Meeting Physical Activity Guidelines and Health-Related Fitness in Youth James R. Morrow Jr, PhD, Jacob S. Tucker, MS, Allen W. Jackson, EdD, Scott B. Martin, PhD, Christy A. Greenleaf, PhD, Trent A. Petrie, PhD This activity is available for CME credit. See page A3 for information.
Background: National physical activity guidelines have been developed for Americans. Interest lies in the relationship between meeting the national physical activity guidelines and physical fıtness outcomes in youth. Theoretically, those who meet the physical activity guidelines are more physically fıt, which translates to better health and reduced risk.
Purpose: To examine the relationship between youth self-reported physical activity behaviors suffıcient to meet DHHS Physical Activity Guidelines for Americans and an external health criterion: achievement of the FITNESSGRAM Healthy Fitness Zone™ (HFZ).
Methods: Logistic regression was used to examine achievement of the HFZ for three physical fıtness measures (i.e., aerobic capacity, BMI, and muscle fıtness) separately, and for all three combined, based on self-reported physical activity of 7 days per week for aerobic activity and ⱖ3 days per week of muscle-strengthening activity. One model examined the direct relationship between physical activity and fıtness measures, and a second model assessed the same relationship while controlling for gender, age, ethnicity, economic status, and school. Data were collected during the 2009 –2010 academic year and analyzed in 2012.
Results: Adolescents failing to meet national aerobic and muscle-strengthening physical activity guidelines have higher odds of not achieving healthy physical fıtness levels of aerobic capacity, BMI, muscle fıtness, and the combination of all three. An increase in the number of days of aerobic activity was related to decreased odds of being in the Needs Improvement Fitness Zone. Conclusions: The fındings provide further support that meeting the national physical activity guidelines produces health benefıts for youth. (Am J Prev Med 2013;44(5):439 – 444) © 2013 American Journal of Preventive Medicine
ealth-related physical fıtness (fıtness) is an important health marker shown to be predictive of cardiovascular disease, morbidities, and mortality.1– 4 Fitness is partially determined by age, gender, health status, and genetics and is influenced by environmental determinants.2 The principal modifıable determinant is habitual physical activity.1 Establishing healthrelated physical activity habits early in life is important for increased fıtness (i.e., aerobic capacity, body compoFrom the Department of Kinesiology, Health Promotion, and Recreation (Morrow, Tucker, Jackson, Martin), the Department of Psychology (Petrie), University of North Texas, Denton, Texas; and the Department of Kinesiology (Greenleaf), University of Wisconsin–Milwaukee, Milwaukee, Wisconsin Address correspondence to: James R. Morrow Jr, PhD, Department of KHPR, 1155 Union Circle #310769, University of North Texas, Denton TX 76205-5017. E-mail: [email protected]
sition, muscular strength and endurance, and flexibility), especially during adolescence.2 The DHHS published the 2008 Physical Activity Guidelines for Americans (PAG) suggesting the important influence of physical activity behaviors on health outcomes.3,4 The PAG were developed based on the evidence relating fıtness, physical activity, and energy expenditure to health outcomes. Those with higher physical fıtness levels or with greater weekly physical activity or energy expenditure have been shown to have fewer health risks. Guidelines for children and adolescents are daily physical activity behaviors of 60 minutes or more. The physical activity behaviors should include a minimum of 3 days per week of aerobic, muscle-strengthening, and bone-strengthening activities. Meeting the physical activity guidelines results in enhanced fıtness and ultimately, improved health. However, no research was identifıed that shows a relationship between physical activity behaviors and the attainment of
© 2013 American Journal of Preventive Medicine • Published by Elsevier Inc.
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an external criterion of fıtness. Identifying such a relationship can help validate current physical activity guidelines for youth. This study was conducted to determine whether self-reported amounts of aerobic and musclestrengthening behaviors relate to fıtness outcomes. Specifıcally, is meeting national physical activity recommendations associated with health-related standards for cardiorespiratory fıtness, body composition, and muscular strength as measured by the FITNESSGRAM®? The FITNESSGRAM is a comprehensive health-related fıtness testing battery designed specifıcally for youth. The items measure aerobic capacity, body composition, and muscular strength and endurance and flexibility. Based on measured fıtness, students are identifıed as being in either a Healthy Fitness Zone (HFZ), which indicates that they are suffıciently fıt to be at reduced risk for hypokinetic diseases, or in a Needs Improvement Zone (NIZ). The FITNESSGRAM, developed by The Cooper Institute more than 30 years ago, is the testing protocol used in the recently established Presidential Youth Fitness Program, created by the President’s Council on Fitness, Sports & Nutrition. The American Journal of Preventive Medicine recently published a Supplement illustrating validation of the FITNESSGRAM HFZs.5 No studies to date address whether physically active youth are healthy based on concurrently determined criterion-referenced standards of fıtness.6 Specifıcally, information is lacking on the association of public health physical activity recommendations, the process, and the immediate outcome: fıtness. The FITNESSGRAM HFZ categorization provides an excellent concurrent measure of fıtness with which to compare physical activity behaviors.
Methods Participants The participants were 4621 middle school students in Grades 6 – 8 from a suburban school district. Not all participants had information on their economic status and ethnicity, nor did all complete the fıtness testing and respond to both physical activity items of interest in this study. More than 4200 (90%) respondents had data on each variable with the exception of economic status, for which 3344 (72%) had data.
Measurements Self-reported physical activity. Students responded to two questions reflecting aerobic and muscle-strengthening physical activity. The physical activity behavior items, part of a larger battery of items (Table 1), were based on FITNESSGRAM items and the Youth Risk Behavior Surveillance System of the CDC. The aerobic activity question references the 60 minutes suggested in the 2008 PAG,4 but the muscle-strengthening item focuses solely on days per week. Students were classifıed into a dichotomy of meeting or not meeting the PAG recommended levels for aerobic (7 days per week
Table 1. Physical activity behavior questions For each of the following questions, think about what you have done during the past 7 days. 1. On how many days were you physically active for a total of at least 60 minutes? This includes moderate activities (walking, slow bicycling, or outdoor play) as well as vigorous activities (jogging, active games, or active sports such as basketball, tennis, or soccer). (Add up all the time you spend in any kind of physical activity that increases your heart rate and makes you breathe hard some of the time.) 0 days 1 day 2 days 3 days 4 days 5 days 6 days 7 days 2. On how many days did you do exercises to strengthen or tone the muscles such as push-ups, sit-ups, or weight lifting? 0 days 1 day 2 days 3 days 4 days 5 days 6 days 7 days
versus ⬍7 days per week) and muscle-strengthening physical activity (ⱖ3 days per week versus ⬍3 days per week).
Health-related physical fitness. The FITNESSGRAM test battery was used to assess fıtness.7 The FITNESSGRAM assesses aerobic capacity (i.e., cardiorespiratory fıtness); body composition; muscular strength; endurance; and flexibility. Fitness results were classifıed into a dichotomy of HFZ and NIZ based on gender and age. The HFZs and NIZs are criterion-referenced standards representing the minimum fıtness level at which protection against the diseases of sedentary living is achieved.7 The FITNESSGRAM-specifıc measures used to assess fıtness in this study were aerobic capacity, an estimate of VO2max derived from performance on the PACER (Progressive Aerobic Cardiovascular Endurance Run); BMI, curlup, 90° push-up, and trunk lift.7 For aerobic capacity and BMI, the NIZ has two levels: “NI-Some Risk” and “NI-High Risk.” In the present study, those in either of these levels were identifıed as in the NIZ for aerobic capacity and BMI. Achieving the HFZ for muscle fıtness was operationally defıned as achieving the HFZ for any two or all three of the curl-up, 90° push-up, and trunk lift tests. A dichotomy was created based on achieving the HFZ on all three of the fıtness components. Participants in the HFZ for all three of the fıtness measures (i.e., aerobic capacity, BMI, and muscle fıtness) formed one group, and failure to achieve the HFZ for any one of the three fıtness components characterized the contrasted group. This categorization illustrated the multidimensional nature of fıtness by identifying those in all three HFZs.
Design and Procedures Study approval was received from the University of North Texas IRB, as well as the school district and the principals at each of the six middle schools. Prior to data collection, parental consent and child assent were obtained. The authors and research assistants assisted the physical education instructors with administration of the FITNESSGRAM protocol to conduct the state-required, annual healthrelated fıtness testing. Fitness testing took approximately 1 week at each middle school, during which students, for whom consent and assent were available, completed surveys as part of a larger project investigating their physical fıtness/activity, psychological wellbeing, and academic performance. Data were collected during the
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Table 2. Demographic variables Aerobic physical activity guideline, n (%) Variable, n (%) Gender c
Boys, 2264 (50.6)
Muscle-strengthening guideline, n (%)
Girls, 2208 (49.4) Ethnicity White, 2495 (55.9) Nonwhite, 1971 (44.1) Economic status Lunch support, 1368 (40.9) No support, 1976 (59.1) Aerobic capacity HFZd In HFZ, 2990 (70.4)
441 muscle fıtness separately, and for achieving the HFZ on all three. Primary independent variables were the dichotomies, meeting or not meeting the PAG recommended levels for aerobic physical activity, and musclestrengthening physical activity. Model 1 assessed the direct relationship between fıtness and physical activity measures. Model 2 assessed the same relationship, but controlled for gender, age, ethnicity, economic status, and school. Alpha level was set at 0.05, and 95% CIs were calculated for the ORs derived. A public health approach was taken wherein failure to conduct a healthy behavior (⬍7 days of physical activity) was related to a negative health outcome (being in the FITNESSGRAM NIZ).
In NIZ, 1259 (29.6) Achieve BMI HFZ In HFZ, 2440 (55.0) In NIZ, 1998 (45.0)
Results Descriptive Statistics
Table 2 contains prevalence of meeting aerobic and In HFZ, 3531 (80.9) 112 (13.5) 719 (86.5) 572 (68.7) 261 (31.3) muscle-strengthening PAG by gender, ethnicity, In NIZ, 831 (19.1) economic status, and a Met ⫽ 7 days per week; not met ⫽ ⬍7 days per week. FITNESSGRAM HFZ for aerob Met ⫽ ⱖ3 days per week; not met ⫽ ⬍3 days per week. c bic capacity, BMI, and Totals are not consistent as not all participants completed all phases of data collection d ® muscle fıtness. Participant FITNESSGRAM HFZ e FITNESSGRAM NIZ age ranged from 10 to 16 HFZ, Healthy Fitness Zone; NIZ, Needs Improvement Zone years (M⫽12.5⫾1.0). Approximately half were boys; 2009 –2010 academic year and analyzed in 2012. All survey items most (56%) were white; and 59% received no lunch support. took approximately 45 minutes to complete. Demographic characteristics generally reflect the entire The school district provided information on participant gender, district. Achieving the HFZ depended on the health economic status, age, and ethnicity. Economic status is based on component: aerobic capacity (70%); body composition federal guidelines determining which students qualify for free or (55%); and muscle fıtness (81%). Table 2 also presents reduced-price lunch. Those receiving free or reduced-price lunch categorization by meeting aerobic and musclewere one group; those not were the contrasting group. Age was defıned by FITNESSGRAM completion date. For ethnicity, particistrengthening PAG. Achieve muscle fitness HFZ
pants were categorized as being either white or nonwhite. Code numbers were used to link FITNESSGRAM results with data supplied by the district. No other identifying information (e.g., names) was obtained. As an incentive for participation, participants were entered into a drawing for a series of cash prizes at each school.
Data Analysis Descriptive statistics including mean, SD, and prevalence for appropriate variables were calculated. Logistic regression was the primary analysis procedure. SPSS, version 20, was used for all analyses. The dependent variables were the dichotomies (HFZ or NIZ) for the three fıtness measures—aerobic capacity, BMI, and May 2013
Aerobic Physical Activity Guidelines Table 3 presents ORs from logistic regression assessing the relationship between self-reported amount of aerobic physical activity and HFZs for aerobic capacity, BMI, muscle fıtness, and all three HFZs for both models. From a 7-day recall, participants self-reporting ⬍7 days per week of at least 60 minutes of aerobic physical activity did not have higher odds of being in the NIZ for cardiorespi-
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Table 3. Odds of being in the FITNESSGRAM® Needs Improvement Zone based on aerobic ratory fıtness or BMI. physical activity behavior Failure to meet the physical activity aerobic guidePhysical activity Model 1a Model 2b line resulted in increased c Dependent variables guideline OR (95% CI) OR (95% CI) odds of being in the musAchieve aerobic capacity HFZ Metd (ref) 1.00 1.00 cle fıtness NIZ d (OR⫽1.62, 95% CI⫽ Not met 1.13 (0.94, 1.35) 1.13 (0.92, 1.38) 1.25, 2.10, p⬍0.001) and Achieve BMI HFZ Met (ref) 1.00 1.00 across all three NIZs Not met 1.18 (1.01, 1.38) 1.08 (0.90, 1.30) (OR⫽1.88, 95% CI⫽ 1.25, 2.32, p⬍0.002). Achieve muscle fitness HFZ Met (ref) 1.00 1.00 These models controlled Not met 1.44 (1.16, 1.79) 1.62 (1.25, 2.10) for gender, age, ethnicity, Achieve HFZ for aerobic capacity, Met (ref) 1.00 1.00 economic status, and BMI, and muscle fitness school. Not met 1.51 (1.09, 2.09) 1.88 (1.25, 2.82) To further interpret a the relationship between Direct relationship between physical activity behaviors and FITNESSGRAM Healthy Fitness Zone achievement. days of aerobic physical b Controlled for gender, age, ethnicity, economic status, and school activity and fıtness outc OR represents the odds of being in the FITNESSGRAM Needs Improvement Zone if participant fails to meet come, a logistic Model 2 the physical activity guideline. d Met ⫽7 days per week; Not met ⫽ ⬍7 days per week. (data not shown) includHFZ, Healthy Fitness Zone ing days as a continuous variable (0 –7 days per HFZs for both logistic models. From a 7-day recall, week) was calculated. The odds of being in the aerobic participants self-reporting ⬍3 days per week of NIZ decrease by 6% (p⬍0.001) for each additional day of muscle-strengthening physical activity had higher aerobic physical activity. Similarly, the odds of being in the NIZ for BMI decrease by 4% (p⬍0.008) for each odds of being in the NIZ for cardiorespiratory fıtness additional day of aerobic physical activity. When con(OR⫽1.64, 95% CI⫽1.32, 2.03, p⬍0.001). Additiontrasting those who achieve all three HFZs with those not ally, those failing to meet the muscle-strengthening doing so, the odds decrease by 15% (p⬍0.001) that one physical activity guideline were at increased odds of achieves all three HFZs for each additional day of aerobic being in the NIZ for BMI (OR⫽1.39, 95% CI⫽1.14, activity. This fınding is consistent with the PAG Table 4. Odds of being in the FITNESSGRAM® Needs Improvements Zone based on for adults, which suggest muscle-strengthening physical activity behavior that doing some physical activity is better than Physical activity Model 1a Model 2b c none. This suggestion apDependent variables guideline OR (95% CI) OR (95% CI) pears to generalize to Achieve aerobic capacity HFZ Metd (ref) 1.00 1.00 youth. Achieve BMI HFZ
MuscleStrengthening Physical Activity Guidelines Table 4 presents ORs from logistic regression assessing the relationship between self-reported amount of muscle-strengthening physical activity and NIZs for aerobic capacity, BMI, and muscle fıtness, and all three
Achieve muscle fitness HFZ
Achieve HFZ for aerobic capacity, BMI, and muscle fitness
1.63 (1.36, 1.95)
1.64 (1.34, 2.03)
1.36 (1.16, 1.60)
1.39 (1.14, 1.70)
3.40 (2.85, 4.07)
3.42 (2.75, 4.25)
3.37 (2.56, 4.42)
3.31 (2.37, 4.63)
Direct relationship between physical activity behaviors and FITNESSGRAM Healthy Fitness Zone achievement. Controlled for gender, age, ethnicity, economic status, and school c OR represents the odds of being in the FITNESSGRAM Needs Improvement Zone if participant fails to meet the physical activity guideline. d Met ⫽ ⱖ3 days per week; Not met ⫽ ⬍3 days per week. HFZ, Healthy Fitness Zone b
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1.70, p⬍0.001); the muscle-strengthening NIZ (OR⫽3.42, 95% CI⫽2.75, 4.25, p⬍0.001); and across all three HFZs (OR⫽3.31, 95% CI⫽2.37, 4.63, p⬍0.001) when adjusting for gender, age, ethnicity, economic status, and school.
Discussion This study examined the relationship between self-reported amounts of physical activity and fıtness test results in youth. Amounts of aerobic and muscular-strengthening physical activity were found to be related to achieving fıtness HFZs. From a public health perspective, this means that youth should be encouraged to meet national PAG because this increases the odds that they will achieve the HFZ. Generally, the prevalence of students who achieved the HFZ for each of the three fıtness components was slightly greater for those who met the aerobic physical activity or muscle-strengthening guideline. An exception is for the BMI HFZ, where 83.9% of those in the NIZ met the aerobic physical activity guideline, and 81.5% of those who met the aerobic guideline achieved the BMI HFZ. The most dramatic difference is in achieving the muscle fıtness HFZ: 88.2% of those who achieved the HFZ met the musclestrengthening guideline; only 68.7% of those in the NIZ reported meeting the muscle-strengthening guideline. This may be a reflection of the accuracy of self-reporting musclestrengthening behaviors as contrasted with reporting general aerobic behaviors. Odds ratios from logistical regression revealed notable fındings. Participants who reported ⬍7 days in the past week of at least 60 minutes of aerobic physical activity did not have increased odds of being in the NIZ for aerobic capacity and body composition. However, they were more likely to be in the muscle-fıtness NIZ and less likely to achieve all three HFZs simultaneously. Increasing the number of aerobic days reported was associated with increased odds of being in the HFZ for both aerobic capacity and body composition. Muscle-strengthening physical activity revealed the stronger indication of meeting health-related fıtness standards. Engaging in ⬍3 days of muscle-strengthening physical activity during the past week resulted in greater odds of being in the NIZ than did not participating in aerobic physical activity during the same time period. Hass et al.8 reported that strength training plays a key role in improving many aspects of health. Muscle-strengthening guidelines are included in PAG because of the increasing evidence relating musculoskeletal fıtness to morbidities and mortality.4 One possible explanation for muscle-strengthening activities being more powerful is that it may be easier for youth to recall muscle-strengthening physical activity May 2013
than aerobic physical activity. Self-reporting of aerobic activity on a daily basis could be more diffıcult than identifying muscle-strengthening activities during the same period because of the all-inclusive nature of walking, outdoor, and general physical activity behaviors associated with aerobic physical activity. The specifıc nature of muscle-strengthening activities may be more easily recalled and summarized than the more generic aerobic-related physical activity that queries about moderate and vigorous physical activity (Table 1). Another important observation is the limited effect that control of the confounders— gender, age, ethnicity, economic status, and school— had on the relationship between physical activity and fıtness. Although the individual confounders were related to fıtness (p⬍0.05), they had little effect on the ORs from the logistic regression when comparing Model 1 and Model 2 results. Thus, the relationship between physical activity and fıtness were consistent across gender, age, ethnicity, economic status, and school. Controlling for school differences had little impact on the ORs, suggesting that the results generalize across schools and that achievement of fıtness status is not a function of the nature of programs delivered at individual schools. The results of the current study revealed that engaging in ⬍7 days of aerobic (for at least 60 minutes) and ⬍3 days of muscle-strengthening physical activity per week means participants are less likely to be in the HFZ for selected FITNESSGRAM components and to achieve all three FITNESSGRAM HFZs simultaneously.
Strengths and Limitations The results indicate that physical activity assessment is related to fıtness standards in youth. Potential confounders, including gender, age, ethnicity, economic status, and school, were controlled. A strength of the HFZ associated with FITNESSGRAM as a fıtness assessment is use of the criterion-referenced standards that are based on related health outcomes. Participants’ cardiorespiratory fıtness assessments were based on their age, gender, run performance, and BMI; they are then classifıed as being in the HFZ or NIZ. Participants’ scores on all other fıtness assessments are based on only their age and gender, and then they are classifıed as being in the HFZ or NIZ. The cross-sectional nature of the data collection limits causal conclusions. Another potential limitation to the FITNESSGRAM testing procedure is the reliability of those administering the test. Not all physical education teachers are well trained in conducting the FITNESSGRAM assessment. Because of this, measurements are prone to error, causing problems with internal validity. To reduce the potential for this problem, a certifıed FITNESSGRAM administrator was on site overseeing the testing process at all times. The FITNESSGRAM certifıcation
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process consists of completing an online training course. The course presents test protocols and takes one through the philosophy of the FITNESSGRAM program. At the end of the course, participants take an exam, and if they pass it, they are issued a certifıcate of successful completion. The measurement data are likely to be more accurate when a certifıed FITNESSGRAM administrator is present or actually administering the test.9 Morrow et al.10 also report that school-based teachers generally obtain trustworthy results, particularly when trained. Assessment of physical activity behaviors is diffıcult, particularly in youth. Discrepancies have been reported between self-reported physical activity and objectively measured physical activity data (e.g., accelerometers and pedometers).11–15 Nevertheless, self-report physical activity behaviors are used for large-scale studies. Foley et al.16 and Janz et al.17 indicate that students in the current age range can do so validly. Another potential limitation is that participants could over-report their physical activity due to social desirability. However, because the FITNESSGRAM physical activity questions were on the reverse side of their fıtness results card, this may have reduced the possibility of socially desirable response bias. Because they did the fıtness testing fırst, the participants’ self-reported physical activity responses may have been more accurate.
Conclusion The current results are the fırst to report on the relationship between adolescents meeting national physical activity guidelines and achieving well-established criterionreferenced health standards. Meeting national physical activity guidelines is related to achieving science-based criterion-referenced fıtness standards for health status. These results suggest that encouraging students to engage in physical activity suffıciently to meet national guidelines could have ultimate health benefıts. The results have direct implications for policy and curricular decisions and may also provide insight for public health researchers, school districts, and state politicians considering similar large-scale testing endeavors. For example, teachers may choose to assess both fıtness (the attribute) and physical activity (the behavior). There is a relationship between self-reported physical activity behaviors and actual achievement of criterion-referenced health-related fıtness standards. This fınding suggests that schools, districts, or states desiring to assess fıtness achievement levels might also opt to assess physical activity behaviors. CAG was affıliated with the Department of Kinesiology, Health Promotion, and Recreation, University of North Texas, Denton, Texas, at the time this research was conducted.
This work was supported by a grant to SBM, CAG, and TAP from the National Association for Sport and Physical Education. No fınancial disclosures were reported by the authors of this paper.
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