Sex Difference in the Effect of Peer Influence on Submaximal Running in Recreational Runners.

Carnes, Andrew J. ; Barkley, Jacob E.

Social facilitation (Zajonc, 1965) describes the phenomenon of increased physical performance in the presence of others. Fitness professionals and popular media sources frequently cite this theory when recommending exercise with a partner in order to increase the motivation to exercise, or the intensity or duration of an exercise session (Dolan, 2008; Kravitz, 2011). Existing social facilitation research in the athletic setting focuses primarily on the enhancement of maximal effort during competition. Just as Triplett's (1898) early study showed increased speed in cyclists competing against others, later studies on weightlifters (Rhea, Landers, Alvar, & Arent. 2003), swimmers (Williams, Nida, Baca, & Latane, 1989), and cyclists (Corbett, Barwood, Ouzounogluo, Thelwell, & Dicks, 2012; Wilmore, 1968) suggest that the presence of an audience or competition improved maximal performance. While competition at maximal effort is athletes' primary concern, a substantial amount of their training occurs below maximal (i.e., submaximal) effort. However, experimental research examining the impact of peer influence on athletes' submaximal training behavior is limited.

Experimental work examining the effect of peer influence on submaximal, free choice exercise in non-athlete adults (Grindrod, Paton, Knez, & O'Brien 2006; Plante, Madden, Mann, Lee, Hardesty, Gable, et al., 2010) and children (Barkley, Salvy, Sanders, Dey, von Carlowitz, & Williamson, 2014; Rittenhouse, Salvy, & Barkley, 2011; Sanders, Peacock, Williamson, Wilson. Carnes, & Barkley, 2014; Salvy, Bowker, & Roemmich, 2008) suggests that the presence of others can positively impact exercise behavior (i.e., increase the amount and intensity of physical activity) and enjoyment. A similar effect in athletes could have important practical implications. Higher intensity when training with a partner could enhance fitness, but also lead to overtraining if intended low intensity exercise becomes too strenuous (Seiler, 2010; Midgeley, McNaughton, & Jones, 2007; Foster. Heimann, Esten, Brice, & Porcari, 2001). Additionally, greater enjoyment could promote adherence (Hagberg, Lindahl, Nyberg, & Hellenius, 2009) and/or prevent athletic burnout (Lemyre, Hall, & Roberts, 2007; Smith, Gustafsson, & Hassmen, 2010). Distance runners are a suitable population for the investigation of social facilitation during submaximal exercise, as they commonly perform training sessions together (Kolata, 2009) and a substantial amount of their training is submaximal (Esteve-Lanao, 2005; Seiler, 2010). Furthermore, running is increasingly popular (Running USA, 2016) and the proposed benefits of running with others are widely accepted. For instance, running periodicals often suggest that doing so will increase intensity and enjoyment(Jarvis, 2012; O'Mara, 2013) but largely rely on anecdotal evidence to support this recommendation.

The results of initial studies by our research group examining the impact of the presence of a peer on distance runners' exercise behavior have not aligned with those on competitive performance in athletes or submaximal exercise in non-athlete adults and children. During self-paced submaximal treadmill exercise, both competitive male runners and non-runner controls exhibited no difference in exercise intensity or enjoyment between exercising alone or next to a familiar peer(Carnes, Barkley, Williamson, & Sanders, 2013). However, the use of treadmills limited these results, since participants remained stationary regardless of speed and did not need to alter speed to remain beside their peer. In a subsequent study (Carnes and Barkley, 2015) that used outdoor running to address the constraint of treadmill use, collegiate male track athletes ran more slowly with a single teammate or two other teammates versus an alone condition, but reported greater enjoyment in both peer conditions than alone. However, participants were paired with peers who they considered to be friends, possibly lessening the need to project a favorable self-presentation, i.e., the desire to demonstrate competence in a task when in the presence of others (Bond, 1982).

These unexpected results highlight the need for greater empirical understanding of how peer influence may affect exercise behavior and enjoyment, which could allow more effective recommendations regarding the potential benefits of exercise partners. Because our previous studies on runners only included males and familiarity between peers may have reduced the need for positive self-presentation (Bond, 1982), the current study included both sexes and paired participants with an unfamiliar peer. The purpose of this study was to determine if running with a same-sex, unfamiliar peer, relative to running alone, affected average speed, enjoyment, and/or perceived exertion during a self-paced outdoor run in male and female recreational runners. We hypothesized that the presence of a partner would increase average speed and enjoyment during a submaximal run.

Materials and Methods

Participants

Participant characteristics are shown in Table 1. Sixteen (n = 8 male, 8 female) recreationally competitive adult distance runners participated in the current study. Participants were recruited from a local five kilometer race. All participants reported habitually running at least four days per week and were free of any medical diagnoses (e.g., metabolic, orthopedic, cardiovascular disorders) that could be considered contraindications to physical activity. Prior to participation, all participants provided written informed consent and completed a medical health history questionnaire. All study procedures complied with the guidelines of the Declaration of Helsinki and were approved by the University Institutional Review Board.

Procedures

Participants reported to the laboratory to sign a consent form, be measured for height and weight, and complete fitness testing. After completing fitness testing they were sent home. Seven to ten days after the initial fitness test, participants completed the first of two experimental running trials, each under a different social condition, in a randomized order. The remaining experimental trial was scheduled seven days after the first. Participants were instructed to refrain from strenuous training or physical activity on the day prior to and following fitness testing and both experimental trials. Running or other aerobic activities were to be limited to a light intensity not exceeding 45 minutes, and participants were asked not to perform any resistance training on these days. Participants were also instructed to maintain their customary dietary habits, but to abstain from alcohol and any stimulatory dietary supplements (caffeine, energy shots, etc.) for twenty-four hours prior to fitness testing and both experimental trials. Habitual coffee consumption was allowed at participants' customary amount. All participants indicated that they would not compete in any races or other athletic competitions during their participation in the study.

Fitness Testing. Participants reported to the laboratory alone. Body mass was assessed to the nearest 0.2 kg and height to the nearest 1.0 mm using a balance beam scale (Health O Meter, Alsip, IL) and calibrated digital stadiometer (Charder Medical, Da Li City, Taiwan, China) respectively. Participants then completed a 10-minute warm-up run on a treadmill (Quinton MedTrack CR60, Bothell, WA) at a self-selected pace in a climate neutral environment (19-21[degrees]C, -40% relative humidity). After wanning up, participants selected a comfortable running speed, which was held constant for the duration of the test. The grade was then increased by 2.5% every two minutes until volitional exhaustion (Costill and Fox, 1972). Oxygen consumption (V[O.sub.2] ml*[kg.sup.1]*[min.sup.-1]), heart rate, and respiratory exchange ratio (RER) were monitored throughout the test. Heart rate was monitored using a downloadable telemetry monitor (RS800, Polar, Kempele, Finland). Expired air was collected and analyzed to determine peak oxygen consumption (V[O.sub.2] peak) using indirect calorimetry (True One 2400, ParvoMedics, Salt Lake City, UT). V[O.sub.2] peak was recorded as the peak V[O.sub.2] in ml*[kg.sup.1]*[min.sup.-1] achieved during the progressive treadmill test. Undifferentiated, whole-body ratings of perceived exertion (RPE) were obtained in the last 15 seconds of each stage using the validated Borg 6-20 RPE scale (Borg, 1982). A large RPE scale was held in front of the participant, who could point at the number matching his/her perceived exertion.

Experimental Trials. Each trial was performed outdoors on a measured asphalt path closed to motor vehicles and free of any uneven terrain. Each running trial consisted of a self-paced 6.4 kilometer run, and all trials were completed on the same measured portion of the trail. Participants were instructed to run to the end of the path (3.2 km from the starting point), turn around, and run back to the starting point (6.4 km total). An additional researcher was stationed at the end of the path to ensure participants' safety and that each participant reached the turnaround point. Trials were conducted as close to the same time of day as possible ([+ or -] two hours) for each participant and occurred between 1:00 PM and 5:00 PM. Ambient temperature, relative humidity, and wind speed were recorded at the start of each session. All experimental sessions were completed in temperatures between 5[degrees]C and 15[degrees]C, with wind speed below 7 m*[s.sup.-1] and no precipitation. Participants were not permitted to wear personal music players or electronic timing or monitoring devices during the trial. The following primary dependent variables: elapsed time, liking (i.e., enjoyment) of the activity, and RPE were recorded at the conclusion of each trial. The elapsed time and set distance of the course were used to calculate average running speed for each trial.

Alone condition. The participant reported alone to the starting point at a predetermined time to complete the running trial described in the previous section. Research personnel gave the following instructions:

Today you are going to complete a four-mile run on the path by yourself. Run two miles to the end point of the path, turn around, and return to the starting point. This is not a test to see how fast you can go. Treat this as a normal run on a day when you do not do a structured 'workout', such as intervals, a 'threshold' or 'tempo' run, or a long run. You are free to run at any pace you choose and you may change your pace at any time. Do not run with anyone you encounter on the path. When you return, we will ask you some questions about your run. Do you have any questions?

Peer condition. Two participants simultaneously completed the same exercise trial described in the alone condition. Pairs of participants had finished the 5k race used for recruitment within 60 seconds of each other, and had V[O.sub.2] max values within 5 ml*[kg.sup.1]*[min.sup.-1] of each other, as determined in the baseline session. Upon reporting to the starting location, participants were introduced and each indicated that he/he did not know the other participant, nor had they previously run together. Participants received the same instructions as in the alone condition, with an added statement that they would be running with a partner. As in the alone condition, participants were instructed not to run with anyone else on the path, excepting the assigned partner. Measures were identical to the alone condition. Each participant reported liking and reported RPE at the completion of the run in a private area separate from the other participant.

Measurements

Speed. Elapsed time of the run was recorded in minutes and seconds using a digital stopwatch. Average speed was calculated in km * [hr.sup.1] by dividing the distance (6.4 km) by the elapsed time in hours (i.e., 30 minutes = 0.50 hours).

Liking. Participants rated their liking of each exercise session using a visual analog scale (VAS) consisting of a continuous 100-millimeter line anchored by do not like it at all on the left and like it very much on the right (Motl, Dishman, Saunders, Dawda, Felton, & Pate, 2001). The participant was shown the scale and instructed to make a mark on the line to indicate his level of liking of the session. The position of the mark was measured in millimeters from the left anchor of the line, with a higher value indicating greater liking.

Rating of Perceived Exertion. Undifferentiated, whole-body RPE was obtained at the conclusion of each run using the validated Borg RPE scale (Borg, 1982). The RPE scale was explained to the participant, who was then asked to rate their average exertion over the course of that day's run.

Statistical Analyses

All statistical analyses were conducted using SPSS for Windows (version 17.0, SPSS Inc., Evanston, IL) with an a-priori a level of [less than or equal to] 0.05. Means and standard deviations were calculated for all physical characteristics (height, body mass, age, V[O.sub.2] peak) and the primary dependent variables (average speed, liking of the activity, and RPE) for each social condition (alone, peer). Physical characteristics were compared between sexes using independent t-tests. Because all individuals in the study were participants, there was interdependence within each pair of participants who completed the peer condition together. Therefore, mixed-effects regression models were utilized to examine all dependent variables over the two social conditions. Mixed models assume that the data within participants are dependent among the observations and can therefore be utilized to analyze data such as these where interdependence must be accounted for Gibbons and Hedeker, 1994). Separate models were performed for each of the dependent variables (average speed, liking, perceived exertion). All regression analyses utilized the following model:

Dependent variable = [alpha] + [beta](social condition) + [beta], (sex) + [beta]3 (social condition*-sex)

Post-hoc t-tests were performed between sexes and across social conditions for any significant main or interaction effects.

Results

Male participants (67.3 [+ or -] 3.44 ml-kg min-1, 14.1 [+ or -] 0.70 km-hr1) had a significantly greater V[O.sub.2] max (p<0.001) and ran faster across both social conditions (p<0.001) than female participants (52.3 [+ or -] 2.20 ml-kg-mhr1, 11.5 [+ or -] 0.45 km*[hr.sup.1]). Mixed model regression analysis revealed a significant sex by condition interaction for average speed (p=0.01), as illustrated in Figure 1. Relative to running alone (11.2 [+ or -] 0.35 km-hr1), women significantly decreased running speed (p=0.05) in the presence of an unfamiliar peer (11.9 [+ or -] 0.78 km*[hr.sup.1]). While male runners exhibited a nonsignificant (p=0.156) increase in speed (13.9 [+ or -] 0.89 to 14.3 [+ or -] 0.51 km*[hr.sup.1]), their positive change in speed across social conditions (0.38 [+ or -] 0.58 km*[hr.sup.1]) significantly differed (p=.01) from female runners' negative change in speed (-0.65 [+ or -] 0.78 km*[hr.sup.1]). Men and women reported greater enjoyment in the peer condition than the alone condition, but this increase was not significant (p [greater than or equal to] 0.149). There were no main or interaction effects for RPE (p [greater than or equal to] 0.25). Data for all dependent variables, grouped by sex, are shown in Table 2.

Discussion

The present study aimed to empirically examine the widely accepted idea that exercise partners will universally increase the intensity and/or enjoyment of a bout of exercise. We examined how the presence of an unfamiliar peer would affect recreational runners' speed, liking of the activity, and perceived exertion during a self-paced, submaximal run. Relative to running alone, female runners significantly decreased average speed with a peer while men increased speed. To our knowledge, this sex specific response to a peer during exercise has not been previously observed.

While past experimental research has shown enhanced athletic performance during competition(Corbett, Barwood, Ouzounogluo, Thelwell, & Dicks, 2012; Rhea et al., 2003; Williams et al., 1989; Wilmore, 1968) the current study more closely relates to those on non-athlete adults and children (Barkley et al., 2014; Grindrod et al., 2006; Plante et al., 2010; Rittenhouse et al., 2011; Sanders et al., 2014; Salvy et al., 2008) that showed a positive effect on physical activity behavior and enjoyment during submaximal exercise. By contrast, a preliminary study by our research group (Carnes and Barkley, 2015) examined the effect of peer influence on athletes during submaximal exercise. Unlike past non-athlete adult and pediatric studies, highly competitive collegiate runners decreased running speed but reported greater liking in the presence of teammates they considered to be friends. This may have been due to the college runners being accustomed to training with teammates and not feeling pressure to demonstrate competence.

The current study differed from that on collegiate runners by examining recreational runners, including female runners, and using pairs of unfamiliar peers. Male recreational runners, in contrast to the previous observations on collegiate runners, increased running speed in the presence of an unfamiliar, same sex peer. This difference may have resulted from peers in the present study being unfamiliar and wanting to present themselves in a positive way (Bond, 1982), or the less-advanced ability of the recreational runners (relative to collegiate runners) increasing their desire to demonstrate competence. The most notable finding was the differential response to a peer between men and women, as female runners substantially reduced speed when running with an unfamiliar female partner. Several authors (Deaner and Mitchell, 2006; Deaner, Masters, Ogles, & LaCaille, 2011 ; Frick, 2011) have suggested higher competitiveness in male distance runners than females, possibly explaining the sex difference that occurred here. Kilpatricket al. (2005) has also pointed to men reporting higher levels of exercise motivation for competition and social recognition. However, this concept must be clarified. It is without doubt that female athletes possess the capacity and motivation to train just as hard and reach the same levels of achievement as males (Frick, 2011). However, the evolutionary psychology perspective of higher competitiveness in males (Jonason, 2007) may manifest in males' competitiveness permeating to a greater proportion of interactions. As Deaneret al. (2011) suggest, men may more actively pursue opportunities to "show off." It is clear that in a race environment, female athletes are highly motivated to compete against their opponents. However, in a noncompetitive situation like the submaximal runs in this study, men may be more likely to see an opportunity to compete where women do not.

Another possibility to explain the divergent response to a same-sex, unfamiliar running partner observed here is not that social facilitation was absent in female runners, but that their behavioral response was different than that of males. Anecdotally, several female participants provided unsolicited comments that they were talking during the peer condition and wished to be "friendly" or "nice", while no male participants made such comments. In light of the Bond (1982) perspective that individuals are motivated to present themselves in a positive way, males may have attempted to create a positive self-image by displaying running ability while women did so by presenting themselves as friendly and sociable. Likewise, in alignment with the evaluation apprehension model (Geen, 1991; Good, 1973) of social facilitation, men may have increased speed in anticipation of the peer's evaluation of their running ability, while women decreased speed in anticipation of the peer's evaluation of their friendliness. This would agree with studies demonstrating larger tendencies in women toward sensitivity (Del Giudice, Booth, & Irwing, 2012), warmth, openness, and agreeableness (Costa, Terracciano, & McCrae. 2001). Furthermore, previous studies have shown males to place higher value on competition in sport while while women tend to value teamwork (Cashdan. 1998; Weinberg, Tenenbaum, McKenzie, Jackson, Anshel, Grove, & Fogarty, 2000).

Running slower in the presence of a female partner may possibly reduce female runners' training stimulus during unstructured, submaximal workouts. However, such a slowing influence could potentially be advantageous, as recreational runners often struggle to properly modulate training intensity between intended low and high intensity sessions (Foster et al., 2001). Particularly, conducting intended low intensity sessions with excessive exertion could reduce the effectiveness of key high intensity sessions (Bruin, Kuipers, Keizer, & Vandewalle, 1994), impair performance gains (Hydren and Cohen. 2015), or contribute to overtraining or injury (Lehmann et al., 1991). If running with a same sex partner encourages a slower pace, it could be used as a method to prevent running too hard on intended "easy" (Daniels, 2013; Noakes, 2004) days. For males, the tendency shown here to increase speed in the presence of a peer could be used as a method to increase submaximal training intensity and perhaps the adaptive response (Swain and Franklin 2002), but caution is warranted to avoid excessive intensity on intended "easy" days. Because the present study only investigated unstructured, self-paced running, inferences cannot be made pertaining to the male or female response to a partner during intended high intensity sessions, such as intervals or "threshold" (Midgely, 2007; Daniels, 2013) runs. Both female and male runners may benefit by objectively monitoring training intensity through the use of widely available heart rate or GPS devices to ensure the maintenance of appropriate individualized intensities during specified low and high intensity training sessions (Hydren and Cohen, 2015; Midgley et al., 2007). Additionally, it may prudent to select a training partner with a similar intended training pace and performance capability.

The primary limitation of this study was its small sample size. The sex difference in the response to a peer shown should thus be interpreted cautiously and tested in a larger sample of runners. Potential sources of variability in the present sample must also be taken into account: There was greater variation and a trend (p < 0.10) toward greater age in the female participants, and the entry criteria specified a training frequency (i.e., days per week) instead of race performance times or weekly training volumes (e.g., miles per week). However, recommendations to train with a partner are made widely to recreational runners of all ages, whereas the range in our participants' age (20 - 44 years) was relatively small. Although the entry criterion of training frequency would have made possible a range of training volumes among participants, peers in the peer condition were matched for fitness (V[O.sub.2] max) and running performance (5-kilometer time). Beyond the small sample size and potential for variability in participant characteristics, the distance of the trials was held constant, restricting the ability to determine if peer influence could affect how long (i.e., duration or distance) participants would voluntarily choose to run. The effect of peer influence was investigated only during unstructured, self-paced running, precluding inferences about the effect of a running partner during an intended high intensity training session. Runners were also observed only for a single training session in each social condition, but the behavioral and/or enjoyment effect(s) of a partner may not be apparent in a single exercise bout (relative to multiple bouts). Participants only ran with a same sex partner, ruling out the possibility of assumptions regarding the effect of an opposite sex partner. Lastly, only running was observed in this study, such that these findings cannot be extrapolated to other modes of exercise.

Conclusion

This study presents the novel finding of a sex difference in the response to the presence of an unfamiliar running partner during a submaximal training session. Female recreational runners' decreased exercise intensity versus an increase for males in the presence of another, same sex runner has important implications and shows the need for further empirical research on sex differences in exercise behavior. Runners of both sexes are universally recommended to recruit a partner to increase exercise motivation, intensity, duration, or enjoyment, but the results of the current study suggest that the effect of a partner may not be consistent between sexes. Coaches, trainers, and sport scientists should be aware that the individual response to a running partner is likely variable, and individualize recommendations for training with others accordingly. Objective monitoring of training intensity and a judicious selection of training partners are advised in order to promote individually appropriate workloads for specific types of training sessions (e.g., intervals or "threshold" runs). In addition, further research is needed to determine if peer influence alters voluntary exercise volume or frequency, or has a different effect with an opposite sex partner, during high intensity exercise, or during other modes of exercise.

Andrew J. Carnes

Bellarmine University

and

Jacob E. Barkley

Kent State University

Address correspondence to: Andrew Carnes, PhD; phone: 1-502-272-7612, Fax: 1-502-7602; Email: acarnes@bellamiine.edu. Bellarmine University Department of Exercise Science, 2001 Newburg Road, Louisville, KY 40205.

* Significantly different change between sexes.

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Caption: Figure 1. Average Speed Across Social Conditions. There was a significant sex by condition interaction (p = 0.01) on average running speed. When paired with an unfamiliar same sex peer, women ran significantly slower while men showed a positive change in speed relative to females' decrease. Table 1 Participant Characteristics Men Women Age (yr) 24.0 [+ or -] 2.56 31.0 [+ or -] 10.4 Body Mass (kg) 70.0 [+ or -] 3.33 57.4 [+ or -] 5.77 Height (cm) 177 [+ or -] 4.42 163 [+ or -] 5.44 V[O.sub.2] Max 67.3 [+ or -] 3.44 52.3 [+ or -] 2.20 (ml * [kg.sup.-1] * [min.sup.-1]) Note. Values are reported as means [+ or -] SD, N=16. Table 2 Elapsed Time, Average Speed, Enjoyment, and RPE Across Social Conditions Men Elapsed Alone Peer Time (min) * 27.5 [+ or -] 1.91 26.9 [+ or -] 1.03 Speed 13.9 [+ or -] 0.89 14.3 [+ or -] 0.51 (km * [hr.sup.1]) * Enjoyment 62.5 [+ or -] 12.5 72.9 [+ or -] 18.1 (mm) RPE 13.3 [+ or -] 1.28 13.8 [+ or -] 2.05 Women Elapsed Alone Peer Time (min) * 32.4 [+ or -] 2.13 34.2 [+ or -] 1.07 Speed 11.9 [+ or -] 0.78 11.2 [+ or -] 0.35 (km * [hr.sup.1]) * Enjoyment 69.0 [+ or -] 27.6 81.9 [+ or -] 23.5 (mm) RPE 13.8 [+ or -] 2.12 12.8 [+ or -] 1.75 Note. Values are reported as means [+ or -] SD, N=16. * Significant sex by condition interaction (p < 0.05).