Scientific Training
Well, I finally sacked up and incorporated high-intensity interval training (HIIT) into my fat loss arsenal, and, man, it's taken my progress to the next level! I do have one question, though. I've heard from other "sources" that doing some low-intensity aerobic exercise after HIIT is beneficial for fat loss. Is this for real, or just another scam? First off, I'm glad that you;ve ventured out of the "fat-burning zone" and into some real quality of training. That's what it's all about anyway. Ever wonder why hardly anyone else is doing intervals (high-intensity intervals, anyway)? Because it hurts! That's why. Intervals may hurt, but they produce results...rapidly. So, let those low-intensity advocates have at it for hours on end. Back to your question. I've seen evidence to support the recommendation that some low-intensity aerobic work may be beneficial for fat loss following a bout of high-intensity exercise. Romijn et al. (1993) found that the rate of appearance (Ra) of free fatty acids (FFA) and plasma FFA concentrations increased abruptly with the cessation of exercise at 85% VO2max (i.e. 90-95% maxHR). This is interesting because of the fact that plasma FFA concentrations are relatively low during this intensity of exercise, and as such, are not a significant source of energy during HIIT or the like. But, most of us know that the actual source of fuel during exercise isn't necessarily the most important factor to consider. During high-intensity exercise, the body's cardiac output (i.e. blood flow) is redirected such that a very high percentage of it is going to the active musculature. Obviously, increased metabolism demands increased blood flow. In this very case, there is less blood flow to the adipose tissue (i.e. fat tissue) and, even though the rates of lipolysis may not slow down, the release of fatty acids into the bloodstream is blunted. Upon cessation of high-intensity exercise, blood flow is redistributed throughout the body, and those fatty acids that were essentially "trapped" in the adipose tissue are now free to roam in the plasma as FFA. Depending on the duration of your high-intensity bout of exercise, you may very well have returned your body to a hormonal environment mimicking the fasted state. Add on top of that the above-mentioned abrupt increase in plasma FFA and the elevated concentration of catecholamines from the intense exercise, and you are now the happy owner of a first-rate fat-burning furnace! Putting this aforementioned physiology into practice, if fat loss is your primary goal--and especially as you get into the final stages of shedding those last few pounds--I suggest that you incorporate 15 minutes (or more) of low-intensity aerobic exercise after your high-intensity exercise. Spinning at a relatively low wattage on the bicycle or walking at an incline or brisk pace are solid examples. Romijn et al. Regulation of endogenous fat and carbohydrate metabolismin relation to exercise intensity. Am J Physiol 265 (Edoncrinol. Metab. 28): E380-E391; 1993. -TS A trainer buddy of mine recently told me that cutting sodium way down while dieting will increase fat loss and/or too much sodium while dieting will inhibit fat loss. His contention was that too much sodium (although he did not mention how much) would cause water retention which then "protects" the fat. While I am well aware that sodium causes water retention, I have never heard of it inhibiting fat loss. Is there any truth behind this? First let me address a statement that you made in the latter part of your question. You say that you are "well aware that sodium causes water retention"- this is only partly true. You see, the hormone aldosterone acts on the kidneys to conserve sodium for bodily functions; however, when sodium is consumed in high amounts, aldosterone release is blunted and any excess sodium will simply be excreted. As a result, sodium balance remains normal. Yes, there will be some initial water retention with an increased sodium intake, but as soon as the body becomes accustomed to the higher intake, aldosterone release will be blunted and the excess water will be excreted. So, even if there was any truth (which there is not) to the statement that subcutaneous water retention "protects" fat stores and inhibits lipolysis, it wouldn't even be an issue because the water retention doesn't occur in the first place. Furthermore, it should be noted that while a high sodium intake will not have an adverse effect on lipolysis, it may actually speed your fat loss along. How so? Well, it is mostly due to the fact that adequate blood iodine concentrations are a must for sufficient release of thyroid hormone- a powerful hormone when it comes to the regulation of metabolism. Myxedema (hypothyroid syndrome/hyperthyroidism) results when iodine is chronically deficient (eventually leading to endemic goiters). Although the follicle cells of the anterior pituitary gland continue to churn out loads of colloid to attempt to increase TH (which, naturally, results from plentiful and effective TSH), this colloid is useless because the follicle cells don't have the raw materials needed to iodinate it (necessary to make TSH functional). As such, TH and, in turn, T3 and T4 output decrease appreciably. So how does this apply to our discussion? Table salt is probably the most abundant source of iodide, so adding salt to food may help keep your thyroid levels from dropping off too much during your diet. But, an even greater reason not to decrease your sodium intake while dieting is that a low sodium intake will decrease the flow of blood to muscles at work during exercise, which will undoubtedly have a detrimental effect on your performance. Conversely, a high sodium intake yields a greater overall blood volume and blood flow to the working muscles. With increased blood flow, the amount of oxygen and nutrients delivered to the working muscles is maximized. This is particularly important when an amino acid containing beverage is consumed prior to the workout, as more aminos will be delivered to the working muscles, resulting in greater rates of protein synthesis (muscle growth). Also, increased blood flow will actually increase performance in that removal of various fatigue toxins (lactic acid, CO2, etc) will occur at a faster rate. Now that you understand all the benefits (and fallacy behind certain arguments) of a high sodium intake, you may be wondering just how much sodium you should look to consume each day. Pre-contest diet guru Scott Abel has recommended in the past that trainees consume 2 grams of sodium for every liter of water they drink daily. So, if you normally consume about a gallon of water daily, that's about 8 grams of sodium that you should be taking in along with it. I have found this approach to be bang on from both my own experiences and the experiences of numerous individuals I have worked with. Good luck, and add salt! -JM with help from EC I was reading an article the other day, and the author mentioned something called the "length-tension relationship." What is it, and why is it important for an ordinary gym rat like me? You'll need to consider this from an exercise physiology and kinesiology and biomechanics perspective. Here's the Cliff's Notes version: All muscles are composed of muscle fibers, the smallest contractile element of which is the sarcomere. Actin and myosin filaments are arranged horizontally within the sarcomere. In a nutshell, myosin cross bridges attach to the actin filaments, pulling them inward in what is known as the "sliding-filament theory of muscular contraction." (Note: it really isn't this simple, so I apologize in advance to every professor that I've ever had for this synopsis). This process is repeated rapidly in order to shorten the individual muscle fiber and, in turn, the entire muscle. However, it is important to note that there is an optimal length-tension relationship. That is, when a sarcomere is too short, its force production capabilities are decreased because the actin filaments are already overlapping; there is not enough space for the myosin cross bridges to attach. Likewise, if the sarcomere is overly lengthened, the actin filaments will be too spread out; the myosin cross bridges cannot reach them. In short, a muscle is strongest when its sarcomeres are at their optimal resting length; when outside this optimal zone (resting length or slightly longer), the muscle will be unable to generate ideal force. On a larger scale, a muscle's response to chronic training (and often overuse) is to shorten. Meanwhile, its antagonist (opposite) is often left untrained altogether, and lengthens as a result of the overused muscle. A perfect example of this is the moron with the "What's your MAX BENCH?" t-shirt and rounded shoulders; he only benches, but never does any rows. As such, his pectoralis major, anterior deltoid, and subscapularis are somewhat strong (due to hypertrophy and increased CNS efficiency from all the practice), but still not as strong as they could be (due to shortening of the pecs and the resulting undesirable length-tension relationship). Meanwhile, several important antagonists in this instance--rhomboid major and minor, the mid and lower trapezius, posterior deltoid, infraspinatus, and teres minor--are overly lengthened and very weak (also known as inhibited). Please note that I don't include the latissimus dorsi or teres major in this example because they are serve as both synergists and antagonists to the pectoralis major, anterior deltoid, and subscapularis in this instance. Besides being at chronic mechanical disadvantages, when muscles become overly lengthened or shortened, the risk of injuries greatly increases. Likewise, faulty movement patterns develop as a compensatory response to try to overcome the weakness of certain muscles. Certainly, posture plays a crucial role in the cause and manifestation of these less than optimal length-tension relationships. Generally speaking, there are four sure-fire ways to alleviate such problems (or avoid them in the first place): 1. Don't just train what you can see. 2. If you train a muscle a lot, consider reducing your volume while simultaneously making an effort to stretch it frequently. 3. Watch your posture. 4. Train the stabilizers. -EC |