The Great Exercise Debate

People should exercise from 20 to 60 minutes, at least three days a week. No debate there, right? Wrong. Recently, the health world has been debating whether exercise periods need to be done all in one chunk, or whether smaller amounts of exercise can be added up over the course of a day to equal 20 to 60 minutes of exercise.

There hasn’t been much research to clarify the debate. The goal of this study was to test the theory that exercise results in the same energy
expenditure (EE) whether done all at once or over the whole day. Thirty women wore a device to measure their EE over three days. On one of the days, they took a brisk 30-minutes walk. On another, they took three brisk 10-minute walks. On the third day, they didn’t do any exercise.

As expected, the walking days resulted in higher EE. But the researchers found that the days of continuous 30-minute walking resulted in significantly higher EE than the days of three 10-minute walks. In fact, the women’s EE rates were higher throughout the day when they took a 30-minute walk, even when they were done exercising.

The authors related a separate study that was recently published. It was done with very overweight subjects and showed opposite results.
It found that breaking the exercise sessions into smaller amounts of time is at least as good as one longer exercise period. The authors of this study aren’t sure what accounts for the differences between the two studies. They suggest more research will be needed to find out which variables affect how, why, and when people exercise. 

The Total Truth about Total Joints

Total joint replacement is very successful for most people. As a result, it has become much more common–and its drawbacks are becoming more obvious. One of the major problems with artificial joints is called creep. Creep is a gradual change in the shape of the plastic as it is pressed down. Creep tends to happen within the first 18 months of surgery.

A bigger problem is joint wear, erosion of the replacement parts that happens over the life of the joint. As the parts rub or move against each other, the joint starts to wear, causing small wear particles to build up in the joint. The wear particles are like the sawdust that results from sanding a piece of wood.

Today’s replacement parts are affected by different causes of wear. Adhesion happens when the bonded surfaces get pressed together, causing one of them to loosen up. Abrasion is when the harder surface rubs the softer one like sandpaper, releasing wear particles into the joint. Fatigue is when the components get overstressed from heavy or repeated activity, contributing to wear particles and to possible failure of the artificial joint.

Some types of joint wear are unavoidable. Other types of wear happen when the parts rub and move in unintended ways. The authors highlight some of the causes of wear, including problems with anchoring the replacement joint, unusual stresses, and methods of sterilizing the components.

The authors also addressed the problem of bone loss in the bone that connects to the replacement parts. This bone loss is called bone resorption. It happens from a reaction to the small wear particles that build up. It can also happen if the artificial joint somehow allows the bone to come in contact with joint fluid.

The authors conclude that improving the durability of artificial joints requires finding ways to limit wear and the resulting wear particles. It will also require finding ways to keep joint fluid from coming into contact with the underlying bone.

Pumping Iron to Pump Up Bone Health

Weight lifting has been shown to help reduce the bone loss that often happens with menopause. Until lately, however, it was not clear which method of weight lifting helped bones the most: lifting small amounts of weight with a lots of repetitions, or using more weight and fewer repetitions.

The question of osteoporosis is on the minds of many women over forty. Menopause signals a significant drop in estrogen and other hormones that support and maintain bone strength throughout a woman’s lifetime. It is estimated that in the early years after these hormones drop, a woman may loose up to 5% of her bone density per year. Though there are medications that can reverse some bone loss, much of this loss is irreversible.

One way of preventing this loss is through muscle strengthening exercises. The bones respond to muscles tugging on them by releasing bone-building chemicals, resulting in denser bones. Or at least that’s the hypothesis.

So is it better to lift in the style of Arnold Schwarzenegger–or will a Pee Wee Herman approach suffice? Researchers addressed this question to see which kind of weight lifting impacted bone density the most.

Twenty-five women with an average age of 51 (all from one to seven years postmenopausal) were selected. There were two main requirements for participation in the study. Participants could not be on estrogen replacement therapy, and they were not to have done any resistance training in the past six months. The women were divided into three groups. One group served as a control group and didn’t do or change a thing. The other two groups began an exercise program. High-intensity exercisers did twice as much weight and half as many repetitions as the women doing low-intensity exercises.
Subjects were trained on proper upper and lower body weight lifting techniques. Both groups trained three days a week for six months. Their workouts included a 10-minute warm-up, a 45-minute weight lifting session, and a five-minute cool down. 

How did the exercisers fare? Both groups ended up having stronger muscles, but not stronger bones. Yet neither group showed a loss of bone. Past studies spanning nine to 12 months have shown measurable improvements in bone density. This made the authors question whether the women in their study would have shown higher bone densities had this study lasted longer.

The fact that these women gained stronger muscles is still good news. Better muscle strength means better balance and coordination, which helps lower the chances of falling and fracturing a bone. So the bottom line is that the styles of lifting used by Pee Wee and Arnold both seem to help keep women’s bones strong.

The Rat Race Proves Good for Immune Function

We all know that exercise is good for us. It tones the body and improves cardiovascular function. Researchers have also found that exercise may even boost your immune function–unless you exercise too intensely.

Swedish researchers tested rats to see how different levels of exercise affected the immune system. The rats were kept in separate cages. One group had cages without exercise wheels. Cages of the other rats had exercise wheels. Researchers tracked how much and how far each rat ran.

Those in the rat race followed a running schedule. They ran every day for either five or 11 weeks straight. Or they started out running every day for five weeks and then ran only four days a week for the final six weeks. At the end of the study period, the rats were injected with cancer cells that congregate in the lungs. Researchers then checked the rats’ lungs to see how well their immune systems had managed to clear the cancer cells.

All of the running groups showed better immune function than the sedentary group. The rats that ran every day for 11 weeks showed the poorest clearance of cancer cells of all the running groups. The researchers also grouped the rats by how far they ran each day. All of the runners showed better immune function than the sedentary group. And the rats that ran more often showed better immune function than the rats that ran the least.

The authors conclude that exercise–at least in rats–does seem to boost immune function. But the study also shows that doing too much training for too long seems to erode the benefits. It’s hard to make conclusions for humans based on animal studies. But the authors say that their results suggest there should be more research on “the important role of adequate rest in prevention and treatment of overtraining in humans.”

Making Moguls of Molehills to Improve the Safety of Kids Who Ski

Snow conditions, temperature, and kids’ attitudes about risk-taking have a big influence on their ski safety, among other factors. Studying these factors is a mogul-sized task. By snowplowing through the many possible risks faced by kids who ski, these researchers attempted to pinpoint the ones that seem to matter the most. By discovering these risks, better safety programs for young skiers can be offered.

Researchers targeted four possible risks that parents and young skiers could change once they learned about them. The four risk areas were lack of formal ski instruction, poorly adjusted bindings, rented equipment, and low skill levels. Information was collected during the 1995-1996 ski season at a large ski area in Canada. A total of 387 youths were assigned to either an injury or control group. The authors sent a survey to the parents of young skiers between the ages of three and 12, and children who skied by themselves were also invited to be part of the study.

When compared to the control group, the injured skiers tended to have low skill levels, use rented equipment, and have poorly adjusted bindings. Skill level mattered the most. Skiers with low skill levels had more injuries. However, formal ski instruction did not seem to have an affect on whether a child was injured. The authors suggest that future studies might show when and where young skiers with low skills are most often injured.

Skiers who used rented equipment also had a higher risk of injury, possibly because they are less skilled than those who own their equipment. Another reason might be that rented equipment is lower quality and not fitted properly. Also, poorly adjusted bindings were a factor in many of the injuries.

According to the authors, parents should be aware that poorly fitted equipment and low skill levels increase the risk of injury in young skiers. They also suggested that ski shops practice a standard way of fitting equipment and adjusting bindings for each person.

Teenage Girls Get a Jump on Building Stronger Bones

By strengthening bones during their teenage years, people may be better prepared to ward off the harmful affects of osteoporosis later in life. It is well known that bone health is improved by doing weight-bearing exercises. The authors put these two ideas together to develop the first study of its kind, a test to see whether high-intensity jump training could strengthen the skeletons of teenage girls.

The authors assigned 56 ninth-grade girls to two groups, an exercise group and a control group. At the beginning, all participants filled out surveys about their diet and took tests of balance, strength, and power. Bone mineral density testing was done to check the amount and quality of the bones in various parts of their skeletons. These measurements were used to track how the specialized exercise program affected bone health.

For the first three months, the girls in the exercise group prepared their muscles by doing graded resistance exercises. They also advanced through a series of jump training, called plyometrics. This specialized training is an effective way to improve muscle strength and power, but it has not been tested to see whether it can strengthen bones. Participants received high school credit for exercising up to 45 minutes, three times each week. The control group did their routine activities but did not do any specialized exercises.

After nine months, participants repeated the tests of balance, strength, power, and bone density. For the most part, the bones of both groups showed improvement, which might have to do with normal growth patterns. However, compared to the control group, the exercisers showed a lot more bone strength in the upper part of the hip, had up to 29% better side-to-side balance, and had better leg strength.

Based on these measurable improvements and the consistent participation with the program, the authors conclude that “high school PE programs could include plyometric training and potentially reduce future risk of hip fracture.”

Joint Injury Increases the Risk of Future Osteoarthritis

By keeping a close eye on the rearview mirror of time, researchers have traced what happens after an injury to a hip or knee joint. When a joint is injured in a person’s early years, the chances of having future osteoarthritis (OA) in that joint increase.

Researchers tracked 1337 medical students graduating from Johns Hopkins University in Baltimore between 1948 and 1964. When the study first began, 64 participants reported having injured a hip or knee joint. The average age at injury was 16. Significantly, 13.9% ended up with OA, compared to only 6% of the participants who didn’t have injuries before the study. Also, people who injured their hip or knee joint over the course of the study were much more likely to end up with OA in the injured joint.

Clearly, people who have had an injury to the hip or knee joint, especially in their earlier years, are at higher risk for developing OA. Accordingly, the authors believe these people should be targeted for programs to prevent OA, and younger patients who have had a joint injury should be shown ways to limit extra strain on that joint. They conclude by encouraging doctors to “advocate use of proper sports equipment under safe conditions to prevent joint injuries” to avoid future problems.

Reality Check for the Effectiveness of Glucosamine and Chondroitin

Reports abound about the effectiveness of glucosamine and chondroitin, granting them newfound stardom in the treatment of osteoarthritis. But as the stardust settles, the actual benefits appear to fall short of the hype.

Researchers recently pooled the best studies done on these two supplements between 1966 and 1999. The studies tested these compounds in the treatment of hip and knee osteoarthritis over at least four weeks.

After plotting the details of the studies, the researchers found that the study methods could exaggerate the actual benefits. Also, the fact that manufacturing companies sponsored nearly all studies made the researchers concerned that the actual benefits might be inflated. When the authors looked at only the highest quality research, the actual benefits of these compounds were the smallest.

The authors note that these compounds are safe and that they do show some benefits. So even if glucosamine and chondroitin don’t live up to their star billing, they may still play an important role in treating the symptoms of osteoarthritis.

Minor League Baseball Rookies at Higher Risk of Injury Than Veteran Players

Rookies entering the minor leagues run a greater risk of injury than veteran players, according to this study. The authors say that rookies may not be prepared physically for the new demands of higher levels of play. Playing at such a high level requires the tissues of the body to adapt over a longer period of time. Rookies simply haven’t made these adaptations, which could account for their higher injury rates.

By reviewing the injury reports of six minor league teams from 1985 to 1997, the authors were able to compare how often players of different experience levels were injured. The rate for rookies was calculated at 2.42, a significantly higher rate than the 1.62 figure for veteran players.

The researchers also categorized how bad the injuries were to see who suffered the worst injuries. Even though the differences were slight, veteran players tended to have less severe injuries than rookies.

The authors suggest several reasons why rookies were injured more often. The authors believe longer seasons, insufficient training, and extra effort during high school or collegiate play may put players at risk of overuse. Then when they enter professional careers, their tissues are more likely to get injured. New injuries could also be related to injuries that happened earlier in players’ careers. The lower numbers of injuries in veteran and higher-ranked players could have to do with better training than in amateur levels of play.

To help offset the risks of injury for rookies, the authors suggest that they undergo specially designed strength and conditioning training before moving to a higher level of competition. The authors also recommend that players who move up be tested to see what kind of conditioning program will help the most.