For the new study, published this month in the Journal of Applied Physiology, Beck and his colleagues looked for healthy young men, as well as women, who had never or almost never worn high heels. By recruiting heel virgins, the researchers hoped to be able to track changes inside people’s legs associated with starting to wear the higher footwear.

They wound up with five male and three female volunteers.

The scientists then created high-heeled shoes acceptable to all recruits by attaching foam wedges to the soles of flat Chuck Taylor All-Star Low Top sneakers. Each pair was custom fitted so that a participant’s foot would be flexed downward at a 14-degree angle. In practice, this meant the shoes sported about a 2½- to 3-inch wedge heel.

This summary above should alert you to one of the potential problems with this study: its small sample size.

b) Why might it be a problem to have a sample of only eight people in any study? Your answer should talk not about generalization, but about how a small sample might result in results that are unusual and cannot be replicated. 

The study was a pretest-posttest design. The Post article explains that the researchers tested each of the participants on their walking efficiency (as a pretest), and then gave them their high heeled Chuck Taylors to wear for 14 weeks. After the 14 weeks, everybody's walking efficiency was tested again. 

As you know from Chapter 10, in a pretest-posttest design,  participants are tested on the dependent variable (here, walking efficiency) twice, once before and once after exposure to one level of the independent variable. So let's read more about the independent variable. Some people wore high heels and some did not, but....

[The researchers] asked them to go forth into the world and wear their new heels every day for 14 weeks. Not everyone did. Some of the volunteers “were kind of embarrassed” by the makeshift stacked sneakers, Beck said. Others complained of squished toes or other discomforts, quibbles familiar to any flat-shoe habitue who dons heels on occasion.

But more than half of the volunteers, male and female, wore the shoes most of the time. After 14 weeks, everyone returned to the lab and repeated the earlier tests. Those volunteers who had mostly given up early on wearing heels showed no changes in their legs or walking. But those who wore the heels fairly consistently tended to have shorter calf muscles and stiffer Achilles tendons than before.

c) Check that paragraph again, and ask yourself, Did the researchers randomly assign people to the "high heels" and "no high heels" conditions? Why or why not? 

d) Looking back at c), think about how this poses an internal validity problem for the study. Which of the internal validity threats (from Chapter 10 or 11) does it seem to be? 

e) Why do you think this particular study (which had a tiny sample, put only 5 people in one group and 3 in the other, not randomly assigned) was picked up by the Washington Post and by Yahoo news?  Do you think the study should have been covered by the press? 


You can find the original empirical journal article here