para325air
19 January 2002, 11:30
What makes you tick, run, perform? It’s a combination of matter and either: the strength of your muscles and bones, the resiliency of your heart, and the interplay of brain and body via a series of electronic signals.
CARDIOVASCULAR SYSTEM
Your athletic potential begins inside the 4 chambers responsible for moving oxygen and nutrients throughout your body. The heart, about the size of a fist, is actually 2 pumps: the 2 right chambers exchange blood with the lungs, where the blood is infused with oxygen, while the left chambers funnel blood to your muscles. The circulating blood performs another crucial activity; after it drops off the fuel, it carts away waste product like lactic acid and carbon dioxide, biological “pollutants” that are created when your muscles burn fuel.
At rest, your heart circulates only about 5 liters of blood per minute, whatever your level of fitness. Very little of that goes to supplying the skeletal muscles, the ones you need for movement. However, during intense physical activity, your muscles can siphon off as much as 90% of all blood that’s circulating your body. Your heart responds by pumping out greater volumes of blood, as much as 40 liters of blood per minute in an elite athlete.
If the muscles can’t get enough oxygen from the blood, they go after other energy sources like glycogen, a muscle fuel made from carbohydrates you take in through your diet. Burning glycogen doesn’t occur in significant amounts unless you either are exercising very intensely or are so out of shape that any activity makes you gasp for air. Because glycogen depletes rapidly, it’s not an ideal fuel source for endurance activities – while oxygen is. The more efficient you use oxygen, the better you’ll perform. That’s why oxygen is considered the gold standard of athletic fitness. It’s measured by a figure known as VO2 max, or maximum aerobic capacity, and it defines the limits of the hardest work you’re able to achieve using oxygen for fuel.
You can increase your VO2 max with exercise. When you begin to follow a targeted, progressive exercise program, you’ll achieve what experts call the training effect. Your aerobic capacity improves because:
1) Stroke volume, the amount of blood pumped per beat, increases.
2) Cardiac output, the amount of blood pumped per minute, increases.
3) Heart rate, the number of times the heart beats each minute, decreases. That means the heart works less hard while moving more blood.
WHAT IS AEROBIC ACTIVITY?
Any exercise that causes your heart and lungs to work hard enough to improve your capacity for producing muscular energy is an aerobic exercise. Any exercise can be an aerobic exercise if it’s done long enough and at the right intensity. Generally, the most effective exercise for aerobic improvement are those that involve rhythmic, continuous movement of the large muscle groups.
FUEL SYSTEMS
Your muscles draw energy from one of three metabolic systems:
ATP-PC (adenosine triphosphate-phosphocreatine): An anaerobic fuel source that provides immediate, intense power of very short durations. I.e. short sprints.
Anaerobic glycolysis (lactate system): Another anaerobic fuel that provides up to approximately three minutes of energy for intense muscular exertion. Examples: Longer sprints such as quarter and half milers.
Aerobic systems: Uses oxygen to fuel activity that is maintained at a moderate level of intensity. It can continue to provide energy for prolonged periods. Examples: Long jogs, runs, bike rides.
The body uses 3 different fuel systems to power its muscles during athletic activity, 2 of which are anaerobic (meaning without oxygen) and one which is aerobic (powered by oxygen). The anaerobic systems provide energy quickly for intense bouts of exercise but cannot sustain energy production for extended periods of time. The body uses the aerobic system when energy is needed for exercise that is less intense and longer in duration.
In the 100m sprint – which athletes run in under 10 seconds, or the equivalent of about 25 miles per hour – the ATP-PC system is the primary source of energy. This tiny but potent fuel reserve becomes completely depleted in less then 8 seconds, and the entire body contains no more then 3 ounces of it. In fact, it runs out before the sprint is even over, and for the last 20m the athlete runs on sheer momentum. Given 30 seconds of recovery, the ATP-PC system can replenish itself for yet another powerful burst if needed.
A second potent anaerobic fuel source, known as the lactic acid system, supplies an additional 2 or 3 minutes of intense power. Rowers and speed skaters rely on this form of energy. However, it has the unpleasant side effect of causing a waste product known as lactic acid to build up in the muscles. You may have experienced lactic acid buildup after running uphill or climbing stairs. Your thighs start to burn until eventually your muscles stall out. That’s lactic acid leaving its mark.
The third fuel source is the aerobic system. Three ingredients go into the efficient use of aerobic energy:
· Processing: When you breathe in air, your lungs extract oxygen.
· Delivery: Your heart sends unoxygenated blood into the lungs, where the blood picks up oxygen. The oxygenated blood returns to the heart and is then shipped out to the working muscles.
· Utilization: The ability of working muscles to absorb all the oxygen being delivered is a function of how well trained the muscles are. This is usually the limiting factor in how well you are able to perform. If you are a swimmer and your cardiovascular system is in peak condition, running may still leave you winded – that is, until your leg muscles adapt to the requirements of running. Generally speaking, you will use oxygen more efficiently in the exercises you are most accustomed to doing.
ATP – A FUEL FOR ALL REASONS
No matter which of the 3 fuel systems your body is using, each is merely a facilitator for resuppling the body with its real source of power – ATP, or andenosine triphosphate (sp called because it has three phosphate molecules), the muscle fuel. ATP-PC is one of the processes for replenishing ATP. It uses phosphocreatine (PC) stored in the muscles to create new ATP molecules. When ATP separates during muscle contraction, it loses the phosphate molecule. PC supplies the phosphate molecule for more ATP.
When an electrical signal from the brain arrives at the site of a muscle, it triggers the release of calcium, which in turn causes a reaction in ATP that sends one of the phosphate molecules flying off on its own and releasing energy in the process. That mini-explosion is what provides the energy for the muscle fibers to shorten – they pull together like telescoping rods (sliding filaments is the technical term), resulting in the contractions that give you speed, strength and power. This combustible compound resides right inside the muscle tissue, in tiny manufacturing plants known as mitochondria.
But while exercising can increase the size and number of mitochondria (and hence the potential number of ATP molecules) in your body, ATP remains in very short supply and needs constant replenishment.
That’s where anaerobic and aerobic energy come in. In the ATP-PC system, the PC restores the missing phosphate molecule. But just like ATP, PC also is in limited supply and runs out in under 8 seconds.
The lactic acid system replenishes ATP with a chemical reaction that involves glucose molecules – the stuff derived from your food intake, primarily carbohydrates. Unfortunately, in the lactic acid system, the exchange rate between glucose and ATP is costly – 1 glucose molecule will get you only 2 new ATP molecules., thus limiting your energy span. In addition, you have the lactic acid buildup to contend with.
In the aerobic system, the exchange rate is much better – when you’re exercising at an intensity that allows you to process adequate levels of oxygen, you get 36 ATP molecules for each glucose molecule. The more fit you are, the more intensely you will be able to exercise and still stay in this aerobic zone, even when you are working at a pace that makes other people gasp to catch up. In fact, that’s the whole point of aerobic exercise – to get to the point where oxygen is your main currency for manufacturing more ATP.
In case you’re wondering what happens to the “missing” phosphate that ATP keeps losing in the mini-explosion, it goes on to become something of a biological renegade. Like other molecules released during chemical reactions in the body, the phosphate becomes a free radical and has the potential of causing cellular damage in the form of oxidation. Because vigorous exercise can increase the number of free radicals circulating in the body, it’s particularly important for athletes to eat nutritious foods high in antioxidants, such as cruciferous vegetables.
When you wake up in the morning and go for a jog, the first systems to provide fuel are the anaerobic ones. That’s because it takes several minutes for the aerobic process to kick into gear. Your heart rate needs to reach a point where it is pumping a sufficient amount of oxygenated blood to the muscles, and the capillaries leading to the muscles need to be dilate in order to adequately exchange that oxygen with the muscles.
During those first few moments, while you are waiting for your aerobic system to kick in, depending on how hard you run, you’ll accumulate some lactic acid that won’t be completely cleared out until after you’ve stopped exercising and your heart rate has returned to its resting rate. Here’s important advice for your exercise routines: a good, slow warm-up will leave you with less lactic acid buildup, and thus you’ll be more comfortable and less fatigued throughout the remainder of your workout.
OXYGEN DEBT
If you’ve ever wondered why your heart rate doesn’t immediately return to it’s resting rate after you finish exercising, that’s because you are repaying a debt that you owe.
When you exercise anaerobically – either at the start of a workout before your aerobic system kicks in, or when increasing the intensity of exercise during a workout – your muscles are working with less oxygen then they need. Due to the good graces of your anaerobic system, the muscles comply, but eventually you have to repay them that oxygen. That happens after you’ve finished exercising – so your heart takes awhile to calm down because it’s still working aerobically to cover that debt.
Now here’s the real surprise: if you want to recover quickly following an aerobic workout, you should keep exercising at a very light pace. Since it’s the transport of oxygenated blood that repays the oxygen debt and clears lactic acid away from your muscles, exercising at about 30% of your VO2max (that’s a light jog or brisk walking pace) will speed your recover time. So if you’re playing multiple sets of tennis, walk around a bit between sets and get that lactic acid out of your system.
The more fit you are, the more rapidly your heart will recover from exertion. If you play a sport that involves fast sprints and charges – such as basketball, tennis, soccer, or football – Then it’s important to have a good recovery rate. To improve your recovery rate, perform sprint intervals; run hard on a track or treadmill for 30 seconds to 2 minutes, and then recover for an equal length of time. Sprint intervals should be done for 6 to 10 sets each workout session.
To build short-term sprint power, you need to perform some training at a much higher intensity, above the threshold at which the body’s fuel system switches to anaerobic energy. This is known as anaerobic threshold (AT) training. It works by both increasing your tolerance for lactic acid buildup and by raising the threshold at which your body dips into its anaerobic fuel reserves. Some studies have shown that elite distance runners can function at 90% of their aerobic capacity for up to 30 minutes without accumulating lactic acid – that’s about 20% higher than the range at which most people go anaerobic and nearly run out of energy.
MORE TO COME......
CARDIOVASCULAR SYSTEM
Your athletic potential begins inside the 4 chambers responsible for moving oxygen and nutrients throughout your body. The heart, about the size of a fist, is actually 2 pumps: the 2 right chambers exchange blood with the lungs, where the blood is infused with oxygen, while the left chambers funnel blood to your muscles. The circulating blood performs another crucial activity; after it drops off the fuel, it carts away waste product like lactic acid and carbon dioxide, biological “pollutants” that are created when your muscles burn fuel.
At rest, your heart circulates only about 5 liters of blood per minute, whatever your level of fitness. Very little of that goes to supplying the skeletal muscles, the ones you need for movement. However, during intense physical activity, your muscles can siphon off as much as 90% of all blood that’s circulating your body. Your heart responds by pumping out greater volumes of blood, as much as 40 liters of blood per minute in an elite athlete.
If the muscles can’t get enough oxygen from the blood, they go after other energy sources like glycogen, a muscle fuel made from carbohydrates you take in through your diet. Burning glycogen doesn’t occur in significant amounts unless you either are exercising very intensely or are so out of shape that any activity makes you gasp for air. Because glycogen depletes rapidly, it’s not an ideal fuel source for endurance activities – while oxygen is. The more efficient you use oxygen, the better you’ll perform. That’s why oxygen is considered the gold standard of athletic fitness. It’s measured by a figure known as VO2 max, or maximum aerobic capacity, and it defines the limits of the hardest work you’re able to achieve using oxygen for fuel.
You can increase your VO2 max with exercise. When you begin to follow a targeted, progressive exercise program, you’ll achieve what experts call the training effect. Your aerobic capacity improves because:
1) Stroke volume, the amount of blood pumped per beat, increases.
2) Cardiac output, the amount of blood pumped per minute, increases.
3) Heart rate, the number of times the heart beats each minute, decreases. That means the heart works less hard while moving more blood.
WHAT IS AEROBIC ACTIVITY?
Any exercise that causes your heart and lungs to work hard enough to improve your capacity for producing muscular energy is an aerobic exercise. Any exercise can be an aerobic exercise if it’s done long enough and at the right intensity. Generally, the most effective exercise for aerobic improvement are those that involve rhythmic, continuous movement of the large muscle groups.
FUEL SYSTEMS
Your muscles draw energy from one of three metabolic systems:
ATP-PC (adenosine triphosphate-phosphocreatine): An anaerobic fuel source that provides immediate, intense power of very short durations. I.e. short sprints.
Anaerobic glycolysis (lactate system): Another anaerobic fuel that provides up to approximately three minutes of energy for intense muscular exertion. Examples: Longer sprints such as quarter and half milers.
Aerobic systems: Uses oxygen to fuel activity that is maintained at a moderate level of intensity. It can continue to provide energy for prolonged periods. Examples: Long jogs, runs, bike rides.
The body uses 3 different fuel systems to power its muscles during athletic activity, 2 of which are anaerobic (meaning without oxygen) and one which is aerobic (powered by oxygen). The anaerobic systems provide energy quickly for intense bouts of exercise but cannot sustain energy production for extended periods of time. The body uses the aerobic system when energy is needed for exercise that is less intense and longer in duration.
In the 100m sprint – which athletes run in under 10 seconds, or the equivalent of about 25 miles per hour – the ATP-PC system is the primary source of energy. This tiny but potent fuel reserve becomes completely depleted in less then 8 seconds, and the entire body contains no more then 3 ounces of it. In fact, it runs out before the sprint is even over, and for the last 20m the athlete runs on sheer momentum. Given 30 seconds of recovery, the ATP-PC system can replenish itself for yet another powerful burst if needed.
A second potent anaerobic fuel source, known as the lactic acid system, supplies an additional 2 or 3 minutes of intense power. Rowers and speed skaters rely on this form of energy. However, it has the unpleasant side effect of causing a waste product known as lactic acid to build up in the muscles. You may have experienced lactic acid buildup after running uphill or climbing stairs. Your thighs start to burn until eventually your muscles stall out. That’s lactic acid leaving its mark.
The third fuel source is the aerobic system. Three ingredients go into the efficient use of aerobic energy:
· Processing: When you breathe in air, your lungs extract oxygen.
· Delivery: Your heart sends unoxygenated blood into the lungs, where the blood picks up oxygen. The oxygenated blood returns to the heart and is then shipped out to the working muscles.
· Utilization: The ability of working muscles to absorb all the oxygen being delivered is a function of how well trained the muscles are. This is usually the limiting factor in how well you are able to perform. If you are a swimmer and your cardiovascular system is in peak condition, running may still leave you winded – that is, until your leg muscles adapt to the requirements of running. Generally speaking, you will use oxygen more efficiently in the exercises you are most accustomed to doing.
ATP – A FUEL FOR ALL REASONS
No matter which of the 3 fuel systems your body is using, each is merely a facilitator for resuppling the body with its real source of power – ATP, or andenosine triphosphate (sp called because it has three phosphate molecules), the muscle fuel. ATP-PC is one of the processes for replenishing ATP. It uses phosphocreatine (PC) stored in the muscles to create new ATP molecules. When ATP separates during muscle contraction, it loses the phosphate molecule. PC supplies the phosphate molecule for more ATP.
When an electrical signal from the brain arrives at the site of a muscle, it triggers the release of calcium, which in turn causes a reaction in ATP that sends one of the phosphate molecules flying off on its own and releasing energy in the process. That mini-explosion is what provides the energy for the muscle fibers to shorten – they pull together like telescoping rods (sliding filaments is the technical term), resulting in the contractions that give you speed, strength and power. This combustible compound resides right inside the muscle tissue, in tiny manufacturing plants known as mitochondria.
But while exercising can increase the size and number of mitochondria (and hence the potential number of ATP molecules) in your body, ATP remains in very short supply and needs constant replenishment.
That’s where anaerobic and aerobic energy come in. In the ATP-PC system, the PC restores the missing phosphate molecule. But just like ATP, PC also is in limited supply and runs out in under 8 seconds.
The lactic acid system replenishes ATP with a chemical reaction that involves glucose molecules – the stuff derived from your food intake, primarily carbohydrates. Unfortunately, in the lactic acid system, the exchange rate between glucose and ATP is costly – 1 glucose molecule will get you only 2 new ATP molecules., thus limiting your energy span. In addition, you have the lactic acid buildup to contend with.
In the aerobic system, the exchange rate is much better – when you’re exercising at an intensity that allows you to process adequate levels of oxygen, you get 36 ATP molecules for each glucose molecule. The more fit you are, the more intensely you will be able to exercise and still stay in this aerobic zone, even when you are working at a pace that makes other people gasp to catch up. In fact, that’s the whole point of aerobic exercise – to get to the point where oxygen is your main currency for manufacturing more ATP.
In case you’re wondering what happens to the “missing” phosphate that ATP keeps losing in the mini-explosion, it goes on to become something of a biological renegade. Like other molecules released during chemical reactions in the body, the phosphate becomes a free radical and has the potential of causing cellular damage in the form of oxidation. Because vigorous exercise can increase the number of free radicals circulating in the body, it’s particularly important for athletes to eat nutritious foods high in antioxidants, such as cruciferous vegetables.
When you wake up in the morning and go for a jog, the first systems to provide fuel are the anaerobic ones. That’s because it takes several minutes for the aerobic process to kick into gear. Your heart rate needs to reach a point where it is pumping a sufficient amount of oxygenated blood to the muscles, and the capillaries leading to the muscles need to be dilate in order to adequately exchange that oxygen with the muscles.
During those first few moments, while you are waiting for your aerobic system to kick in, depending on how hard you run, you’ll accumulate some lactic acid that won’t be completely cleared out until after you’ve stopped exercising and your heart rate has returned to its resting rate. Here’s important advice for your exercise routines: a good, slow warm-up will leave you with less lactic acid buildup, and thus you’ll be more comfortable and less fatigued throughout the remainder of your workout.
OXYGEN DEBT
If you’ve ever wondered why your heart rate doesn’t immediately return to it’s resting rate after you finish exercising, that’s because you are repaying a debt that you owe.
When you exercise anaerobically – either at the start of a workout before your aerobic system kicks in, or when increasing the intensity of exercise during a workout – your muscles are working with less oxygen then they need. Due to the good graces of your anaerobic system, the muscles comply, but eventually you have to repay them that oxygen. That happens after you’ve finished exercising – so your heart takes awhile to calm down because it’s still working aerobically to cover that debt.
Now here’s the real surprise: if you want to recover quickly following an aerobic workout, you should keep exercising at a very light pace. Since it’s the transport of oxygenated blood that repays the oxygen debt and clears lactic acid away from your muscles, exercising at about 30% of your VO2max (that’s a light jog or brisk walking pace) will speed your recover time. So if you’re playing multiple sets of tennis, walk around a bit between sets and get that lactic acid out of your system.
The more fit you are, the more rapidly your heart will recover from exertion. If you play a sport that involves fast sprints and charges – such as basketball, tennis, soccer, or football – Then it’s important to have a good recovery rate. To improve your recovery rate, perform sprint intervals; run hard on a track or treadmill for 30 seconds to 2 minutes, and then recover for an equal length of time. Sprint intervals should be done for 6 to 10 sets each workout session.
To build short-term sprint power, you need to perform some training at a much higher intensity, above the threshold at which the body’s fuel system switches to anaerobic energy. This is known as anaerobic threshold (AT) training. It works by both increasing your tolerance for lactic acid buildup and by raising the threshold at which your body dips into its anaerobic fuel reserves. Some studies have shown that elite distance runners can function at 90% of their aerobic capacity for up to 30 minutes without accumulating lactic acid – that’s about 20% higher than the range at which most people go anaerobic and nearly run out of energy.
MORE TO COME......