Recovery Study Assesses 24/48 and 48/96 Firefighting Shift Schedule

In the world of higher education, it is common practice for universities to conduct experimental research. Research can be defined as an “investigation or experimentation aimed at the discovery and interpretation of facts, revision of accepted theories or laws in the light of new facts, or practical application of such new or revised theories or laws." Generally, the research process should begin with creating tens, hundreds, if not thousands of research questions, based on observations. The research questions that stem from this process propels investigators to construct research methods to answer said questions. One of the unique challenges in this scientific research process is that these research projects typically only scratch the surface, thereby slightly unveiling an answer, while ultimately providing multiple other questions to be investigated.

Tactical Research

Now, let’s classify a niche of research into a category most often labeled as “tactical research.” Tactical research could be looked at as a sub-set of investigation and experimentation pertaining to common practices, application of theory, or beliefs integrated within tactical professions, such as law enforcement, military, and fire and rescue. The issue we observe in many cases is that, research is simply just that, RESEARCH. The bottom line with many research projects is that the conclusion only creates additional questions, rather than actionable items. Without speaking for all agencies and departments, the project that the Texas A&M University – Commerce ROARHP Lab research team have collaborated with, seek actionable items when participating in any form of research project. The TAMUC ROARHP research team has been involved in determining the effectiveness of a strength and conditioning program (Linked: intervention 1 and intervention 2), observing hydration status/patterns, and administering pre/post assessments of strength and conditioning programs (Linked: fire academy or police academy), to name a few.  In those projects TAMUC ROARHP research team has embedded to produce data driven decision-making for improved wellness programs, health policies, professional integration, and continued education opportunities.

What is Heart Rate Variability?
Heart rate variability, known as HRV, is the measured interval between heartbeats utilized as a marker of the capacity to regulate internal and external demands (Young, & Benton, 2018). A higher HRV is associated with better health (Young, & Benton, 2018), while a lower HRV has been associated with many negative health effects (shown below). The measured interval between beats is not always constant (Young, & Benton, 2018), therefore monitoring protocol should allow for a duration of time to develop a baseline for participants. Utilizing devices that monitor HRV is a noninvasive way of evaluating autonomic cardiac function (Harris, et al., 2014).

In a clinical setting, low HRV is associated with mortality in patients with:

• coronary artery disease
• chronic heart failure
• history of myocardial infarction

Low HRV associated with:

• hypertension
• end-stage renal disease
• diabetes

(de Geus, et al., 2019)

Reduction of HRV also associated with the following:

• diabetes
• cardiovascular disease
• inflammation
• obesity
• psychiatric disorders

(Young, & Benton, 2018)

What is Daily (Accumulated) Strain?

The best way to explain daily strain is to identify it as how hard the heart has to work for a duration of time. For example, how high your heart rate is for how long. An accumulation of strain can display a metric of the amount of stress an individual experiences over a set duration of time (for instance: each day or per shift). Monitoring daily strain could assist participants in both 1) regulating task/activity load off-shift, 2) address tasks/activities that acquired an excessive amount of strain on-shift, and 3) manage intensity levels of physical activity bouts.

Adjusting to the Device

Once the WHOOP® devices have calibrated to the unique metrics of each participant over a period of time (we typically refer to as the “on-boarding process”), you will not only receive your HRV scores but also a recovery score. This score provides the firefighters with daily feedback on their overall preparedness level when approaching any form of organized physical activity or off-shift strenuous tasks. These significance of the recovery feedback allows participants to adjust lifestyle habits, fitness programs, and off-shift activities based on individualized preparedness/health metrics.

The study was designed to:

• Provide a platform to assist participating firefighters in observing data to help regulate their off-shift physical activity
• Provide a means for participating firefighters to understand the impact that sleep, nutrition, job-tasks/workload, and physical activity has on the body
• Provide a line of communication for personnel to engage in conversation with collaborating parties regarding fitness and nutrition
• Provide insight on the impact that specific shift work has on recovery of participating firefighters
• Assess the difference in recovery rates/patterns when comparing a 24/48 schedule with a 48/96 schedule

The Current Study

Recently, we began investigating recovery patterns of fire fighters who perform the shift work of 24 hours on and 48 hours off. This sequence of work is frequently interrupted by overtime shifts obtained by personnel. Findings of that study were insightful (will be published with extended research study) and have expanded into an additional question of comparing recovery patterns with the shift schedule of 48 hours on and 96 hours off. As you are aware, many departments and municipalities have been structuring committees to make policy driven decisions, such as exploring whether to transition from a 24/48 shift schedule to a 48/96. To accommodate the development of our efforts, we reached out to 3 additional fire departments, 2 with a 48/96 schedule and 1 with a 24/48 schedule (as our last collaboration was with a 24/48 department). The identity of the departments will remain confidential at this time. Participants in this study utilized WHOOP® straps, which are wrist worn devices that monitor health metrics, such as sleep patterns, heart rate / resting heart rate, respiratory rate, blood oxygen, and skin temperature. Vital metrics we focused on were observing both HRV and daily (accumulated) strain. After the extension of the initial “pilot”, we are performing this research project in two sections:

• Fire departments #1 and #2 will utilize the WHOOP® devices for 3-months
• After 3 months, the devices will be collected, sanitized, cleaned, and damaged/lost parts replaced
• The devices will then be transitioned to Fire department #3 for 3-months

The research project is currently on going, as our research team will publish findings at the conclusion of the study. 

Author: Hussien Jabai, MS, CSCS, TSAC-F, CPT 

Contributions: Dr. Michael Oldham

References

de Geus, E., Gianaros, P. J., Brindle, R. C., Jennings, J. R., & Berntson, G. G. (2019). Should heart rate variability be “corrected” for heart rate? Biological, quantitative, and interpretive considerations. Psychophysiology, 56(2), e13287. https://doi.org/10.1111/psyp.13287

Harris, P. R., Stein, P. K., Fung, G. L., & Drew, B. J. (2014). Heart rate variability measured early in patients with evolving acute coronary syndrome and 1-year outcomes of rehospitalization and mortality. Vascular health and risk management, 10, 451–464. https://doi.org/10.2147/VHRM.S57524 

Young, H. A., & Benton, D. (2018). Heart-rate variability: a biomarker to study the influence of nutrition on physiological and psychological health?. Behavioural pharmacology, 29(2 and 3-Spec Issue), 140–151. https://doi.org/10.1097/FBP.0000000000000383 

Additional References

Retrieved from https://www.merriam-webster.com/dictionary/research on Aug 10, 2022.

Retrieved from https://www.whoop.com/ on Aug 10, 2022.