|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?|
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.
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
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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
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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.