Wednesday, April 11, 2012

Why Stroke Volume Made Me Quit University Soccer

When I was in university, I tried out for the soccer team, but I quit after three sessions. We had a 2-hour session, and for the first 75 minutes, we ran around the field, and never touched a ball.  Even the goalkeeper ran with us. Would you have stayed?

All training should have an objective. If you're coaching based what you did when you played, because your coach told you to, and he did that because his coach told him to, it’s time to re-evaluate your methods. And for players, ask politely if your coach can explain the relevance of what he is asking you to do. I don't know about you, but I put in more effort when I know that what I am doing will actually make me a better player. So what is stroke volume, and what does it have to do with soccer? First, some basic cardiac physiology.





VO2max is the maximal amount of oxygen consumption by the body during exercise. It is a product of heart rate (HR) and stroke volume (SV). Fitter athletes have a higher  VO2max  than their counterparts.

VO2max= HRmax x SV

HRmax stands for Maximum Heart Rate, and refers to the highest number of beats your heart produces in a minute. Go for a sprint, and measure your heart rate straight after. A general estimation of  HRmax  can be also calculated using the formula 220- age.

Stroke volume refers to the amount of blood your heart expels from its chambers with each beat.

HRmax is largely unchangeable, but research has shown that stroke volume is. Basically, if your heart can pumped more blood to the exercising muscles with each beat, you can play at a higher intensity or the same intensity for longer. Your ability to recover from a sprint bout, a series of tackles, etc., is enhanced. It is now known that there is NO PLATEAU in stroke volume in well trained athletes. This means as long as you continue to train appropriately, you can continue to improve (to a point, of course!)

Endurance training should be designed to improve stroke volume, rather than aimlessly running around the field. Because soccer is an intermittent sport, comprised of lots of stop-start activities, laps are pointless. Short intense bursts, including changes in direction and ball contact should be incorporated in training for endurance. The research supports this. 

In an unpublished observation, researchers found that work at 90-95% of HRmax  for 3-8 minutes was an "extremely effective" method for improving SV. Intervals were separated by 2-3 minutes of active recovery. Different protocols involving running uphill (Helgerud et al., 2001) as well as short sided games (Hoff et al.39) have been used to try to improve SV. Reilly (1994) showed that running with the ball increased the energy cost by an approximated 8% than when running without it. 


Small sided games mean more touches on the ball as well as increased SV


Consider also that soccer is inherently an intermittent sport. Games are won and lost by successful short bursts onto the ball or into space. Reilly and other authorities who have extensively studied the physiology of the game suggest that there is somewhere between 70 and 90 seconds between successive high intensity bouts in soccer. The rest of the time, players will be walking, jogging or running at a moderate speed. This suggests repeated sprint ability (RSA) rather than 75 minutes of running around the field.

Therefore, I propose the following for endurance training, adopting the principles these investigators have used: (Since this is in training, and the aim is still to develop RSA, rest periods are slightly longer so that each bout can be performed maximally.)

Basic Sprints:

4 x 30m sprint. Walk back to the start each time. Rest for 3 minutes and perform another set of 4.

Incorporating the ball:

4 x 40m sprint. run with the ball from the 30m mark to the end, turn back and continue sprinting. Leave the ball at the same 30m on your way back. Walk the rest of the way. Rest for three minutes, then perform another set of 4. 

Progress to picking up the ball at the 20m mark to increase contact with the ball and improve technical ability as well.

Keep the game beautiful!

References

Helgerud J, Engen LC, Wisløff U, et al. (2001) Aerobic endurance training improves soccer performance. Med Sci Sports Exerc. Nov; 33 (11): 1925-31

Hoff J, Wisløff U, Engen LC, et al. Soccer specific endurance training. Br J Sports Med 2002 Jun; 36 (3): 218-21 al., editors. Science and football. London: E&FN Spon, 1988:

Reilly T. Physiological aspects of soccer. Biol Sport 1994; 11:3-20.  In Stølen, T; Chamari, K; Castagna, C and Wisløff U (2005). The Physiology of Soccer. Sports Med 35 (6): 501-536

Stølen, T; Chamari, K; Castagna, C and Wisløff U (2005). The Physiology of Soccer. Sports Med 35 (6): 501-536

Wiebe CG, Gledhill N, Jamnik VK, et al. Exercise cardiac function in young through elderly endurance trained women. In Stølen, T; Chamari, K; Castagna, C and Wisløff U (2005). The Physiology of Soccer. Sports Med 35 (6): 501-536


Zhou B, Conlee RK, Jensen R, et al. (2001). Stroke volume does not plateau during graded exercise in elite male distance runners. In Stølen, T; Chamari, K; Castagna, C and Wisløff U (2005). The Physiology of Soccer. Sports Med 35 (6): 501-536


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