Principles of Conditioning

This article addresses the principles of conditioning and how these fundamental principles can be appropriately incorporated into school-based physical education. The components of health-related fitness discussed in the overview are muscular strength, muscular endurance, and aerobic endurance as conditioning principles directly apply to each of these components. The principle of overload and the FITT principles are discussed as they relate to resistance training, which develops muscular strength and muscular endurance, and aerobic conditioning, which develops aerobic endurance. Physical education teachers must follow several guidelines and consider teaching strategies when designing developmentally appropriate resistance training and aerobic conditioning programs for their students. Perhaps most important, teachers must understand that their role in students' physical fitness development is to educate students about how to make healthy choices as they relate to their level of physical activity in an effort to decrease the rate of childhood obesity and diseases related to sedentary lifestyle.

Keywords Aerobic/Cardio-Respiratory Endurance; FITT Principle; Health-Related Fitness; Hypertrophy; Muscular Strength; Overload; Physical Fitness; Resistance Training; Skill-Related Fitness; Target Heart Rate Zone

Overview

Principles of conditioning are those tenets of exercise science that address the physiological processes by which individuals improve their muscular strength, muscular endurance, aerobic and anaerobic capacity, and flexibility. The scientific theories and tenets that these principles are based upon are addressed in the fields of exercise and muscle physiology. For the purpose of this article, the specific physiological processes that occur during physical activity will not be discussed; rather the focus will be to provide a synopsis of the principles of conditioning based on how they are relevant to physical education. Principles of conditioning, within the context of physical education, involve the application of physiological principles to the learning objectives and teaching methods that are employed in the classroom in order to design activities and curricula in a manner to enhance the students' level of physical fitness and knowledge and understanding of conditioning concepts.

The National Association for Sport and Physical Education (NASPE) has set forth recommended content standards for teaching and learning in physical education (NASPE, 2007). The six national standards provide a framework to guide state and local school administration in the development of physical education curricula and also demonstrate the purpose of physical education and its academic merit and value as a component of education (NASPE, 2007). The third and the fourth standards state that students should engage in regular physical activity and demonstrate or achieve and maintain a level of physical fitness that enhances health (NASPE, 2007). With the number of obese and overweight youth having increased dramatically over the last few decades, it has become increasingly important for physical educators to focus on achieving these standards by incorporating physical activity and health-related fitness education into the physical education curriculum (Greer & Gilbert, 2006). A 2010 position statement by NASPE, "Appropriate Uses of Fitness Measurement," affirms these standards and the NASPE's position that fitness measurement should be used to improve student health and physical activity programs, and should focus on the process of achieving fitness rather focusing on individual achieved outcomes to assign student grades or teacher effectiveness ratings. Physical education can also play an important role in a student?s general education, addressing measures such as problem-solving and personal growth, as argued by Thorburn and MacAllister (2013).

Physical fitness is defined as the ability to perform physical activity (Casperson, Powell, & Christenson, 1985). Health-related fitness is a term that is used to indicate physical activity that aims to promote good health and wellness as opposed to conditioning that is specifically designed with performance as the focus. Performance-focused training is called skill-related fitness and focuses on the development of speed, power, reaction time, balance, coordination and agility, which are related to enhancing performance and/or sport skill development (Corbin, 2004). Health-related fitness, which is applicable to the physical education setting, encompasses five components: 1) muscular strength, 2) muscular endurance, 3) aerobic endurance, 4) flexibility, and 5) body composition (Maina, Griffin, Ryan, & Schlegel Maina, 2001).

Muscular strength, muscular endurance, and aerobic endurance are the health-related fitness components that are directly related to physical conditioning in the physical education setting. Muscular strength is defined as the force that a muscle can produce or exert in a one time maximal effort or the greatest amount of weight or resistance a muscle can move or lift for one repetition only, also known as a "one rep max" (Maina et al., 2001). Muscular endurance is defined as the ability for a muscle group to perform, or contract, repeatedly at a resistance below the maximum resistance that the muscle can move (Maina et al., 2001). Aerobic endurance is defined as the body's ability to engage in activity over a prolonged period of time and utilizes oxygen in the process of energy generation (Universal Fitness Tester, 2007).

Applications

Resistance training, or weight training, is a mode of exercise that aims to increase muscular strength and endurance through the process of overloading the muscles. The conditioning principle of overload requires that the body must undergo a level of stress that is greater than the norm in order for the body to undergo physiological adaptations that increase muscular strength and endurance. Resistance training as a form of conditioning for youth has been investigated to determine whether or not this type of exercise is appropriate for children and adolescents and what benefits result (Kraemer, Fry, Frykman, Conroy, & Hoffman, 1989). Research has shown that resistance training is appropriate for youth when programming is dynamic and individualized. Resistance training has been shown to improve body composition, prevent injury, and improve blood lipid profiles in youth (Kraemer et al., 1989). There has been evidence indicating that training prior to puberty increases strength as a result of neuromuscular adaptations and improved technique; however, research has shown that during adolescence the increases in strength are due to neuromuscular adaptations, muscle hypertrophy, and improved technique (Langford & McCurdy, 2005). Research that examined the differences in strength based on sex have indicated that prior to puberty strength in boys and girls is the same, at 11-12 years the average strength of girls is 90% less than boys, at 13-14 years this decreases to 80%, and at 15-16 years girls have approximately 75% of the strength of boys (Langford & McCurdy, 2005). These research findings lend support for physical educators to incorporate resistance training and its underlying principles of conditioning into their physical education curriculum.

Muscular Strength & Muscular Endurance

It is recommended that prior to starting a resistance training program with a child the teacher should be sure that the child has medical clearance, an understanding of the purpose of the program, a willingness to try the program, and an understanding that strength training is a lifetime pursuit. Resistance training programs for children need to take into account physiological and psychological factors. Teachers must consider the physiological maturation of each child as well as the psychological maturation and readiness of the students in order to develop resistance training programs that are developmentally appropriate (Kraemer et al., 1989). While generalized programs are best used as starter programs, maturation and readiness are factors that make it imperative that resistance programs for children are individualized and dynamic (Kraemer et al., 1989). Resistance training programs designed for children need to address several factors including: 1) the choice of exercise, 2) the order of the exercises, 3) the rest period between exercises, 4) the number of sets, and 5) the load (Kraemer et al., 1989). The activity choice is important because the child's size needs to be considered as the child must fit the equipment properly. Proper technique and skill must be taught in order for the exercise to be effective and not lead to injury (Kraemer et al., 1989). Major muscle groups should also be the focus of the exercises that are included in the program (Kraemer et al., 1989). The program should set the order of the exercises with large muscle groups being worked first, smaller muscles second and typically alternating upper body exercises with lower body exercises (Kraemer et al., 1989).

Rest periods may vary. Rest between sets should be longer with heavy weights (2-5 minutes) and during the early phases of the learning process (Kraemer et al., 1989). Shorter rest periods can be added as the students' progress through the beginning phases of learning and when muscle hypertrophy is desired. The number of sets that are incorporated into a program is the volume of work. For physical education students it is recommended that single sets are implemented in the early phase of the program (the first 2-3 weeks) and then after this period, the teacher can increase the number of sets to achieve the best results and encourage student interest in the program (Kraemer et al., 1989). Elementary and middle school students should be lifting sub-maximal resistance that should not exceed 70% of their one repetition maximum (Fees, 2003; Maina et al., 2001). In general, when designing resistance training programs, teachers should provide a 'safety zone' of two repetitions with 8-10 repetitions for heavy weight, 12-15 repetitions for moderate weight, and 18-20 repetitions for light weight (Kraemer et al., 1989). Programs for children should incorporate the principle of progressive overload. Progressive overload is when a specific muscle group is stressed throughout a set of an exercise so that the maximum muscular contraction ability is reached within that set (Kraemer et al., 1989). If a student reaches the point in a set where a weight is too heavy to lift without a spotter, it is recommended that the student increase repetitions prior to making an increase in weight (Langford & McCurdy, 2006). This type of approach to programming will help to decrease the possibility that students will list with incorrect technique as well as decrease the chances of incurring an injury through resistance training.

Resistance training is complex and therefore an area of physical education curricula that needs to be well planned. Programming must take into consideration such factors as each student's maturation, motor skill ability, and their affective needs (Langford & McCrudy, 2005). It is necessary for the teacher to provide basic strength training instruction about safety when engaging in this activity (consider maturity of students), proper mechanics, the importance of technique, and basic weight lifting principles so that students understand the basic scientific premise of resistance training (Maina et al., 2001). Once the students have a solid knowledge and understanding of safety, mechanics, and basic principles, the physical education teacher can then introduce one to two concepts per class period related to understanding the muscle groups, the basic muscle physiology of contraction and relaxation, range of motion, breathing techniques, and more in depth information about form and technique (Maina et al., 2001). Physical education teachers can develop resistance training programs that use weights or body weight as the resistance. Body weight training allows the teacher to design programs that include individual, partner, and group work (Langford & McCurdy, 2005). Once the resistance training program has started, there should always be adult supervision watching for proper technique and spotting while students engage in a workout that has 4-8 basic exercises taking no more than 15-30 minutes, 2-3 times per week (Gardner, 2003). The primary goal of the program should be the students' form and technique and getting and maintaining student interest with strength development being the secondary goal (Gardner, 2003).

Aerobic Endurance

Aerobic endurance can be addressed in the classroom using numerous techniques and strategies. Aerobic endurance can be explained simply as the "ability of the heart and lungs to work hard for a long time without getting too tired (providing as much oxygen as needed by muscles to work for a long time)" (Sander & Ratliffe, 2002, p. 16). The same principle of overload that applies to increasing muscular strength and endurance is applied to the development of aerobic endurance. In order to develop or increase one's aerobic endurance, an individual must engage in physical activity that forces the heart and the lungs to work harder than normal. By regularly overloading the cardio-respiratory system, the body begins to make physiological adaptations and increase the capacity of the body to engage in prolonged and more intense activity. These adaptations are evident in the increased efficiency of the heart and lungs to pump oxygen to the muscles in order for the muscles to sustain the activity level. The efficiency and any improvement in efficiency of the heart and lungs can be assessed by taking and recording heart rates and monitoring the rate of breathing. The heart rate is a measure of how often the heart goes through one full cardiac cycle and the more efficient the heart, the lower the number of times the heart will beat in a minute due to the heart's ability to pump a sufficient or increased amount of blood in one cardiac cycle. When an individual engages in regular physical activity, he or she begins to train the heart and lungs to become more efficient through the process of overloading the heart muscle and respiratory system, which results in a decreased heart rate and breathing rate.

The FITT Principle

The FITT Principle is used to guide individuals in their pursuit of physical activity (Insel & Roth, 2006). FITT stands for Frequency, Intensity, Type, & Time. Frequency is the number of times per week an individual should engage in physical activity. Intensity is the level of activity that can be assessed by the heart rate during exercise. It is important for an exerciser to attain a heart rate within the Target Heart Rate Zone for there to be cardio-respiratory benefit with a particular bout of exercise (Insel & Roth, 2006). The more intense the activity, the higher the heart rate will fall in the target zone; however, once the body becomes trained the individual will have to work harder to achieve the same heart rate level. This is an indication that the cardio-respiratory system is becoming more efficient and trained. The type of activity should involve large muscle groups and allow the individual to maintain constant activity over a period of time. The recommended amount of exercise that is appropriate varies depending on age and fitness level.

The Centers for Disease Control and Prevention recommend that young people (ages 6 through 17) take part in at least 60 minutes of physical acidity daily, and that physical education be provided to students in all grades. However, neither standard is consistently met by American children: for instance, according to the Centers for Disease Control and Prevention, a 2011 survey found that only 29% of U.S high school students h had taken part in at least 60 minutes of daily physical activity in the preceding seven days, and only 31% took part in daily physical education classes.

Children should participate in physical activity, within their target heart rate zone, in multiple bouts over the course of a day through participation in a variety of activities as opposed to one specific activity (Corbin, 2004). Research has shown that for children heredity, maturation, and chronological age have more to do with physical fitness than participating in physical activity. Not until the teen years does exercise begin to have a more direct impact on physical fitness. With this in mind, and with the limited time spent in the physical education class setting, it is impossible for elementary and early middle school physical education classes to have a significant impact on a students' actual fitness development, therefore it is important for physical education teachers to understand that teaching the students about physical activity, how to engage in activity, how to self-assess activity and fitness levels, about the value physical activity, and to find activities that can be enjoyed over the course of a lifetime is more important than focusing on getting the students more physically fit (Corbin, 2004; Ng, Gannon, & Halas, 2006).

Erwin, Beighle, Carson, and Castelli (2013) recommend a comprehensive school physical activity (CSPAP) to promote physical activity among young people. The key to CSPAP is to develop a school culture promoting physical activity beyond the physical education class, with five key components: physical education, physical activity during school hours, physical activity outside school hours, school staff involvement, and family and community involvement.

Further Insights

In developing the physical education curriculum, teachers need to determine how many class periods/lessons there are available and then establish how many outcomes will be addressed (Ratliffe, 2000). Physical education teachers must consider the experience level of students in terms of how much information or the concepts they have been taught about physical fitness. For example, a teacher who has had the opportunity to work with students over several years of school and who has incorporated fitness concepts each academic year, has the opportunity to begin with more advanced concepts; whereas a teacher who is introducing conditioning concepts into the curriculum for the first time or does not have students in successive academic years will not be able to begin at an advanced level of content knowledge (Ratliffe, 2000). Teachers can also gain valuable information by networking with fellow physical education teachers in and outside of their school district. Networking provides an opportunity for teachers to exchange and share ideas that have been successful and unsuccessful (Ratliffe, 2000). New technologies may also aid in instruction: for instance, Pasco (2013) argues that virtual reality technology may enhance learning and conceptual change in physical education.

It is important for teachers to consider a number of strategies when teaching and promoting cardio-respiratory health within the physical education class in order to promote health-related fitness behaviors as well as to foster motivation in the students to engage in physical activity in and outside of the classroom. These strategies include:

• Providing students with concrete examples of fitness concepts (Sander & Ratliffe, 2002).

• Applying fitness concepts to everyday activities and relevant experiences by using visual aids, objects, and action-oriented demonstrations ((Ng, Gannon, & Halas, 2006; Sander & Ratliffe, 2002).

• Creating a curriculum that is both developmentally appropriate to target the cognitive and physical maturation of the students (Ng, Gannon, & Halas, 2006; Sander & Ratliffe, 2002).

• Focusing on only 1-2 concepts or objective per class period and check for students' understanding (Ratliffe, 2000).

• Providing students with the opportunity to have a choice in what activities they engage in (Ng, Gannon, & Halas, 2006).

• Designing class activities that are challenging, fun, novel, and promote intrinsic motivation (Corbin, 2004; Ng, Gannon, & Halas, 2006).

• Implementing criterion-referenced standards (e.g., Fitnessgram), which provide information about level of fitness, as opposed to normative standards (Corbin, 2004).

• Teaching students how to self-manage by instructing and encouraging them how to self-assess their fitness levels and interpret their own results to then use in planning future physical activity programs (Corbin, 2004).

• Planning activities that are not too regimented or focused on performance (Corbin, 2004).

• Encourage a social support system within the classroom setting to encourage all students to become active (Corbin, 2004).

• Utilizing cooperative learning techniques to encourage positive student interaction and cooperation (Kane & Kane, 2004).

• Inviting guest speakers to speak to classes (e.g., college or professional athletes, individuals with high blood pressure, etc.) (O'Hara & Titlebaum, 2000).

• Creating after-school or evening wellness programs for students and/or students and their parents (O'Hara & Titlebaum, 2000).

• Incorporating the use of pedometers into the physical education class and/or school culture to allow students an opportunity to monitor their own physical activity and set personal, self-referenced goals (Beighle, Morgan, & Pangrazi, 2004).

This list of teaching strategies provides evidence that there are numerous ways to incorporate components of physical activity and the underlying principles of conditioning into the physical education classroom setting. It is most important to find a way to engage students in learning about the concepts and their application to encourage students to enjoy and participate in regular physical activity in order to increase cardio-respiratory health and reduce the chances of the onset of disease that is related to a sedentary lifestyle.

The principles of conditioning are an important foundation to the understanding of physical fitness and how we can improve students' levels of muscular strength, muscular endurance, and aerobic endurance. Physical education teachers have the responsibility to incorporate these principles into their physical education classrooms in a manner that is developmentally appropriate, enjoyable, and motivating for the students so that they will make educated choices related to their current and future physical activity levels in and outside the classroom. Muscular strength, muscular endurance, and aerobic endurance are components of health-related fitness that can directly affect the other two components, body composition and flexibility. Students who are able to work toward and achieve an improved level of fitness in each of these areas are less likely to suffer from psychological and physical disorders and diseases.

Terms & Concepts

Aerobic/cardio-respiratory endurance: The body's ability to engage in activity over a prolonged period of time, which utilizes oxygen in the process of energy production (Universal Fitness Tester, 2007).

FITT Principle: Principle of conditioning that guides individuals in their pursuit of physical activity (Insel & Roth, 2006). FITT stands for Frequency, Intensity, Type, & Time of the physical activity.

Health-Related Fitness: Health-related fitness is a term that is used to indicate physical activity that aims to promote good health and wellness as opposed to conditioning specifically designed with sport training as the focus.

Hypertrophy: Increase in muscle mass.

Muscular Strength: The force that a muscle can produce or exert in a maximal effort one time, in other words, the greatest amount of weight or resistance a muscle can move or lift for one repetition only (Maina et al., 2001). This measure of strength is also known as the "one rep max" or 1 RM.

Muscular Endurance: The ability for a muscle group to perform, or contract, repeatedly at resistance below the maximum resistance the muscle can move (Maina et al., 2001).

Overload: The body must undergo a level of stress that is greater than the norm in order for the body to undergo physiological adaptations that increase muscular strength, muscular endurance, and aerobic endurance.

Resistance Training: Exercise that aims to increase muscle strength by forcing the muscle to work harder than normal against some force or weight (e.g., body weight, medicine ball, dumbbells, etc.)

Skill-Related Fitness: Skill-related fitness is a term used to indicate physical activity that focuses on performance improvement through the development of speed, agility, balance, power, reaction time, and coordination.

Target Heart Rate Zone: Calculated by taking into consideration the maximal heart rate (based on age) and resting heart rate and is the zone in which the heart rate should reach to receive cardio-respiratory benefit from exercise. Exercising at different intensities will achieve different heart rates and as a result different physiological effects.

Bibliography

Beighle, A., Marogan, C. F., & Pangrazi, R. P. (2004, Jan.). Using pedometers in elementary physical education. Teaching Elementary Physical Education,15 17-18. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=11901673&site=ehost-live

Casperson, C. J., Powell, K. E. & Christenson, G. M. (1985). Physical activity, exercise, and physical fitness: Definitions and distinctions for health-related research. Public Health Reports, 100, 126-131.

Corbin, C. B. (2004, January). What every physical educator should know about teaching physical activity and fitness. Teaching Elementary Physical Education, 15 , 7-9. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=11901667&site=ehost-live

Erwin, H., Beighle, A., Carson, R.L., and Castelli, D.M. (2013, Oct.). Comprehensive school-based physical activity promotion: A review. Quest 65 , p. 412-428. etrieved December 29, 2013 from EBSCO Online Database Education Research Complete. http://search.ebscohost.com/login.aspx?direct=true&db=ehh&AN=91536930&site=ehost-live

Gardner, P. J. (2003, Jan.). Youth strength training. Athletic Therapy Today, 42-43. Retrieved April 9, 2007 from EBSCO Online Database Academic Search Premier. http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=8904322&site=ehost-live

Greer, F. & Gilbert, J. N. (2006). Standards-based activities for elementary physical education. Teaching Elementary Physical Education,17 , 18-24. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=20195072&site=ehost-live

Insel, P. M. & Roth, W. T. (2006). Core Concepts in Health Brief (10th Ed.). New York: McGraw-Hill.

Kane, J. L. & Kane, R. J. (2004, Jan.). Using cooperative learning strategies to teach children fitness. Teaching Elementary Physical Education,15 , 24-27. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=11901678&site=ehost-live

Kraemer, W. J., Fry, A. C., Frykman, P. N., Conroy, B., & Hoffman, J. (1989). Resistance training and youth. Pediatric Exercise Science, 1 , 336-350. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text.

Langford, G.A. & McCurdy, K.W. (2005, July). Resistance training for elementary school age children. Teaching Elementary Physical Education, 16 , 39-44. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=17659702&site=ehost-live

Maina, M. P., Griffin, M., Ryan, S., & Schlegel Maina, J. (2001, Nov.). Muscle building activities for elementary and middle school children. Teaching Elementary Physical Education, 12 , 13-18. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text.

National Association for Sport and Physical Education, (2007). NASPE sets the standard. American Alliance for Health, Physical Education, Recreation, and Dance. Retrieved March 21, 2007, from http://www.aahperd.org/naspe/template.cfm?Template=publications-nationalstandards.html

Ng, C., Gannon, G., & Halas, J. (2006, Spring). The challenges of teaching "fitness" in an era of physical inactivity: Examples of effective practice. Physical and Health Education, 72 , 4-9. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=21924302&site=ehost-live

O'Hara, R.B. & Titlebaum, P.J. (2000, January). Strategies and activities to reduce cardio- vascular risk in children. Teaching Elementary Physical Education, 11 , 14-16. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text.

Pasco, D. (2013, Oct.). The potential of using virtual reality technology in physical activity settings. Quest 65 , p. 429-441. Retrieved December 29, 2013 from EBSCO Online Database Education Research Complete. http://search.ebscohost.com/login.aspx?direct=true&db=ehh&AN=91536931&site=ehost-live

Ratliffe, T. (2000, Sept.). Designing your fitness curriculum. Teaching Elementary Physical Education,11 , 35-37. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=6422819&site=ehost-live

Sander, A. N. & Ratliffe, T. (2002, Nov.). Teaching aerobic fitness concepts. Teaching Elementary Physical Education, 13, 14-20. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=8557313&site=ehost-live

Thorburn, M., and MacAllister, J. (2013, Oct.). Dewey, interest, and well-being: Prospects for improving the educational value of physical education. Quest 65 , p. 458-468. Retrieved December 29, 2013 from EBSCO Online Database Education Research Complete. http://search.ebscohost.com/login.aspx?direct=true&db=ehh&AN=91536933&site=ehost-live

Universal Fitness Tester (1999). Aerobic fitness information: Its meaning and significance. Universal Fitness Tester. Retrieved April 13, 2007, from http://www.aerobictest.com/fitnessInfo.htm

Suggested Reading

Hannon, J. & Ratliffe, T. (2004, January). Resources for teaching fitness in elementary and middle school physical education. Teaching Elementary Physical Education, 15 , 23, 27. Retrieved April 9, 2007 from EBSCO Online Database SPORTDiscuss with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=s3h&AN=11901676&site=ehost-live

Hinkle, J. (1992). Aerobic fitness and school children. Elementary School Guidance & Counseling, 27, 140.

Hopple, C.J. (1995). Teaching for outcomes in elementary physical education: A guide for curriculum and assessment. Champaign, IL: Human Kinetics.

Ratliffe, T. & Ratliffe, L. M. (1994). Teaching children fitness: Becoming a master teacher. Champaign, IL: Human Kinetics.

Swaim, D. & Edwards, S. (2003). High school healthy hearts in the zone: A heart rate monitoring program for lifelong fitness. Champaign, IL: Human Kinetics.

Welk, G. J. (2002). (Ed.) Physical activity assessments for health-related research. Champaign, IL: Human Kinetics.