Q: I have a 9 year old son who plays football, soccer, and basketball. Should I have him doing any type of strength training or plyometrics program?
A: At his age Ron I would primary concern myself with provinding the widest range of movement experiences possible to ensure he can move efficiently in a variety of manners and develop the sport skills themselves. The more activities he can participate in the better. At this point I wouldn't worry too much about organized strength training or organized plyometrics. Just playing should cover that territory well enough. Certainly exercises like pushups, pull-ups and other bodyweight exercises can be beneficial additions, just make sure he enjoys doing them and aren't something he resents. Organized training that's not perceived as play for young ones can be boring to them.
Many are under the misguided assumption that children shouldn't lift weights because they will injure their growth plates. However, if your child jumps from a piece of furniture, he is doing a depth jump (plyometrics) and putting much more force on is structure then he could weight training. This type of activity is normal and natural and nothing to be concerned about. It's just play, but also creates an important training effect for later in sporting life. The reason weight training is sometimes contraindicated is because it won't be all that effective until your child hits puberty (due to hormones like testosterone), and it takes up time that could be better spent learning movement skills at this stage in his development.
Q: I have heard that the amount of Fast twitch muscle fiber a person is born with is the determining factor on how fast a person can run or the height of their jump and they are born with a certain amount and nothing can be done to change it. Is this true?
A: Ahh, this is a very common question. I spend a whole chapter answering this question in my upcoming book but let me touch on the key points for you.
1. Fast twitch muscles are the biggest, fastest, and stongest fibers but if the FT to ST ratio theory held 100% true then strong people would also be the fastest and biggest. The fastest would be the biggest and strongest, and the biggest also be the strongest and fastest, which is obviously not true.
2. The speed and force at which we can signal all the muscle fibers (slow twitch and fast twitch) to contract by our nervous system is the limiting factor in speed, jumping ability and other activity requiring significant power.
3. Most people are only able to contract around 50-60% of their potential muscle cells in a given movement anyway, be it a sprint, jump or what have you. So even if you didnt have much FT muscle fiber you could make up for this by training your body to use more of what you do have.
4. Muscle fibers can change more then once thought so you're not born with a certain ratio that can't be changed. Recent evidence suggests 40% of the fiber type expression is related to what we do with our training while 60% is genetic.
5. Speed and power training increase FT fiber % with the largest increases in the fastest contracting group of fibers (the fast of the fastest) demonstrated with accelerated eccentric training (plyometric weight training), which also demonstrate a very high level of activity in the nervous system.
6. A group of Slow twitch fibers will transform to fast twitch fibers if the electical impulse which activates them from the nervous system is of fast twitch character.
7. Endurance training causes a decrease in FT fiber % and an increase in slow twitch %.
8. Structure and length of the bones, tendons, and muscles determines in large part whether we best demonstrate force through speed or strength, regardless of fiber type.
9. Sedentary people tend to have more FT fiber then most athletes!
As you can see there is much more to it then just FT fiber % and even if that was THE major factor a lot can be done to change it. I personally know people who were naturally more like marathon runners but with the right type of training were still able to develop awesome speed and explosiveness.
Q: I've been getting stronger but not any faster. My squatting and bench press poundages are all well up over the past few months, but I'm not seeing a transfer into my sprinting times. I haven't gained much bodyweight and I've been running twice per week while weight training 4 days per week. Any ideas?
A: Could be a few things:
1. Training with heavy weights 4 times a week along with sprinting places a lot of strain and drain on the central nervous system. A draining of the CNS will tend to show itself first in movements that require a high speed of force application, such as sprinting or anything requiring a high force output along with great speed. So even though you're making gains in training poundages you could still be slightly overworked and that is showing up as less running speed. Try cutting your weight training back to 2 whole body days per week, cycle the poundages down a bit and keep your track workouts the same and see what happens.
2. You may be naturally stronger then you are fast and by training with heavy weights at a frequency 2x greater then you engage in speed training you're favoring your natural adaptation which is slow speed strength rather then high speed-strength.
3. Pay attention to the speed at which you lift. Use bar speed to dictate your weight training poundages rather then weight. You don't have to get fancy or technical with this but once you can no longer complete the positive portion of a repetition in 3 seconds or less stop increasing the weight on that movement. So for example, you might be able to squat a maximum of 400 lbs in 6 seconds, 350 lbs in 5 seconds, and 280 lbs in 3 seconds. Don't go over 280 lbs in that exercise until you can increase the speed. This makes your lifting strength more speed-strength oriented. Attempt to apply maximum force and speed on every repetition.