The Real World, San Francisco!
This is the true story of three scientists picked to attend the ACSM's conference to find out what happens when people stop being polite and start getting real.
No, this isn't a reality show on MTV featuring brats in nice apartments, but T-mag's annual report of the American College of Sports Medicine's big meeting. This year's meeting in San Francisco was a five day orgy of cutting edge training and nutrition research. Since this ACSM thing gets bigger and bigger every year (a fact highlighted by the 405 page encyclopedia of abstracts – over 2200 total!), I enlisted the services of fellow T-man David Barr and T-vixen Cassandra Forsythe to help review the ever burgeoning list of interesting research submissions.
In the first part of this three-part series, Cassandra will cover the interesting abstracts related to dietary fat, fat metabolism, and gender differences. She'll also get intoxicated, get naked, and jump into the hotel pool. Too bad this isn't reality TV, huh?
Part 1 – Fat Consumption, Exercise Recovery and Intramuscular Fat
Dietary fat has gotten a bad and undeserved rap. While some fats may be bad, certain fats will improve our health and help us lose weight. Besides these benefits, fat is an important fuel source for exercise. Regardless of whether fat excites you academically or physiologically, the latest round of ACSM science provides us with some interesting fat facts. Check out the summaries below!
SKELETAL MUSCLE FAT AND CARBOHYDRATE METABOLISM DURING RECOVERY FROM GLYCOGEN DEPLETING EXERCISE IN HUMANS
What's your body's primary fuel source after a hard workout? Is it fat, protein, or carbohydrates? And does your body use exogenous or endogenous stores of these fuels? In this study, eight endurance-trained men cycled to exhaustion for 90 minutes, which greatly depleted their glycogen stores. During the seven hours post-workout, they ate carbohydrate rich meals consisting of 65% carbohydrates totaling ~490 grams of carbs.
These meals caused blood glucose and insulin to increase significantly and muscle glycogen was quickly replaced. Metabolic rate measurements showed that despite the high intake of carbohydrates, fat was the primary fuel post-exercise. However, the fat source burned wasn't intramuscular fat, but rather storage fat (from adipose) and blood lipids.
This study shows us that after an intense workout, fat is used as the main source of energy. The fat in muscle (intramuscular fat) isn't burned, though. To our advantage, the fat used for energy comes from body fat stores, even after eating a post-workout meal high in carbs.
So, even if you're trying to lose body fat, your first post-workout meals should contain at least 50% carbohydrates to replace your muscle glycogen stores. Your body will still burn fat off and you'll provide it with the right nutrition to work out just as hard the next day. (1)
INTRAMYOCELLULAR LIPIDS IN SKELETAL MUSCLES OF SPRINT AND ENDURANCE-TRAINED ATHLETES
As mentioned in the previous study, intramuscular lipids represent an important energy source in the contraction of human skeletal muscle. This study compared fat storage within (intra-) and outside (extra-) the muscle of endurance trained, sprint trained, and recreational athletes.
The investigators found that endurance athletes had more intramuscular fat than sprint trained and recreational athletes. In fact, the amount of intramuscular lipid storage was in the order of endurance>recreational>sprinters. The amount of extramuscular fat was similar among all groups.
It appears that intramuscular fat storage is an adaptation to endurance training and is meant to enhance aerobic power. Endurance athletes like triathletes and marathon runners need energy sources to sustain their intense, long-duration exercise sessions and intramuscular fat is an excellent fuel. Sprint-trained athletes engage in short bursts of anaerobic exercise and don't need to store intramuscular fat since the phosphagen system (i.e. stored ATP and PCr) and intramuscular glycogen meet their energy demands.
In relation to those who weight train, powerlifters and strict resistance trained athletes would be similar to sprinters and they wouldn't need to develop stores of intramuscular fat. Fitness athletes who weight train and do cardio would have more muscle fat than recreational athletes, but not quite as much as endurance athletes. (2)
INTRAMUSCULAR TRIGLYCERIDE REPLETION FOLLOWING PROLONGED ENDURANCE EXERCISE
Because intramuscular fat (IMTG) is important for prolonged exercise (endurance activity), this study determined what type of post-workout diet is best to replenish IMTG after three hours of endurance exercise.
Two types of diets were fed for three days to endurance athletes after the exercise protocol. One diet was the typical high carbohydrate diet of 62% carbohydrate, 14% protein, and 24% fat (HC) and the other, a higher fat diet of 49% carbohydrate, 14% protein, and 39% fat (HF).
Magnetic resonance spectrometry and muscle biopsy analysis of muscle during the recovery period showed that the HF diet was superior for replacing IMTG and the typical HC diet used by most athletes actually limited post-exercise IMTG repletion. In the 48 hours after the exercise, all the IMTG was replaced with the HF diet whereas it wasn't completely replaced with the HC diet.
For endurance athletes who need to compete at full power within two days of a current competition, a higher fat diet with at least 35% fat will benefit their performance by replenishing intramuscular fat stores more rapidly than a typical high carb diet. Awesome! An even better reason to fire up the BBQ and cook yourself a big, juicy steak.
Remember though, not all fats are created equal, so endurance athletes should be sure to consume lots of healthy fats if they're going to use fat as a post-workout recovery measure. (3)
ADDITION OF FAT TO POST-EXERCISE MEALS DOES NOT ALTER THE EXERCISE-INDUCED REDUCTION IN FASTING PLASMA TRIGLYCERIDES
It's been shown that a single exercise session can improve blood triglyceride (TG) clearance for at least one day, but what would happen to blood TG if you added fat to your post-exercise meal?
In the few hours after a glycogen depleting endurance exercise session (90 minutes at 65% VO2), moderately trained men consumed either high fat (45% fat, total 177 grams) or low fat (5% fat, total 12 grams) meals. The carbohydrate content of the meals was the same in both groups meaning that low fat (LF) group ate less total calories than the high fat (HF) group.
Despite the added fat in the HF meal group, blood TG levels the morning after the endurance exercise test weren't any higher than the LF meal group. It appears the added fat in the HF meals was stored in the muscle immediately after the exercise or oxidized. In the LF group, fat oxidation was higher the next day, probably due to the calorie deficit.
Again this emphasizes that extramuscular fat oxidation is the primary fuel source after intense exercise. Adding fat to your post-workout meals won't hinder your ability to burn fat. Furthermore, your body readily clears blood triglycerides even after the consumption of a high-fat meal.
In the same study the researchers looked at how the HF vs. LF meals after exercise influences the increase in insulin sensitivity seen as a result of exercise. The results showed that even with the added 177 grams of fat in the HF meals, insulin sensitivity was still improved and dietary fat didn't impair glycogen resynthesis.
During exercise, insulin levels drop and glucagon rises so you can tap the fuel from glycogen and triglyceride for energy. Therefore, your muscles become more insulin sensitive (i.e. they respond to lower levels of insulin) and will react to glucose better.
Immediately after your workout, you want to increase your insulin levels even further in order to promote muscle protein and glycogen resynthesis. This will expedite the recovery process as well as promote gains in muscle protein (in resistance-trained individuals).
Clearly, eating a meal rich in carbohydrate will promote an anabolic environment via increased insulin metabolism. However, as this study demonstrates, the addition of fat to your post-workout meal won't hinder your ability to replenish muscle glycogen. Also, insulin sensitivity will still be improved. So, maybe those cream puffs I ate after my workout last night weren't all that bad. (4)
EFFECTS OF DIFFERENT MACRONUTRIENT CONSUMPTION FOLLOWING RESISTANCE EXERCISE ON INSULIN, GLUCOSE, AND TRIACYLGLYCEROL CONCENTRATIONS
Now that we know endurance exercisers should consume some fat in the hours following a workout, what about resistance trained individuals?
Nine young, resistance-trained men worked out for three days with a program of eight exercises at 3 x 10 reps each. Immediately after their last workout, they ate either a high fat meal (37% carb, 18% protein, 45% fat, HF), a high carbohydrate meal (79% carb, 20% protein, 1% fat, HC), or just water (CON).
Blood analysis showed that insulin and glucose were both higher after the HC vs. the HF meal and CON. Insulin levels were higher with the HC meal vs. the HF, at 15, 30, 45, 60, 90 and 120 minutes post-workout, but with the HF meal, insulin was also significantly higher than CON at all time points. Blood triglycerides (TG) were higher after the HF meal vs. the HC meal and CON. The investigators concluded that meals too high in carbs or fat after resistance exercise could induce an environment that would promote the development of cardiovascular disease or atherosclerosis.
Interesting observation, but this garners the distinction of "Worst Conclusion of 2003"! Based on a three day dietary intervention (and only post-workout), the investigators conclude that post-workout meals too high in carbs or fat may promote a more atherogenic environment. Also, I believe they might have mentioned something about diabetes in there... Whatever happened to peer review? That process must've broken down with this submission.
What the authors should've concluded is that the elevation of insulin post-workout via the consumption of carbs, protein, and fat are necessary to stimulate the recovery process. Also, a higher carb meal post-workout is a better stimulus of insulin secretion versus a high fat meal. Your best post-workout nutrition plan would be to drink your high carbohydrate/moderate protein shake immediately after you train, and then consume a meal higher in fat and protein an hour or so later. (5)
Part 2 – Exercise, Fat and Iron Deficiency
In the continuing battle to defend the honor of dietary fat, the white coats at the ACSM present us with more hard science to prove that the combination of the right fats and exercise can help us live longer and look better!
EFFECT OF EXERCISE AND OMEGA-3 FATTY ACID SUPPLEMENTATION ON REVERSE CHOLESTEROL TRANSPORT VARIABLES
Reverse cholesterol transport (RCT) is a pathway in our blood intended to reduce cholesterol levels by transporting cholesterol from bad LDL to good HDL and thus decrease our risk for coronary heart disease. This study investigated how the interaction of omega-3 fatty acid-rich fish oil supplementation and aerobic exercise would affect the variables associated with reverse cholesterol transport.
In this study, ten active men took four grams per day of fish oil (60% EPA, 40% DHA) for four weeks. Before and after supplementation, subjects completed a 60 minute session of treadmill exercise at 60% VO2 max. Researchers found that fish oil supplementation plus exercise was better than either supplementation or exercise alone to increase levels of HDL, but the enzymes involved with RCT didn't seem to be improved.
Although it didn't appear that fish oil and exercise improved RCT, the combined treatments did increase HDL. High HDL levels will also reduce your risk of heart disease, meaning that this dose of fish oil was beneficial. Perhaps if the dose was increased there might have been an improvement in RCT, but we'll have to wait until next year's conference for this to be seen.
Overall, this means that fish oil burps are good for us! We should all take at least four grams a day of fish oil capsules or eat n-3 rich fish like salmon, trout, herring, and sardines at least three times a week. Remember, cardiovascular disease is the number one killer in North America. Supplementing with fish oil combined with exercise will increase your good cholesterol levels and reduce the amount of triglycerides in your blood. These help reduce your risk of dying from stroke or heart attack. (6)
EXERCISE AND FISH OIL: ADDITIVE EFFECT ON POSTPRANDIAL LIPEMIA?
Postprandial Lipemia (PPL) is the poor metabolism of dietary fat after a meal. The fat hangs around in blood for a dangerously long time because it's not burned for energy or stored away. PPL is dangerous since this fat can then be deposited in your arteries and lead to atherosclerosis and eventually heart disease.
This study examined whether or not omega-3 supplements and exercise would help reduce PPL after eating a high fat meal. In this study, ten recreationally active men were given four grams of fish oil a day for three weeks. Just like the above study, subjects completed a 60 minute treadmill run at 60% VO2 max. PPL was measured as the amount of triglycerides (TG) in blood after supplementation with fish oil plus exercise or with exercise or supplementation alone.
Results showed that the greatest reduction in PPL was with supplementation and exercise versus either one separately. There was significantly less TG in blood after the high fat meal in the men who took fish oil and exercised.
Summary: The combination of fish oil supplements and exercise is greater than either treatment alone to clear fat out of the blood after eating. Once again, another reason to take your fish oil to protect your heart! (7)
THE EFFECT OF 9-WEEKS STRENGTH TRAINING ON POSTPRANDIAL LIPEMIA
Here's a study that looks at how resistance/strength training can affect PPL. In this study, 19 healthy young men (22-28 years of age) strength trained three days a week. Blood triglyceride levels were measured in the morning after consumption of a high fat breakfast (55 grams of fat, 149 grams of carbohydrate, 22 grams of protein).
Results: After nine weeks, body weight increased, muscle mass increased, and three rep max (3RM) for bench press increased, but no changes were seen in body fat levels. More importantly, no positive change was seen in fasting blood cholesterol or TG levels, and PPL didn't improve. This indicates that strength training alone won't reduce risk for heart disease such as we see with aerobic exercise.
At first glance, this sure doesn't look good for resistance-trained athletes, but keep in mind that blood samples weren't taken immediately after the workout such as in the previous studies. The blood was taken the next morning after the workout program and we can't make a direct comparison between this study and the ones conducted with aerobic exercise. This study also didn't compare TG levels after eating a high fat versus a low fat meal to see if there was a difference between treatments.
Good things noted from this study were that nine weeks of strength training did increase body weight, muscle mass and 3RM, which is great news for those hardgainers out there. But in order to prevent heart disease, it appears that cardio is still number one. (8)
EFFECTS OF CONTINUOUS AND INTERMITTENT EXERCISE ON POSTPRANDIAL LIPEMIA
What type of aerobic exercise will decrease PPL more? Is it long continuous cardio (jogging on a treadmill for 30 minutes at 60% VO2) or intermittent training (three separate bouts of running at the same intensity for ten minutes each with 20 minutes rest between each)?
The study: Three sedentary men and nine women performed each type of exercise and then ate a high-fat meal (HFM) containing 1.5g fat (88% of calories), 0.05g pro, and 0.4g CHO per kg body weight. The results: Each aerobic exercise protocol burned the same total amount of calories, the same amount of body fat, and the same amount of glycogen. However, intermittent exercise was better for reducing PPL after the high fat meal.
This is good news for sedentary persons and those of us who hate doing long boring cardio. We can still burn the same amount of calories and fat by exercising for three separate ten minute periods as doing 30 minutes of cardio straight. Plus, intermittent cardio will improve our cardiovascular health even more.
Summary: Intermittent cardio will burn just as many calories and fat as continuous cardio of the same intensity and it's far superior for clearing blood triglycerides after a fatty meal. (9)
RELATIONSHIP BETWEEN POSTPRANDIAL LIPEMIA AND LDL PARTICLE SIZE DURING A KETOGENIC DIET IN MEN
Ah, the moment you've all been waiting for: ketogenic diets. What topic of fat metabolism would be complete without it?
In this study, Dr. Jeff Volek's research group looked at how a ketogenic diet could improve PPL and blood cholesterol levels. Rationale: Small-dense LDL cholesterol particles are associated with a three times greater risk for CVD in men, which is believed to result from poor PPL. This group hypothesized that reducing PPL with a ketogenic diet would increase LDL particle size and decrease CVD risk.
The study: Twenty-five healthy men ate a low calorie, low carbohydrate, ketogenic diet for six weeks. After the diet treatment, fasting blood triglyceride levels, insulin, body fat and PPL were greatly reduced. As hypothesized, the improvement in PPL resulted in larger LDL particles.
This study shows that low carbohydrate diets will improve blood lipids (TG and LDL), reduce fasting levels of insulin, and decrease PPL in healthy men. Plus, these diets are awesome for shedding ugly body fat! (10)
LOW CARBOHYDRATE DIET INDUCES WEIGHT LOSS AND CHANGES IN FUEL OXIDATION DURING EXERCISE IN OBESE ADULTS
Again, low carb/high protein diets are claimed to be the best for weight loss, but some researchers believe the weight loss is due primarily to glycogen depletion and water loss and not necessarily fat. This study examined this theory in obese men and women.
The diets provided were lower in calories than subjects' habitual intake (~1500 kcals/day), lower in carbohydrates (~0.3 g/kg day), higher in protein (1.7 g/kg day), but had the same amount of fat (1.3 g/kg day). After two weeks of dieting, both men and women lost significant body weight and fat mass. The men lost more total body weight, which turned out to be mostly a loss of lean muscle mass, whereas the women didn't lose any lean mass.
During exercise and at rest, the diets resulted in less carbohydrate and more fat to be burned for energy. Overall, body weight and fat lost by both men and women appears to be from the caloric deficit of the diets and increased fat oxidation during exercise. In men, the lean mass loss was believed to be a result of increased glycogen and water loss and enhanced gluconeogenesis from muscle protein.
Once again, low carb diets are excellent for weight loss, and the weight loss is a result of fat loss and not just glycogen and water. During exercise, more fat was burned likely as an attempt to spare muscle glycogen. The fact that men lost some lean mass is a little scary, but understandable. Since men have more lean mass and less fat mass than women to begin with, they'd need to use some muscle protein to create glucose (via gluconeogenesis).
Overall, if you want to lose fat and body weight in a short period of time, a low calorie, low carbohydrate diet is the crème de la crème. (11)
ENHANCED FATTY ACID OXIDATION IS ASSOCIATED WITH IMPROVEMENTS IN INSULIN SENSITIVITY IN OBESE SUBJECTS
One of the consequences of obesity and physical inactivity (can we say couch potato?) is insulin resistance (IR), which then further leads to diabetes and other chronic diseases. IR also causes a decrease in fat oxidation, which may explain why obese people have a harder time losing body fat.
This study determined if a program of exercise and diet to induce weight loss would increase fat oxidation and improve IR in obese men and women. Subjects walked or biked for 30 to 50 minutes, five days a week, reduced their caloric intake by ~500 kcals a day, and ate <30% fat. After four months, both men and women lost significant fat mass and improved their VO2 max. Insulin sensitivity was increased and more fat was oxidized throughout the day.
Diet and exercise with concurrent weight loss will decrease body fat and reduce insulin resistance. The increase in insulin sensitivity does appear to improve the body's ability to burn fat, which then further enhances weight loss. The health benefits of diet and exercise are greater than just weight loss. The two methods combined will help improve insulin sensitivity and increase your fat burning potential. (12)
FAT OXIDATION DURING EXERCISE HAS STRONGER LINKS TO PHYSICAL ACTIVITY AND VO2 MAX THAN BODY FAT
Does your ability to burn fat depend on the amount of fat you have on your body? And at what exercise intensity is fat oxidation maximized? This study showed that the maximum fat burning (oxidation) in men and women during exercise was strongly linked to physical fitness level and physical activity intensity (VO2 max).
The study: 300 volunteers (157 males, 143 females) all performed an incremental treadmill test to exhaustion. Researchers measured the exercise intensity (VO2 max) that elicited maximal fat oxidation (FATmax).
Results: The average exercise intensity for FATmax occurred at 61.5 +/- 0.6 %Hrmax, which is equivalent to 48.3 +/- 0.9 %VO2 max. Females demonstrated a higher rate of maximal fat oxidation than males during exercise. Also of note, females reached the MFO point at a slightly higher exercise intensity than males. MFO increased as lean mass, body weight and level of physical fitness increased, but it wasn't related to amount of fat mass.
It's true! If you want to burn mostly fat during cardio, you should train at a moderate intensity rather than working extremely hard. Additionally, your ability to burn fat will improve as your lean body mass, weight and fitness level increase!
Women have to attain a slightly higher heart rate than men to burn maximum fat, but as a result, their rate of fat oxidation is also higher. Higher levels of body fat don't explain this phenomenon, as fatness wasn't related to maximum fat oxidation. So, it appears there's a gender difference in rates of fat oxidation during exercise. When women are compared to men with the same lean body mass, body weight, and level of physical fitness, they can achieve a higher rate of fat oxidation.
Even if men work out more intensely, most of them still won't have the same fat oxidation rate as women. However, it's important to note it's well established that in order to expend more energy both during and after a workout and produce a greater overall calorie deficit to lose body fat, higher intensity interval training (HIIT) will give you more bang for your buck. Just for the record, though, if you're a man and you only want to burn more fat during exercise, you might want to consider getting a sex change... (13)
IRON DEFICIENCY AND ANEMIA
Two studies looked at iron deficiency (ID) and anemia. ID is the most common nutritional deficiency in the world. It can result in anemia when it causes reduced hemoglobin concentrations. ID is more common among women and, although the effect of ID on physical performance is debated, there's no doubt about the effect of anemia on maximal aerobic performance.
The first study looked at male and female junior athletes (16-19 years old). Results: ID was found in 55% of the woman and 11% of the men. Only 3% of the total population had anemia. Conclusion: These findings suggest that ID is common in elite female high school athletes, but males are also affected. The explanations for ID in this group of athletes might be a combination of inadequate dietary intake in both sexes and primarily losses by menstruation for women. Subjects with ID and anemia should be treated by iron supplementation, which is an effective treatment. (14)
In the second study, investigators looked specifically at the prevalence of iron deficiency and anemia among male and female top-level basketball players. Results: Iron deficiency was found among 22% of study participants (15% in males vs. 35% in females). Anemia was found among 25% of athletes (18% in males vs. 38% in females). Iron deficiency anemia, defined as both iron deficiency and anemia in the same subject, was found among 11% of players (5% in males vs. 22% in females). These deficiencies can unnecessarily affect athletic performance, but they shouldn't since they can easily be prevented with proper diet and supplementation. (15)
Since iron deficiency is common in both male and female elite athletes, special attention should be paid to their diets. Two sources of dietary iron exist. HEME iron is found only in meat (beef, pork, lamb), fish and poultry and is absorbed much more easily than non-HEME iron which is found primarily in fruits (dried raisins and apricots), dark green leafy vegetables, dried beans, nuts (peanuts and almonds, pumpkin seeds), and grain products.
To increase absorption of iron, include vitamin-C rich foods with meals. Some foods rich in vitamin C are bell peppers, oranges, grapefruit, berries, kiwis, tomatoes, cauliflower, broccoli, and 100% juices with vitamin C added. Avoid excess consumption of high fiber foods or bran supplements because the phytates in such foods inhibit absorption. And finally, don't drink large amounts of tea or coffee with a meal because polyphenols in these drinks lower the amount of non-HEME iron the body can absorb.
Part 3 – Girl Stuff
What differences (if any) are there between the sexes? Do women recover from strength training better than men? Should women train differently? Let's see what the latest research tells us.
GENDER DIFFERENCES IN CENTRAL AND PERIPHERAL FACTORS OF SKELETAL MUSCLE FATIGUE
Typically, women are less prone to fatigue during weight training than men due in part to the differences in muscle mass. Lower amounts of muscle seen in most women require less oxygen and use oxygen faster at the same workload as men. This equates to higher endurance during strength training (and perhaps more stamina during other activities, like a good romp in the sack!).
However, what happens when you compare women and men with the same amount of muscle mass? Does this observation still stand? The study: During a leg extension exercise protocol, women were matched with men with the same amount of lean muscle mass. The results showed that women were no longer more resistant to fatigue, and interestingly, the men weren't any stronger.
So really, there's no gender difference in muscle oxygen demand and use, and therefore, no difference in resistance to fatigue. Women's muscle is the same quality as men's and demands the same requirements–at least in the leg extensors.
Also, there are no differences in strength when you compare women and men with the same amount of muscle. Since most women tend to have less muscle than men, guys who want a great workout partner should hook up with the T-vixen hottie in the gym or get their girlfriends or wives to train with them. A female training "buddy" would keep his stamina up in more ways than one! (16)
CFOS MRNA EXPRESSION IN SKELETAL MUSCLE AFTER EXERCISE DEPENDS ON THE PHASE OF THE MENSTRUAL CYCLE IN FEMALE ATHLETES
Although the title of this study may sound a little too "nerdy" for most T-people, don't turn away just yet. Have you ever heard a woman say she didn't feel as strong during certain "times of the month" as she did during others? I know, I know, some women turn into super bitches just before they have their periods. Those are the times when you T-men know to just stay very far away until she morphs back into her normal self (whatever that may be).
Well, also during this time you may notice she's not as powerful in the gym as she normally is, and she lacks the energy to perform her normal training program. She might try to blame it on cramps or some other female term that you'd rather not hear about, but interestingly there appears to be a gene-mediated mechanism behind her complaints.
The purpose of this study was to measure the concentration of cFOS gene and certain hormonal receptors in female athletes after one hour of endurance or power exercise during the first and last part of their menstrual cycles. cFOS is a gene believed to be involved in the regulation and expression of a variety of other proteins in the muscle, and therefore would have an impact on muscular strength and power.
In this study, females performed an endurance exercise test (cycling one hour at 70% of their VO2max) and a series of maximal power exercise bouts (one hour total) in the follicular phase (day 4-5) and the luteal phase (day 20-21) of their cycles. Muscle biopsies were taken and the mRNA expression of cFOS and of estrogen (ER), progesterone (PR), and androgen (AR) receptors were determined.
Results: There were no differences in expression of ER, PR, and AR between each exercise test and during different phases of the menstrual cycle. However, cFOS gene expression was increased in response to exercise and it was amplified more in the follicular phase.
Conclusion: These results demonstrate (for the first time) cycle dependent differences in the responsibility of a skeletal muscle gene to exercise. cFOS as a transcription factor may be involved in the regulation of the expression of a variety of other muscle genes responsible for differences in a phase dependent trainability in female athletes.
Finally, scientific proof that there's a decline in a woman's strength during certain times of the month! Higher levels of cFOS after training during the follicular phase would help skeletal muscle to recover quicker and may aid in growth of muscle protein. This gene would enable a woman to train harder because her muscles would be more anabolic.
It was interesting to see that hormonal receptors like ER and AR weren't altered in response to exercise and they didn't change throughout the menstrual cycle.
In summary, the best time for a woman to train intensely would be a few days after her period. This is an aspect that trainers and athletes can utilize to structure their training programs. A woman would be encouraged to lift heavier in the follicular phase and go lighter during the luteal phase.
So T-men, have a little sympathy for your favorite vixen. PMS has a new meaning. It now stands for "Piss-poor Muscular Strength," which would make any T-vixen bitchy! (17)
CONTINUOUS VS FRACTIONALIZED EXERCISE ON CALORIC EXPENDITURE IN NON-OBESE AND OBESE FEMALES.
The study by Altena et al showed us that continuous and intermittent (fractionalized) aerobic exercise burned the same total amount of calories in men and women. The following study is specific to women and looks at differences in caloric expenditure in these two types of exercise and whether obesity affects the total amount of calories burned.
The study: Eight obese and non-obese young women performed either 30 minutes of continuous exercise, 3 x 10 minute sessions of intermittent exercise, or no exercise at all (control group). Caloric expenditure of total energy, fat, and carbohydrate were measured after each protocol and after eating a meal (post-prandial caloric expenditure).
Results: There were no differences in total calories burned between the two exercise sessions, and more calories were burned with exercise than after no exercise whatsoever. Non-obese women burned more total calories and more carbohydrate than obese women during exercise but there were no differences in fat oxidation between either of the exercise groups. After a post-workout meal, there was no increase in caloric expenditure compared to sedentary post-prandial caloric expenditure.
Conclusion: Contrary to previous findings in men, women utilize less fat and more carbohydrate during exercise, and prior exercise doesn't affect post-prandial caloric expenditure.
Once again, equal calories are burned during 30 minutes of continuous and fractionalized cardio at the same exercise intensity. So, if you find it difficult to do 30 minutes of cardio (or any cardio at all for that matter), you can do three separate ten minute sessions any way you want and you'll burn the same amount of calories (assuming you're working at the same intensity overall).
Also, two studies appear to contradict previous findings. First, as suggested by Katsiaras et al, while obese women did oxidize less energy and carbohydrate than non-obese women, they didn't appear to burn less fat, at least during an exercise session, since fat oxidation at rest wasn't measured.
The second contradiction is with the work of Venables et al. The current study in question noted that women burned less fat and more carbs than men during training, and exercise didn't enhance metabolism after a meal. Venables et al., on the other hand, demonstrated the opposite: females had higher fat oxidation rates compared to males.
These opposing results may be explained by differences in exercise intensity, and the fact that subjects exercised to exhaustion in the study by Venables et al. Also, the small sample size in this study could've influenced the results. To date, there's no clear consensus on whether there's a gender difference in substrate utilization during exercise; some studies find that women burn more fat and less carbs, whereas others find the opposite. Maybe you men should reconsider that sex change after all!
The bottom line is that if you want to lose any body fat at all, regardless of your gender, you need to be consistent with your workouts and stop bingeing on donuts and pop! (18)
1) N.E. Kimber, G.J.F. Heigenhauser, FACSM, L.L. Spriet, FACSM, D.J. Dyck. University of Guelph, Guelph and McMaster University, Hamilton, ON CANADA
2) Y.Nakagawa, M.Hattori, K.Harada, R.Shirase, H.Ohmoto, M.Bando, G.Okano Otaru University, Hokkaido Tokai University and Sapporo Medical University, Hokkaido, Japan
3) L.J.C. van Loon, V.B. Schrauwen-Hinderling, R. Koopman, M.E. Kooi and W.H.M. Saris. Nutrition Research Institute Maastricht (NUTRIM), Maastricht University, Department of Radiology, University Hospital Maastricht, The Netherlands. (Sponsor: Harm . Kuipers, FACSM)
4) AE Kaufman, AK Fox, JF Horowitz Division of Kinesiology, The University of Michigan, Ann Arbor, MI
5) K.J. Bosher, K.A. Shannon, P.E. Luebbers, R.M. Shannon, C. Gennings, and J.A. Potteiger, FACSM Virginia Commonwealth University, Richmond Virginia (Sponsor: Dennis J. Jacobsen, FACSM)
6) T.R.Thomas, O.M.Donahue, B.K.Smith, G.Y.Sun, M.James-Kracke University of Missouri, Columbia, MO Sponsor: Thomas P. LaFontaine, FACSM
7) B.K. Smith, G.Y. Sun, T.R. Thomas. University of Missouri, Columbia, MO. (Sponsor: D.J. Jacobsen, FACSM)
8) J.R. Grantham, M.J. Mayo, G. Balasekaran Physical Education and Sports Sciences, National Institute of Education, Nanyang Technological University, Singapore
9) T.S Altena, T.R.Thomas, J.L. Michaelson. University of Missouri-Columbia, Columbia, MO (Sponsor: Thomas P. LaFontaine, FACSM)
10) J.S. Volek, M.J. Sharman, A.L. Gómez, D.N. French, M.R. Rubin, C. DiPasquale, G. Watson, B. Sökmen, M. Roti, A. Pumerantz, and W.J. FACSM, FACSM University of Connecticut, Storrs, CT (Sponsor: William J. Kraemer, FACSM)
11) J.I. Komorowski, G. Schuler, J. Murrin, M. Farnoush, E. Doucet, J. Kerr University of Ottawa, Ottawa, ON, Canada
12) A. Katsiaras, B. Goodpaster, C. Kelley, A. Matthews, J. Mancino, P. Harper, D. Kelley. University of Pittsburgh, Pittsburgh, PA.
13) M.C.Venables, J.Achten, C.Ring and A.E.Jeukendrup, FACSM. Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UNITED KINGDOM
14) G.Landahl, M.Börjesson,S.Rödjer Sahlgrenska University Hospital/Östra, Sweden
15) N.W. Constantini, FACSM, G. Dubnov Ribstein Center for Sport Medicine Sciences and Research, Wingate Institute, Netanya, Israe
16) S.A.Gore, B.A.Keller, J.C.Ives Ithaca College, Ithaca, NY
17) P. Platen, A. Käferstein, S. Braun, L. Hoffmanns, D. Schiffmann, P. Diel Institute of Cardiology and Sports Medicine, German Sport University, Cologne, Germany
18) D. Watson-Winfield, K. Frick, J. Weltman, J. Patrie, S.M. Anderson, J.D. Veldhuis, G.A. Gaesser (FACSM), A. Weltman (FACSM) University of Virginia, Charlottesville, VA.