fast twitch/slow twitch muscles

[ralph]

I am interested in the concept of fast twitch/slow twitch muscles but can not seem to find much about it. There are servers that I have seen who do not do much in terms of biomechanics but simply toss the ball up and hit but generate tremendous speed - no body coil or knee bend. Can they just be blessed with fast twitch muscles? Questions that I have: Are we born with a certain number of one type of muscle over the other? Can fast twitch muscles be developed? If so, how can they be developed?

Thanks,

Ralph

[johnyandell]

Great question but I have no info or answers. Anyone else out there? Crazy lefty?

[moderntennis]

Fast-twitch muscles which enable a quick power reaction like starting off the blocks sprinting or swinging effectively at a fast-moving ball unfortunately can only be enhanced by the cocktail of steroids and human growth hormone that a number of sprinters (it can decrease times by .2 of a second in the 100 metres!) , baseball players(the "steroid" homerun era but hgh is just as much a factor - it's more than just mere strength, it's reaction time) and in tennis Puerta (a futures tour player who cheated his way into a French Open final) took/take - instead of watching a serve hit the back fence, you're ripping it back faster than it came in. These muscles decay rapidly with age which is why without cheating you see homerun totals diminish in a player's mid-30s or you see someone like Agassi aced a lot more. Kudos to tennis for trying to keep the sport honest.

[stroke]

Getting back to Ralph's original question, I don't think there is any question some athletes are blessed with fast twich type muscles, and some are more the slow twitch type. In track and field, I think it would be safe to say that all the long distance type runners are all of the slow twich variety. Also, the world class sprinters, clearly of the fast twich variety, could never become world class long distance/marathon type runners, they are just not set up that way. Now how all this relates to tennis, that is a good question. The French Open, for instance, really seems to test the fitness level of a player. Endurance is huge, which would seem to favor, at least to some extent, the slow twich type athlete. For serving, someone like Roddick, with his fast twich motion, is obviously going to be able to produce a higher impact serve. His extreme external rotation, as John has pointed out, is also key. Wayne Arthurs also has that "shoulder touched by God", as John would say.

[GregRyan]

Fiber types, genes and trainability

There are three types of muscle fibers, slow oxidative (type 1), fast oxidative (type 11a) and slow glycolytic (type 11b). Everyone possesses a combination of these fibers that are specific for the task they perform.
Slow oxidative create energy by metabolizing oxygen and fat at a relatively slow rate, but high energy yield. Therefore, they have a slow contraction velocity, produce low forces and are resistant to fatigue. They are characterized by large amounts of mitochondria (energy producing cells) and dense blood capillaries (oxygen distribution) that give them a red color (dark meat of a chicken). These types of muscles are predominantly used in aerobic activities and are found in high concentration in postural muscles.
Fast glycolytic fibers generate energy quickly by using glycogen (sugars), but in an inefficient manner that yields low amounts of energy. They have a slow contraction velocity, produce large forces and fatigue very fast. These fibers do not need oxygen to create energy, have few mitochondria, low density blood capillaries and are white (white meat of the chicken). These fibers are used for short, high intensity tasks and are found in high concentrations in the arms.
Fast oxidative fibers are a combination of types 1 and 11b. These intermediate fibers use oxygen/Fat for metabolism, have the capacity to contract fast and are fatigue resistant. These fibers are predominantly used for longer bouts of high intensity exercise.
There is a large genetic component to the percentage of each fiber type an individual possesses. An example is the Kenyan runners and Dutch speed skaters. Each of these fibers can be trained to be more efficient through specific exercises, but there is controversy to the extent of which they can be transformed. There is some evidence to suggest that these fibers can be converted from one type to another. It seems that the fast glycolytic fibers can be transformed, to a certain extent, to fast oxidative fibers. This may be beneficial in tennis specific training.
Tennis is a highly anaerobic sport that is characterized by short (usually less than 10 seconds) high intensity (70-80% V02 Max) bouts of exercise with rest periods (25 seconds). Matches can last long durations which give the sport an aerobic component as well. It seems that tennis players would benefit from a large percentage of fast oxidative fibers.
Training to improve fast oxidative muscles would include longer length sprints (200m) and hill running. Resistance exercises would be characterized by relatively low weight and high repetitions (20-30) with fast movements.

GR