Don T. Kirkendall, Ph.D. –
Exercise Physiologist, Duke University
It is common knowledge that high-intensity or prolonged physical activity of any kind can cause muscle damage. However, for the long-time mature resistance training individual, in addition to the above comments above, another catabolic process is slowly and silently gaining momentum with each passing year called, sarcopenia. Sarcopenia is characterized by a substantial decline in both the amount and quality of muscle mass. Overall, according to a 1993 study published in Exercise and Sport Sciences Reviews, over time muscle mass decreases almost 40% and strength by 30% compared to performance at age 20. Naturally human muscle tissue consist of about a 50/50% mixture (give or take) of both slow and fast twitch muscle fibers that most of the muscles use for movement. Unfortunately, loss of muscle mass and strength is partially due to a significant decline in the numbers of both Type I and Type II muscle fibers, plus a decrease in the size of muscle cells. However, type II muscle fiber deterioration appears to decline at a faster rate. As you recall, Type I or slow twitch fibers are regarded as the weaker or low force power based fibers that sustain energy longer. Conversely, Type II fibers are the power based muscle fibers that are built for short power based movements, but tire quickly. Due to this reduction in the number of muscle fibers, over time the ability of existing muscle fibers to contract efficiently can be compromised, as well as the physiological processes that trigger and facilitate muscular movement as cited by in the above comments concerning the glycolytic and aerobic enzymes. As a note here, glycolytic enzymes breakdown glucose which the muscles uses for fuel.
Aerobic enzymes include systems in the cell's mitochondria, which oxygen utilizes to form the cellular energy molecule called ATP, short for adenosine-tri-phosphate. Unfortunately, declining reformulation of ATP in aging muscle has been definitively linked to declining muscle performance.
Mechanical Disruptions in Aging Muscle: Based on cross-sectional and short-term prospective studies conducted by researchers of the Department of Physical Medicine and Rehabilitation at Harvard Medical School and the Nutrition, Exercise Physiology, and Sarcopenia Laboratory at Tufts University, there are several potential physiological mechanisms that cause muscle strength decline in aging muscle. They include impaired neuromuscular function, hormonal changes, increased inflammation, poor nutritional status, various chronic conditions, and decreased physical activity. On the other hand in a recent study appearing in The FASEB Journal, Dr. Donato A. Rivas and colleagues at Tufts University remind us that in order for the body to make proteins that build muscle, certain genes need to be turned on. These researchers found that the level of microRNAs, small RNA molecules that have a prominent role in regulating genes, was lower in the muscle tissue of older men compared to younger men. They concluded that the possible suppression of these microRNAs sets off a chain of events that cause mature individuals to be less efficient in developing muscle.
Mature and Young Muscle Adapt Similarly: As cited above by Dr. Don T. Kirkendall of Duke University neither reduced muscle demand nor the subsequent loss of function is inevitable with aging. He states that progressive resistive training in older individuals results in muscle hypertrophy (increase in size of skeletal muscle) and increased strength, if the training stimulus is of a sufficient intensity and duration. He also argues that since older individuals adapt to resistive and endurance exercise training in a similar fashion to younger counterparts, the decline in the muscle's metabolic and force-producing capacity can no longer be considered an inevitable consequence of the aging process. Paradoxically, although strength training and exercising can help minimize the natural catabolic consequences of sarcopenia, post-exercise pain and loss of strength tend to last much longer for the aging resistance training individual or fitness enthusiast. Consequently, the goal of this report is to take a look at some of the ways that mature resistance training individuals can minimize this double catabolic anomaly, naturally occurring aged muscle wasting and exercise induced muscle catabolism.
When Aging Muscle Is Slow to Respond--Strength Training and Exercise: Based on what we have learned thus far, exercise and resistance training appears to be the key to down-regulating age-related loss of muscle mass and strength. In fact, researchers at the Department of Human Movement Sciences at Maastricht University, recently reported that emerging evidence shows that resistance type exercise training increases type II muscle fiber size and reverses the age-related decline in skeletal muscle satellite cell content. As a note here, repair of adult skeletal muscle depends on satellite cells that are considered to be the chief contributors to regenerative myogenesis (the formation of muscular tissue) following muscle injury. These researchers also noted that prolonged resistance type training in mature individuals increased type II muscle fiber size by 24 ± 8%. Additionally, researchers at Duke University remind us that endurance training can improve the aerobic capacity of muscle, while resistance training on the other hand improves central nervous system recruitment of muscle and increases muscle mass. As you know, the central nervous system regulates transmission of impulses to your muscles which contribute to muscular power and output capacity. Furthermore, physical activity has an impact on insulin growth factor (IGF-1) levels in the body. Studies have shown that a one week period of strenuous exercise raises IGF-1 blood levels significantly, however, when your workouts decline, so does your IGF-1 levels. Moreover, current data indicates that when HGH and IGF-1 levels remain stable, physiologically, growth hormone (GH) triggers IGF-1 and the more GH present in the body, the more IGF-1 present in the body.
Correspondingly, this is why not only sports medicine researchers but healthcare professionals insist that physical activity throughout life prevents and can reverse much of the age-related catabolic aspects of sarcopenia and its impact on skeletal muscle.
Cortisol Reduction: Cortisol is known as the stress or muscle wasting hormone begins to elevate as a response to all types of trauma, physical and or emotional. However, the most common stressor to bodybuilders and fitness enthusiast is that of exercise. To counter exercise induced elevation of cortisol at post-workout consuming 40-50g of protein coupled with 50-70g of simple carbs causes insulin to spike which helps clear elevated cortisol levels. Consume 6 to 8 smaller meals daily, also helps reduce cortisol. Additionally, supplements like Branch Chain Amino Acids (BCAA’s), Creatine, Magnesium, Vitamin C, Vitamin D3, and Zinc help balance and or reduce elevated cortisol levels.
Creatine and Mature Muscle: Studies have confirmed that creatine in mature individuals, as in younger persons can increase the short-term capacity to perform quick repeated bouts of intense activity. For instance, researchers at the Department of Health and Exercise Science at the University of Oklahoma recently reported that 14 days of creatine supplementation increased upper body grip strength (+6.7%) and increased physical working capacity (+15.6% ) by delaying neuromuscular fatigue in mature men and women. Similarly researchers at McMaster University in Canada followed mature subjects participating in a whole-body resistance exercise routine 3 days per week for 14 weeks with one group receiving 5 g/d of creatine plus 2 g of dextrose while the placebo group received 7 g of dextrose only. Fourteen weeks of training resulted in significant increases in all measurements of strength, functional tasks, and muscle fiber area in both groups. However, the creatine group experienced significantly greater increases in fat-free muscle mass, isometric knee extension strength, isometric dorsiflexion (ankle) strength, and intramuscular creatine levels. As you know an isometric muscle contraction is one in which the muscle fires but there is no movement at a joint. Furthermore, creatine increases cellular hydration and myogenic transcription factors which speed-up the activity of muscle specific-genes such as myosin which can turn on genes which accelerate muscle hypertrophy (an increase in size of skeletal muscle).
Lastly here, researchers at the University of Saskatchewan in Canada recently discovered that creatine’s positive effects on strength and lean tissue development in older adults continued for at least 12 weeks after they discontinued its use. Uniquely here, withdrawal from creatine had no effect on the rate of strength, endurance, and loss of lean tissue mass during12 weeks of reduced-volume training.
Hormone Production: It is common knowledge that hormone production begins to decline as we age. The fact is, most men lose about 10% of their innate testosterone levels a decade and GH can decline by 50% every seven years after the ages of 18 to 25. However, maintaining the activity of various anabolic hormones like IGF-1, GH and testosterone is critical to your continued success as they assist in driving the anabolic continuum. Fortunately, physical activity has a positive impact on IGF-1, GH and testosterone production. As stated earlier physiologically, GH triggers IGF-1 and the more GH present in the body, the more elevated IGF-1 remains. As you know GH is also released at a greater rate during sleep. Lastly here, anti-aging researchers now know that the stability of these two hormones extends the life expectancy.
Maintaining Hormone Production and Activity: Based on current knowledge researchers have established some guidelines to help maintain levels of these anabolic hormones. For example, besides the continuation of strength training, get enough sleep, and avoid late night snacking, especially sugary packed snacks, as well as simple carbs. This practice will spike your insulin levels, which can restrict your body’s production of GH because insulin and GH can’t coexist in your body at high levels at the same time. Also, researchers suggest reducing your alcohol intake substantially, as studies indicate that alcohol suppresses the activity of enzymes that assist in the breakdown of testosterone, as well as interfere with the production of IGF-1/GH and decreases protein synthesis. Additionally, there are a number of nutritional supplements that can help you in your efforts to maintain stable levels of these hormonal anabolic activators. They are: alpha-GPC (alpha-glycerylphosphorylcholine-GH production), citrulline (GH release) , D-Aspartic acid (testosterone), glutamine (GH), L-arginine L-ornithine and L-Lysine(GH), and Vitamin D ( testosterone).
Protein: it is a well established fact that committed athletes need more protein than the RDI of protein 0.8 grams per kg bodyweight per day. Studies indicate that this amount results in establishing a negative nitrogen balance, which is a condition in which protein catabolism (breakdown) exceeds protein anabolism (synthesis) resulting in tissues losing protein. For this reason researchers maintain that mature athletes as per their younger counterparts, should consuming 1.2–1.4 g/kg/day of protein if they are endurance athletes and resistance training individuals should shoot for 1.7 to 1.9 grams per kg bodyweight per day. According to researchers at the University of Arkansas although the mechanisms of action aren’t fully understood, intakes of protein at 1.6/kg/day appears to up-regulate RNA synthesis accompanied by increased protein synthesis.
Rest and Recuperation: The hallmark of any sound resistance training program is planned cycles of rest recuperation and 8hrs of sound sleep. A case in point, current data indicates that it can take up to 72hrs or more to fully recover from a workout. Many researchers even suggest that a full week of rest between working each muscle group is needed to realize full recovery. Additionally, it can also take up to 7-14 days for the neuro - muscular system (the muscles of the body together with the nerves supplying them) to fully recover from an intense strength training session. For this reason well-known exercise physiologist like Jim Stoppani Ph.D. recommends split training. The one advantage you have as a mature trainer, especially if you have been committed to your craft, your body has adapted to the training. However, split training allows you more recovery time in-between working various muscle groups. According to Dr. Stoppani some pro bodybuilders train only one major muscle group each workout.
Last Words: Aging muscle appears to recover at a slower pace than younger muscle tissue. However data clearly shows that aging muscle adapts to resistance training a manner similar to its younger counterparts. The key to sustaining this physiological attribute appears to be proper training guidelines versus over-training, as well as the right combination of nutrients and supplements to assist in maintaining your muscle's growth potential.
About the Author: George L. Redmon, Ph.D.
Dr. Redmon has been associated with the vitamin and health industry for over 25years, having served as The National Product and Education Director for one of the country’s largest retailers of nutritional supplements. He has been widely published in many major bodybuilding, fitness and alternative medicine publications. He is the author of Natural Born Fat Burners, Managing and Preventing Arthritis: The Natural Alternatives, Energy for Life and is a member of The National Academy of Sports Medicine and The International Society of Sports Nutrition.
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