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Human Kinetics Publishers, Inc.


By Joe Friel
ISBN:   978-1-4504-2380-9
Binding: Paperback
Pages:   Approx. 680

Price: $27.95
Available: March 2013



Why understanding the science of triathlon is critical to success

Legendary endurance sport coach reveals how a triathlete processes energy

CHAMPAIGN, IL—A triathlete’s physical ability may be an important factor, but when it comes to success in the sport, knowledge of the science of triathlon is equally critical. According to legendary endurance sport coach Joe Friel, knowledge of the science of triathlon is crucial to success in the sport. “A significant amount of energy is required to train for and compete in triathlon,” says Friel. “A practical knowledge of the physiology of energy production can help you design effective workouts and pace yourself more effectively during races.”


According to Friel, triathletes must first understand how their bodies process energy. “The basic unit of energy in the human body is adenosine triphosphate (ATP),” Friel says. “A simple way to think of a molecule of ATP is as an energy dollar bill. There are millions of molecules of ATP in the human body providing energy, and triathletes are constantly using and replenishing ATP, even when not exercising.” Friel notes that ATP utilization and production are similar to the daily scenario of spending money to pay bills and maintain a lifestyle.


In the forthcoming Triathlon Science (Human Kinetics, 2013), Friel explains how the body produces energy and offers practical knowledge of the three energy systems used by the body during exercise.

  1. Immediate energy system
    The technical name for the immediate energy system is adenosine triphosphate and is one of the two anaerobic energy systems. “The immediate energy system has the advantage of producing ATP very quickly but the disadvantage of producing a very limited supply of ATP,” says Friel. “In terms of athletic performance, the immediate energy system is the dominant energy system during very high-intensity, short-duration exercise lasting approximately 10 seconds or less.” Examples of the immediate energy system in athletic performance are the 100-meter sprint in track, 10-meter diving event, and weightlifting events.
  2. Short-term energy system
    The short term-energy system is also anaerobic and is known as glycolysis because the first of several biochemical reactions in this energy system involves the conversion of glycogen to free glucose. The short-term energy system has the advantage of producing more ATP than the immediate energy system, but the disadvantage of taking longer to do so. “Another disadvantage is the short-term energy system produces lactic acid, which is quickly converted to lactate and positively charged hydrogen ions (H+),” Friel explains. “High concentrations of H+ create the acidic burning sensation in exercising skeletal muscle and, along with other biochemical, neural, and biomechanical factors, contributes to premature fatigue.” The short-term energy system is the dominant energy system used during high-intensity, moderate-duration exercise lasting approximately 30 to 120 seconds. Examples of the short-term energy system in athletic performance are the 400-meter sprint in track, 100-meter sprint in swimming, and 1,000-meter track cycling event.
  3. Long-term energy system
    The technical name for the long-term energy system is oxidative phosphorylation and is aerobic in nature, requiring oxygen to produce ATP. “The long-term energy system has the advantage of producing very large amounts of ATP compared with the other energy systems, but it has the disadvantage of taking more time to produce that relatively large amount of ATP,” Friel says. “The long-term energy system takes longer because it uses oxygen to produce ATP.” The long-term energy system is the dominant energy system in low- to moderate-intensity exercise lasting longer than 5 minutes. Examples of the long-term energy system in athletic performance are the marathon, 800-meter swim, and road cycling events. “The long-term energy system is the dominant energy system used during triathlon training and racing,” Friel says. “However, it is important to understand that it is not the only energy system used in triathlon.”

Although the dominant energy system used in triathlon is the long-term energy system, Friel stresses the importance of remembering the roles of the immediate and short-term energy systems in triathlon performance. “A triathlete should apply the scientific principles of the three energy systems to the design of daily workouts in order to consistently meet the specific goals of the training program,” Friel says. “Knowing when to train and how much time to devote to training each of the three energy systems is an important ingredient of success in triathlon and is reflective of a well-designed and scientifically based training plan.”


For more information, see Triathlon Science.


About the Authors

Joe Friel, MSc, has trained endurance athletes since 1980. He served as head coach of the U.S. national triathlon team for the world championships in 2000, and athletes he has worked with have competed in the Olympic Games. He is cofounder of the USA Triathlon’s National Coaching Association, serves on the USA Triathlon Coaching Certification Committee, and is an elite-level coach for USA Cycling. Friel is a Colorado State Masters Triathlon champion, a Rocky Mountain region and Southwest region duathlon age-group champion, and a perennial USA Triathlon All-American duathlete. As a member of several national duathlon teams, Friel was a top 5 contender in world-class events and competed in road running and United States Cycling Federation races. He is the author of The Triathlete’s Training Bible, Your First Triathlon, Your Best Triathlon, Total Heart Rate Training, and The Paleo Diet for Athletes. He is a contributor to Precision Heart Rate Training and USA Triathlon’s Complete Triathlon Guide


Jim Vance is a coach of triathlon and duathlon, running, and cycling at TrainingBible Coaching and the founder and head coach of TriJuniors, a USAT high-performance team in San Diego. For his coaching, he has been named the 2009 Tri Club of San Diego Coach of the Year and was appointed U.S. elite national team coach for the Duathlon World Championships in 2011. He has coached athletes who have won and qualified for events including the U.S. Elite National Championships, Elite ITU World Championships, Ironman World Championships, 70.3 World Championships, and XTERRA European Tour Elite. A former professional triathlete who spent time at the U.S. Olympic Training Center, Vance placed third in the Florida Ironman and was an ITU age-group world champion, an XTERRA amateur world champion, and a letter winner at the University of Nebraska.





Part I Physical Attributes of Triathletes

Chapter 1 Physiology and the Multisport Athlete
Chapter 2 Genetics and Inheritance in Triathlon Performance

Chapter 3 Gender and Age Considerations in Triathlon


Part II Technical Execution and Efficiency in Each Event

Chapter 4 Swimming Biomechanics for Triathlon

Chapter 5 Cycling Biomechanics for Triathlon

Chapter 6 Running Biomechanics for Triathlon


Part III Environmental Factors and Equipment Options

Chapter 7 In the Water

Chapter 8 On the Bike

Chapter 9 For the Run

Chapter 10 Triathlon Training Technologies


Part IV Physiological Function in Triathlon Training

Chapter 11 Aerobic Capacity

Chapter 12 Economy

Chapter 13 Anaerobic Threshold

Chapter 14 Muscle Types and Triathlon Performance

Chapter 15 Fatigue Resistance and Recovery


Part V Training Modes and Methods for Triathletes

Chapter 16 Warm-Up and Cool-Down

Chapter 17 Flexibility and Postural Stability

Chapter 18 Strength Training

Chapter 19 Aerobic and Anaerobic Base Building

Chapter 20 Interval Training


Part VI Training Strategies in Triathlon

Chapter 21 Duration, Frequency, Volume, and Intensity

Chapter 22 Periodization

Chapter 23 Tapering and Peaking for Races

Chapter 24 Physiology of Overtraining


Part VII Training Base Building for Triathlon

Chapter 25 Swim Base Building

Chapter 26 Bike Base Building

Chapter 27 Run Base Building


Part VIII Multisport Event-Specific Training and Racing Tactics

Chapter 28 Sprint

Chapter 29 Olympic

Chapter 30 Half-Ironman

Chapter 31 Ironman

Chapter 32 Duathlon

Chapter 33 Combination Workout Training


Part IX Sports Medicine for Triathletes

Chapter 34 Triathlete Body Maintenance and Medical Care

Chapter 35 Triathlon Injuries and Preventive Measures

Chapter 36 Triathlon Injury Recovery Techniques


Part X Nutrition for Triathletes

Chapter 37 Energy Needs, Sources, and Utilization

Chapter 38 Nutrition Periodization

Chapter 39 Nutrient Timing for Triathlon Training and Racing

Chapter 40 Supplements for Triathletes


Part XI Psychology of Multisport

Chapter 41 Mental Toughness for Triathlon

Chapter 42 Psychology of Triathlon Training

Chapter 43 Mental Skills for Peak Triathlon Performance


Joe Friel
Joe Friel

Jim Vance
Jim Vance




“Joe Friel is a founding father of our sport, so you can be confident that Triathlon Science will be a valuable addition to your triathlon library.”


Gordon Byrn

Founder of

2002 Ultra Man World Champion


“Triathlon Science is invaluable for any athlete looking to decipher the vast information available and achieve immediate results.”


Adam Zucco

Triathlon Coach

2009 USAT Developmental Coach of the Year

Five-Time Hawaii Ironman Finisher




“The scientific information discussed in Triathlon Science will give every reader a deeper understanding of the how and why behind a training program. It is a great resource for coaches and athletes alike.”


Linda Cleveland

Coach Development Manager

USA Triathlon 


Background Facts

  • The ability to perform aerobic or anaerobic exercise varies widely among people, partially depending on muscle fiber composition. In untrained people, the proportion of slow-twitch (type I) fibers in the vastus lateralis muscle is typically around 50 percent (range 5 to 90 percent), and it is unusual for them to undergo conversion to fast-twitch fibers. Endurance-oriented athletes are reported to have a remarkably high proportion of type I fibers in their trained muscle groups, whereas sprinters and weightlifters have muscles that consist predominantly of type IIa and IIx fibers.
  • Research on aerobic endurance clearly shows that some people respond more than others to training.In the same study the maximal heritability estimate of the VO2max response to training adjusted for age and sex was reported to be 47 percent. This result means that genetically gifted athletes have a much greater response to training. For example, evidence that many of the world’s best endurance runners originate from distinct regions of Ethiopia and Kenya, rather than being evenly distributed throughout their respective countries, appears to sustain the idea that the success of East African runners is genetically determined. Studies have shown that African distance runners have reduced accumulation of lactic acid in muscles, increased resistance to fatigue, and increased oxidative enzyme activity, which equates with high levels of aerobic energy production.
  • Male triathletes have larger muscle mass, correlating with greater muscular strength and lower relative body fat compared with females. Low body fat is an important predictor variable for total time performance in triathlon. For example, Knechtle, Knechtle, and Rosemann showed that low body fat was associated with faster race times in male Ironman triathletes but not in females. Men retain on average 7 to 9 percent less percent body fat than women, which is likely advantageous for men. Therefore, gender differences in percentage of body fat, oxygen-carrying capacity, and muscle mass appear to be responsible for gender differences in triathlon performance. Note also that pregnancy and the menstrual cycle may affect training and racing.
  • The ability to sustain a high relative workload, as a percentage of either VO2max or peak exercise work rate, for long periods is crucial to success in triathlon. We have seen that in a group of similarly performing endurance athletes, aerobic capacity is often a poor predictor of success. One of the reasons for this is the crucial importance of being able to sustain high relative exercise intensities in competition. Regardless of the definition, the threshold concept is a key factor for success in triathlon.

Facts taken from Triathlon Science.



Interview Questions

  • Why is knowledge of the science of triathlon critical to success in the sport, particularly in the Ironman race format?
  • Economy refers to how efficiently oxygen is used at submaximal intensities, and it provides an indirect measure of the energetic cost of swimming, cycling, or running. How can economy be measured and how does measurement differ between sports?
  • Explain what bonking is and why almost all triathletes have experienced it.
  • How does training affect the general fiber type classification of muscle and muscle metabolic properties, leading to improved performance?
  • What should a triathlete look for when purchasing a race bike?
  • What are the differences between swimming in the pool and swimming in the open water, and how can triathletes prepare?
  • How do genetics affect triathlon performance?
  • How do you define anaerobic threshold?

Media Contacts

United States

Maurey Williamson
Publicity Manager


Alexis Koontz
Associate Publicity Manager


UK & Europe

Graham Smith
+44 (0) 113 255 5665



Christine Traverse
1-800-465-7301 x11



Bec Rosewall
(08) 8372-0999


New Zealand

Bec Rosewall
Toll Free: +61 (0) 8 8372 0999


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