Topics Covered:

1. Background
2. Drive for Muscularity Scale: Overview
3. Drive for Muscularity Scale: Scoring Notes
4. Drive for Muscularity Scale: Reliability
5. Drive for Muscularity Scale: Validity
6. Using the Drive for Muscularity Scale in Your Research Program
7. The Drive for Muscularity Survey (in HTML)

Background

The Drive for Muscularity (DM) represents an individual's perception that he or she is not muscular enough and that bulk should be added to his or her body frame, in the form of muscle mass (irrespective of a person's percentage of actual muscle mass or body fat). DM is more prevalent in men, where past research has shown that a muscular mesomorphic body shape is considered to be more desirable than any other. However, recent research has shown that women also tend to show fairly high levels of DM, suggesting that this concept may be important for them too (but perhaps in different ways than for men).

A more detailed overview of the Drive for Muscularity and the Drive for Muscularity Scale can be found in the following book chapter:

  McCreary, D.R. (2007). The Drive for Muscularity Scale: Description, psychometrics, and research findings. In J.K. Thompson & G. Cafri (Eds.), The muscular ideal: Psychological, social, and medical perspectives (pp. 87-106). Washington, DC: American Psychological Association.

Drive for Muscularity Scale: Overview

To study the Drive for Muscularity, researchers need a way of measuring the construct. Working with Doris Sasse (and supported by a small grant from Brock University), we created the Drive for Muscularity Scale (DMS), a 15-item, self-report, pencil and paper survey that both boys/men and girls/women can complete. On the DMS, respondents are asked to indicate the extent to which a series of attitudes and behaviors are descriptive of themselves (i.e., how often they act or feel that way). The DMS was patterned after the Eating Attitudes Test, a measure of attitudes and behaviors associated with a desire to be thinner. The initial development paper describing the DMS was published in May 2000 issue of the Journal of American College Health. It's reliability and validity are outlined in McCreary (2007; see reference above). Since its publication, the DMS has been used in numerous studies worldwide.

McCreary et al. (2004) used factor analysis to show that the DMS has a single, higher order factor structure. In other words, a simple mean or sum of the items can be used to summarize people's responses to the scale. However, the same study showed that, in samaples of boys or men, there are two lower-order factors for which researchers can code: Muscularity-Oriented Body Image Attitudes and Muscularity-Oriented Behaviors.

Drive for Muscularity Scale: Scoring Notes

Reverse-Direction Scoring:
The DMS uses a reverse-direction scoring procedure for all items, but does not use any reverse-worded items. That is, every item is scored on a Likert-type scale from 1 (Always) to 6 (Never). Because high scores on the DMS are indicative of higher levels of the Drive for Muscularity, all items need to be reverse-coded before summing or averaging responses (see below for an example of the SPSS syntax for this procedure). This procedure was used instead of reverse-wording some of the DMS items because research has shown that, when reverse-worded items are used in smaller scales, they often create psychometric problems, including method factors that can lower the scale's overall reliability. Using a reverse-direction scoring procedure keeps the rating scale salient to the respondent because it is counter-intuitive and, in combination with the short nature of the questionnaire, helps to protect against response acquiescence.

Lack of Variance on Item 10:
One item on the DMS (item 10, which asks the respondent about the extent to which they think about using anabolic steroids to increase muscle mass), sometimes has very little variability and, as a result, detracts from the scale's reliability (see McCreary et al., 2004, for more information about this). However, in some samples there is sufficient variability to give the item an acceptable corrected item-total correlation. Researchers may want to examine the psychometric properties of this item in their own samples. If the item detracts substantially from the scale's reliability, they should consider removing it from the analyses; if not, then they can keep the item in the analyses.

Coding for the Subscales:
We use the following standard coding statements (for SPSS) to recode the DMS items and create the DMS scale scores:

*note that dms10 can be included in the scale computations, or not (in some samples, this item has no variability). If you include it, it should go in the Behaviors subscale.

*note that the DMS Muscle Development Behaviors and DMS Muscularity-Oriented Body Image Attitudes subscales should be computed only for men.

*note that there is no difference in averaging or summing the scales; one is just a mathematical transformation of the other.

recode dms1 to dms15 (1=6)(2=5)(3=4)(4=3)(5=2)(6=1).

compute dms = mean(dms1 to dms9,dms11 to dms15).

compute dmsbehav = mean(dms2,dms3,dms4,dms5,dms6,dms8,dms12).

compute dmsatts = mean(dms1,dms7,dms9,dms11,dms13,dms14,dms15).

Drive for Muscularity Scale: Reliability

The DMS has shown consistently acceptable reliability, whether using the original 15-item version or the 14-item version with the question about possible future anabolic steroid use having been removed. Among male respondents, the DMS has had alpha reliability estimates ranging from .85 to .91 in both published reports and in reports presented at conferences, but not yet published. When female respondents have completed the DMS, reliability estimates have been above .80. However, coefficient alpha is not the only indicator of acceptable reliability. Corrected item-total correlations of DMS items have ranged from .37 to .65. These are well within the range recommended by Nunnally & Bernstein (1994). Finally, Cafri and Thompson (2004) reported high, 7-10 day test-retest correlations in a sample of men: .93 for the entire scale, .84 for the muscularity attitudes, and .96 for the muscularity behaviors.

For more information about the reliability of the DMS, see McCreary (2007).

Drive for Muscularity Scale: Validity

There are several types of scale validity to be considered when evaluating a measurement tool. These include construct validity, concurrent validity, convergent validity, and discriminant validity. Each will be addressed here.

Construct validity can be determined in several ways, including analyses of a scale's factor structure and potential contamination from social desirability biases. With regard to the DMS factor structure, research conducted by McCreary et al. (2004) has shown that, for males, the DMS has two lower-order factors: muscularity-related attitudes and muscle-enhancing behaviors. Those two lower-order factors also load onto a single, higher-order Drive for Muscularity factor for men. For women, the two subscales do not emerge from factor analyses. Thus, for men, researchers can compute separate attitude and behavioral subscale scores and an overall DMS score. But for women, only the overall DMS score can be computed. In the only study to explore the association between socially desirable response biases and the DMS, Duggan and McCreary (2004) asked a self-selected sample of heterosexual and homosexual men to completed Paulus' Balanced Inventory of Desirable Responding, in addition to the DMS. There were no significant correlations between two measures for either group of men.

Concurrent validity assesses the extent to which DMS scores differ between groups that they theoretically should be able to distinguish between (i.e., by using a known-groups procedure). Gender would be one known-groups comparison with which to test the concurrent validity of the DMS. Gender differences have been found for both the overall DMS scale score, as well as for many of the individual DMS items. Men scored higher than the women when the differences were significant. A second known-groups comparison is between those who weight train and those who do not. While McCreary and Sasse (2000) showed a positive correlation of .24 between DMS scores and the number of times each week the respondents typically engaged in weight training activities, other researchers (e.g., Rutsztein, 2004) have observed that men and women who weight train (either regularly or intermittently) tend to score significantly higher on the overall DMS than a group who do not weight train. Finally, a comparson could be made between weight trainers who abuse anabolic-androgenic steroids (AAS) and those who do not. Choi, Pitts, and Grixti (2005) showed that AAS users scored significantly higher on the DMS than the non-AAS-using group.

Convergent validity examines the degree to which the DMS is associated with constructs with which it theoretically should be associated. Research by Cafri and Thompson showed that ratings on the DMS were uncorrelated with ratings on a muscular-based figure silhouette scale. Baxter and von Ranson, however, found that scores on the DMS were positively correlated with scores on a modified version of the Swansea Muscularity Attitudes Questionnaire (i.e., modified to suitable for use by both men and women). The DMS also should be negatively associated with self-esteem. This has been found in samples of men (e.g., Duggan & McCreary, 2004; McCreary & Sasse, 2000; Jacobs et al., 2004), but not in women. The DMS also should be correlated with various dimensions of personality. Holden et al. (2002) showed that DMS was positively correlated with appearance orientation in a sample of college males. This study was replicated and extended Davis et al. (2005), who showed that the scores on the DMS were positively associated with neuroticism, self-oriented perfectionism, appearance orientation, and fitness orientation. Finally, scores on the DMS should be correlated with measures of masculine-typed gender role socialization. This has been demonstrated in two studies (Mahalik et al., 2003; McCreary et al., 2005).

Discriminant validity explores the degree to which the DMS is uncorrelated with measures with which it should not, theoretically, be correlated. Because DM is not considered to be the opposite of the Drive for Thinness, DMS scores should not be negatively correlated with scores on measures such as the EAT or EDI. However, because muscle is situated underneath body fat, people who want to show off their muscularity also will need to have a low percentage of body fat. This means that DMS scores should be correlated to a small extent with those from the EAT and EDI. To date, several studies have shown the correlation between these two types of measure are approximately .30 to .40 (r² = 9% to 16%) (e.g., McCreary & Sasse, 2000).

See McCreary (2007) for more comprehensive information about DMS validity issues.

Using the Drive for Muscularity Scale
in Your Research Program

The DMS is freely available and I hope you can find a place for it in your own research. However, if you do use the DMS, I would appreciate hearing about it. I also would like to read any conference papers and published reports that use the DMS.

Below is a link to the current version of the Drive for Muscularity Scale:

  The Drive for Muscularity Scale (in HTML)