The variety of exercise equipment and physical activity participation in children.

Barkley, Jacob E. ; Ryan, Edward J. ; Bellar, David 等

Both the American Alliance for Health, Physical Education, Recreation and Dance (Council for Physical Education for Children, 2003) and the United States Department of Health and Human Services (2008) physical activity guidelines for children emphasize that children participate in a variety of physical activity options. In these recommendations it is proposed that participating in a variety of different physical activities may prevent against monotony and increase the likelihood that children will discover a physical activity behavior they enjoy. While this rationale is logical, basic research examining the potential pro-behavioral effects of increasing variety on physical activity is very limited.

While not focusing on physical activity, a series of experiments have demonstrated that increasing the variety of available options increases consummatory behaviors when purchasing goods (Kahn & Isen, 1993; McAlister & Pessemier, 1982; Menon & Kahn, 1995; Steenkamp & Gielens, 2003). Basic laboratory studies of eating behavior also have shown that an increased variety of foods increases energy intake (McCrory et al., 1999; Myers Ernst & Epstein, 2002; Raynor, Jeffery, Tare, & Wing, 2004; Raynor & Wing, 2006; Rolls, 1985; Rolls, Rowe, & Rolls, 1982; Rolls et al., 1981; Temple, Giacomelli, Roemmich, & Epstein, 2008). Increasing the variety of food options may negatively affect weight control as individuals consume greater energy when presented with a variety of foods than when presented with a single food (McCrory et al., 1999; Raynor et al., 2004; Raynor & Wing, 2006; Rolls, 1985). Increasing variety, however, also can be used to encourage healthy weight control behaviors by increasing children's consumption of fruits and vegetables (Adams, Pelletier, Zive, & Sallis, 2005; Temple et al., 2008). Following this reasoning, increased variety also may be effective for increasing children's participation in physical activity. While no studies have directly examined the effect of altering the variety of exercise options on exercise behavior in children, a single observational study reported increases in youth physical activity during school recess when exercise equipment was available versus recess with no equipment available (McKenzie, Hardung, Baquero, Arredondo, & Elder, 2006). This increase in activity could be due to the greater variety offered by the presence of equipment. However, this study did not seek to examine the effect of variety on physical activity and as such only indicated whether equipment was present or not, so that a single piece of equipment (e.g., a ball) constituted a with-equipment condition, and neither the total amount nor variety of equipment available was reported or controlled.

A single study of adults demonstrated that varying the type of exercise prescribed every two weeks over an eight-week exercise intervention increased adherence to the intervention relative to adults receiving an unchanging exercise prescription (Glaros & Janelle, 2001). While the available options were altered every two weeks, the total number of options in the variable condition, during each two-week period, was equal to that of the unchanging condition. Therefore, while variety of the total exercise program was different, a single exercise session in the variable condition did not offer greater variety than any of the other individual sessions. While adherence was greater in the variable condition, the amount of physical activity individuals participated in per session was fixed across conditions and therefore the ability of variety to increase the amount of exercise within a single exercise session was not tested. Unlike research focusing on the effect of altering the variety of options on eating behavior (Myers, Ernst & Epstein, 2002; Rolls et al., 1982; Rolls et al., 1981; Temple et al., 2008) neither of these two physical activity studies evaluated the potential of increasing the variety of physical activity options to increase such behavior in a controlled laboratory environment during a fixed period of time.

Thus, the purpose of the present study was to determine whether increasing the variety of exercise equipment choices a child has access to increases the amount of exercise they participate in and their enjoyment (liking) of the exercise session in a controlled laboratory environment setting. This was the first study designed to directly examine the basic pro-behavioral effects of altering the variety of exercise equipment in children. This also was the first study to examine if an exercise session with a high variety of equipment options increases exercise behavior relative to a session of equal duration with a low variety of equipment in individuals of any age. Resistance training was chosen as the physical activity model because it allows the variety of choices to be easily manipulated by controlling access to the number of different movements within a single mode of exercise. Additionally, resistance training allows for easier measurement of physical activity and work performed compared to aerobic exercise equipment such as treadmills, cycle ergometers and elliptical trainers. It was hypothesized that, in a controlled laboratory environment and at an identical relative intensity, children would perform more repetitions, lift a greater total amount of weight and report greater liking of the exercise session when provided access to a greater variety of resistance training equipment than when provided access to a single piece of resistance training equipment.

Methods

Participants

Study participants included 10 boys (N = 10 Caucasian) and 10 girls (N = 9 Caucasian and N= 1 African American) who were between 8-12 years of age (M= 9.8 [+ or -] 0.9 years). Children were recruited through flyers and from a database of subjects who had previously contacted the laboratory to participate in unrelated studies. Children were excluded if they had any disorders that would affect their ability to exercise, including cardiovascular, neuromotor, cognitive or orthopedic disorders. All children indicated that they had previously sampled resistance training equipment as part of physical education classes, sports programs or home exercise equipment. However, no children had previous experience with regular resistance training programs. Children were studied separately and given identical instructions and no verbal encouragement from the investigators to eliminate the influence of peers and investigators on liking ratings, exercise choices, or the amount of exercise performed. Written informed parental consent and child assent were obtained for each subject prior to participation. This study was approved by the university institutional review board.

Procedures

Children reported to the Applied Physiology Laboratory at Kent State University for three visits and were tested without the presence of their parent or other children.

Visit one. During visit one, children were measured for height and weight and were then fitted for and sampled the following Cybex (Medway, MA) resistance training equipment in a random order; leg press, leg extension, leg curl, chest press, biceps curl, triceps extension and latissimus pull. Before sampling, an exercise physiologist with experience and knowledge of safe weight training techniques for children carefully demonstrated and instructed each child as to proper lifting technique defined as moving the apparatus through a complete range of motion, as depicted by the manufacturer on each piece of equipment, in a controlled fashion while exhaling during the concentric portion of each repetition and inhaling during the eccentric portion. After a piece of equipment was demonstrated, children sampled it by performing 2 sets of 8-10 repetitions with a minimum of 2 minutes rest between sets. During each of these two practice sets resistance was set at the lowest possible setting (one plate) for that piece of equipment. The resistance for each piece of equipment was as follows; leg press: 9.1 kg, leg extension: 4.6 kg, leg curl: 4.6 kg, chest press: 5.7 kg, biceps curl: 5.7 kg, triceps extension: 5.7 kg and latissimus pull: 4.6 kg. The equipment was designed to be adjustable for a wide range of body sizes including the children studied. All of the participants were able to be properly fit on each piece of equipment. Fit was assessed during the sampling sets. Proper fit was defined as the child being able to sit on each piece of equipment and complete the requisite two sets of 8-10 repetitions at the lowest possible resistance setting using a full range of motion and proper lifting form, per manufacturer instructions, on each piece of equipment. If a child was not capable of properly performing the requisite two sets of 8-10 repetitions using the proper lifting form they would have been excluded from the study.

After completing these two sampling sets children rated their liking of each piece of equipment using a visual analog scale (VAS), which required the child to make a mark upon a 10 cm line anchored by "like it very much" and "do not like it at all." Liking was assessed after the two sample sets and not after one-repetition maximum (1RM) testing as the number of attempts required to attain a 1RM were not consistent neither from one exercise to the next nor from one child to the next. After assigning a liking score children were assessed for their 1RM using a previously described methodology designed for children (Faigenbaum, Milliken, & Westcott, 2003). The maximum amount of weight children successfully lifted through a full range of motion using proper form was considered 1RM. To provide ample recovery, children were given a 5 minute rest period after completing the 1RM before repeating the process (sampling, assigning a liking score and determining 1RM) on the next piece of equipment until 1RM was assessed for all seven pieces of equipment. A previous evaluation of this 1RM method was deemed to be safe for children as no injuries were reported in the 64 children who completed the protocol (Faigenbaum et al., 2003). All children in the present investigation also successfully completed the entire study without injury.

Visit two and three. During the second and third visits, children returned to the laboratory to participate in a low-variety and high-variety exercise condition. The order of the high-variety and low-variety conditions was counterbalanced across subjects. For the low-variety condition, children had access to only their most liked piece of resistance training equipment, determined from visit one, and were told they could not exercise on any other pieces of equipment in the room. For the high-variety condition children had access to all seven pieces of equipment. During each condition children had access to the exercise equipment for 30 min. The resistance used for each piece of equipment was set at 70% of the participant's 1RM, determined from visit one. During the 30-minute session children were informed that they could exercise on the specified equipment choices in any pattern they wish, they could walk around the room or they could sit and rest on any piece of equipment. No constraints were placed on the number of sets or the number of repetitions performed per set. All children indicated that they understood these instructions. A trained exercise physiologist (JEB, EJR, DB or MVB) supervised each session to ensure that proper lifting form was utilized, but did not interact with the child unless they had to correct exercise form or provide other instructions for safe exercise. The supervisors neither encouraged nor attempted to suppress the amount of resistance training exercise the children performed. Activity during each exercise condition was measured via observation for repetitions of resistance training exercise and by accelerometry for any ambulation around the experimental room. Ambulation could take place during the expected recovery between resistance training sets or as an alternative behavior to weight training, if the child did not wish to resistance train at that time. At the conclusion of each exercise condition children completed a VAS to determine their liking for that session.

Instrument

Anthropometry. All anthropometric measures were performed by an experienced anthropometrist (JEB). Weight was assessed to the nearest 0.2 kg using a balance beam scale

(Health O Meter, Alsip, IL). Height was assessed to the nearest 1.0 mm using a calibrated stadiometer (Health O Meter, Alsip, IL).

Liking of physical activity. Children rated their liking of each piece of resistance training equipment and each of the two exercise conditions using a VAS that consisted of a 10 cm line anchored by 'do not like it at all' on the left side and 'like it very much' on the right side. The ratings were made immediately after sampling each piece of resistance training equipment (visit one) and immediately after the final minute of the high-variety and low-variety conditions. Utilizing a VAS to assess liking or hedonics as an affective rating of a behavior is considered both reliable and valid (Flint, Raben, Blundell, & Astrup, 2000) and measures of liking directly correlates with physical activity participation (Craig, Goldberg, & Dietz, 1996; DiLorenzo, Stucky-Ropp, Vander Wal, & Gotham, 1998; Motl et al., 2001; Roemmich et al., 2008).

Resistance exercise observation. The number of repetitions performed on each piece of exercise equipment were carefully observed and recorded. The total amount of weight lifted was calculated by multiplying the number of repetitions performed during each set by the amount of weight lifted (kg) per repetition for each piece of equipment and then summing the total weight lifted on each piece of equipment per condition. The number of repetitions performed in the high-variety and low-variety conditions was the primary dependent variable because each repetition, regardless of the individual exercising or the piece of equipment used, represented 70% of maximum effort. Conversely, the amount of weight lifted per repetition varied across pieces of equipment and from one individual to the next. Therefore, this comparison is less indicative of differences in relative work performed across conditions.

Accelerometer counts. Children wore an ActiGraph GT 1M accelerometer (ActiGraph, Pensacola, Florida) around their waist to determine the amount of ambulatory activity during each visit. The ActiGraph GT1M is a valid and reliable method of estimating physical activity in children (Freedson, Pober, & Janz, 2005; Puyau, Adolph, Vohra, & Butte, 2002; Trost et al., 1998). The total number of accelerometer counts accumulated during each of the 30 minute experimental conditions served as the outcome variable.

Statistics

Statistical power Statistical power was deemed adequate to test the primary outcome variable of total number of repetitions. Subjects performed 241.1 [+ or -] 105.4 repetitions in the high-variety condition compared to 148.0 [+ or -] variety condition. This difference yielded an effect size of 1.07, which required nine participants to achieve a statistical power of [greater than or equal to] .80 at an a level of < .05. Thus, the current sample size (N = 20) was more than sufficient. A differential effect of equipment variety on the number of repetitions performed by boys and girls was not expected. In the current study, boys performed an average of 193.2 [+ or -] 50.6 repetitions across both conditions while girls performed 195.9 [+ or -] 109.7 repetitions, which yielded an effect size of 0.04. Based on this observed effect size, 12,113 participants would have been needed in order to achieve a power of [greater than or equal to] .80 at an et level of < .05 for demonstrating sex differences. In addition to a lack of gender differences in the primary dependent variable, independent samples T-tests demonstrated that boys and girls did not differ in the physical characteristics of age (9.7 [+ or -] 0.9 years boys, 9.0 [+ or -] 1.0 years girls, t(18) = .24, p = .81), height (140.4 [+ or -] 4.3 cm boys, 136.8 [+ or -] 11.0 cm girls, t(18) = -.6l, p = .55), weight (36.1 [+ or -] 6.6 kg boys, 34.4 [+ or -] 12.3 kg girls, t(18) = -. 75, p = .48) or BMI percentile (64.8 [+ or -] 22.0 boys, 45.3 [+ or -] 31.2 girls, t(18) = -1.62, p = .12).

Analytic plan. Given that there were no significant gender differences in the physical characteristics or for the primary outcome variable the data from boys and girls were analyzed as a single group. Four, separate paired-samples T-tests were performed to examine differences in the total number of repetitions performed, the total amount of weight lifted, liking (VAS) scores and total accelerometer counts between the high-variety and low-variety conditions. A-priori significance was set at [alpha] [less than or equal to] .05.

Results

Children performed a greater number of repetitions (241 [+ or -] 105 high-variety, 148 [+ or -] 81 low-variety, t(19) = 4.76, p < .001 ), lifted more weight (3094 [+ or -] 1229 kg high-variety, 2114 [+ or -] 1672 kg low-variety, t(19) = 2.56, p < .05) and indicated greater liking (9.1 [+ or -] 1.1 cm high-variety, 6.7 [+ or -] 2.8 cm low-variety, t(19) = 4.20, p < .001) in the high-variety condition relative to the low-variety condition. There were no significant differences (17122 [+ or -] 15489 high-variety, 14061 [+ or -] 14509 low-variety, t(19) = .99, p = .33) in the alternative behavior of ambulation around the experimental room as assessed by the number of accelerometer counts children accumulated in the high-variety condition compared to the low-variety condition.

Discussion

While the American Academy of Pediatrics (Council on Sports & Fitness, 2008), the American College of Sports Medicine (ACSM) (American College of Sports Medicine, 2009) and National Strength and Conditioning Association (NSCA) (Faigenbaum et al., 2009) all recognize properly-supervised resistance training exercise as sale and beneficial for children the purpose of this investigation was hot to develop specific recommendations regarding resistance training exercise programming in children, but to assess the basic effect of increasing the variety of exercise options on exercise behavior in a controlled laboratory environment. All children tolerated the protocol well and there were no injuries during any part (exercise sampling, 1RM testing and 30-minute sessions) of this investigation. Children performed a greater number of repetitions, lifted a greater amount of weight and reported greater liking when exercising in a high-variety condition than in a low-variety condition. These results are similar to basic studies of the effects of variety on increasing eating behavior. Access to a greater variety of foods reliably increases food consumption in children and adults (McCrory et al., 1999; Raynor et al., 2004; Raynor & Wing, 2006; Rolls, 1985; Temple et al., 2008). Not surprisingly, long-term exposure to high-variety, palatable diets increases adiposity in both animals (Louis-Sylvestre, Giachetti, & Le Magnen, 1984; Rolls, Van Duijvenvoorde, & Rowe, 1983) and humans (Louis-Sylvestre et al., 1984; McCrory et al., 1999). However, the variety effect also can be used to increase healthy food options as increasing the variety of fruits and vegetables individuals have access to increases their consumption (Adams et al., 2005; Temple et al., 2008). Based on the results of the present laboratory study and previous observational (McKenzie et al., 2006) and training (Glaros & Janelle, 2001) studies, the effect of variety also may extend to physical activity participation. While much more basic research is needed, these results may have important implications for physical activity promotion programs. Researchers have begun to examine the efficacy of weight loss interventions that target long-term reductions in the variety of energy dense foods and increasing the variety of low energy dense foods (Ello-Martin, Ledikwe, & Rolls, 2005; Epstein et al., 2001; Raynor et al., 2004; Raynor, Niemeier, & Wing, 2006; Raynor & Wing, 2006). Physical activity promotion treatments that focus on increasing the variety of exercise options may also effectively increase physical activity behavior.

Variety may have a general effect on consummatory behavior. A series of studies (Kahn & Isen, 1993; McAlister & Pessemier, 1982; Menon & Kahn, 1995; Steenkamp & Gielens, 2003) have indicated that consumer purchasing behavior increases with the number of available purchasing options. Consumers rate having a wide variety of choices as very important when purchasing goods (Sellers, 1991) and regularly exhibit variety-seeking behavior even when purchasing items from the same product class (Kahn, 1995; Menon & Kahn, 1995). Although too many options of a type of product can lead to regularly choosing the same option in an effort to reduce the complexity of choosing, this approach typically results in feelings of monotony and boredom and eventually the reinstatement of variety seeking (Menon & Kahn, 1995).

Although children performed less resistance training in the low-variety condition, they did not increase their participation in the alternative physically active behavior of ambulating around the exercise room. While total ambulation did not differ between the low- and high-variety conditions anecdotal observation suggested that the pattern of ambulation differed across conditions. In the high-variety condition children moved around the room to go from one piece of equipment to another while in the low-variety condition, despite having access to only one piece of equipment, children often walked around the room rather than remaining seated at their favorite piece of exercise equipment.

The results of the present study are encouraging but, there are some study limitations. In the low-variety condition, children had access to only one piece of exercise equipment compared to all seven pieces of exercise equipment in the high-variety condition. The decision to provide access to only one piece of equipment in the low-variety condition was made to maximize the difference between the conditions. This decision may have reduced the children's ability to participate in as much exercise because there may have been more local muscular fatigue when using a single piece of equipment than when they had access to multiple pieces. While a pediatric specific fatigue scale does not presently exist, future research should assess fatigue in the high- and low-variety conditions perhaps utilizing a pediatric rating of perceived exertion scale (Pfeiffer, Pivarnik, Womack, Reeves, & Malina, 2002; Robertson et al., 2005; Robertson et al., 2002; Robertson et al., 2000; Utter, Robertson, Nieman, & Kang, 2002).

Future research also could utilize more than a single option low-variety condition and high variety condition. For example, a medium-variety condition which provides access to the most-liked upper and lower body exercises would reduce much of the chance of fatigue. It is important to note that despite the potential limitation of having only a single option in the low-variety condition, no children complained of being fatigued. In fact, one child performed a greater number of repetitions in the low-variety condition than the high-variety condition demonstrating the possibility of children to do so. Furthermore, if fatigue was a factor in why children performed more resistance training exercise in the high-variety condition, the results would suggest that a wide variety of exercise options should be provided in an effort to reduce fatigue and increase physical activity in a given exercise session.

The results of this study are limited to the type of physical activity performed. While monitoring total work performed will be more difficult, future research should examine the effect that increasing the variety of non-resistance training, physical activity options has on the amount of physical activity children participate in.

In conclusion, to our knowledge this is the first controlled laboratory study which sought to examine the basic effect of altering the variety of exercise equipment on the amount of resistance training exercise children perform. Children performed a greater number of repetitions, lifted more weight and indicated greater liking during a high-variety condition as compared to a low-variety condition. These results support the hypothesis that increasing the variety of exercise options may increase children's physical activity behavior. Future research should consider including a middle-variety condition, utilizing non-resistance training physical activity and attempt to assess the level of fatigue after a high-variety and low-variety condition to determine if the level of fatigue contributes to the greater amount of activity children participate in during a high-variety condition. The pro-behavioral effects of variety on physical activity in children may have important clinical implications. Those designing interventions to increase physical activity behavior in children should consider offering a wide variety of options in an effort to increase both adherence, as demonstrated previously in adults (Glaros & Janelle, 2001), and the total amount of exercise performed per session. This may result in greater physical activity participation during each session and greater adherence to the exercise program.

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Author's Note

Funding Source: This work was supported by a grant from the School of Exercise Leisure and Sport at Kent State University.

Jacob E. Barkley, Edward J. Ryan, David Bellar, and Matthew V. Bliss

Kent State University

James N. Roemmich

University at Buffalo

Address Correspondence to: James E. Barkley, School of Exercise Leisure and Sport, Kent State University, Kent, Ohio 44242. Phone: (330) 672-0209. Fax: (330) 672-2250. Email: [email protected].