Thursday, April 29, 2010

Barefoot Running

Harvard evolutionary biologist Dan Lieberman believes that modern running shoes may explain why fifty percent of serious runners are injured at least once a year (Nature, January 2010). Modern running shoes have features that cause runners to land on their heels with forces of at least three times body weight at 6-minute mile pace. The faster a runner runs, the greater the force, which causes stress fractures of the feet and lower legs, shin splints, tears in the fascia on the bottom of the feet, knee and hip pain, tendon and joint damage and more.

Hitting the ground with the heel first generates tremendous force because it stops the foot suddenly. On the other hand, landing on the front of the foot allows the foot to keep on moving as the heel is lowered toward the ground to distribute the forces throughout the entire lower leg. If you drop a pen on its tip, it hits with tremendous force because it stops when it hits the ground and then falls forward. However, if the pen were dropped on the side of one end, it would hit the ground with much less force because after hitting on that side, the force would be distributed as the pen falls backward to the other end.

In the 1960s doctors thought that most running injuries were caused by excessive pronation, a rolling inward of the foot after the heal strikes the ground. They felt that the foot rolled inward toward the arch to dissipate the tremendous heel strike forces. This, in turn, caused the lower leg to twist inward and they blamed the frequent running injuries on the inward twisting motion of the leg after heel strike. So they invented running shoes with special arch supports to limit inward rolling, and with padded heels to cushion some of the shock of the heel hitting the ground. However, these features reinforce the runners' habit of landing on their heels.

Dr. Lieberman has shown that barefoot runners are more likely to land on their forefoot or mid-foot. He has shown in elegant experiments that landing on the front part of the foot reduces the force of the foot strike very significantly. However, he has no data to show that running injuries can be prevented by running barefoot. Furthermore, stones and cut glass can cause injuries, and most runners have such thin skin on the bottom of their feet that they couldn't possibly run barefoot.

New on the market are running shoes with very thin soles and minimal heels called Vibram FiveFingers shoe and the Dunlop Volley. Vibram is supporting Dr. Lieberman's studies. Dr. Lieberman has shown only that
• modern running shoes tend to encourage a runner to land on his heels, and
• heel strike generates more force than front foot strike.
He has not yet shown that:
• modern running shoes cause injuries, or that
• injuries can be treated or prevented by running barefoot or in thin-soled shoes.
Dr. Lieberman's website

Sunday, April 25, 2010

Good Carbohydrates Help to Prevent Heart Attacks

This month, separate studies from Denmark and Italy show that heart attack risk is lowered by replacing saturated fats with good carbohydrates that do not cause a high rise in blood sugar, while heart attacks can be caused by replacing saturated fats with carbohydrates that cause a high rise in blood sugar (American Journal of Clinical Nutrition, April 7, 2010; Archives of Internal Medicine, May 2010). Those who ate the most foods that cause high rises in blood sugar levels had more than twice the risk of having heart disease as those who ate the least.

In the 1940s, Ancel Keys, of the University of the Minnesota started groundbreaking research that showed that saturated fat in meat causes heart disease and premature death, while carbohydrates from intact plants in a Mediterranean-type diet help to prevent these complications. Further research showed that replacing saturated fats with polyunsaturated fats in plants also helps to prevent heart attacks.

Carbohydrates found IN plants are combined with other components that prevent a high rise in blood sugar. When these same carbohydrates are extracted from plants or ground into powders, they can cause blood sugar to rise too high.

• Whole grains are capsules with a tough outer coating that prevents a high rise in blood sugar. They can resist digestive enzymes and pass through your digestive system virtually intact. Grinding whole grains into flour breaks the capsule so the small particles are easily absorbed to cause a high rise in blood sugar.

• The carbohydrates in vegetables and fruits are attached to fiber that markedly slows absorption. When sugars are extracted from plants they pass into the bloodstream almost immediately (see the list of extracted sugars below.)

• Before food can pass from the stomach into the intestines, it must be converted to a liquid soup. No solid food passes into the intestines. When solid food enters your stomach, the pyloric sphincter at the end of the stomach closes and the stomach continuously squeezes the food until it is turned into a liquid soup. This can take up to four hours which markedly delays the rise in blood sugar. Therefore you want to limit foods made from ground-up grains (flour), extracted sugars, and sugars in liquid form including fruit juice, because they can cause the highest rises in blood sugar levels.

How a high rise in blood sugar causes heart disease: When your blood sugar level rises too high,
• your pancreas releases huge amounts of insulin which
• converts sugar to triglycerides, which clog up your bloodstream to increase risk for clots, so
• you use up huge amounts of your good HDL cholesterol in carrying triglycerides and your bad LDL cholesterol from your bloodstream into your liver.
• Low HDL (good) cholesterol causes heart attacks becaues HDL is not available to carry cholesterol and triglycerides from your bloodstream.
• High insulin levels constrict arteries to cause heart attacks. • High blood sugar levels cause sugar to stick to the surface membranes of cells to destroy them and cause all the horrible side effects of diabetes.
• High triglycerides in your liver cause a fatty liver that can lead to diabetes.

A diet rich in plants has also been shown to help prevent Alzheimer's disease (Archives of Neurology, April 2010). Based on these and many other studies, I recommend that you:

1) Eat unlimited amounts of unprocessed fruits, vegetables, whole grains, beans, nuts and other seeds.
2) Avoid all sugared drinks including fruit juices (except while you exercise; contracting muscles remove sugar from your bloodstream without insulin).
3) Restrict all ground up carbohydrates (foods made from flour).
4) Choose cereals made from whole grains and with little or no added sugar. See How to Pick a Breakfast Cereal
5) Restrict meat from all mammals. Poultry has not been associated with increased risk for heart attacks, and fish is associated with reduced risk.
6) Read labels on all processed foods. Extracted (added) sugars have many names, including: barley malt, beet sugar, brown sugar, buttered syrup, cane-juice crystals, cane sugar, caramel, carob syrup, corn syrup, corn syrup solids, date sugar, dextran, dextrose, diastase, diastatic malt, ethyl maltol, fructose, fruit juice, fruit juice concentrate, glucose, glucose solids, golden sugar, golden syrup, grape sugar, high-fructose corn syrup, honey, invert sugar, lactose, maple syrup, malt syrup, maltodextrin, maltose, mannitol, molasses, raw sugar, refiner's syrup, sorghum syrup, sucrose, sugar, turbinado sugar, yellow sugar.

Tuesday, April 20, 2010

Recovery Days: Rest or Easy Exercise?

Virtually all competitive athletes train by taking a hard workout on one day, feeling muscle soreness on the next, and then recovering at a reduced intensity for as many days as it takes for the soreness to go away. Then they take their next intense workout. Intense workouts cause muscle damage, as evidenced by bleeding into the muscles themselves and disruption of the fibers and Z bands that hold muscle fibers together. Significant increases in muscle strength and size come only with workouts intense enough to break down muscles. When muscles heal they become stronger and larger. The faster you move on your hard days, the faster you can move in competition. However, continuing intense exercise when muscles feel sore causes injuries and an overtraining syndrome that can takes weeks and months for recovery.

Most athletes in endurance and strength sports exercise on their recovery days and do not plan to take days off. However, they work at a markedly reduced intensity to put minimal pressure on their muscles. If you develop pain anywhere that gets worse as you continue exercising, you are supposed to stop for that day.

Active recoveries on easy days at low intensity make muscles tougher and more fibrous so the athlete's muscles can withstand harder hard days. Almost all top runners, cyclists and weight lifters do huge volumes or work, and most of it is on their less intense recovery days. The stresses of intense workouts are extreme; the recoveries take a tremendous amount of time and are done at low pressure on the muscles. Top endurance runners run more than 100 miles/week, cyclists do more than 300 miles per week and weight lifters spend hours each day in the gym.

Research data comparing active and passive recovery are scant. I am amazed at how few quality studies are available to answer this question. New training methods are developed by athletes and coaches. Then when these athletes win competitions, scientists do studies to show why the new training methods are more effective. A recent report from The University of Western Australia shows that runners recover faster by taking a relaxed swimming workout 10 hours after high intensity interval running, rather than just resting (International Journal of Sports Medicine, January 2010). However, in another study, runners recovered strength and power faster aftr a marathon by resting for five days compared to those who ran slowly (Journal of Applied Physiology, December 1984).

Active recovery should be of limited intensity that does not interfere with the healing process. German researchers showed a one-hour recovery ride is more effective than a three-hour ride for recovery from 13 days of intense bicycle training. Those who rode for 3 hours on their four recovery days had much lower maximal heart rates and maximal lactic acid blood levels, lower power output and slower 30 minute time trials, showing that they were unable to exert themselves as intensely (Scandinavian Journal of Medicine & Science in Sports, June 2009).

What else can you do to recover faster? Athletes in intense training recover faster by getting off their feet immediately after they finish their hard workouts and not even walking until it's time for their next day's recovery workout. Eating a high-carbohydrate meal within one hour of intense workouts hastens recovery (Journal of Sports Sciences, January 2004). Adding protein to that meal hastens recovery even more (Sports Science Exchange, 87:15, 2002). Adding salt and drinking lots of fluids are also necessary for a faster recovery (Journal of Sports Sciences, January 2004). So within one hour after your intense workouts, eat fruit, vegetables, cereals and grains (for carbohydrates), seafood or corn and beans (for protein), add salt to replace what you have lost, and drink plenty of fluids.

IF YOU EXERCISE ONLY FOR FITNESS: Recent research shows that intense exercise is more effective than casual exercise in preventing cancers, heart attacks and premature death. However, you should not exercise intensely more often than every other day. The hard-easy principle applies to all exercisers, even if your hard days are far less intense than those of competitive athletes. Intense exercise can cause heart attacks in people with blocked arteries, so you should check with your doctor before you increase the intensity of your exercise program.

Thursday, April 15, 2010

Arginine: Will it Make You Faster?

It pays to be skeptical. An article from the University of California at Los Angeles showed that cyclists over age 50 who took a commercially available supplement containing the amino acid, arginine, and antioxidants gained a 16.7 percent increase in their anaerobic threshold at three weeks (Journal of the International Society of Sports Nutrition, March 23, 2010).

Muscles need oxygen to convert food to energy. Anaerobic threshold occurs when lactic acid starts to accumulate in the muscles, meaning that a person cannot bring in enough oxygen to cover the amount of fuel muscles use for energy, so the person becomes severely short of breath and has to slow down. Arginine is an amino acid protein building block that can stimulate the blood vessels to increase production of nitric oxide. This dilates blood vessels which can increase blood flow to muscles. The authors demonstrated that arginine did not increase the maximal amount of oxygen that a person can take in and use (VO2max).

1) The only people who can benefit from increased anaerobic threshold are those who are exercising as hard as they can. It does not benefit people who are exercising at less than their maximal capacity. If you take these supplements and do not exercise at your maximum, you are wasting your money. Several studies show that nitric oxide releasers may help athletes exercise longer, but the data are weak, sparse and not very impressive. If you are already exercising as hard and as fast as you can, taking these supplements may let you do more work, which may make your muscles stronger (Medicine & Science in Sports & Exercise, December 2000).

2) Promoters of these supplements recommend doses of 6,000-10,000 mg per day and most athletes who use them take far more than that. Each pill used in this study contained 5200 mg. Side effects include nausea, stomach cramps, diarrhea, gout and a worsening of asthma. High doses may drop blood pressure which could harm performance. During exercise you need higher blood pressures to enhance ciruclation to muscles. A person with resting blood pressure of 120/80 can expect it to rise to 200/80 while jogging.

3) The study subjects took arginine at bedtime. We do not know if arginine taken at night would have any effect whatever on nitric oxide production the next day. Exercise, by itself, raises blood levels of nitric oxide (American Journal of Hypertension, August 2007). So if you want your arteries to make more nitric oxide, go out and exercise.

4) Arginine is so readily available from food that deficiencies of arginine are virtually never reported. Your body can make it and it is abundant in meat, poultry, seafood, diary products, all grains, nuts, legumes and other seeds, and in chocolate.

Tuesday, April 13, 2010

High Blood Pressure During Exercise

Does an exaggerated rise in blood pressure during exercise predict who will develop high blood pressure in the future?

For athletes, probably not. Many research articles have shown that people who develop very high blood pressure during exercise are the ones most likely to develop high blood pressure in later years (American Journal of Hypertension, April 2004). Textbooks explain that these people have arteries that do not expand as much as normal arteries when blood is pumped to them. When your heart beats, it squeezes blood from inside its chambers to the large arteries. This sudden bolus of blood causes normal arteries to expand just as balloons do when they fill with air. The walls of arteries have sensors that allow arteries to expand with each pulse of blood. If the arteries do not expand enough when blood enters them, blood pressure can rise very high. So exercise-induced systolic blood pressures greater than 190 in non-exercisers predict high blood pressure in the future. It's different for athletes who have the strongest hearts that push blood with the greatest force, so they have the highest rises in blood pressure during aerobic exercise (American Journal of Hypertension, November 1996). Blood pressure is determined by the force of the heart's contraction times the resistance in the blood vessels. Normal blood pressure is no higher than 120 when the heart contracts and 80 when it relaxes. During exercise, blood pressure increases markedly, with the highest blood pressures in experienced weight lifters occurring during a double-leg press where average values are 320/250 mm Hg, with pressures reported as high as 480/350 mm Hg (Journal of Applied Physiology, March 1985). It is normal for conditioned athletes to have blood pressures of 200/70 when they run on a treadmill.

The good news about exercise is that just 20 minutes of running on a treadmill or lifting weights lowers blood pressure for about seven hours of normal physical activity (Journal of Strength and Conditioning Research, November 2009).

Ninety percent of North Americans will develop high blood pressure, which increases risk for heart attacks, strokes, kidney damage and sudden death. If you have an exaggerated blood pressure rise during exercise and you are an athlete, you probably need only be concerned with your blood pressure at bedtime, but we have no good data on this. If it is above 120, you have high blood pressure and need to be treated.

However, if you are not a regular exerciser and your exercise-induced blood pressure is above 190, you should go on a heart attack prevention program that includes a diet that is high in plants and low in meat and refined carbohydrates, check with your doctor for clearance to start exercising regularly, lose weight if overweight, avoid smoke and stimulants or drugs that raise blood pressure. Diet to control high blood pressure

Sunday, April 11, 2010

Benefits of High-Intensity Interval Training

To be competitive, all athletes must train very intensely some of the time. New research from McMaster University in Canada shows that short term, high-intensity interval training on a bike can also provide you with all the health and fitness benefits of exercising less intensely for a much longer period of time (The Journal of Physiology, March 2010). Subjects used a standard stationary bicycle and performed a workout of ten 1-minute sprints with a 1-minute rest between each at 95 percent of their maximal heart rate, three times a week. This takes less effort than an all-out sprint at close to 100 percent of maximal heart rate. The study supports other research that shows that high-intensity training improves speed and endurance far more than long slow distance and is necessary for training for athletic competition.

The same authors showed that a similar short workout of all-out sprinting at maximal heart rate took about 90 minutes per week (three workouts of 30 minutes each) and was as effective in achieving fitness and health benefits as many hours of exercising at a much more leisurely pace (The Journal of Physiology, September 2006). High intensity, short-interval training improves fuel and oxygen delivery to muscles, helps the removal of waste products, and increases the number and efficiency of mitochondria that help muscles use oxygen to burn food for energy. These changes have been shown to reduce risk for heart attacks, strokes, diabetes, weight gain and even some cancers.

The authors make no mention of alternating intense stress and low-intensity recovery workouts, in which you spend more than 80 percent of your exercise time going at a very low intensity. Training intensely without recovery workouts markedly increases your chances of injuring yourself.

High-intensity training can cause heart attacks in people with blocked arteries and muscle injuries in anyone. Before starting, a) check with your doctor to make sure your coronary arteries are open and b) you should be able to pedal on a stationary bicycle slowly for at least an hour a day for several weeks. A program of high-intensity intervals:

• will improve speed and endurance much more than slow long- distance workouts

• should not be done when muscles feel sore or you feel sick because it increases your chances of injuring yourself

• should be part of a "stress and recover" program in which you go intensely never more often than three times a week and spend far more time exercising less intensely.

High-intensity interval training causes muscle burning and severe shortness of breath, so don't do it unless you enjoy the thrill of competition.

Sunday, April 04, 2010

Vitamin D Deficiency May Be Genetic

A report from University of Toronto shows that genetic factors cause some people to develop severe vitamin D deficiency while others do not (Clinical Biochemistry, July 2009). An earlier study showed that some people and mice have abnormal Vitamin D binding protein (VDBP) and therefore cannot respond to vitamin D normally (Endocrine Reviews, June 2008). They are at increased risk for heart attacks, strokes, certain cancers, depression, athletic injuries, muscle weakness and so forth.

Over the years I have been unable to run effectively in the winter and injuries forced me to miss six Boston Marathons. This same pattern of winter-time weakness and injuries plagued me when I switched to cycling. It wasn't until a few years ago that I drew blood and found that my vitamin D3 (Cholecalciferol) was 22 nmol/L (normal is greater than 75). Taking as much as 3000 IU of vitamin D failed to get my blood levels much over 30. I moved to Florida and rode my bike very well last winter. This winter was extremely cold and often cloudy, and my injury and weakness pattern recurred from January through March. I notice that a good day in the sun allows me to ride well for about three or four days, but the weakness and injuries recur until the next day of warm sunlight. My skin has never been damaged by sunlight, has no pre-cancers and looks much younger than my 74 years.

Vitamin D deficiency is associated directly with muscle weakness (Scandanavian Journal of Medicine & Science in Sports, October 2009) and athletic injuries (Current Opinion in Clinical Nutrition & Metabolic Care, November 2009; Molecular Aspects of Medicine, December 2008). It is my opinion that:

• Certain people are genetically susceptible to vitamin D deficiency
• These people are likely to be injured when they try to exercise vigorously in the winter
• Vitamin D pills will help some athletes, but many do not regain their athleticism at conventional doses
• These people may get better when they are exposed to sunlight during exercise. Of course they should be concerned about skin cancer from excess sunlight, but I think that people who are at high risk for vitamin D deficiency are at reduced risk for skin cancer. However, I have no available data to support that impression.
More on vitamin D deficiency