Energy expenditure and energy efficiency

Daily Energy Expenditure

The daily energy expenditure of an individual has 3 components:

  1. The energy required to maintain the body at rest: referred to as resting metabolic rate or RMR.
  2. The energy required for all activity: referred to as the thermic effect of activity or TEA
  3. The energy required by food consumption: referred to as the thermic effect caused by food consumption or TEF.
A pie chart of the 3 components of daily energy expenditure

RMR is the energy cost of maintaining all body systems including temperature regulation while the individual is at complete rest. Excluded from RMR is any biological work done by the body in regard to recent food intake or recovery from recent physical activity (27).

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Concurrent Strength and Endurance Training

Graph that compares strength gains of athletes training in strength only compared with athletes training strength and endurance concurrently.
Figure 4: Hickson (1980): Graph that compares strength gains of athletes training in strength only compared with athletes training strength and endurance concurrently.

Is it possible to adapt simultaneously to strength training and endurance training? Considerable research has been undertaken in an attempt to answer this question. While there is a preponderance of evidence that suggests that training on endurance compromises strength development, particularly when the same body part is involved, some studies have not found an ‘interference effect’ on strength development as a result of endurance training. The variation between the many studies however may be a result of differences in study design, duration of study, pre-test fitness of subjects, the mode and intensity of training, and strength assessment procedures (Leveritt et al. 2003).

The first study to discuss the interference effect of endurance training on strength development was by Hickson (1980). In this study subjects were assigned to one of three groups: training on strength and endurance simultaneously (SE group), training on strength only (S group) or training on endurance only (E group). The exercise regimen of the SE group combined the separate training of the S and E groups. Hickson’s finding was that the SE group increased in strength for first 6-7 weeks, levelled off in week 8 and then surprisingly lost strength in the final 2 weeks as Figure 3 shows. However the S group continued to improve in strength.

Hickson’s conclusion, therefore, was that at the upper limits of strength development, aerobic training inhibits or interferes with further increases in strength.  This view is supported by several studies. Hennessy and Watson (1994) found that improvements in power (vertical jump) and speed (20m sprint time) developed only in a group engaging in strength training but not in a group engaging in combined strength and endurance training (running training 4 days per week). Hennessy and Watson concluded that a combination of strength and endurance training resulted in gains in upper body strength gains but compromised power and strength development in the lower body. This finding adds weight to the view that fatigue is an underlying cause of the interference effect and that it develops as a result of reduced recovery time between strength training sessions. The diminished recovery time may also result in reduced muscle-glycogen content (Nader, 2006).

But in studies where the interference effect is confirmed, subjects have engaged in one form of training or another almost daily. What about if training sessions are spaced more apart does this ease the fatigue effect? A study by Häkkinen and colleagues (2003) found that endurance training conducted simultaneously with strength training did not affect the development of maximal strength or hypertrophy.  In this study a subject group performing strength training only (S group) was compared with a subject group performing strength and endurance training (SE group). Subjects in both groups trained only twice per week for 21 weeks. However the study did find a difference regarding the rate of force development (power). The S group improved in rate of force development but the SE group did not. This study raises further questions particularly for those involved in sports where explosive power is a necessity. In Weightlifting, there is a need to carefully consider the content of the training program in regard to speed of movement and power development.

Another reason put forward to explain the interference effect between endurance and strength training is that these two modes of training produce contradictory training stimuli (Sale, MacDougall, Jacobs and Garner, 1990; Bell et al. 1997) and conflicting physiological changes (Hennessy & Watson, 1994). For example, these modes of training are known to have a different effect on the composition of muscle in terms of fibre type and cross-sectional area. Strength training is known to cause hypertrophy particularly in Type IIa fast twitch muscle fibre whereas endurance training does not have this effect. Endurance athletes show a much higher distribution of Type 1 ‘slow twitch’ muscle fibre than do athletes that engaged purely in strength training. There is no evidence that combined strength and endurance training leads to both an increase in the proportion of Type 1 slow twitch muscle fibre and an increase in cross-sectional area of Type IIa fast twitch muscle fibre. Therefore, continual fluctuation between strength and endurance training provides confusing stimuli for adaptive change.

Differences in endocrine response to strength and endurance modes of training should also be taken into account. A study by Kraemer and colleagues (1995) found that subjects engaging in combined strength and endurance training (SE group) showed significant stepping up of levels of the hormone cortisol at each testing stage of the 12 week training period. In addition, the same subjects also showed a significant increase in testosterone in the final 4-week period of the study. Other groups engaging in strength training or endurance training only did not show this dramatic change in testosterone or cortisol, nor did the group that engaged in strength training of only the upper body while performing endurance training. The endocrine response to the combination of concurrent strength and endurance was considered by Kraemer and colleagues to be possible signs of overtraining. Cortisol and testosterone are both hormones that influence total muscle protein and muscle fibre adaptations. Cortisol stimulates conversion of proteins to carbohydrates and therefore is catabolic (degrades muscle protein), and thus negatively influences muscle fibre size, power and strength. Testosterone stimulates protein synthesis and is anabolic in nature. Therefore Kraemer and colleagues considered the rise in testosterone in the SE group in the last 4 weeks to be a compensatory mechanism needed to override the earlier catabolic environment created by high intensity concurrent strength and endurance training.  The result that the group engaging in upper body strength plus running training did not show the same elevated cortisol response as the group that performed whole body strength plus running training lead Kraemer and colleagues to also conclude that endurance training appears to compromise strength improvement only when both modes of training are performed using the same musculature.

There may possibly be a gender difference.  A study by Bell and colleagues (1997) found that concurrent endurance and strength training programs compromised strength development in women but not in men. A reason given for the gender difference was that in regard to concurrent endurance and strength training, the female subjects showed elevated urinary cortisol during the last 8 weeks whereas the men did not. The combined strength and endurance training (6 days per week) may have induced a catabolic state with reduced recovery time as compared to the 3 days per week strength group. Bell and colleagues cited earlier research by Tsai et al. (1991) that women may adapt differently to men in response to endurance training and, in fact, women may be prone to be hypercortisolic.

For the weightlifting coach, these studies provide evidence that the inclusion of regular high-intensity endurance exercise in the training regimen of the weightlifter is incompatible with long-term goals of strength development and hypertrophy. This will be of interest for those who advocate that it is possible for an athlete to excel in both Weightlifting and Crossfit. If indeed this happens, there is substantial argument that the athlete could go further in strength development if unhindered by prolific endurance training. However, if an athlete is determined to participate in both Weightlifting and Crossfit, it may be possible to design training programs that minimise the interference effect of strength and endurance training by either not training the same muscle group for endurance and strength on the same day, or by extending the recovery interval after endurance training before strength training.

References

Bell, G., Syrotuik, D., Socha, T., Maclean, I., &  Quinney, H.A., (1997). Effect of strength training and concurrent strength and endurance training on strength, testosterone and cortisol.  Journal of Strength and Conditioning Research, 11(1), 57-64

Häkkinen, K., Alen, M., Kraemer, W.J., Gorostiaga, E., Izquierdo, M., Rusko, H., Mikkola, J., Häkkinen, A., Valkeinen, H., Kaarakainen, E., Romu, S., Erola, V., Ahtiainen, J., Paavolainen, L., (2003). Neuromuscular adaptation s during concurrent strength and endurance training versus strength training. European Journal of Applied Physiology, 89(1), 42-52, doi:10.1007/s00421-002-0751-9

Hennessy, L.C., & Watson, W.S., (1994). The interference effects of training for strength and endurance simultaneously. Journal of Strength and Conditioning Research, 8(1), 12-19

Hickson, R.C. (1980). Interference of strength development by simultaneously training for strength and endurance. European Journal of Applied Physiology, 45(2-3), 255-263

Kraemer, W.J., Patton, J.F., Gordon, S.E., Harman, E.A., Deschenes, M.R., Reynolds, K., Newton, R.U., Triplett, N.T., & Dziados, J.E., (1995). Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations.  Journal of Applied Physiology, 78(3), 976-989

Leveritt, M., Abernethy, P.J., Barry, B., and Logan, P.A., (2003). Concurrent strength and endurance training: The influence of dependent variable selection. Journal of Strength and Conditioning Research, 17(3), 503-508

Sale, D.G., MacDougall, J.D., Jacob, I., & Garner, S., (1990). Interaction between concurrent strength and endurance. Journal Applied Physiology, 68(1), 260-270

Tsai, L., Johansson, C., Pousette, Å., Tegelman, R., Carlström, K., & Hemmingsson, P., (1991). Cortisol and androgen concentrations in female and male elite endurance athletes in relation to physical activity. European Journal of Applied Physiology, 63(3-4), 308-311

Qualitative Analysis of the Snatch

The link below will provide you with a checklist that can be used to qualitatively evaluate an athlete’s technical ability in the snatch. The checklist provides an indication of how to evaluate 5 key elements of the snatch: (1) Explosive leg drive at the finish of the pull (2) Stability in the receiving position (3) Keeping the back angle constant in the first pull (4) Keeping the shoulders over the bar in the mid thigh and (5) The trajectory of the bar in the pull. There are a number of criteria to assess under each of the above 5 elements. Each criteria may be assessed as (i) Excellent (ii) Proficient or (iii) Needs attention.

Click on the picture below to download the 2 page document:

Qualitative Analysis of the Snatch

2 Page downloadable document providing a checklist for qualitative analysis of the Snatch

 

Affect of Weightlifting on the Cardiovascular System

At moments when the Weightlifter applies maximal force, the internal pressure in working muscles is sufficiently great to interrupt blood flow. How does this affect the cardiovascular system, particularly the heart?

Blood Pressure

It is unsurprising, for those who have some experience of the sport, that an extreme elevation of blood pressure has been found to occur during high-intensity Weightlifting movements (MacDougall et al, 1985). Blood pressure (BP) was measured by MacDougall and colleagues by inserting a pressure transducer into the Brachial artery in subjects who performed a double-leg press. The recorded highest pressures were 480mmHg systolic and 350mmHg diastolic and this amounts to a four-fold increase over normal BP . This extreme elevation in BP is a another example of homeostasis at work, and is the body’s mechanism to preserve blood flow in the extraordinary circumstance of lifting very heavy weights.

Principally, three factors contribute to this elevation of BP:

  • A very high fluid pressure within contracting muscles that causes the occlusion of blood vessels
  • A build up of pressure in the chest and abdomen caused by the Valsalava Manoevre
  • An autonomic reflex that constricts arterioles (MacDougall et al, 1985)

The occlusion of blood vessels within contracting muscles is the first factor in the elevation of BP.  During a heavy lift, the tension created within working muscles puts pressure on blood vessels and blood flow ceases completely if this pressure is sufficiently great. According to MacDougall and colleagues (1985), occlusion occurs when intra-muscular pressure reaches 350mmHg and it is interesting to note that researchers have obtained values far in excess of this figure. In one study,  a maximal value of 570mmHg was found for intra-muscular pressure in the vastus medialis in subjects performing isometric contraction (Sejersted et al, 1984). Similarly, in another study in which subjects performed isometric contractions, a maximal value of 1025mmHg was found for intra-muscular pressure in the quadriceps (Sylvest & Hvid, 1959).  While these two studies have produced significantly different maximal values, the complete occlusion of blood vessels in the legs during heavy lifts appear to be a strong possibility.

The second factor in the elevation of BP is the build up of pressure in the chest and abdomen through the use of the Valsalva Manoevre by the athlete (Haykowski et al., 2002). In Weightlifting it is common, if not necessary, for participants to fully inflate their lungs and then hold breath completely during brief moments of high-intensity exertion.  In effect what happens is that the athlete prevents any escape of air from the lungs by closing the glottis, mouth and nose, while at the same time the chest and diaphragm muscles forcefully squeeze on the column of air contained within (Wilmore, Costill & Kenney, 2008). This is known as the Valsalva Manoeuvre and as a result of this action, the athlete can develop very high pressure in the chest and abdomen (intrathoracic pressure) and in Weightlifting this is greatly important in maintaining rigidity of the upper body. If rigidity of the upper body is not maintained during heavy lifts, a significant amount of force that the athlete generates during the course of a lift will be absorbed by the body and not transmitted to the bar. A useful analogy to consider is how a tyre becomes more rigid when a greater amount of air is pumped into it. A slack tyre absorbs the impact of every bump that the wheel runs over.

The third factor involved in the extreme elevation of BP during Weightlifting is an autonomic reflex that constricts blood vessels in areas of the body which are not vital to the exercise so as to route more blood to working muscles (MacDougall et al, 1985). For example, the walls of arteries and arterioles that supply blood to the intestines will constrict to decrease blood flow as a result of innervation by the sympathetic nervous system. This factor is the lesser of the three contributing factors.

The Weightlifter’s Blackout

An annoying phenomenon in Weightlifting is the light-headedness that athletes sometimes experience after standing up out of a heavy clean. The often given explanation is that during the clean the bar presses into the neck and restricts blood flow in the carotid artery thus reducing the perfusion of oxygenated blood to the brain. However, this explanation is not correct. Although the Weightlifters’ blackout is caused by a reduced cerebral perfusion pressure, that is a lack of oxygen to the brain (Van Lieshout et al., 2003), the impact or pressure of the bar on the carotid artery is not the reason. The weight of the bar is acts downwards on the shoulders not on to the carotid artery in the neck. Instead, the phenomenon can be attributed to the reduced cardiac output as a result of a lack of venous return to the heart and a delay in the filling of the heart’s left ventricle. As the Weightlifter catches the clean and begins to rise, blood pressure is very high due to factors described above. However at the end of the movement, when the athlete has completed the clean, there is a sudden and acute drop in BP as a result of:

  • A reduction in the occlusion of blood flow in working muscle thereby causing an increase of blood perfusion into the lower body; and
  • A release of the very high pressure within the chest and abdomen as the Valsalva Manouevre ends when the athlete releases air and takes a breath (Compton, Hill, & Sinclair, 1973; MacDougall et al., 1985)

These factors conspire to momentarily reduce BP to 25-50mmHg (Compton, Hill, & Sinclair, 1973) causing a lack of blood returning to the heart and a reduction in cardiac output. This situation has a potential to cause insufficient blood flow to the brain and threatens the athlete’s ability to maintain consciousness. It may assist the athlete to avoid this situation by completing the jerk as soon as possible i.e. beginning the dip within 1-3 secs of rising out of the clean. Trying to regain full consciousness by hyperventilating or waiting for the head to clear does not assist and may endanger the athlete further.

Changes to the heart

How does the heart adapt, if at all, to dealing with phenomenal increases in blood pressure during Weightlifting movements? Unfortunately there is no complete agreement between researchers as studies have produced different findings.  Some findings suggest that a form of adaptation known as concentric hypertrophy (see illustration below) appears in Olympic Weightlifters (MacDougall et al, 1985; Haykowski et al., 2002; Mihl, Dassen and Kuipers, 2008). Other researchers, however, have refuted this and put forward the view that the effects of strength training on the heart are small or insignificant in comparison to untrained individuals (Wernstedt, et al., 2002; Lalande & Baldi, 2008). It is probable that changes to the heart in many of the subjects examined was small and close to the methodological error of echocardiography. (Haykowski, et al, 2002).

Concentric Hypertrophy Increase in mass and wall thickness of the left ventricle with a minimal decrease in internal cavity dimension (Haykowski, Dressendorfer, Taylor, Mandic and Human, 2002)
Eccentric Hypertrophy Increase in mass and wall thickness of the left ventricle and increase in internal cavity dimension (Mihil, Dassen and Kuipers, 2008)

There are a number of reasons for the disparity of results put forward by researchers include: (Haykowski et al, 2002)

  • Whether athletes use, or how effectively they use the Valsava Manoeuvre
  • Whether athletes use of have used anabolic steroids
  • Specific type of resistance training performed e.g. Olympic Weightlifting, Powerlifting, or Bodybuilding
  • The age of the individual

The cardiovascular fitness of Weightlifters

In reality, all forms of high intensity training are associated with adapative changes of the heart, and in particular hypertrophy of the left ventricle (MacFarlane) from which blood is pumped around the body. What is in question is whether there are different adaptive changes in Weightlifters as compared to endurance athletes, or for that matter other strength athletes. Furthermore, if there are differences, which are beneficial? It has been stated that eccentric hypertrophy of the left ventricle is found in elite distance runners (Macfarlane et al, 1991) and bodybuilders (Haykowski et al., 2002).  This suggests that the type of training performed by bodybuilders, where repetitions are commonly performed to failure, has a significant endurance training effect. In eccentric hypertrophy, the internal cavity dimension of the left ventricle is increased and this allows the heart to pump a greater volume of blood per beat (stroke volume).  In concentric hypertrophy, which according to some researchers is more prevalent in Olympic Weightlifters, the left ventricle is unchanged or is smaller in internal cavity dimension. This reflects the predominance of low repetitions in the training of Weightlifters, where intensity is far more important than endurance. But then comes Crossfit, in which athletes strive for fitness in both strength and endurance.  A study by Edwards (2012) provided not unexpected evidence that Crossfit athletes showed greater ventricular cavity dimensions and greater ventricular wall thickness, adaptations exhibited by endurance athletes and bodybuilders.

In relation to the training of Weightlifters, there is a common understanding among coaches that training with intensities greater than 80% is fundamentally necessary. At such intensity, only low repetitions can be performed and this is particularly the case when fatigue interrupts the execution of good technique. Weightlifters tend to perform one set of low repetitions every 2-3 minutes in training and this is not particularly challenging in terms of their endurance. As a result, Weightlifters are often not concerned about their endurance fitness and probably the vast majority have little or no knowledge about cardiovascular adaption. It is worthwhile therefore to pose several questions:

  • Is there any benefit to the Weightlifter to engage in some form of endurance training to encourage eccentric hypertrophy, that is larger internal cavity and higher stroke volume?
  • Is there a negative aspect of concentric as opposed to eccentric hypertrophy for Weightlifters?
  • Is endurance training in some form incorporated into the training of elite Weightlifters who occupy the top 10-15 positions at World Championships?
  • Is it a time limitation decision? For the majority of competitive Weightlifters who train 8-10 hours per week, is it a matter that endurance training is a low priority as compared with time spent on strength training?
  • Does it become increasingly more important for the Weightlifter to incorporate some endurance work into the weekly training schedule the more they advance in qualification, or is it completely the reverse and that beginners in Weightlifting need greater amounts of endurance training?
  • If Weightlifters had greater endurance fitness would they be able to withstand a higher volume of training?

Answers to these questions probably do exist somewhere in the world, and of course many people involved in all sports that utilise some form of resistance training will likely have an opinion. In the author’s opinion, there has been no radical shift in the training of weightlifters with regard to endurance in the past 4 decades. Personal observations provide anecdotal evidence of a consistent lack of endurance training in any form among Weightlifters at all levels of ability, working with different coaches and in different regions. At times of the year, Weightlifters will commonly undertake higher repetition training in which the average number of reps per set is increased to 5 on all exercises. For the majority of Weightlifters, this form of training is the nearest resemblance of endurance training that they experience and is often maintained only for 4 weeks at a time due to the preference of athletes and coaches to return to “normal” high-intensity, low repetition training. It is possible that the influx of Crossfit athletes into Weightlifting will, in time, have an impact on standard training methodology employed in Weightlifting. But even if it just causes the Weightlifting fraternity to re-examine current practise, it will be a good thing.

References

Compton, D., Hill, P. M., & Sinclair, J. D. (1973). WEIGHT-LIFTERS’BLACKOUT. The Lancet, 302(7840), 1234-1237.

Haykowski, M.J., Dressendorfer, R., Taylor, D., Mandic, S., & Humen, D., (2002). Resistance trainiung and cardiac hypertrophy: Unravelling the training effect. Sports Medicine, 32(13): 837-849

Lalande, S., & Baldi, J.C., (2007). Left ventricular mass in elite Olympic Weight Lifters. American Journal of Cardiology, 100(7): 1177-1180

MacDougall, J.D., Tuxen, D., Sale, D.G., Moroz, J.R., & Sutton, J.R., (1985). Arterial blood pressure response to heavy resistance exercise. Journal of Applied Physiology, 58(3): 785-790

MacFarlane, N., Northridge, D.B., Wright, A.R., Grant, S., & Dargie, H.J., (1991). A comparative study of left ventricular structure and function in elite athletes. British Journal of Sports Medicine, 25(1), 45-48

Mihil, C., Dassen, W.R.M., Kuipers, H. (2008). Cardiac remodelling: concentric versus eccentric hypertrophy in strength and endurance athletes. Netherlands Heart Journal, 16(4), 129-133

Sejersted, O. M., Hargens, A. R. , Kardel, K. R.,  Blom, P.,  Jensen, O.,  Hermansen, L., (1984). Intramuscular fluid pressure during isometric contraction of human skeletal muscle. Journal of Applied Physiology, 56, 2, 287-295

Sylvest, O. & Hvid, N. (1959). Pressure measurements in human striated muscles during contraction. Acta Rheumatologica Scandinavica, 5 (1-4), 216-222.

Van Lieshout, J. J., Wieling, W., Karemaker, J. M., & Secher, N. H. (2003). Syncope, cerebral perfusion, and oxygenation. Journal of Applied Physiology, 94(3), 833-848.

Wernstedt, P., Sjöstedt, C., Ekman, I., Du, H., Thuomas, K. Å., Areskog, N. H., & Nylander, E. (2002). Adaptation of cardiac morphology and function to endurance and strength training. Scandinavian journal of medicine & science in sports, 12(1), 17-25.

Proprioception in Weightlifting

Proprioception is a sense in just the same way as vision, hearing, touch, taste and smell. It relies on sensory organs called proprioceptors located within muscles, tendons and joints that enable the sensation of tension, force, pressure and movement (Sherrington, 1906). This sensory feedback enables us to detect the position of our limbs and entire body (Gollhofer, 2003; McMorris, 2014) and therefore is critically important to the athlete in learning sport skill. The ability to detect movement as a result of feedback from proprioceptors is also instrumental in enabling the calibration of force required to produce movement.

Table 1: Proprioceptors
ReceptorLocationRole
Muscle SpindlesDeep within muscle tissueDetect movement, detect changes in muscle length, detect the rate at which muscle length changes
Golgi Tendon OrgansWithin the tendon of the muscle at the junction of muscle and tendonMonitor degree of muscle tension
Ruffini CorpusclesIn the connective tissue that forms the joint capsule (Halata & Baumann, 2008)Detect stretch or excessive load  on joints cause by excessive range of motion
Pacinian CorpusclesIn the connective tissue that forms the joint capsuleRespond to vibration stimuli (Halata & Baumann, 2008).

Source: Levine, 1997

Knowledge of proprioception enhances the coach’s ability to teach sport skills and to understand the differences among athletes in functional capability (Levine, 1997). Proprioception is the key sense involved in learning new movement patterns and knowledge of this persuades the Weightlifting coach that issuing verbal instructions is much less important than physical manipulation of the athlete to “feel” the correct body positions required at various stages of the lifts. Furthermore, in the process of learning any new movement patterns, there is always considerable ‘trial and error’ on the part of the learner and it is proprioceptive feedback that plays a vital role in this process.

In just the same way that humans are not equal in sight, hearing, smell or touch, it may well be that differences in coordination and movement efficiency may be due to differences in proprioception. It is obvious to those involved in sport coaching that there is a significant difference among individuals in the ease with which new skills are learned. A reasonable hypothesis for this difference is that individuals who gain a frequent and wide variety of physical education and sport experience at a young age, develop an enhanced capacity of the brain to interpret proprioceptive feedback. This early adaptation of the brain and central nervous system allows the individual to more easily learn new physical skills at a later stage of life. This phenomenon is observable when individuals with years experience in gymnastics begin to learn Olympic Weightlifting movements.

In Weightlifting, the predominant interest is in what makes muscle tissue contract and whether we can find methods of training to enhance the athlete’s ability to contract muscle tissue more strongly. However, we give less thought in general to the systems of the body (afferent systems) that detect and control movement, and provide an awareness of the force that muscles produce (Gollhofer, 2003). In our constant search for improved training methodology, the question needs to be asked as to whether the early learning phases of the Weightlifter should include a greater variety of movement patterns that develop proprioception. For example, the training of the beginner Weightlifter might include a wide variety of non-weightlifting explosive movements, balance and stability exercises, and spatial awareness activities as can be found in other sports. Such a varied diet of movement patterns may enhance the proprioceptive capacity of the athlete.

Efferent systemRelays information from the central nervous system to stimulate and cause changes in body tissue, for example muscle contraction.
Afferent systemRelays information to the central nervous system about what is happening inside and outside the body (Wilmore, Costill and Kenney, 2008)

The importance of variety in the exercise schedule for Weightlifting was discussed in classical Russian literature on Weightlifting (Korneluk, 1977; Vorobiev, 1978). Bearing in mind that Womens Weightlifting did not exist in Vorobiev’s day, he stated “An essential part of young Weightlifters’ training is using every possible means that will nurture all-round physical development and fitness. All-round physical preparation allows a young weightlifter to successfully develop his physical abilities, improve his nervous system, his musculo-skeletal system, his cardiovascular system, his respiratory system, and other vitally important organs, and to enhance the motor skills needed in sports and work activities” (Vorobiev, 1989).

References

Costill, D. L., Wilmore, J. H., & Kenney, W. L. (2008). Physiology of sport and exercise. Human Kinetics.

Gollhofer A. Proprioceptive training – Considerations for strength and power production. In: Komi PV (ed). Strength and Power in Sport. Oxford: Blackwell Science, 2003: 331 – 342

Halata, Z., & Baumann, K. I. (2008). Anatomy of receptors. In Human Haptic Perception: Basics and Applications (pp. 85-92). Birkhäuser Basel.

McMorris, T. (2014). Acquisition and performance of sports skills. John Wiley & Sons.

Sherrington, C. S. (1906). Yale University Mrs. Hepsa Ely Silliman memorial lectures. The integrative action of the nervous system.

Vorobyev, A. N. (1978). A textbook on weightlifting. International Weightlifting Federation.

Muscle Coactivation and Strength

This article provides some theory about the concept of muscle coactivation and strength. The importance of this theory is that it helps to explain why Weightlifters must engage in training that is highly specific  to the movement patterns of the Olympic Lifts rather than generalist strength training.

It is presumable that there are few muscles of the body that are not involved in the performance of the Olympic Weightlifting movements of the Snatch and the Clean and Jerk. In virtually every part of the body, large and small muscles will make a contribution to the required execution of a lift as agonists, antagonists or fixators. The following table provides some explanation of these terms:

ActionExplanation of role
AgonistMuscles that contract to create movement of a joint
AntagonistMuscles that oppose the contraction of agonists  and limit movement of a joint
FixatorMuscles that increase in contractile tension to stabilise segments of the body while the action of agonists and antagonists cause movement.

When we think of the force required to lift a weight, there is a tendency to think mostly about muscle contraction within the agonist muscle group. For example, while performing a squat exercise we tend to focus on the contraction of the quadriceps muscle group to cause extension of the knee joint. However, contraction also takes place within the opposing antagonist muscle group, in this case the hamstrings. This contraction of agonist and antagonist simultaneously is called co-activation and thus movement in the knee joint will be the net effect of force generated by the opposing muscle groups (Aagaard et al., 2000).

This co-activation of the antagonist is considered to have an important function in stabilising and protecting the joint (Quinzi et al., 2015, p48). Thus, at every angle of joint articulation, the extent of forces developed within agonists and opposing antagonists controls the speed and extent of movement within a joint.

In the context of Olympic Weightlifting, the performance of the classical lifts requires a high degree of precision of co-activation across multiple joints and this poses a significant motor learning problem. The development of precise co-activation is aspect of neural adaptation. An excellent example of this is found in the actions of muscles that cross the knee joint. During any extension of the knee joint as a result of contraction of the quadriceps, the Biceps Femoris (BF) is co-activated. The BF is bi-articular (crosses two joints) and has a hip extension action and a knee flexion action. These dual actions of the BF create an interesting phenomenon during the pull in Weightlifting. As the weightlifter raises the bar from the floor to the knee, the legs straighten at the knees as a result of the agonist action of the quadriceps. However, as the bar passes the knee, it is normal to see the knees re-bend. This knee re-bending is not as a consequence of purposeful learning of technique but as a result of tension developed in the BF which is acting not only as an antagonist to the quadriceps but also as agonist in hip extension.

Example of muscle coactivation and strength of quadriceps is counterbalanced by strength of hamstrings
Figure 1: Co-activation of Muscle Groups that Extend or Flex the Knee

The problem for the Weightlifter is exacerbated by the action of the Gastrocnemius, another bi-articular muscle, which not only extends the ankle but flexes the knee. This re-bending of the knee is favourable to the athlete if it occurs after the bar passes the knees. However, for many athletes it is common to see the knees thrust too far forward as the bar approaches the knees. The angle of the knee thus created causes either the bar to hit the shins or else the athlete must develop a pull technique that moves the bar around the knees.

The moment-by-moment precision of tension developed in agonists, antagonists and fixators is a wonderfully complex phenomenon controlled by our central nervous system. The achievement of this control provides efficiency of movement and is perhaps another way to understand what is meant by skill.

However the degree of precision achieved in muscle coactivation and strength of contraction achieved across all joints depends on whether the exercise is familiar or unfamiliar (Busse et al., 2005). A common phenomenon observed by Weightlifting coaches occurs when someone with extensive training experience with weights (but not Weightlifting) attempts to learn the classical lifts. What is observed is a tremendous struggle to cope with quite basic movements because the exercise is unfamiliar and there is excessive coactivation that impairs movement (Busse et al., 2005). The learned coactivation that results from the regular performance of non-Weightlifting exercises becomes a major source of interference and annoyance. In such circumstances, there is not an efficiency of movement and the athlete appears to work excessively hard, even harder than someone with no previous weight-training experience. With persistence, however, the central nervous system modifies the previously learned patterns and thus co-activation appears to reduce in response to learning a new skill (Vereijken, Whiting and Newell cited in Busse et al., 2005).

References:

Aagaard, P., Simonsen, E. B., Andersen, J. L., Magnusson, S. P., Bojsen‐Møller, F., & Dyhre‐Poulsen, P. (2000). Antagonist muscle coactivation during isokinetic knee extension. Scandinavian journal of medicine & science in sports, 10(2), 58-67.

Busse, M. E., Wiles, C. M., & Van Deursen, R. W. M. (2005). Muscle co-activation in neurological conditions. Physical therapy reviews, 10(4), 247-253.

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