Name: Dr. Jacob Carson
Affiliations: Herbert Wertheim School of Public Health & Human Longevity Science, University of California, La Jolla, San Diego, CA 92093, USA

“Agreement Between Consumer and Research-Grade Physical Activity Monitors in a Public Health Intervention for Adolescent Latinas”
by Jacob Carson, David Wing, Job G. Godino, Michael Higgins and Britta Larsen
Int. J. Environ. Res. Public Health 2025, 22(11), 1663; https://doi.org/10.3390/ijerph22111663
Available online: https://www.mdpi.com/1660-4601/22/11/1663

We had the pleasure of speaking with Dr. Jacob Carson, whose recent publication in the International Journal of Environmental Research and Public Health (IJERPH, ISSN: 1660-4601). Here, he shares insights into his academic journey, research focus, and the motivation behind his recent work.

The following is the interview with Dr. Jacob Carson:

1. Congratulations on your recent publication! Could you briefly introduce yourself and your current research focus?

My name is Jacob Carson, and I am a fourth-year PhD candidate in Health Behavior in the joint doctoral program between the University of California, San Diego, and San Diego State University. My research focuses on the built environment and health, particularly on how walkability is measured and how policies can support walkable environments to promote physical activity.

2. What initially drew you to study physical activity monitoring in adolescents?

This interest developed through my work with the principal investigator, Dr. Britta Larseon, who has conducted physical activity promotion research using randomized controlled trials for some time. We became increasingly interested in how physical activity is measured, especially because traditional tools such as ActiGraph accelerometers can be expensive and burdensome for participants. With the rise of consumer wearables like Fitbits, an important question emerged regarding how these devices compare to established methods. While some validation work has been done in laboratory settings, much of physical activity promotion research occurs in free-living environments, which motivated us to examine these tools in real-world contexts.

3. Compared to existing studies (or literature), what are the differences or innovative aspects of your research?

One key difference is the sample size, which is larger than that used in many previous studies. More importantly, the study focuses on adolescent girls, a group that is among the least physically active in the United States. This is particularly relevant from a health equity perspective, especially given the inclusion of Latina adolescents as a subgroup. This study focused entirely on a cohort of Latina adolescents. Methodologically, we examined physical activity at both the minute level and the day level, which allowed us to assess granularity as well as aggregated patterns. We also used multiple cut points, reflecting the lack of a well-established standard for this age group and highlighting the need to reconsider how these thresholds are applied.

4. What do you think is the most important academic contribution or practical value of your research?

I see the study as a reflection point for researchers working in physical activity measurement. Many studies rely on cut points that were used in previous work without fully questioning their appropriateness. Our findings show substantial mismatches between Fitbit and ActiGraph measurements at the minute level, while aggregation changes how these differences appear. The main takeaway is that researchers should be more careful and intentional when deciding what they treat as a gold standard for physical activity measurement, rather than assuming that one device or approach is inherently superior. Moreover, I would like to see more work that breaks down specific activities and considers the environmental and contextual factors in free-living settings. Certain activities, such as weightlifting, cycling, or swimming, are not well captured by traditional accelerometry, while heart-rate-based devices can be influenced by stress or temperature. Understanding how different activities and contexts affect measurement accuracy is essential so that researchers can apply these tools more thoughtfully.

5. For other students who are also interested in conducting similar research, what suggestions do you have?

One important area for younger researchers to explore is the opacity of consumer wearables. These devices rely on proprietary algorithms, and researchers often do not fully understand how the data are generated. I believe wearables represent the future of physical activity measurement, particularly in research on 24-hour activity cycles that integrate sleep and movement. However, it is critical to move beyond treating these tools as black boxes, especially since algorithm updates can change how data is processed. I think we are clearly moving toward greater reliance on consumer wearables, regardless of ongoing debates. There is increasing interest in using data that already exists, often in collaboration with companies such as Google through Fitbit or other platforms like Garmin. This places us in a transitional period where it is essential to understand how historical measurement approaches compare with newer methods. Doing so allows us to maintain continuity in physical activity surveillance and make meaningful comparisons over time.

6. What appealed to you about the journal that made you want to submit your paper? How was your experience submitting to IJERPH?

IJERPH has a broad scope that includes both public health and environmental research, which aligns well with the interdisciplinary nature of our work. There was also relevant research already published in this area, which made the journal feel like a natural fit. Additionally, I appreciated the relatively fast review turnaround, as lengthy review processes can be a challenge at other journals.