It used to be that the popular bodybuilding magazines were full of training routines used by the "Pros". I remember anxiously, if not naively, awaiting each new issue in hopes that I might find the secret exercise that would give me the physique I was dreaming of. There was an endless array of different exercises, each promising to give me biceps as tall as Arnold's or quads as monstrous as Tom Platz's. Train as I might, at the ripe old age of eight, there was nothing monstrous about me or my muscles. Over the last 21 years I have tried every exercise and routine that has found its way to print. Some of them have worked, at least for a time, and some of them haven't.
Now days all you will find in the bodybuilding magazines are reviews of the latest professional contest and adds for overpriced nutritional supplements. Of course these "ads" are very wordy as if to presume they are actually articles written by unbiased authors. The level of integrity has fallen dramatically in order to bow low enough before the mighty dollar.
This emphasis on sensationalism and commercialism has taken a toll on the informative content of these publications, even to the extent of preventing many good authors from publishing more informative yet less commercially viable material. In this new environment of "Low molecular weight peptides", natural "growth hormone releasers", designer European steroids, and adrenal androgens going by the name of "prohormones" it is easy to give inadequate attention to ones training. Over the last several years, science, rather than idol worship, has directed my training efforts. Approaching my training planning from a more scientific approach has allowed me to train more efficiently and to avoid nagging injuries that so easily best me in years past.
There seems to be an assumption that the process of bodybuilding is so simple that only beginners would have a question about the proper way to train for inducing muscular hypertrophy and strength. If you have ever been in a gym where bodybuilders train, you can feel the air so thick with machismo. It is this intimidating environment that keeps people, new at weight training, from asking questions about proper methods of developing mass and strength. People are then left to imitate those people who, they assume, know what they are doing. More often than not, it is the blind leading the blind. As a result, there are very few bodybuilders who train according to scientific principles. The overwhelming majority of these misguided bodybuilders struggle endlessly to get over needlessly premature plateaus in physique development because of this. This often leads to a premature dependence on anabolic/androgenic drugs. Hereafter we will briefly discuss the origins of resistance exercise. We will then move on to the specificity of adaptation and what effects hypertrophy can have on muscle function.
Much of the research to be discussed was done in the former Soviet Union. Because of the difficulty in obtaining access and adequate translations of this literature, I will rely heavily on the work of Yuri Verkhoshansky and Mel Siff for Eastern Block references. Dr.Yuri Verkhoshansky is probably best known here in the U.S. for his innovative training techniques involving "shock" plyometric training. He has been a researcher and professor for many years at the State Central Institute of Physical Culture in Moscow. His original techniques have been used successfully by some of the best athletes of the former Soviet Union. He has numerous scientific publications and has lectured extensively in the U.S. and other countries. He was awarded the 1988 Olympic Year gold medal for his contributions to the scientific advancement of Soviet sport.
Dr. Mel Siff is a senior lecturer in the School of Mechanical Engineering at the University of the Witwatersrand in Johannesburg, South Africa. His major areas of research are strength conditioning, biomechanics, injury rehabilitation, electrostimulation, and ergonomics. He received his Ph.D. in physiology, on a topic involving the biochemical analysis of soft tissues. He has published widely and lectured in countries including the U.S., England, Australia and Israel. He received two Meritorious Service awards for "exceptional contribution to sport" at this university, whose Sports Council passed a resolution (20/78) thanking him "for doing more for Wits (University) sport than any other individual in the history of the university".
It is probably nothing new to you that people have been exercising to increase strength and muscularity for many years. Nevertheless, it has been considered a "scientific" field of study for only a short time. At first, trial and error was the driving mechanism to increase our knowledge of the effectiveness of different training routines and stimuli. Since then modern science has contributed significantly to our understanding of muscle physiology and the process of adaptive tissue growth. It has been a very long road to where we are today.
There are references to emperors requiring strength training exercise for their subjects in Chinese texts dating back to 3,600 BC (Webster,1976). There are records of soldiers being required to pass strength tests before being admitted in to the army during the Chou dynasty (1122-249BC). The major world powers throughout history have all left evidence of weight training being utilized during their respective periods of rule. These countries include ancient Egypt and India. The ancient Indian culture valued strength to such an extent as to offer blood sacrifices to their gods during Vedic Soma festivals (Stutley,1977). This also involved drinking a ceremonial hallucinogenic liquor called vajepeya, which means, "the drink of strength". The Greeks even left illustrations of their athletes training with stone weights. I wonder if any of those rocks had "Ivanko" chiseled into them by some enterprising business man. I don't imagine paying way too much for a rock is any different than paying way too much for scrap iron. Even the mighty Heracles, or Hercules, was said to have used resistance exercise under the direction of his tutor and coach, Chiron (Forbes, 1929). The 6th century came to be known as the "age of strength" with competitions involving athletes lifting heavy stones being popular. It was in the 6th century that the famed, Milo of Crotona, military hero and six time Olympic champion (Bullfinch, 1959), first practiced a form a true "progressive resistance exercise". The ancient physician and philosopher, Galen, wrote about weight training in his treatise Preservation of Health. Galen discussed two distinct classes of exercise, one being termed "quick" which did not involve lifting weights and the other being called "violent" which did involve lifting heavy weights or "halteres" as it was termed. In 1st century Rome, the poet Martial wrote, "Why do the strong men labour with their stupid dumbbells? A far better task for men is digging a vine trench." My own grandfather has voiced the same opinion on several occasions. All I had to do was complain about being sore from my workouts to hear the seemingly memorized discourse on the virtues of manual labour and walking to school uphill both ways. In the end it can be said that the habitually organized Romans originated formal weight training (Zeigler, 1973) and with it developed one of the most feared armies in history.
As the availability of paper and print grew, so did the number of actual texts on weight training. In 1531, Sir Thomas Elyot published a book on exercise to build strength. Weight training entered academia in Europe in 1544 with universities in both Germany and France offering weight training classes along with the publication of several books at the same time recommending weight training as an essential part of a model school. The fields of physical rehabilitation began to recognize the benefits of strength training in 1728 with the publication of, A physiological, Theoretical and Practical Treatise on the Utility of Muscular Exercise for Restoring the Power to the Limbs, by John Paugh. About a century later, the British Army began a formalized training regimen involving dumbbells and barbells.
With the beginning of the twentieth century, scientists were beginning to develop a better understanding of the physiology behind adaptation to resistance exercise. As early as 1897, Morpurgo wrote that as muscles become stronger they also increase in size. He went on to insightfully explain that this increase in size was not a result of an increase in fiber number, but instead an increase in fiber hypertrophy. Later in 1927, Eyster, using dog hearts and rubber bands wrapped around their aorta's, showed that it was not the "work" done by the muscle that caused hypertrophy, but instead the resistance that induced both strength and hypertrophy. These first steps into the science of adaptive hypertrophy, set the stage for many years of research further exploring the cause and effect relationship between tension and hypertrophy.
Virtually any method of strength training will produce results in a beginning bodybuilder during the first few months. This poses a serious problem when one tries to apply results from scientific studies lasting less than at least six months in duration. The time frame for most resistance exercise studies is based on the typical length of an academic quarter or semester. After that, all of the student/subjects have a new schedule or go away for the summer. Conclusions drawn from short term training studies involving previously untrained subjects should be interpreted with caution and a discerning eye. The rapid and inevitable progress seen in beginners also perpetuates misleading information and flawed training methods used by uneducated trainers who only work with inexperienced lifters. As a bodybuilder, or any strength athlete for that matter, becomes more experienced, the inter-individual differences in training effectiveness become more apparent. With experienced lifters the exact same routine will produce different results among different people. Achieving continued growth in veteran lifters is extremely difficult and requires careful application of well thought out methods during specific phases of their training program.
When beginning weight training for the first time, it is important to understand that the increases in strength are primarily a factor of learning and coordination. An individual can even experience a neurological increase in strength within the first training session. In addition to novice lifters, exercises that are new to an experienced lifter will also produce rapid gains in strength do to neurological learning. All bodybuilders go through a series of chronological stages of adaptation:
Although an amateurish approach to training will produce significant gains in the beginner, this is not in the best interest of the beginning bodybuilder or strength athlete because without the proper sequence of training methods, injury and overuse problems can become a chronic nuisance for the individual.
At first thought I was inclined to break down this article into sections dealing only with repetitions, sets, and frequency. But as I began to really ponder what was lacking in the average bodybuilder's understanding of training, it was clear that a more esoteric approach might be more valuable. I am going to assume that most of you have already spent some time in the gym. From doing this you have experienced some gains in strength and size. Those of you interested in exaggerated muscle growth have probably even experienced a considerable number of different weight training routines. Assuming that you have had this experience I think it would be most valuable to also include those issues that are not usually included in books written about weight training. These issues include the potential for hypertrophy to cause negative effects on muscle recovery and function. A topic that most bodybuilders don't really want to hear but it can effect them nonetheless by inhibiting continual progress. Any bodybuilder or strength athlete that is interested in long term involvement in their sport must be aware of all the issues that might prevent continued progress and plan their training accordingly.
The first principle upon which all adaptation is based is "specificity". This means that the organism, or in this case "muscle", will adapt in a manner specific to the demands that are placed upon it. As an example, if you train with reps ranging from 8-10, you will become more proficient at performing sets consisting of "8-10" reps, leaving your potential to perform sets at greater or lesser work loads underdeveloped. The neurological, metabolic, and mechanical demands placed on the muscle to perform strong, repeated contractions for 30-40 seconds of total work will cause an increase in the work potential of this muscle to perform the aforementioned set. These adaptations will take place in three areas, namely: neurological; involving motor units, metabolic; involving "fuel management" within the cell and body, and structural; involving the physical structures of the muscle.
As an untrained individual begins a strength training program for the first time they will experience quite dramatic increases in muscular strength. These improvements in strength will continue almost linearly for about 8-12 weeks. The dominating mechanism of these initial strength gains are neurological in nature(Morianti,1979; Sale,1988). These adaptations take place with or without increases in muscle cross sectional area (CSA). Muscle hypertrophy usually begins after 4-6 weeks of training while the contributions of neural adaptations to increases in strength slowly diminish. Some ways that a muscle may undergo neural adaptation include cross-education, increases in electromyographic (EMG) activity, reflex potentiation, alterations in the co-contraction of antagonist muscles, and improved coordination of synergist muscles. The nature of the changes are determined by the nature of the stimulus. If you regularly allow only very slow contractions of a given muscle, that muscle will improve its ability to contract slowly, at times at the expense of its ability to contract rapidly and powerfully. If you train a muscle for endurance, it will improve its ability to use slow twitch fibers and even begin to change the contractile properties of other fibers in favor of endurance-type activity. All this due to chronic, and specific neural activity patterns.
There are three enzyme complexes that may be involved in adaptation to weight training. The phosphocreatine-ATP complex, the glycolysis/glycogenolysis complex, and the lipolysis complex. The research in this area is limited as far as direct application to bodybuilding. For our purposes only a brief discussion is required.
Phosphagens are very important in high intensity muscle activity. The energy requirements of short duration, high intensity exercise are met primarily through the recycling of ATP and phosphocreatine (PC). Despite the relative importance of this system to performance, relatively little definitive research has been done to elucidate whether this system undergoes significant adaptation. The research which exists suggests that phosphagen and related enzyme adaptations are effected specifically by the type, duration and structure of resistance training. Nevertheless, there is still no clear understanding nor consensus as to the extent of adaptation as a result of resistance training.
Cross sectional data (Tesch, 1989) support that belief that resistance training does indeed increase the activity of phosphagens. Data gathered from a cross section of bodybuilders, Olympic lifters and power lifters indicate that myokinase activity is greater in these groups than in non-trained individuals. It is not certain whether this is a result of a true training effect, sample bias, or just a genetic predisposition of elite strength athletes towards elevated myokinase activity. A subsequent study performed by the same researcher (Tesch,1990) showed no increase in enzyme activity levels in resistance trained men over twelve weeks. Clearly more research is needed before any claims can be made about ATP related adaptations to resistance exercise.
Although glycogen metabolism is important during resistance training it is usually not the limiting factor in strength production unless prior glycogen depletion is present. Increases in glycogen storage are not seen in training programs lasting less than 6 weeks (Grimby, 1973). However training programs lasting 20 weeks have shown significant increases in intramuscular glycogen storage (MacDougall,1977). Tesch (1986) recorded significantly elevated glycogen stores in a sample of bodybuilders. The results of these studies is obviously effected by acute dietary intake of carbohydrates yet evidence testifies of the ability of "chronic" resistance training to increase glycogen storage "capacity". Studies involving diabetics and resistance exercise also point out the fact that non-oxidative glucose disposal is increased with high intensity training (Eriksson,1998). These changes in glucose disposal involve hexokinase activity, phosphofructokinase (PFK) and glycogen synthase activity along with enhanced GLUT-4 activity.
It has been shown that lipids do in fact contribute fuel substrate during high intensity exercise (Essen,1990). The role of lipids may be greater during exhaustive high volume training typical of that used by bodybuilders as opposed to power lifting methods (Dudley,1988). However, changes in structures related lipid metabolism as a consequence of resistive training are difficult to discern because as the volume of the cell increases the density of mitochondria decreases. In addition, training that increases fiber hypertrophy appears to dilute endogenous lipid density within fibers.
Voluntary isometric muscle strength is related to the cross sectional area (CSA) of a muscle(Maughan1984). This is only a "correlation" however and varies with the degree of training. Long term (years) training induces significant increases in muscle mass and strength. These changes in bodybuilders are a result of increases in the CSA of fast and slow twitch fibers. However, the ratio of FT/ST hypertrophy is much greater in power lifters and Olympic lifters (Tesch, 1989). Once again, specificity is responsible for these differences. Bodybuilders often incorporated workouts with an exaggerated volume of training leading to increased slow twitch fiber participation and subsequent hypertrophy. Power lifters and Olympic lifters seldom experience muscle tension of sufficient duration to elicit such a response.
The first structural adaptation to a single bout of heavy resistance exercise is to increase the strength of the tissue itself, as opposed to an increase in the strength of contraction. In animal studies the initial signs of fiber hypertrophy could be attributed mainly to an increase in connective tissue.(Antonio,1993) This is proposed to be the explanation for the "rapid training effect" or as some researchers call it, the "repeated bout effect". This term is used to describe the fact that after an initial bout of heavy resistance exercise, no further damage is seen in the muscle tissue following subsequent bouts. The amount of delayed onset muscle soreness is greatly reduced as well. There is also an increase in the echointensity of the tissue when seen through ultrasound imaging.(Nosaka,1995) The increased echointensity is due to the fact that fibrous connective tissue is much more dense than muscle tissue. This protective effect of the initial bout is present as soon as 48 hours after the first bout.
After chronic training, increases in muscle cross sectional area (CSA) are due not only to increases in connective tissue, but also to enlargements of individual muscle fibers by an increase in the number and size of individual myofibrils (McDonagh andDavies,1984). This increase in muscle protein is dependent on the ratio of protein synthesis and protein breakdown. If you can increase the rate of proteins synthesis and/or decrease the rate of protein breakdown, you will get a net increase in the protein content of the muscle cell, effectively leading to an increase in its CSA. Two types of hypertrophy may occur (Siff and Verkhoshansky,1996): Sarcoplasmic hypertrophy and/or Sarcomere hypertrophy.
With sarcoplasmic hypertrophy the volume of non-contractile protein and semi fluid between the muscle fibers increases. Although the CSA of the muscle increases there is not a proportional increase in voluntary muscle strength. It is this type of hypertrophy that has lead to the assumption that bodybuilders are in large part (no pun intended), weaker than their Olympic lifting and power lifting counterparts.
Sarcomere hypertrophy involves an increase in the number and size of the sarcomeres which comprise the myofibrils. These are added in series and/or in parallel with the existing myofibrils. It should be noted that only parallel growth will lead to an increase in the ability to produce tension. In contrast to sarcoplasmic hypertrophy, with sarcomere hypertrophy there is an increase in myofibril density and a significantly greater ability to exert muscular strength. The type of hypertrophy that you experience from your training depends on the manner in which you train. High volume/moderate rep(8-12) training leads to more sarcoplasmic hypertrophy, while lower volume/low rep(1-6) training leads to more sarcomere hypertrophy (Nikituk and Samoilov, 1990).
I decided to include information on rational adaptation and irrational adaptation simply because it is absent in bodybuilding literature. Hypertrophy can enhance muscle function (rational) or reduce muscle function (irrational). With the development of irrational hypertrophy, the increase in volume of the muscle cell outstrips the functional ability of the vascular system. Rapid increases in the volume of a muscle cell leads to diminished nutrient and oxygen supply, slowing down the metabolic processes in the muscle and less efficient disposal of metabolic waste products from the muscle tissue (Zalessky and Burkhanov, 1981). It is not only a matter of degree of hypertrophy, but also matter of the ratio of sarcomere/sarcoplasmic hypertrophy. Another effect of irrational hypertrophy is a decreased ability of connective tissue to repair and strengthen itself. Any increase in strength made possible by increased muscle mass without adequate increases in connective tissue deposition leads inevitably to damage to tendons and ligaments (Zalessky and Burkhanov, 1981). Rapid and excessive hypertrophy usually leads to slower muscle recovery after exercise, deterioration in contractile properties as well as an increased incidence of injury.
Studies involving chickens are also furthering our understanding of muscle hypertrophy and its effects on muscle function (Soike I. and II.,1998). These researchers compared the muscle tissue characteristics of two different types of chickens, ones bred for eggs ("layer type"), and ones bred for meat ("meat type"). Meat type chickens grow significantly faster than layer type chickens and, as you would expect, are much more muscular particularly in the chest. What these studies revealed is that meat type chickens have a significantly higher proportion of glycolytic fibers in the chest than layer type chickens. The results of further fiber analysis indicate that the oxidative capacity of skeletal muscle in meat-type chickens is significantly reduced by a lower proportion of oxidative fibers. The morphometric analysis demonstrates that selective changes of fibre diameters (meat type having greatly hypertrophied fibers) additionally reduce the oxidative capacity.
Disseminated fibre degeneration and other myopathological changes occurred more frequently in muscles of meat-type chickens than in layer-type chickens of the same age (Soike I. and II.,1998). The breast region of meat-type chickens, highly developed as a breeding aim, is particularly affected. Experimental exercise protocols demonstrated the limited adaptability of skeletal muscle to training stress in meat-type chickens. Meat-type chickens showed a higher increase of histopathological muscular lesions after repeated wing exercise than layer-type chickens. Ultrastructural lesions caused by muscle activity were classified as adaptive-reversible (rational adaptation) in layer-type chickens. As opposed to this, irreversible destruction (irrational adaptation) of myofibrillar architecture in meat-type chickens are an indication of muscle ischaemia after exertion. The enhanced muscular hypertrophy and fiber type characteristics are the presumable cause of these negative effects on muscle adaptability and function. Once again the lack of sufficient oxygen supply and the inability of the muscle to cope with oxidative stress lead to serious compromises in muscle function and its ability to respond positively to exercise.
Does any of this sound familiar? Torn pecs and biceps are not all that uncommon among bodybuilders using high amounts of anabolics. One of, if not "the" top bodybuilder in the world right now may be unable to compete in the upcoming Olympia do to musculoskeletal injuries, there by handing over a hefty purse to the next eager competitor.
Now all of this might lead you to believe that I think all muscle hypertrophy is bad, not to mention the freakish muscle growth so many of us dream about. This is not necessarily the case. Hypertrophy is an adaptive response to muscle tension and activity. Most adaptive hypertrophy does offer a number of benefits. Increases in mitochondrial "surface area", which allows the cell to produce and manage ATP more efficiently, is preferable than a simple increase in the "number" of these organelles. With rapid loading, and consequent irrational hypertrophy, the size of the mitochondria continues to increase dramatically, but their number actually decreases and the concentration of ATP drops, thereby diminishing the partial volume of the contractile myofibrils (Siff and Verkhoshansky,1996). The ensuing energy deficit soon inhibits the formation of new structures and the decrease amount of ATP stimulates various destructive processes associated with decreases in the number of myofibrils. This is the very definition of irrational adaptation.
Growth of all cells is effected by the ratio of its surface area and its volume. In muscle tissue it is also related to the number of myonuclei and is often referred to as the "nuclear to cytoplasmic ratio". In muscle tissue, the surface of the fibers grows more slowly than their volume, and according to Hartwig and Mezia, this imbalance causes the fibers to disintegrate and restructure in a way that preserves their original thermodynamic state (Nikituk and Samoilov, 1990). Moderate increases in loading require less energy, facilitate cellular repair, minimize the occurrence of oxidative destruction, and lead to the synthesis of new, non-hypertrophied organelles (Siff and Verkhoshansky,1996). This type of training leads to dramatic increases in muscle performance and significant hypertrophy. This is referred to as rational adaptation.
The above information leads us to the conclusion that an over reliance on high dose anabolics and high volume "to failure" training routines may not be optimal for long term, functional muscle growth. If sarcoplasmic hypertrophy is induced too rapidly you create a self limiting environment (irrational adaptation) within the cell and stagnation, or the inability of the cell to grow further, is experienced. The proper application of periodized strength training, hypertrophic training, and in countries where anabolic steroid use is not illegal, the carefully timed application of supportive anabolics, can effectively prevent such periods of stagnation. I am not ignoring the fact that after several years of training that gains come more slowly. It should just be recognized that the reason for this is not always that your muscles have simply "adapted" to the training load. It could be that your muscles have "irrationally" adapted to your training style and new growth will not be possible unless attention is given to the oxidative capacity and myofibrillar density of the muscle. Of course there are a whole host of other possible reasons for stagnation from one individual to the next, nevertheless, when proper training methods are used in their proper sequence, identifying causes for stagnation becomes less of a guessing game and more a matter of simple inventory.
Thus far we have discussed "principles" of adaptation as they pertain to strength athletes and bodybuilders. We have not talked about the "mechanisms" that these principles are based on. In part 2 of this article we will delve further into the physiology of exercise induced muscle growth. We will then continue our discussion with ways to apply different training methods to take advantage of our new understanding of the principles and physiological mechanisms of adaptive muscle growth.
Antonio J, Gonyea W.J., (1993) Skeletal muscle fiber hyperplasia. Med. Sci. Sports Exerc. 25(12): 1333-45
Behm, D. (1995) Neuromuscular Implications and Applications of Resistance Training. J Strength and Cond Res. 9(4):264-274.
Bullfinch, T. (1959) Bullfinch's Mythology. Thomas Crowel, New York
Dudley GA (1988) Metabolic consequences of resistive-type exercise. Med Sci Sports Exerc. 20(5 Suppl):S158-S161
Eriksson, J. Aerobic endurance exercise or circuit-type resistance training for individuals with impaired glucose tolerance? Horm Metab Res 1998 Jan;30(1):37-41
Essen-Gustavsson B, Tesch PA (1990) Glycogen and triglyceride utilization in relation to muscle metabolic characteristics in men performing heavy-resistance exercise. Eur J Appl Physiol. 61(1-2):5-10
Forbes, C.A. (1929) Greek Physical Education. The Century Press, New York
Grimby G, Bjorntorp P, Fahlen M, Hoskins TA, Hook O, et al. (1973) Metabolic effects of isometric training. Scand J Clin Lab Invest 31(3):301-305
Maughan RJ (1984) Relationship between muscle strength and muscle cross-sectional area. Implications for training. Sports Med. 1(4):263-269
McDonagh MJ, Davies CT. (1984) Adaptive response of mammalian skeletal muscle to exercise with high loads. Eur J Appl Physiol ;52(2):139-155
MacDougall JD, Ward GR, Sale DG, Sutton JR. (1977) Biochemical adaptation of human skeletal muscle to heavy resistance training and immobilization. J Appl Physiol. 43(4): 700-703.
Morianti, T. (1979) Neural factors versus hypertrophy in the time course of muscle strength gain. Am J Phys Med. 58(3): 115-130.
Morpurgo, B. (1897) Ueber activitats-hypertrophic der willkurlichen Muskeln. Archiv fur Pathologische Anatomie und Physiologie (Virchows), 150, 522-554.Cited by Atha, J.
Strengthening Muscle. Exerc Sport Sci Rev 1981;9:1-73
Nikituk, B., Samoilov, N. (1990) The adaptive mechanisms of muscle fibers to exercise and possibilities for controlling them. Teoriya i Praktika Fizischeskoi Kultury 5:11-14
Nosaka K, Clarkson P.M.,(1995) Muscle damage following repeated bouts of high force eccentric exercise. Med. Sci. Sports Exrc.,Vol. 27, No. 9 pp. 1263-1269
Sale, D. (1988) Neural adaptation to resistance training. Med Sci Sports Exerc. 20(5 Suppl):S135-S145
Siff MC., Verkhoshansky YV. (1996) Supertraining: A Textbook on the Biomechanics and Physiology of Strength Conditioning for all Sport. Sports Support Syndicate, Pittsburgh
Soike D, Bergmann V. (1998) Comparison of skeletal muscle characteristics in chicken bred for meat or egg production. I. Histopathological and electron microscopic examination. Zentralbl Veterinarmed A. 45(3):161-167
Soike D, Bergmann V. (1998) Comparison of skeletal muscle characteristics in chicken bred for meat or egg production: II. Histochemical and morphometric examination. Zentralbl Veterinarmed A. 45(3):169-174
Stutley, M., and Stutley, S.(1977) A dictionary of Hinduism. Harper and Row, London
Tesch PA, Colliander EB, Kaiser P (1986) Muscle metabolism during intense, heavy-resistance exercise. Eur J Appl Physiol. 55(4):362-366
Tesch PA, Thorsson AJ.Essen-Gustavsson B (1989) Enzyme activities of FT and ST muscle fibers in heavy-resistance trained athletes. Appl Physiol. 67(1):83-87
Tesch PA, Thorsson A, Colliander EB. (1990) Effects of eccentric and concentric resistance training on skeletal muscle substrates, enzyme activities and capillary supply. Acta Physiol Scand. 140(4): 575-580.
Webster D. (1976) The Iron Game. John Geddes Printers, Scotland
Zeigler, E.F. (1973) A History of Sport and Physical Education to 1900. Stripes, Champaign