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Original Research

The Effect of Variety on Physical Activity

A Cross-Sectional Study

Juvancic-Heltzel, Judith A.1,2; Glickman, Ellen L.2; Barkley, Jacob E.2

Author Information
Journal of Strength and Conditioning Research: January 2013 - Volume 27 - Issue 1 - p 244-251
doi: 10.1519/JSC.0b013e3182518010
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Abstract

Introduction

According to the Centers for Disease Control and Prevention (CDC), in the United States, at least 365,000 “preventable” deaths per year (16% of all deaths), second only to deaths caused by smoking, are the result of poor diet and lack of physical activity (21). The CDC further concluded that “physical inactivity is 1 of the major underlying causes of premature mortality in the United States” (8). Regular physical activity has numerous health benefits for individuals of all ages including improved cardiovascular fitness, weight control, improved self-esteem, reduced risk of cardiovascular disease (37), diabetes (3,37), hypertension (37), certain types of cancer (37), obesity, and depression (15,37). However, the prevalence of overweight and obesity has steadily increased over the past 20 years (23,24). Approximately two-thirds of adults in the United States are overweight (body mass index [BMI] ≥ 25–<30) or obese (BMI ≥ 30) (23). Thirty-three percent of children in the United States are either overweight (≥85th to <95th BMI percentile) or are obese (≥95th BMI percentile) (7). These rates suggest that individuals of various ages are likely not participating in adequate amounts of physical activity.

Despite these known benefits of exercise, <60% of adults participate in regular physical activity, with 25% being considered sedentary (23). Accelerometer data obtained from the National Health and Nutritional Examination Survey revealed that 58% of children ages 6–11 and 92% of adolescents ages 12–19 do not achieve recommended levels of daily physical activity (23). Therefore, scientific evidence identifying factors that may increase physical activity behavior is needed.

Several studies have demonstrated that altering the variety of available food items or consumer goods reliably increases eating and purchasing behavior, respectively (14,18–20,25,26,38). Although much less well studied, increasing the variety of the type of exercise prescribed and available exercise equipment may also increase exercise behavior (4,13). In 1 study assessing adults' adherence to an 8-week aerobic exercise intervention, participants who received varying exercise prescriptions every 2 weeks had greater adherence to the intervention than those who received an unchanging exercise prescription (13). Although adherence was greater, the amount of exercise the participants completed each visit was prescribed and therefore could not fluctuate. Furthermore, although exercise options were changed every 2 weeks, the total number of exercise options per session was the same in the variable and unchanging conditions throughout the study.

In a separate, preliminary study examining the basic effect of altering the variety of resistance training exercise equipment on exercise behavior in children, the participants performed a greater number of repetitions, lifted more weight, and reported greater liking for the exercise during a condition with 7 pieces of resistance-exercise equipment (high variety [HV]) compared to a condition with a single piece of resistance-exercise equipment (low variety [LV]) (4). The fact that there was only a single piece of exercise equipment in the LV condition increases the likelihood that fatigue could have limited the children's exercise participation in that condition. Furthermore, in this study, no effort was made to assess perceived exertion and no alternative activity (e.g., sedentary activity) for children to participate in was provided. Finally, these 2 previous studies examining the effect of variety on physical activity each assessed only 1 age group, young adults (18–35 years old) and children (8–12 years old), respectively, and neither assessed older adults. Because these previous studies assessed only younger individuals and because there is evidence of declining physical activity across the lifespan (33–35) assessing the potential probehavioral effect of variety on physical activity in a population of older adults is warranted.

The purpose of this investigation was to examine the effect of altering the variety of resistance training equipment options on liking, effort perception, and the amount of exercise performed by children (8–12 years old), young adults (18–26 years old), and older adults (≥60 years old). In this study, a greater number of equipment options were used in both the LV (2 pieces) and HV (10 pieces) than in the prior preliminary study (4), rating of perceived exertion (RPE) was assessed, and there were alternative sedentary activities available to participants during both conditions. It was hypothesized that children, young adults, and older adults would perform more exercise (i.e., a greater number of repetitions), allocate more time for physical activity vs. sedentary alternatives, and indicate greater liking during a free-choice, HV resistance training equipment exercise condition than an LV condition. Additionally, there would be no differences in RPEs between the 2 conditions (HV, LV). Finally, there would be no age group by condition or gender by condition interactions for any dependent variable.

Methods

Experimental Approach to the Problem

To assess the effect of altering the variety of resistance-exercise equipment on exercise behavior, liking and RPE, a 3 age group (children, young adult, older adult) by 2 condition (HV, LV) mixed, cross-sectional design was used. Age group was a between-subjects variable and condition was a within-subjects variable. The primary independent variable (variety condition) was a within-subjects variable. Dependent variables included: number of repetitions performed, total weight lifted, time allocated to sedentary alternatives, liking of the exercise, and RPE.

Subjects

Study participants included the following age groups (N = 6 male subjects, N = 6 female subjects per age group): children (10.1 ± 1.3 years old), young adults (21.7 ± 1.6 years old), and older adults (69.9 ± 15.6 years old). The participants were recruited from the local community through posted flyers and from a database of individuals that had previously contacted the laboratory for separate, unrelated studies. The participants were excluded if they had any contraindications to physical activity including: orthopedic, neuromuscular, metabolic, cardiovascular, or cognitive disorders. None of the individuals in the study had a history of regular resistance training or had participated in a resistance training regimen in the 6 months preceding the study. The investigation was performed in the spring and summer. Each participant was studied separately and given identical verbal instructions with no verbal encouragement from investigators to limit the influence of the investigator on participant behavior. The participants were informed of the experimental risks and completed a written informed consent document and child assent forms before the investigation. Parental consent was obtained for all child participants. The study was approved by the Kent State University Institutional Review Board.

Procedures

The participants reported to the Applied Physiology Laboratory at Kent State University and were tested individually on 3 separate occasions.

Visit One

During visit 1, the participants were measured for height and weight using a balance beam scale and stadiometer (Health O Meter, Alsip, IL, USA). The participants were then fitted for and sampled the following Cybex (Medway, MA, USA) resistance training equipment: triceps extension, bicep curl, latissimus dorsi pulldowns, chest press, leg press, leg extensions, and leg curls and Nautilus Bowflex SelectTech BD 552 dumbbells (Vancouver, WA, USA): hammer curls, lateral raise, and dumbbell bench press. All exercise options were sampled in a random order. After demonstration of proper lifting technique by a trained exercise physiologist (J.J.H., J.E.B.), the participants performed 2 sets of 8–10 repetitions on each piece of equipment with a minimum of 2 minutes of rest between sets. Proper lifting technique was defined as moving the apparatus or dumbbells through a complete range of motion in a controlled fashion while exhaling during the concentric portion of each repetition and inhaling during the eccentric portion. During each of these 2 practice sets, the resistance for each piece of equipment for children and adults, respectively, was as follows: leg press: 9.1 kg/18.2 kg, leg extension: 4.5 kg/13.6 kg, leg curl: 4.5 kg/13.6 kg, chest press: 5.7 kg/11.4 kg, biceps curl: 5.7 kg/5.7 kg, triceps extension: 5.7 kg/5.7 kg, latissimus dorsi pulldown: 4.5 kg/13.6 kg, hammer curl: 2.3 kg/3.4 kg, bench press: 2.3 kg/3.4 kg, and lateral raise: 2.3 kg/3.4 kg. After successfully completing the 2 sampling sets, the participants performed an indirect 1-repetition maximum (1RM) as previously described by Brzycki (6). Although the participants were screened for orthopedic, neuromuscular, metabolic, or other limitations that might inhibit their participation in the study, an indirect 1RM assessment was used instead of a direct 1RM assessment to reduce the risk of musculoskeletal injury. The participants were given a rest period of 5 minutes after completing an indirect 1RM before repeating the process (sampling and determining an indirect 1RM) on the next piece of equipment until all 10 pieces of equipment were used. After obtaining an indirect 1RM, the participants completed a 10-cm visual analog scale (VAS) ranging from “do not like at all” to “like very much” to assess liking for that piece of equipment before moving to the next.

Visits Two and Three

During visits 2 and 3, for a period of 20 minutes, the participants had the option of performing resistance exercises and sedentary alternatives in any pattern and amount they wished during an HV and LV exercise session. The order of the exercise sessions was counterbalanced across participants. Throughout the HV session, the participants had access to all 10 pieces of equipment sampled during visit 1 and during the LV exercise session, the participants had access to only their favorite upper and lower body exercises as determined via VAS scores from visit 1. Resistance for each piece of equipment was set at 70% of estimated 1RM. During each session, the participants also had access to age appropriate sedentary activities set up on a table in the exercise room during each session. These sedentary activities included puzzles, crosswords, magazines, Sudoku and coloring, and drawing for the children. During the 20-minute session, the participants were informed they were free to exercise on the specified equipment choices in any pattern they wished, walk around the room, sit and rest on any piece of equipment or sit at the table using the sedentary activities. No constraints were placed on the number of sets or the number of repetitions performed per set. All the participants indicated that they understood these instructions. A trained exercise physiologist supervised each session (the independent variable) to ensure that proper lifting technique was used and to record the number of repetitions performed on each piece of equipment and the amount of time allocated to the exercise equipment and sedentary alternatives (the dependent variables). After completing each session, the participants indicated their overall liking and RPE for that session (dependent variables).

Anthropometry

All anthropometric measures were completed by an experienced anthropometrist. Weight was assessed to the nearest 0.2 kg using a balance beam scale (Health O Meter, Alsip, IL, USA). Height was assessed to the nearest 1.0 mm using a calibrated stadiometer (Health O Meter).

Liking of Physical Activity

The participants rated their liking of each individual piece of resistance training equipment and each of the 2 exercise sessions (HV and LV) by making a mark on a 10-cm line anchored by “do not like at all” on the left side and “like very much” on the right side. The distance, in centimeters, from the left-most portion of the VAS to the mark was recorded as the measure of liking. The ratings were made immediately after sampling each piece of equipment (visit 1) and immediately after the final minute of the HV and LV sessions. Using a VAS to assess liking or hedonics as an affective rating of a behavior is considered both reliable and valid (12) and measures of liking of physical activity directly correlate with physical activity participation (9,10,22,32).

Rating of Perceived Exertion

The RPE was assessed at the end of each exercise session using the OMNI Resistance-Exercise scale (16,29–31). Two validated scales were used, 1 designed for adults (16,29,31) and 1 designed for children (29,30). Instructions for the scales use was described to participants before both sessions 2 and 3.

Indirect 1 Repetition Maximum

The indirect 1RM requires the participants to perform between 2 and 10 repetitions of the given exercise to volitional fatigue. No more than 10 repetitions should be performed at the set weight; if the participant is capable of completing >10 repetitions, the process was completed with a greater weight after a 1- to 3-minute rest period. Once the correct weight is determined, the following calculation was used to determine the indirect 1RM (6).

X is the number of repetitions performed.

Resistance Exercise Observation

The number of repetitions performed on each piece of exercise equipment was carefully observed and recorded. The total amount of weight lifted was calculated using the following equation:

The amount of time out of 20 minutes that the participants allocated to the resistance training equipment relative to the sedentary alternatives was recorded via observation with a stopwatch (Traceable Stopwatch, Fisher Scientific, Waltham, MA, USA). Although total weight lifted was assessed, the number of repetitions performed in each exercise condition (HV and LV) was the primary dependent variable for exercise behavior. Each repetition, regardless of the piece of equipment used, represented 70% of maximum effort. Conversely, the amount of weight lifted per repetition varied across pieces of equipment and participants. Therefore, comparison of total weight lifted is less indicative of differences in relative work performed across conditions than total repetitions performed. Monitoring of resistance exercise (repetitions) and time allocated to the sedentary activities was performed only by trained exercise physiologists who were members of the research team. Both individuals who supervised the exercise sessions have extensive experience in exercise monitoring (4,28).

Statistical Analyses

Two-way analyses of variance (ANOVAs) were used to examine differences in age, height, weight, and BMI between male and female participants and across all 3 age groups (children, young adults, older adults). Separate 3-way ANOVAs with gender (male and female participants) and age group (children, young adults, older adults) as between-subject variables and condition (HV and LV) as within-subject variables were used to determine the differences in the following dependent variables: total number of repetitions performed, total weight lifted (kilograms), amount of time allocated to sedentary activities, OMNI RPE, and VAS (liking) scores. Post hoc analyses of any significant interactions were performed via independent and paired samples t-tests. All of our results were normally distributed.

A priori hypotheses stated that increasing the variety of resistance-exercise equipment would increase the number of repetitions performed and liking of that exercise. It was also hypothesized that increasing the variety of equipment would reduce time allocated to sedentary alternatives. Power analyses for all a priori hypotheses were performed using 1 way, repeated measures ANOVA for differences in repetitions, liking and time allocated to sedentary activity across conditions (HV, LV). The participants performed 126.4 ± 71.7 repetitions in the HV condition and 88.0 ± 48.8 in the LV condition. This difference yielded a partial eta squared (

) of 0.4 which required a sample size of 11 to achieve a power of ≥0.8 and an α ≤ 0.05. The participants reported a liking of 8.1 ± 0.25 cm in the HV condition and 7.1 ± 0.35 cm in the LV condition. This difference yielded a

of 0.21, which required a sample size of 20 to achieve a power of ≥0.8 and an α ≤ 0.05. The participants allocated 5.7 ± 1.4 minutes to sedentary activity in the HV condition and 7.9 ± 1.5 minutes in the LV condition. This differences yielded a

of 0.23, which required a sample size of 18 to achieve a power of ≥0.8 and an α ≤ 0.05. Taken together, these effects required 11–20 participants to achieve adequate power. Therefore, our sample size (N = 36) was deemed to be sufficient to test all a priori hypotheses.

Results

Participant characteristics are provided in Table 1.

Table 1
Table 1:
Participant physical characteristics.*

Repetitions

A main effect of condition for repetitions (Figure 1) performed (p < 0 .001) was seen with significantly more repetitions being performed in HV (126.4 ± 71.7) than the LV (88.0 ± 48.8) condition. Additionally, a significant main effect for age group was observed (p = 0.006). The older adults performed more (p = 0.002) average repetitions (130.6 ± 33.6) than the young adults (74.8 ± 42.8) but not the children (116.3 ± 72.1, p = 0.54). There were no significant (p = 0.10) differences for average repetitions between the children and the young adults. There was a significant main effect for gender (p = 0.04) with male participants (122.1 ± 66.1) performing significantly more (p = 0.04) repetitions than female participants (92.4 ± 40.4). No significant interaction effects (p ≥ 0.20) were observed for repetitions performed.

Figure 1
Figure 1:
Total repetitions. Participants performed a significantly (p ≤ 0.001) greater number of repetitions in the high-variety condition than in the low-variety condition.

Weight Lifted

There were no significant (p = 0.23) main (HV 6,430 ± 5,022 lb, LV 5,660 ± 4,207 lb) or interaction effects (p ≥ 0.06) for differences in weight lifted.

Time Allocated to Sedentary Activity

There was a significant (p = 0.008) gender by condition interaction for time allocated to sedentary activities with female participants allocating less (p = 0.001) time to sedentary activities in the HV (5.7 ± 1.4) condition than the LV condition (9.9 ± 1.5) (Table 2). Conversely, male participants allocated similar amounts of time to sedentary activities in the HV (5.8 ± 1.6) and LV conditions (5.9 ± 1.5) (p = 0.90). There was a significant main effect of condition (p = 0.005) because more time was allocated to weights in the HV condition (14.3 ± 6.3 minutes) than the LV condition (12.1 ± 6.5 minutes) overall. There was a main effect of group (p = 0.05) because the older adults allocated less (p = 0.04) time to sedentary activities than the young adults. There were no significant (p ≥ 0.09) differences between the children and either of the 2 adult groups. No other significant (p ≥ 0.06) main or interaction effects for minutes allocated to sedentary activity were observed.

Table 2
Table 2:
Time allocated to sedentary activity.*†

Rating of Perceived Exertion

Table 3 illustrates the effort perception (RPE) and VAS (liking) data recorded at the conclusion of the HV and LV conditions. A significant (p = 0.01) main effect of group for differences in average RPE was observed with the older adults demonstrating a greater RPE (M = 5.5 ± 2.2) than both the young adults (M = 3.5 ± 2.0) and children (M = 3.0 ± 1.5). No significant (p = 0.53) differences in RPE were observed between the young adults and children. There were no additional significant (p ≥ 0.13) main or interaction effects for differences in RPE.

Table 3
Table 3:
VAS (liking) and average OMNI RPE scores.*†

Liking

There was a main effect of condition (p = 0.009) because participants reported greater liking in the HV condition (8.1 ± 0.25 cm) than in the LV condition (7.1 ± 0.35 cm; Table 3). No additional significant (p ≥ 0.08) main or interaction effects were observed for liking.

Discussion

Although the probehavioral effects of variety on eating and purchasing behavior is well studied (14,18–20,25–27,38), there is far less research examining the effects of variety on physical activity behavior (4,13). This was the first study we are aware of that assessed the impact of altering the variety of exercise equipment on the amount of exercise performed and liking and RPE of the exercise bout using a cross-sectional design. In this study, providing a greater variety of resistance-exercise equipment increased the number of repetitions performed and reported liking of the resistance exercise without affecting RPE in groups of children, young, and older adults. The lack of a difference in RPE suggests that fatigue was likely not the primary factor behind the reduced number of repetitions and enjoyment in the LV condition. The increases in repetitions performed and greater liking agree with a previous preliminary study performed with 8- to 12-year-old children (4). The similar finding occurred despite significant methodological differences between the 2 studies. In the previous study, there was only a single exercise equipment option in the LV condition, no alternative sedentary activities were provided and RPE was not assessed.

The participants in this study did not lift significantly more weight in the HV condition relative to LV condition. This result is contrary to previous findings (4). Although total weight lifted in the HV and LV conditions was not different, the number of repetitions performed represents a better measure of effort. Each repetition represents 70% of maximum effort, whereas, depending upon the exercise equipment, the amount of weight required to achieve 70% of maximum effort varied substantially across the different pieces of equipment and participants. Therefore, the decision to perform more repetitions represents an increase in exercise behavior, whereas weight lifted is more representative of the individual pieces of equipment a participant chose to use.

Contrary to our hypothesis, only female participants reduced their sedentary behavior in the HV condition. This suggests that although increasing exercise equipment options similarly increased the number of repetitions performed across genders, female participants appear more responsive to altering the variety of exercise equipment than male participants it pertains to sedentary behavior. This greater reduction in sedentary behavior during the HV condition in female participants is potentially important. Greater amounts of sedentary behavior are associated with other obesogenic behaviors such as increased energy intake or snacking (5,11,17). If providing exercise environments with a greater variety of exercise equipment motivates female participants to allocate greater amounts of time to the exercise environment at the expense of sedentary alternatives, there may be ancillary reductions in obesogenic behaviors.

Male participants performed a greater overall number of repetitions than did female participants, which is consistent with the findings of previous research (2,35,36). Not consistent with previous research (33–35) findings was the overall greater number of repetitions and lower amounts of sedentary behavior in the older adult group relative to young adults. This result was not expected, and it is unclear why it occurred. Perhaps this group of younger adult participants did not find resistance training as motivating as the older adults. The older adults also indicated a significantly greater OMNI RPE than both the younger adults and child participants. However, this is not surprising given the fact that, relative to younger adults, older adults performed significantly more work in the free-choice conditions.

This study was not without limitations. There were only 2 variety conditions: HV and LV. Including a medium variety condition (e.g., 5 pieces of equipment) in future research may provide information regarding the possibility of incremental increases in physical activity behavior in response to increasing exercise equipment variety. Resistance training exercise was chosen for this study because it allows for the control of the relative intensity across participants, offers multiple exercise options, and is it is easy to monitor the amount of exercise performed. However, testing the effect of altering the variety of exercise options on exercise behavior using different exercise modalities (e.g., cardiorespiratory exercise) is warranted. Furthermore, we did not assess non-resistance training physical activity in this investigation. General physical activity behavior could affect one's response to altering the variety of exercise equipment options. Additionally, there is a need for the development of more effective exercise intervention programs for overweight or obese individuals. If increasing the variety of exercise equipment options can successfully increase exercise behavior and enjoyment in overweight or obese individuals, it may also increase the success rate of exercise interventions. Therefore, additional research on overweight/obese individuals is warranted.

Practical Applications

Maintaining interest in an exercise session is of great importance to not only the strength and conditioning coach working with a group of athletes but also to other fitness professionals working with the general population. Based on the present evidence, increasing the variety of resistance-exercise equipment increases the number of repetitions performed and the enjoyment of that exercise without affecting RPE in male and female participants of a wide range of ages. The females participants also exhibited reduced sedentary behavior when provided with an HV of exercise equipment. The majority of these results agree with those of previous preliminary research assessing the basic effect of variety on exercise behavior in children (4). Greater participation in resistance exercise per session could increase the effectiveness of such exercise and greater liking or enjoyment of that exercise could increase adherence. Although the effect of altering the variety of exercise options on exercise behavior has not been well studied, there is evidence supporting the physiologic benefits of performing a variety of different physical activities. When the same activities are performed chronically, there is the risk of injury from overuse and repetitive motion (1). Conversely, by performing a variety of new activities the body is challenged in new ways (39,40). The present results suggest that in addition to the physiologic benefits of participating in a variety of exercise options, increasing the number of these options also appears to increase physical activity behavior. Although additional research is warranted on different modes of exercise, increasing the variety of exercise equipment available to one's clients may increase their exercise participation and enjoyment of that exercise.

Acknowledgments

This work was supported by a grant from the Graduate Student Senate at Kent State University.

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Keywords:

resistance exercise; children; older adults; exercise behavior

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