Advanced Marathoning

Glossary

This glossary is purposefully short. It contains only the main physiological terms used in this book that are highly pertinent to marathon training and racing. It’s provided here for easy reference if you’re reading the book other than from cover to cover.

biomechanics – How the various parts of your body work together to create your running form. Although some features of your biomechanics, such as the structure of your bones, are primarily genetically determined, stretching and strengthening exercises may improve your running biomechanics and therefore improve your marathon performance.

capillaries – The smallest blood vessels; several typically border each muscle fiber. With the correct types of training, you’ll increase the number of capillaries per muscle fiber. By providing oxygen directly to the individual muscle fibers, increased capillary density allows your rate of aerobic energy production to increase. Capillaries also deliver fuel to the muscle fibers and remove waste products such as carbon dioxide.

fast-twitch muscle fibers – Muscle fibers that contract and fatigue rapidly to power intense short-term exercise such as sprinting. They’re classified into two categories, A and B; fast-twitch A fibers have more of the characteristics of slow-twitch fibers than do fast-twitch B. Although your fast-twitch muscle fibers can’t be converted to slow-twitch fibers, with general endurance training your fast-twitch A fibers gain more of the characteristics of slow-twitch fibers. These adaptations are beneficial because your fast-twitch fibers then become better at producing energy aerobically.

glycogen – The storage form of carbohydrate in your muscles and the main source of energy during running. Endurance training reduces your body’s need to burn glycogen at a given pace and teaches your body to store more glycogen.

hemoglobin – A red blood cell protein that carries oxygen in the blood. The higher your hemoglobin content, the more oxygen that can be carried (per unit of blood) to your muscles to produce energy aerobically.

lactate threshold – The exercise intensity above which your rate of lactate production is substantially greater than your rate of lactate clearance. At effort levels above your lactate threshold, the lactate concentration rises in your muscles and blood. The hydrogen ions associated with lactate production inactivate the enzymes for energy production and may interfere with the uptake of calcium, thereby reducing the muscles’ ability to contract. You can’t, therefore, maintain a pace faster than your lactate-threshold pace for more than a few miles. For well-trained runners, lactate threshold usually occurs at 15K to half marathon race pace.

maximal heart rate – The highest heart rate you can attain during all-out running. Your maximal heart rate is determined genetically. In other words, it doesn’t increase with training. Successful marathoners don’t have particularly high maximal heart rates, so it isn’t a factor in determining success.

maximal oxygen uptake – Commonly referred to asO₂max; the maximal amount of oxygen your heart can pump to your muscles and your muscles can then use to produce energy. The combination of your training and your genetics determines how high aO₂max you have.

mitochondria – The only part of your muscle fibers in which energy can be produced aerobically. Think of them as the aerobic energy factories in your muscle fibers. The right types of training increase the size of your mitochondria (i.e., make bigger factories) and the number of mitochondria (i.e., make more factories) in your muscle fibers.

running economy – How fast you can run using a given amount of oxygen. If you can run faster than another athlete while using the same amount of oxygen, then you have better running economy. Running economy can also be looked at as how much oxygen is required to run at a given speed. If you use less oxygen while running at the same speed as another runner, then you’re more economical.

slow-twitch muscle fibers – Muscle fibers that contract and tire slowly and that power sustained submaximal exercise such as endurance running. Slow-twitch muscle fibers naturally resist fatigue, and they have a high aerobic capacity, high capillary density, and other characteristics that make them ideal for marathon running. The proportion of slow-twitch fibers in your muscles is determined genetically and is believed not to change with training.

O₂max – See maximal oxygen uptake.