Research Blog

Physical Activity Could Cure Teen Smoking

A teenage smoker.




A West Virginia program that promotes physical activity and lends advice to help teens quit smoking is found to increase daily exercise and decrease daily cigarette use.







A health update appearing in the Journal of the American Medical Association highlights physical activity's role in helping West Virginia high school teens quit smoking (Understanding Physical Activity Outcomes as a Function of Teen Smoking Cessation, 2013. Horn K, et al.).

The study used 19 different West Virginia high schools for the study. Participants in the study were 14-19 years of age, had smoked a cigarette in the past 30 days, and were actively seeking to quit smoking. There were a total of 233 participants in three different groups. The groups are as follows. Brief intervention involved a trained facilitator who spent 10-15 minutes giving cigarette quitting advice at the start of the study. No other intervention was given to the Brief intervention group. The second group participated in N.O.T, short for Not-On-Tobacco, a ten week teen smoking cessation program. The N.O.T+FIT group was enrolled in the ten week N.O.T program and, in addition, received five minutes of physical activity motivation and advice with every N.O.T. session. The N.O.T.+FIT group was given a pedometer and physical activity log to help them reach their fitness goals.

Interestingly, every group, regardless of intervention, increased their days of physical exercise 3 months after baseline, or about two weeks after N.O.T. and N.O.T.+F.I.T programs concluded. The group with the greatest mean increase in physical activity was the N.O.T.+FIT group. However, the changes between groups was not statistically significant. The graph below shows the respective changes in daily exercise for teens enrolled in each group. 

Physical activity change by group 3 months post-baseline. Note: Values are means and (standard deviations).  N.O.T is Not-On-Tobacco, a teen smoking cessation program.  FIT is fitness intervention.  N=233.

Those who were in the N.O.T.+FIT group were the most likely to reduce cigarettes smoked on a daily basis. Interestingly, those individuals in the N.O.T.+FIT group who increased the number of days per week where at least 20 minutes of exercise was completed were the most likely to reduce the daily amount of cigarettes smoked. While other studies have shown small or little effect of physical activity on cigarette smoking, this is the first to combine physical activity with an intervention program. None of the groups had a significant change in BMI.

Perhaps a joint physical activity and smoking cessation program can cure two epidemics with one treatment. Adolescent obesity and smoking are two major health challenges facing American adolescents. Increasing physical activity in adolescents can help youth lose weight and quit smoking.

The aforementioned study did not use physical education as their fitness intervention. However, it is likely that physical education would have parallel effect to the FIT program utilized in this study. With physical education programs being cut across the country, this study underlines the consequences that removing physical education can have on the health and well-being of America's youth. Fighting adolescent obesity and smoking should be a priority for school districts because a student's health impacts more than just academic achievement.

Study: Heritable link between cognitive and oxidative function

Ryan lochte grill and gold medal


Ryan Lochte's (right) portrayal in the media epitomizes the dumb jock. However, two studies that came out last year found that heritable endurance running capacity and professional soccer player success are both positively correlated to cognitive function.



A study published last year in Physiology Behavior found that rats selectively bred for endurance running capacity had better cognitive function than rats selectively bred for poor endurance capacity (Selective Breeding for Endurance running capacity affects cognitive but not motor learning in rats, 2012.  Wikgren, et al.). The study bred the rats for 23 generations. With each generation, the rats were tested for endurance running capacity in five separate treadmill trials. The male and female rat with the highest endurance running test over the five trials were mated. Likewise, the male and female rat with the lowest endurance running test were bred. After 23 generations, high endurance bred rats and low endurance bred rats were tested for cognitive and motor function using a T-maze and Rotarod, respectively.

The high-endurance bred rats showed significantly higher ability on the T-maze when the strategy was shifted from a "shift-win" strategy to a "stay-win" strategy. A "stay-win" strategy means that prize food is placed in the same arm as the rat's first trial. When a "shift-win" strategy is employed, the prize food is placed in a different arm from the food in the initial trial. High-endurance bred mice's ability to perform better when the strategy is switched from "shift-win" to "stay-win" suggests either a greater propensity for cognitive learning and adaptability or a greater propensity for the "stay-win" strategy. There is no resin to believe that high endurance runners would be more inclined to the "stay-win" strategy. The ability to switch strategies is probably learned. Rats naturally employ the "shift-win" strategy when foraging for food because they would expect to find no food after eating all the food at a given location.  

Number of correct choices (+/− SEM) as a function of T-maze training. There were no significant differences between the groups in the T-maze test in acquiring the shift-win rule (left pane): both groups learned to a similar extent at a similar rate. However, when the rule was changed to the stay-win rule (right pane), the High Capacity Runner (HCR) rats performed significantly better, but were still unable to reach the chance level.

There was no significant difference in Rotarod performance. Rotarods measure balance, essentially motor learning. Therefore, from the study it can be concluded that high endurance runner bred rats have greater cognitive learning, but not motor learning.  

The authors speculate that the link between cognitive learning and endurance capacity may be oxidative metabolism. A higher level of, or more efficient, oxidative metabolism proteins in the muscles and brain would theoretically enhance cognitive capacity and endurance capacity, respectively. Whether this is the actual link remains to be seen.

Another study, found that successful soccer players had a greater proficiency in design fluency, a measure of cognition, creativity and response inhibition (not giving the same answer twice) than their novice counterparts. The study looked at Swedish soccer players across divisions  and genders (Executive Functions Predict the Success of Top-Soccer Players, 2012. Vestberg, et al.).  

The study found that not only did the professional soccer players have a greater design fluency than their non-professional counterparts, but that design fluency was correlated with success on the pitch, measured with the goals and assists recorded. The graph below shows that both men and women soccer (football) players at the top Swedish division (HD) had a significantly greater design fluency than soccer players in the lower Swedish soccer divisions (LD).

In Design Fluency (DF), a measure of cognition that includes creativity, multi-processing, response inhibition and cognitive flexibility, the High Division (HD) players had significantly better scores than the Low Division players (LD).  This difference was observed for both genders.  Note that High division and Low Division players have superior scores compared with the standard population (not shown).

The reason professional soccer players have a greater executive function is probably not tied to their endurance capacity. Setting up plays that result in goals and assists require strong executive function capacity.  

It is hard to draw any translational conclusions from either of these studies.  Humans, of course, do not have any programs breeding high capacity endurance runners. Because a high level of training is required to become a successful human endurance athlete, it is unlikely that we would see any correlation in humans between endurance capacity and cognitive function. However, both of these studies show that natural athletic ability should not be correlated with reduced cognitive function. These studies certainly seem to contradict the term "dumb jocks".

The Prenatal Environment Influences Adulthood Disease

A developing fetus.


The maternal environment affects prenatal development. Many of the effects are not seen until the onset of adulthood diseases such as hypertension. Telomere length may be one potential way to measure prenatal stress and predict the adulthood diseases implicated.


 




A bounty of new research suggests that stresses placed on an embryo during development can play a factor in disease development up to two generations away.  A team of researchers in the Development, Health and Disease Research Program at the University of California, Irvine have been studying the role that prenatal stress plays in disease risk as well as the part that telomeres play in signaling the subsequent disease risk. Their research appeared in Science Signaling as a presentation (Prenatal Stress, Telomere Biology, and Fetal Programming of Health and Disease Risk, 2012.  Sonja Entringer, et al.). Furthermore, an article appearing in the January 2013 issue of Hypertension found that mice predisposed to hypertension through a maternal low protein diet during pregnancy had higher blood pressure during sympathetic nervous system activation of the cardiovascular system (Prenatal Programming of Hypertension Induces Sympathetic Overactivity in Response to Physical Stress, 2013. Masaki Mizuno, et al.).

Determining the causations of disease alone is challenging.  However, identifying causations of disease during fetal development is particularly challenging because of the interactions between the developing fetus and maternal environment. This is called reciprocal determinism. The two interacting genotypes that result in reciprocal determinism are the maternal genotype and fetal genotype. Stresses that factor into the health outcome of the developing fetus can be categorized by nutrition, infection and psychosocial. They interact with the endocrine and immune systems to affect fetal development. Stress during prenatal development may cause a variety of diseases in adulthood including hypertension, coronary artery disease and diabetes. Studies have previously observed an association between abnormal birth phenotype (i.e. low birthweight) and adulthood diseases. Stresses during fetal development may explain this association. A model of the prenatal environment effects on birth phenotype and adulthood disease is shown in the figure below.

model of effects of prenatal environment.  Explains a correlation observed between abnormal birth phenotype and development of disease later in adulthood.

A plethora of recent human studies have implicated prenatal stress with detrimental affects on cognitive, immune, endocrine and metabolic function.  Researchers are now looking at the role telomeres may play. Telomeres are non-coding DNA sequences capping the ends of chromosomes for chromosomal stability and protection. Telomeres shorten with aging and, as previously reported on ExerciseMed, respond to stress and physical activity. Telomerase is the protein responsible for lengthening telomeres and has recently been found to play a variety of roles in keeping the cell healthy and functioning properly. 

Telomeres.  Telomeres are highlighted in red in on the chromosomes and are responsible for stabilizing and protecting the chromosomal DNA.

Telomeres may be used as a signal for prenatal stress. A newborn with short telomeres may signify prenatal stress and allow doctors to predict adulthood disease and health status later in life. A number of human and animal studies have found a link between shortened telomeres and prenatal stress.  Furthermore, telomere length is correlated to aging. Humans who age prematurely generally have shorter telomeres. Thus, a newborn with shorter telomeres would be expected to see a younger onset of age-related diseases.

Researchers are currently looking into how maternal nutrition, sleep pattern, physical activity and psychological emotions play a role in causing and preventing prenatal stress. Maternal lifestyle choices affect more than just one generation. Humans begin producing their germ cells during fetal development. Therefore, the maternal environment affects not only fetal development, but the development of the fetuses future children as well. 

The aforementioned Hypertension paper showed that prenatal stress caused by low protein intake during pregnancy in rat models causes hypertension via the sympathetic nervous system.  

Pregnant rats were fed a low protein (6% of calories from protein) diet to produce prenatally stressed offspring. At rest, blood pressure of the prenatally stressed rats was not significantly higher. However, when the sympathetic nervous system was activated by stimulating the exercise pressor reflex, blood pressure was found to be significantly higher (see figure below). The exercise pressor reflex activates the cardiovascular system through the sympathetic nervous system using sensors (called proprioceptors) in the muscle during exercise. Patients with hypertension often exhibit high blood pressure during exercise before showing a significantly higher baseline blood pressure. This study implicates sympathetic nervous system development in hypertension generated by stresses during prenatal development.

Sympathetic Nervous System Activation Causes Increased Blood Pressure Change in Prenatal Stressed Rats.

To further determine the role that prenatal development has on adulthood disease and health, future studies may need to enable pregnant women to  monitor their nutritional, psychological, and physical states in real time to develop a more accurate picture of the maternal environment and the health outcome of the developing embryo. 

Controlling Protein Intake to Maximize Muscle Growth

meat, a good source of protein following a workout


A recent study shows that an intermediate balance in the timing and distribution of protein ingestion optimizes muscle protein synthesis following a resistance workout. 




The goal of an anaerobic workout is to induce muscle damage. When the muscle repairs the workout-damage, the muscle ends up stronger as a result of muscle protein synthesis. This period of regeneration is called the anabolic phase following a workout because of the protein synthesis. It has long been known that protein intake following exercise enhances muscle protein synthesis in the anabolic phase. Amino acids, the monomers that make up proteins, must be in a positive balance in the muscle to stimulate muscle protein synthesis. A study published in the most recent issue of the Journal of Physiology showed that the schedule of protein intake in the 12 hours post-exercise session has an impact on muscle protein synthesis (Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis, 2013. Areta, et al.). Apparently, an intermediate level of protein ingestion spaced out over the course of 12 hours optimizes muscle protein synthesis following a bout of resistance training.

The experiment utilized 24 male subjects of average weight (70-80 kg or 150-180 lbs) who performed a resistance training protocol. The subjects were then directed onto three different 12 hour, 80 gram protein ingestion schedules. The resistance training protocol was 3 sets of 5 repetitions at 80% of their one-repetition maximum on a bilateral leg extension. The subjects consumed 80 grams of commercial whey protein isolate following the resistance exercise according to the following ingestion schedules. The Bolus group consumed 40 grams of whey protein immediately following the resistance exercise and six hours later.  The Intermediate group consumed 20 grams of whey protein every 3 hours following the resistance exercise. The Pulse group consumed 10 grams of whey protein every hour and a half following the resistance exercise bout. The experimental protocol is depicted in the figure below.

Schematic representation of the experimental protocol. Negative time points indicate before exercise, positive time points indicate after exercise. LBM, lean body mass; REX, resistance exercise.

The researchers took blood samples and muscle biopsies from subjects to measure  muscle protein synthesis, amino acid balance in the blood, insulin levels and muscle signaling sequences. The muscle protein synthesis increased significantly higher in the Intermediate protein ingestion group than either Bolus or Pulse protein ingestion groups. Over the total course of the 12 hours post-resistance exercise the Intermediate group had a significantly higher rate of anabolic phase protein synthesis than either Bolus or Pulse groups. However, the study found that only the first 40 gram protein intake in the Bolus group significantly increased an amino acid uptake protein in the muscle. The figure below shows the degree of muscle protein synthesis as a function of post-workout protein ingestion schedule.

Myofibrillar fractional synthetic rate (FSR) between time points (A) and mean FSR throughout 1–12 h (B) following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD expressed as %· h−1. Different vs. a, Rest; b, 1–4 h; ‡, Bolus and *, Pulse at equivalent time point (P < 0.05).

In summary, the discussed study found that 20 grams of protein taken every three hours following resistance training optimizes muscle protein synthesis in the twelve hours post-exercsie bout. The optimal protein distribution may have to be adjusted for people who are not of average weight. Finding an optimal nutritional strategy to maximize muscle growth following exercise is useful to recreational and competitive athletes as well as elderly patients looking to increase muscle growth following an anaerobic workout. 

Exercise Changes Body-Image before Physical Body Parameters


Exercise changes your perception of your body before it actually changes your physical parameters of your body. This raises the question: why do people drop out of exercise programs?










Apparently, exercise causes the participant to view their body better before any actual change in body shape or weight. Thats the finding of a study published in the January 2013 issue of Journal of Health Psychology (6 x 40 mins exercise improves body image, even through body weight and shape do not change, 2013. Appleton KM).

Sixteen males and eighteen females exercised moderately for six by 40 minute sessions over the course of two weeks. Body shape and weight were measured before and after the two week exercise program. There was no statistical change in body shape or bodyweight over the course of the two week exercise program. The Multidimensional Body-Self Relations Questionnaire (MBSRQ) was administered before and after the two week exercise period. The 69-question questionnaire evaluates one's satisfaction and relative importance to his or her fitness, appearance, health and bodyweight. As a control, all participants took the MBSRQ prior to and following six by 40 minute sessions of reading over the course of two weeks. The control was administered several weeks before the participants' exercise program. As expected, no change in any of the measured physical or psychological parameters was measured in the reading control program.

Several interesting results came out of the aforementioned study. Body shape, through measurement of body dimensions, and bodyweight did not change in the participants over the course of the two week training program. However, participants were more satisfied with their body's appearance and health following the two weeks of exercise. The importance subjects placed on appearance and health increased over the two weeks of exercise, suggesting exercise triggers a positive feedback loop. Exercising increases ones awareness of health and well being prompting more exercise. Interestingly, evaluation of body weight did not change. Perhaps this is because body weight is more objectively measured; participants could easily determine bodyweight was not changing.

There was no significant difference between male and female participants.  Exercise has a similar effect on body image for both genders. Studies have found that exercise increases self-esteem and self-confidence (The effects of exercise on self-perception and self-esteem, 200. Fox KR). Whether the boost in body image is responsible for increasing self-esteem or a rise in self-esteem increases body image is not known.

Despite the findings of this study, many people who start an exercise program quit in the first several weeks before the exercise benefits kick in. Usually exercise drop out rate is attributed to participants not seeing any noticeable benefits to their body weight or body shape. It is possible that this bump in body image disappears after several weeks if physical body parameters continue to not change.

To keep patients exercising for the long-term it may be beneficial to explain the biological benefits of exercise. These are changes that, as discussed throughout ExerciseMed, occur immediately. Just because the outside of your body is not changing does not mean the inside is not. A similar strategy has been employed by anti-tobacco ads. Of course, in exercise's case, the effect is that the inside of your body becomes more beautiful.


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