Overview

The Healthy Sport Index recognizes that one of the chief contributions of sport participation is physical activity, given the physiological and cognitive benefits that flow to youth whose bodies are in motion. The Healthy Sport Index evaluated this category based on physical activity levels by sport from North Carolina State University original research (75 percent of the score) and expert analysis (25 percent of the score).

Observational methods for assessing physical activity in 20 different high school sports were used to compare physical activity levels of participants during practice time. Findings indicate the amount of physical activity that athletes accrue and energy expended during practice time varies from sport to sport. After juxtaposing the sports’ energy expenditure rates (METs) against each other, a ranking of the sports based on physical activity levels was provided. The sports that are characterized with high amounts of running, such as cross country, track and field, and soccer, had the highest levels of moderate-to-vigorous physical activity (MVPA), which was expected.

Conversely, cheerleading, softball, and baseball were the lowest-scoring sports in regard to MVPA. It was also found that a majority of the boys sports had higher MET values (generating more physical activity) than girls sports. The results add clarity to our understanding of which sports facilitate more participant physical activity during practices.

Additionally, the context that characterizes sport practices is significant in determining how much physical activity occurs. Most sports that place extra emphasis on game simulation, fitness, and skill development drills can be expected to have higher levels of MVPA. Based on how practices are delivered to athletes, we can accurately predict how much physical activity athletes can expect to achieve within a given sport season assuming length and frequency of practices are recorded.

Background

Participation in physical activity has been associated with numerous health benefits in children and adolescents (Janssen & LeBlanc, 2010). Current physical activity guidelines recommend children accrue 60 minutes of moderate-to-vigorous physical activity (MVPA) per day (USDHHS, 2008). Despite the overwhelming evidence of the benefits of physical activity, most U.S. youth are not sufficiently active. Only 8 percent of 12-15 year-old youth meet the national physical activity guidelines (Troiano et al., 2008).

Organized sports have consistently been identified as an environment conducive to physical activity among youth. Sport is one of the most popular leisure-time activities among children and adolescents and is often organized in the forms of private sports clubs, public recreational offerings, or interscholastic athletics at schools. According to the National Federation of State High School Associations (NFHS), over 7.8 million high school students participate in interscholastic sports annually. With over 44 million children participating in organized youth sports in the U.S., these programs facilitate many opportunities for children to obtain recommended amounts of physical activity (National Council of Youth Sport, 2008).

Several studies have examined the relationship between sports participation and physical activity. For example, Wickel and Eisenmann (2007) found that football and soccer participants engaged in 110 and 40 minutes of MVPA, respectively, during weekdays. They also reported levels of MVPA to be 30 minutes lower on a non-sports day. Similar findings were reported by Machado-Rodrigues et al. (2012) in their study of 13-16 year-old boys’ MVPA during sport participation. Sports participants accrued 114 minutes of MVPA per weekday and an average of 97 minutes per day across the entire week. Findings from a study of 9-15 year-old soccer players showed average daily MVPA to be 122 minutes per day (Van Hoye et al., 2013).

Additional research suggests that the amounts of PA accrued during sport participation did not occur during non-playing days and was generally replaced with low-intensity and sedentary activities. This is consistent with other research reporting that children are unlikely to compensate for missed PA resulting from sports (Dale et al., 2000), and suggestive that sport may have the potential to increase levels of PA, and reduce bouts of sedentary behavior (Kanters et al., 2015).

Although research suggests participation in organized sport is associated with increased levels of physical activity, findings are inconsistent and undermined by the use of methods that may be inappropriate with children (e.g., self-report surveys). Consequently, there is a need for more direct and objective measures of physical activity, particularly when examining child and youth populations.

One of the most accurate, comprehensive field measures of physical activity is direct observation (DO). DO is a popular objective method for assessing physical activity, which requires a designated observer to document the physical activity behavior of subjects for a short duration of time. Direct observation exceeds other measures of PA in its ability to provide detailed information on the physical and social context in which it occurs. While children participating in sports are generally more active, have greater energy expenditure, and spend more time in MVPA than non-participants, data are often limited by an inability to differentiate how physical activity varies with types and levels of sports and how variations in the structure and delivery of sport practices influence activity levels. Consequently, levels of physical activity during youth sport may be overestimated in studies involving younger participants. Nevertheless, and regardless of methods, much of the research done within sport and physical activity has concluded that sport participation alone does not guarantee children will reach recommended daily PA levels.

Sport, in and of itself, certainly contributes to daily physical activity levels of participants. However, the manner and context in which sport is delivered can dramatically influence the physical activity amount and intensity of participants. For example, Leek et al.’s (2011) reported levels of MVPA and the proportion of session time engaged in MVPA to be higher in soccer participants than in softball and baseball. Likewise, Katzmarzyk and others (2001), who studied the amount and quality of PA through direct observation of 11-14 year-old boys’ and girls’ recreational sports, found outdoor soccer to be the most robust activity, providing less sitting time than hockey. Outdoor soccer also had the greatest time spent jogging and sprinting. Additionally, indoor soccer provided less sitting time than basketball. Leek et al. (2011) also found that 7-10 year olds were more active than 11-14 year olds, and boys were more active than girls.

Although organized sport creates opportunities for children to be active, its full potential as a strategy to increase PA may be limited by various contexts. Policies that govern the structure and delivery of sport practices and characteristics of the sporting environment can have a major influence on the amount of PA experienced by athletes, yet empirical research is limited in this area. Therefore, the purpose of this research was to objectively measure the physical activity levels of student-athletes across a variety of sport offerings and to draw comparisons between sports based on the physical activity levels and practice context.

Methods

The present study is an offshoot of a much larger research project called the Healthy Sport Index (HSI). The HSI was conceptualized and commissioned by the Aspen Institute based out of Washington D.C., as part of its Project Play initiative. Funding for this research was provided by the Aspen Institute as part of a grant from the Hospital for Special Surgery based out of New York.

Sport Selection. Ten of the most popular team sports among boys and girls at the high school level, as determined by the most recent national High School Athletics Participation Survey, were included in this study (Table 1). High school sports were selected because they represent a regulated sport environment with fairly consistent structure and delivery across the nation; they also offer the richest available research and data sets for youth athletes. It was also determined that only sport practices would be used to assess participant physical activity levels. Practices were selected in lieu of games/competitions as athletes are anticipated to spend more time participating in team practices than in actual games. Practices are also more inclusive than games, involving every athlete regardless of talent level. Therefore, the practice environment was chosen as a more valid and accurate setting for understanding the physical activity outcomes realized by athletes participating in their particular sport.

Table 1: Sports Selected for Study

School selection. A comprehensive list of all high schools in North Carolina was obtained from the North Carolina High School Athletic Association (NCHSAA). High schools that offered a minimum of 18 out of the 20 varsity sports of interest were considered eligible to be included in the study. Next, schools were selected using a stratified random sample to ensure representativeness of schools in the state based on the following criteria:

1. District level per pupil expenditure
2. Percent of student body eligible for free/reduced lunch
3. Percent of student body that is of racial minority
4. Geography (to prevent regional clustering)
5. Availability and proximity to hired data collectors

The final list of 12 high schools invited to participate in the study comprised a representative sample of all North Carolina high schools. Data collectors were primarily teachers and coaches at participating schools.

Instrumentation. The System for Observing Fitness Instruction Time (SOFIT) was used to objectively measure physical activity during high school sport practices. SOFIT is based on momentary time-sampling techniques in which simultaneous objective information on athlete physical activity levels and the practice context in which they occur is captured. Observers were extensively trained in systematic observation protocols prior to data collection.

Procedures. Before each observation, data collectors arrived early to the practice facility and randomly selected four student-athletes in attendance at the practice and made notes of any identifiable characteristics (e.g., the number on the back of the jersey or the color of the athlete’s clothes). Once the practice started, data collectors observed the first athlete for one iteration (20 seconds). During each iteration, the following specific outcome variables were measured:

1. Athlete physical activity levels: number of minutes and % practice time spent in lying down, sitting, standing (Sedentary), walking (Moderate), or Vigorous activity levels.
   
2. Practice Context: minutes and % practice time spent in management, knowledge content, fitness, skill practice, game play, or other.

After 12 iterations were completed for the first athlete, the data collector then repeated this procedure for the second athlete and so on. At the conclusion of the 12th iteration for the fourth athlete, the data collector then circled back to observe the first athlete again. This process was continued until the coach ended practice and dismissed the athletes.

Reliability assessment. Field-based inter-observer reliabilities were performed throughout the study. Two trained data collectors independently coded the same participants during the same practice. Percent inter-observer agreement (IOA) was calculated for observations of physical activity level and practice context. All observers were coded for reliability over a span of 25 practices. Overall IOAs were 73% for both activity levels and lesson context, indicating a high degree of reliability.

Results

Each of the 20 high school sports were observed in their respective Fall, Winter and Spring high school sport season. Observations were conducted at 605 varsity sports practices, for a total of nearly 700 hours, amounting to 2,420 total athletes observed. Table 2 displays the distribution of observations for each season and shows that a total of 125,286 individual observations were recorded.

Table 2: Total Observations of High School Sport Practices

Physical Activity

Overall, 43 percent of the time athletes were observed engaging in vigorous activity. Walking (moderate activity) was observed 17 percent of the time and sedentary (lying down, sitting, standing) was observed 40 percent of the time

A comparison across sports for the three levels of observed physical activity is presented in Figure 2 for girls sports and Figure 3 for boys sports. For girls, cross country and soccer had the highest percent of observed MVPA where cheerleading and softball had the highest amounts of observed sedentary behavior. For boys, cross country and track had the highest amounts of observed MVPA and baseball had the highest amounts of observed sedentary behavior.

Observed physical activity data were converted to standard metabolic equivalents (METs) for each sport to compare sports based on the estimated energy expended during practices (see Figure 4). METs can be calculated by multiplying each observed athletes’ physical activity level with an assigned energy expenditure value: 1.5 for every sedentary athlete, 3.0 for every moderate athlete, and 6.0 for every vigorous athlete. These values have been accepted and widely used in estimating the amount and level of physical activity based on observational data (Ainsworth et al., 2011; Edwards et al., 2014).

Overall, cross country was found to have the highest MET level (p < .05) compared to all other sports while cheerleading was significantly the lowest. Wrestling, swimming, and soccer all had significantly similar high MET values (> 4.0). Boys cross country had the highest MVPA rates with an average MET value of 4.84. Boys track and field (4.62) and girls cross country (4.35) were second and third, respectively. Swimming and soccer for both genders were also included in the top half of the index. The sports that were observed having the lowest physical activity levels (i.e., highest amounts of sedentary behavior) were cheerleading (2.41), girls softball (2.76), boys baseball (3.02), girls track and field (3.23), and girls tennis (3.46). Results also indicated that overall, boys sports generated more physical activity during practices than girls sports.

In addition to observing physical activity, observers also recorded the practice context for every interval. In other words, for each observation sample, a decision is made regarding whether the practice time is being allocated for management, knowledge content, fitness, skill practice, game play, or other.

Management refers to actions performed by athletes not involved in the sport content which can include transition, break times, changing gear, or moving from one space to another.

Knowledge Content refers to time spent where the primary focus is on athlete acquisition of knowledge related to the sport which can include technique, strategy, rules, and teaching from coaches.

Fitness refers to activities whose major purpose is to alter the physical state of the individual in terms of cardiovascular endurance, strength, or flexibility.

Skill Practice refers to actions where the primary goal is to strengthen, or develop skills in an applied setting. The primary characteristic of skill practice is the targeting of a specific skill (e.g., dribbling a basketball) and the athlete repeating the drill to further refine that skill.

Game Play refers to activity time devoted to the application of skills in a game-like setting such as a simulated competition or scrimmage.

Other refers to all other actions performed by the athlete that does not fit into any of the previously discussed categories and usually involves some form of unorganized free play.

Athletes overall spent a majority of practice time performing Skill Practice activities (36 percent), which are defined as activities repeated by the athlete for the purposes of targeting a specific skill. Fitness was the next most common activity (19 percent), followed by Game Play (15 percent), Knowledge Content (14 percent), Management (11 percent), and Other (4 percent) (see Figure 5).

The girls sports with the highest amount of Game Play were soccer, softball, and tennis. The boys sports with the highest amount of Game Play were tennis, cross country, and basketball. The sports with the largest proportion of practice time devoted to Fitness were cross country, swimming, and track and field for both genders.

An examination of how practice context measures were associated with observed physical activity levels during practices indicated practice time devoted to Game Play (4.67 MET average) was associated with higher levels of physical activity (see Figure 6 and Figure 7). Practice time focused on Fitness (4.54) and Skill Practice (4.28) were both also associated with mean physical activity levels above 4.00 METs. Practice time focused on Other (2.18), Management (2.11), and Knowledge Content (1.71) were associated with mean MET levels that indicated a higher likelihood of sedentary activity.

A follow-up regression analysis of practice context measures and physical activity indicated a significant predictive relationship (R2 = .308, p< .001). Practices that focused primarily on skill practice essentially yielded an average level of PA. The more time spent in Game Play and Fitness significantly increased PA levels above the mean. Time spent in Knowledge context, management, and other activities, significantly reduced the mean level of PA within practice. Generalization of this finding is cautioned as the type of game play can vary from sport to sport. For example, softball had low PA levels and high game play.