particularly vigorous sprint. Cramps are among the most frequent complaint in marathon participants (18% in one study). In another study of cyclists competing in a 100 mile race, 70% of male participants experienced cramps (women, interestingly, had a rate less than half as frequent at 30%). Cramps can occur during activity, in the hours afterwards, or the night after a particularly long ride or competitive event. They become more common with age and also are reported to occur as a side effect of certain drugs (i.e., lipid-lowering agents, anti-hypertensives, beta-agonists, insulin, oral contraceptives, and alcohol).

Although cramps may occasionally be exacerbated by a fluid and electrolyte (sodium) imbalance from sweating, that is not universally the case as individuals involved in activities requiring chronic use of a muscle without sweating (musicians for example) will also experience cramps. In one study of marathon runners, there were no differences in sodium or hydration levels between the 15 participants who developed cramps and the 67 who didn't. This was confirmed in another study in ultra-distance runners. And although a low magnesium level can cause severe muscle cramping, another study of magnesium supplements in triathletes failed to show any benefits in preventing cramping. An interesting hypothesis is that muscle cramps associated with exercise are more likely due to an altered spinal cord reflex loop from/to the muscle as a result of muscle fatigue rather than from generalized metabolic or intrinsic muscle cell alterations.

As is often the case when there is no consensus on etiology, you will find many conflicting opinions on treatment options.

• What works for treatment/prevention of muscle cramping while cycling:
  • A focus on preventing premature fatigue by adequate training.
  • Stretching (before bed for night time cramping)
  • Resistance exercise. If muscle cramping is related to exercising beyond the level of your training, the suggestion in this article makes sense. Unfortunately the original scientific study quoted does not support the cramp link although my personal experience with cramping suggests that both pushing my training limits is a factors. I was intrigued by the comment about improving the function of the cellular mitochondria. Along with interval training (a proven method to improve aerobic metabolism) it seems we might be able to add resistance training. So a "3 for 1". You keep your muscles strong with regular resistance training which gives you potential power (stronger muscles = more potential watts), supplement the benefits of interval (aerobic) training to increase the mitochondria to power them. And throw in a possible decrease in exercise related cramping as an additional benefit. So even if the benefit to decrease cramping is only a maybe,yYou can see why I feel resistance training should be a part of every cycling training program.
  • Quinine
  • Pickle Juice (or mustard)
• What doesn't work for treatment/prevention of muscle cramping while cycling:
  • Magnesium supplements
  • Hydration and electrolyte replacement

• training - Exercising beyond your usual level of training (as you push yourself to improve - intervals, long rides) increases the odds of muscle cramping. Thus muscle cramps are to some degree an expected side effect of heavy training. Just as with the two other forms of activity related muscle pain referred to above, increasing your training to better approximate the level of exertion to match the anticipated activity or event will decrease the possibility of incapacitating cramps during the event itself.

• hydration - Dehydration can aggravate muscle cramping, so pay close attention to maintain adequate hydration - both during training and when competing.

• electrolyte replacement - Electrolyte imbalance (as well as magnesium deficiency) is unproven (in physiologic experiments) as a reproducible cause of muscle cramping. None the less, there is significant anecdotal experience that indicates that salt loss (especially in heavy sweaters) is a culprit in muscle cramps in hot conditions. That said, it seems to me it does no harm to make sure you maintain hydration (and to a reasonable degree) electrolyte replacement while exercising.

  Sweat contains approximately 2 grams of sodium/liter, 1 gram chloride/liter, 0.2 gram potassium /liter, and 0.1 gram magnesium/liter (and if you are acclimated to the level of exertion and environmental conditions, these concentrations are even lower). Except in extreme circumstances, dietary intake easily replaces these losses.

  If you will be exercising in excessively hot or humid conditions, most trainers will stress paying close attention to salt intake - and perhaps adding 1/2 tsp of salt (1150 mg of sodium) per day to your food (heavy slating of your meal is probably just as effective). Don't worry about elevating your blood pressure as we are talking about a short term supplement while the sodium effect on blood pressure happens over months to years. A sports drink, with its electrolyte content) will help but it is more likely that maintaining adequate hydration is their most important benefit rather than the small amount of electrolytes they contain. And plain water is still a lot less expensive to keep up the hydration level. But remember that with water "more is not necessarily better" and hyponatremia is always a small risk if you aren't paying close attention to the balance of your intake and losses. The role of other micro-nutrients and vitamins in preventing cramps is generally unproven - and anecdotal experience with the benefits of home remedies (except for pickle juice - one study and this was via a neural reflex mechanism, not an effect on body fluid composition) is unproven.

  Here are 2 interesting anecdotes (unsupported by the medical studies done to date):

  • "I read about a study of cramping during the Hotter'n Hell Hundred in Texas. They took blood samples of riders that cramped and riders that didn't. The most common deficiency wasn't calcium or potassium like many would guess, but magnesium. They suggested using Rolaids as Rolaids have both calcium and magnesium, whereas Tums only contains calcium. I like the fact that Rolaids covers you both ways."
  • "I have been plagued with leg cramps until a friend suggested standard calcium with magnesium supplements. I would take them prior to bed with a large glass of water. Amazingly, no more cramps. I also suffered during long rides and was concerned during a cross-country tour with my wife last summer. I would take one tablet in the morning and afternoon and of course stay hydrated. Not once during even the most arduous days or while sleeping did I suffer any cramps."

• muscle glycogen stores - replenishment of ATP is necessary for proper muscle cell functioning, thus adequate Caloric intake is necessary for optimal physical performance. Whether inadequate glycogen reserves are also a reason for muscle cramping is speculative.

If cramps do occur, gently stretching the affected muscle will give relief, and preventive stretching can prevent cramps. Calf cramps while riding can be relieved by standing on the bike and dropping your heel, while anterior thigh cramps can be stretched out by unclipping and moving your thigh backwards towards your buttocks. Although a number of medications have been suggested as treatments for muscle cramps (vitamin E, verapamil, and nifedipine to name a few) only quinine has been shown to be effective in scientifically controlled studies. But its high incidence of side effects limits its usefulness as a routine treatment. So what would I recommend for those suffering from frequent muscle cramps?

• Most importantly an adequate training program designed in both intensity and duration for the event or riding being considered
• A close second, maintaining good hydration. Weigh yourself before and after training rides, and if your weight drops, your fluid intake needs to be increased.
• Use a sports drink (containing electrolytes) for severe conditions of heat and humidity. If you are using an electrolyte free replacement, use a reasonable amount of salt in your diet to minimize the small risk of hyponatremia.
• A regular program of stretching before, during, and after exercise.
• Magnesium replacement may have some benefit, but that is speculative.
• Consider a trial of pickle juice in those suffering from debilitating cramps.

The first 2 readers' questions below highlight the role training can play in the prevention of cramps - even though it relates to the question of cramps in a non cycling event. (The answer was provided by an associate at my clinic.)

Q: I started cycling about 6 months ago and trained really hard this summer for a double century. In all the training and the race itself I rarely suffer from any muscle spasms. However since I started cycling I (may just be coincidence) get EXTREME spasms when I hike down hill. Hiking uphill doesn't bother me, but my quads and calves literally freeze up after only 5-10 minutes of down hill hiking. It becomes so painful I can barely bend my leg. Last time I only hiked 1/2 mile and I thought they were going to have to carry me out. I've tried stretching before and it doesn't help. Within hours the spasms are nearly gone and by morning I feel fine. This probably sounds crazy, but I can't figure out how I can bike 200 miles and can't hike 1/2 mile.

A: Here's the somewhat technical answer: The ankle plantar flexors and quads act concentrically in cycling - that is they generate tension (fire) while shortening. Through the down stroke the ankle plantar flexes and the knee extends under the influence of the gastrocs, soleus and quads. At the bottom of the stroke and through the up stroke, the hamstrings are shortening too.

In walking down hill the opposite is true. Your friend is repeatedly letting himself down hill under the eccentric firing of the quads, plantar flexors and hamstrings. To keep from falling forward the hamstrings fire to keep the pelvis from rotating forwards. During stance phase the ankle dorsiflexes over the planted foot lengthening the plantar flexors and the knee flexes lengthening the quadriceps muscles. A pack will change the equation in that it will greatly amplify the intramuscular tension and therefore the work performed by the muscle. Work that these muscles are not trained (training meaning the physiologic and anatomic adaptations to repeated work) to do.

And the short version: In terms of improving the situation the answer is really cross training - his muscles are well equipped for steady state aerobic concentric work at 90 to 110 rpm but not the greater intensity, near anaerobic threshold eccentric work of hiking down hill. I would bet that eight weeks of running including 20% speed/interval work will turn the problem around.

Q: I am 42 years old and I have been cycling for 19 years. I have one real problem that I can't seem to shake. CRAMPING. I have trained longer, harder, faster, further and taken every conceivable >concoction used, special supplements and the thing I have found that works the best although it does not work 100% is drinking Indian tonic water for the week leading up to the race. Am I right in saying that I am just one of those people prone to cramping or can I really do something about it. I must add that I have developed a strange ability to endure these cramps and ride through them only for them to reappear and literally bite me so hard I have nearly fallen off my bike. Kind regards. James.

A: Muscle cramps are probably multifactorial in origin - exercise beyond your limits (distance ridden or maximum levels of exertion), dehydration, electrolyte imbalance, etc. And age is a factor as well. I never cramped until I got into my 40s, and leg cramps are a common complaint of older patients of mine. Once you have corrected all the variables which you can control (except age of course) it then becomes a matter of learning your triggers and riding within your limits (usually defined by trial and error) and understanding that these triggers may vary depending on how well you are trained at the time.

Q: I recently got back on my bike about 6 months ago about the same time I started a low calorie diet. Thus, far I've lost about 55 lbs or about 2 lbs per week. I eat a lot of protein (fish, steak, fruits, etc.) except for lunch (salads mostly) and not too much carbs. I consume about 1800 calories per day and burn about 800 per day exercising that mostly consist of bike riding and when the weather does not permit the ride, I'll hop on the (moderate walking) treadmill for about 30-35 min each time. On the weekends, I'll ride 20 miles (AM) and another 10 miles (PM) sometimes. This was my regular routine for about 5 months. I am usually riding about the same distance (except for the weekends) and intensity. The past month after a 40 mile ride, I noticed that I am experiencing muscle fatigue and soreness on my entire leg. My legs feel like jelly. The soreness comes almost immediately after the ride after a short rest on the couch. I also notice that I use to ride on the highest gear and now that's getting too difficult for me and I now have to reduce to lower gears. It just seems that after 6 months of riding my leg muscles should improve, so why am I experiencing muscle fatigue and soreness? - EL

A: A few thoughts on your question.

• My guess is that the muscle weakness is a side effect of what is basically a South Beach diet (high protein, low carbohydrate) with total Calories eaten being less than those expended (which is why you are losing weight). With this scenario, you never really replete muscle glycogen and thus the muscle cells are working on fat metabolism resulting in feeling as if you "have bonked" early on in your rides.

• The soreness is a interesting question. The original theory on next-day muscle soreness is caused by a buildup of lactic acid in muscles, but now we know that lactic acid has little to do it. Next-day muscle soreness is generally attributed to physical damage to the muscle fibers themselves. Muscle biopsies taken on the day after hard exercise reveal bleeding and disruption of the z-band filaments which hold the muscle fibers together as they slide over each other during a contraction.

  Cooling down speeds up the removal of lactic acid from muscles, but as a buildup of lactic acid does not cause delayed muscle soreness, cooling down will not help to prevent this physical injury and muscle soreness. Stretching does not prevent soreness either - although pre ride stretching may help to prevent the physical micro-tears.

  Performing certain exercises beyond your training will almost guarantee delayed soreness: running, hiking or skiing downhill, for example, and lowering weights - what weight lifters refer to as "negatives." In these downhill or downward motions, called eccentric muscle actions, the muscle fibers have to lengthen and then contract, and it's that lengthening-contraction that puts the most strain on the fiber and does the most damage. Cycling is NOT one of the exercises frequently associated with muscle injury and soreness.

  So the question - why your soreness? As it started with your low carbohydrate diet (and weight loss) - and there was no increase in exercise intensity or duration - the low carbohydrate diet is at the top of my list of potential culprits. Other possibilities would be associated dietary deficiencies, such as magnesium, associated with your high protein diet - magnesium deficiency can cause increased muscle cramps for example. As muscles require energy in the form of ATP to work effectively, it is possible that low energy levels are leading to muscle weakness and as a result a greater tendency to actual physical damage to the muscle fibers.

  What would I suggest? For 1 week, eat as many Calories as you use - and make sure 50% of them are from carbohydrate. If you improve, then you have the answer. (a followup email confirmed that a change in diet had helped).

AGING DELAYS THE RESOLUTION OF MUSCLE ACHES/PAINS

ELEVATED SERUM CREATINE PHOSPHOKINASE (CK) POST EXERCISE.

Creatine Kinase (CK) is an enzyme found in all skeletal and heart muscle cells. It catalyzes the formation of phosphocreatine, a rapidly accessible source of energy in high exertion events. When a muscle cell is injured, in a heart attack for example, CK leaks into the circulation and blood levels of CK rise. Blood levels also increase in skeletal muscle injury, rhabdomyolysis being the classic example.

Normal blood CK levels range between 20 and 200 U/L (units per liter) depending on the lab doing the test. After a strenuous workout they will regularly rise into the thousand range, and after extreme events, levels of 10,000 have been reported without ill effect. (In rhabdomyolysis it is the release of an associated muscle protein, myoglobin, that is the culprit in the life threatening kidney damage.) These levels can remain elevated for days after an extreme event - up to 14 days post marathon for example.

An elevated blood CK is most commonly associated with extreme efforts such as lifting heavy weights or climbing on the bike at a low RPM. It is uncommon after a long ride at your normal riding pace. The exercise effect on CK levels is magnified by dehydration.

Blood CK levels have been proposed as a metric to assess and modify a recovery program. As they reflect muscle cell injury, elevated levels may indicate an increased risk of additional injury and support taking a day or two off of the bike. But you get the same clues from DOMS (delayed muscle soreness after extreme exercise), and it is unclear if a CK blood test adds any additional helpful information.

CK, along with cortisol levels, may have a role in assessing excessive fatigue in a heavy training program, i.e. is it a normal response to the heavy training or does it indicate you are nearing a state of overtraining.

Whether this blood test will be useful for the majority of riders is still up in the air. The final paragraph of the Bicycling article says it best: "But before even worrying about your current number, it's worth remembering that the best defense from high CK is a good offense. ....A high CK (and other blood markers) levels are what business textbooks would refer to as "lag metrics," meaning they're what happens after you've already made the mistakes in training and recovery. Instead, focus more on "lead metrics," like feeling great after a workout and paying attention to sleep quality and optimal nutrition. You shouldn't wait until your test results come back with elevated numbers to prioritize your recovery!"

For those interested, additional articles:

• The first one I tracked down suggested an average 10 fold increase in the serum CPK levels, with quite a bit of individual variation. To quote "Muscle soreness in the eccentrically exercised thigh increased from 0 (range, 0-0), to 1.3 (range, 0.8-2.1) and 1.9 (range, 0.8-2.5) arbitrary units (a.u.) on day 1 and 2, respectively (P < 0.05). Creatine kinase increased from 54 U (range, 32-86 U) before the eccentric exercise to 620 U (range, 117- 1571) on day 1 and 2211 (range, 87-8138 U) on day 2."

• A second was a study on caffeine, and whether the increased performance seen after use might lead to an increase in muscle damage and an elevated CPK. In this study, resistance exercise with or without caffeine did increase blood creatine. "...following the caffeine session (415.8+/-62.8 to 542.0+/-73.5) and the placebo session (411.5+/-43.3 to 545.8+/-59.9), with no significant differences between sessions."

• And finally the third and most definitive article notes, and I'll quote directly:
  • The serum activities of those enzymes found especially in muscle, particularly creatine kinase, increase in proportion to the intensity and duration of the preceding exercise, peaking 24 hours after exercise;
  • the effect of duration is dominant, so that the highest post exercise serum enzyme activities are found after very prolonged competitive exercise such as ultra-distance marathon running or triathlon events
  • Weight-bearing exercises which include eccentric muscular contractions such as bench stepping and downhill running induce the greatest increases in serum enzyme activities
  • There is a remarkable individual variability in the degree to which serum enzyme activities increase with exercise; a 50-fold difference in post-race serum creatine kinase activities has been found in healthy and equally trained athletes completing the same 90km ultra-marathon footrace

  This same article also notes that "...serum enzyme activities increase very little even after prolonged participation in those non-weight-bearing activities such as swimming and cycling which do not include eccentric muscular contractions." Interestingly the reader who asked the original question does a lot of out of the saddle riding, so I suspect that aspect of his riding along with being at the upper end of the range of responders to exercise explained his laboratory findings.