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                                             Main Post

 An Intervention Program to Promote Health-Related Physical Fitness in Nurses

             This quantitative, quasi-experimental study conducted by Yaun et al.  (2009) aimed to determine the effects of an exercise intervention on  nurses’ health-related physical fitness. The researchers also expressed  an explicit interest in the relationship between physical fitness and  the incidence of musculoskeletal disorders. Taiwanese nurses from five  different units volunteered to be part of the study. The participants  were divided into two groups with 45 nurses in the experimental group  and 45 nurses in the control group. There was no randomization, but all  the participants gave written informed consent (Yaun et al., 2009). 

Internal Validity 

             According to Polit and Beck (2017), internal validity pertains to the  empirical relationship between the independent variable and the final  results. Researchers must establish that the intended cause created the  effect, and that it was not influenced by other variables (Polit &  Beck, 2017). After all, correlation does not equal causation, and an  astute researcher will adeptly identify and control convoluting  variables. Further, Andrade (2018) asserts that internal validity  assesses whether the design of the study, the conduct of the  researchers, and the analysis of the results answer the research  question without bias (Andrade, 2018). 

Consequently,  the research conducted by Yaun et al. did have some issues that  negatively impacted the internal validity of their research. Firstly,  convoluting variables were not adequately controlled. The exclusion  criteria consisted of cardiovascular disease, diabetes, hypertension,  renal disease, pulmonary disease, severe musculoskeletal aches, and  pregnancy. However, other significant variables such as age, gender,  marital status, educational level, or other medical issues. It is worth  noting that the diet and exercise habits of the participants were not  limited by the researchers.

Moreover,  the nurses in the experimental group worked a fixed schedule whereas  nurses in the control group worked alternating shifts. Secondly, the  lack of randomization coupled with the fact that the participants worked  for the same organization could have contaminated the results. Thirdly,  while the results of the research showed the exercise intervention  improved the physical fitness of the participants in the experimental  group, participants were not evaluated for musculoskeletal  improvements.   

Recommendations to Strengthen Internal Validity

A  different research design would have strengthened internal validity.  Randomization is the most effective way to control individual  characteristics of participants. Randomization also eliminates for the  Hawthorne Effect, which occurs when participants behave differently  because they know they are being studied. Moreover, a cross-over design  is highly effective when groups are being compared to one another.  Although, this design is subject to carryover bias, in which an effect  carries over from one experimental condition to another (Polit &  Beck, 2017). 

I  contend that a randomized control trial with a cross over design would  have increased the strength of the internal validity in this study. In a  cross-over design participants serve as their own control group, which  would negate the convoluting variables that influenced the results of  this study, and would more accurately gauge changes resulting from the  exercise intervention. I would also add a metric to assess the  musculoskeletal status of the participants. To limit the effects of  carryover bias, the health metrics of the participants would be obtained  before the exercise intervention to establish a baseline, then after  the exercise intervention, and finally, after a wash-out period, the  metrics should be re-recorded.

The Impact of Changes on Other types of Validity 

In  contrast to internal validity, statistical validity is not concerned  with the causal relationship between variables, but rather measures the  mathematical correlation of all relationships that occur between the  variables (Polit & Beck, 2017). The randomized control, crossover  design would improve statistical validity because the participants would  serve as their own control group making statistical analysis more  powerful. Construct validity determines if the outcome measured  corresponds to the theoretical construct of the study (Polit & Beck,  2017). In this research, the theoretical construct was Pender’s health  promotion model. Construct validity also would have been improved by  changing the design of the study. The same health promotion strategy  yields different outcomes for different participants based on individual  differences. The modification of the study’s design would have negated  these individual differences. External validity indicates if the results  of the research will remain the same when applied to other people or  settings (Polit & Beck, 2017). Again, a change in the design of this  research would optimize external validity which would increase the  likelihood of the results influencing evidence-based practice.

Failure to Consider Validity in Research

Failing  to properly account for and control variables threatens the validity of  the results yielded from the research. The rigor of the research design  may be the most important factor in strengthening or weakening  validity, as evidenced by the hierarchy of research studies in the  evidentiary pyramid. Other elements such as biased statistical analysis,  unreliable implementation of an intervention, carryover bias, and the  Hawthorne Effect are just a few variables that can threaten the validity  of a research study (Polit & Beck, 2017). Since research guides  evidence-based practice, failure to ensure the validity of results  directly affects patient outcomes; unfortunately, the effects of poorly  executed research impacts all research. People are inherently inclined  to remember negative consequences over positive outcomes. Improper  research regarding vaccines has created an anti-vaccination movement  that is highly problematic. Big tobacco companies produced improper  research that may have resulted in people continuing to smoke longer  than they otherwise would have. The failure to appropriately consider  validity in research is a grave mistake that should be avoided at all  costs. 


Andrade, C. (2018). Internal, external, and ecological validity in research design, conduct, and evaluation. Indian Journal of Psychological Medicine,40(5), 498. doi:10.4103/ijpsym.ijpsym_334_18

Polit, D. F., & Beck, C. T. (2017). Nursing research generating and assessing evidence for nursing practice. Philadelphia: Wolters Kluwer.

Yuan,  S., Chou, M., Hwu, L., Chang, Y., Hsu, W., & Kuo, H. (2009). An  intervention program to promote health-related physical fitness in  nurses. Journal of Clinical Nursing,18(10), 1404-1411. doi:10.1111/j.1365-2702.2008.02699.x