ECR Spotlight – Adam Grimmitt Free

Adam Grimmitt

How did you become interested in biology?

I think that the world works in mysterious ways. When I was young, it felt important to preserve those workings. I liked drawing people and places. I loved stitching together drawings to bring a moment to life. I think that my interest in biology started with animation, wanting to make 2D films. The films needed to be lively; they could be poignant; but most of all I wanted them to feel human. My first animation was about a stick figure who ran in place over the course of 8-frames. When animating at a rate of 12 frames s⁻¹, it takes approximately 0.66 s to complete an 8-frame loop. Aside from just ‘feeling good’, I had no rationale for choosing an 8-frame loop over any other time frame. Later, after discovering biomechanics, I recognized that my bare-boned running loop was a rudimentary form of kinematic analysis: a loop that periodically analyzed gait, in this case starting with heel strike and ending when that same heel hit the ground again. As it turns out, the average human runs at a cadence of 180 steps per minute, or 0.66 s per gait cycle. Thus, while 8 frames felt the most human to me, the reason why it felt human was because 0.66 s is the average time a person takes to complete a running cycle. Perhaps this was studying a living organism.

I studied biology as an undergraduate while competing as a collegiate distance runner. Although it was fun to learn about human anatomy and the ecology of animals interacting with their environments, rotating flagellum and migrating animals no longer satisfied my longing to understand human locomotion. It was not until reading my first research paper, Kipp et al.’s ‘Ground reaction forces during steeplechase hurdling and waterjumps’ (2017; doi:10.1080/14763141.2016.1212917), that I dreamt about doing science. I wanted to study biology with a focus on mechanics.

Describe your scientific journey and your current research focus

I was an undergraduate research assistant, and later a graduate researcher, in the Biomechanics Lab at California State Polytechnic University, Humboldt, USA, with Dr Justus Ortega, where we developed a community-serving running analysis and used research-backed investigations to bust commonly held running myths. My love of running led me to Dr Wouter Hoogkamer in the autumn of 2021, where I spent the first year of my PhD building one of the steepest treadmills in the world and studying young adults across a variety of circumstances. I believe my experiences with community members, and Dr Hoogkamer's experience studying motor control in older adults and neurological populations, helped me pivot away from running research. Together with Dr Douglas Martini, Dr Hoogkamer secured funding for an NIH grant measuring cortical activity in adults during complex gait tasks, for which I have co-evaluated many young, old and older adult fallers.

Recently, I have considered how mobility looks in underserved or low-resource communities. I want to make mobility devices more accessible, and my work with older adults has identified them as one of the more vulnerable populations in my local area. Older adults might benefit from integrating walking poles into their activities of daily living, and so my current research aims are to investigate the effects of dual pole walking on stability and energy cost in older adults.

How would you explain the main findings of your paper to a member of the public?

Walking is more than just putting one foot in front of the other. In fact, all adults walk with steps that are sometimes longer or shorter than average. For older adults and people with neurological conditions (such as Parkinson's or multiple sclerosis), varied steps can use a lot of energy and make walking more difficult. This might be one of the reasons why older adults use ∼15–20% more energy than younger adults when walking. To verify whether step variability specifically makes walking more costly, we tested how much energy a group of young adults use when walking in conditions with variable steps.

Before creating our conditions, we used high-speed cameras to track each person's preferred step length and width while they walked on our treadmill. We then used their step length and width to create a game (like guitar hero but using your feet!) that challenged them to walk with more variable steps: to win the game, we wanted each person to accurately place their foot over a target as it passed. Our first condition projected targets on the ground at familiar step length and width. The other conditions were more variable, and could have been more difficult, because we randomly included some steps that were closer and farther away than normal.

We found that young adults used an additional 1.1% more energy for each unit of variability added to our conditions. If we consider what these results might mean for older adults and those with neurological conditions, we might assume that increased variation in their steps makes up a small portion (∼3%) of the extra energy that they use while walking!

Why did you choose JEB to publish your paper?

I chose to publish in JEB because they stand at the intersection of comparative physiology, with research spanning the molecular to whole animal. Many of my biomechanical heroes published and held leadership roles within the journal as early as the 1980s. More recently, the journal has provided fertile ground for aspiring biomechanists, with insightful special issues. Additionally, one of the key papers we used to frame our current article was published in JEB (Rock et al.’s ‘Interaction between step-to-step variability and metabolic cost of transport during human walking’, 2018; doi:10.1242/jeb.181834).

An anecdote for choosing to publish with JEB is my history with The Company of Biologists. In June of 2023, one of my lab members received a Travelling Fellowship from The Company of Biologists to research fascicle behavior during downhill running at the University of North Carolina, Chapel Hill. Together, Monty Bertschy and I gathered pilot data in early spring, and followed up by collecting muscle activity, kinematics and fascicle dynamics in 10 young adult runners across various speeds and grades that summer. This investigation was pivotal to my growth as a biologist, and I appreciated the ways in which both The Company of Biologists and JEB have supported our research.

What do you enjoy most about research, and why?

I love the stories that people tell me. I work with participants at all stages of the ageing spectrum. In my department, we ask them to walk, run, dance and balance. Before each data collection, there is a brief period where we prepare the participant. Within this window, I am often graced with a story that transforms a participant from numbers on a page to a slice of living history. When I ask them why they participate in our studies, their answers can be simple: they were in a research database or saw a flyer in the hallway. Other times I catch a glimpse of something I never considered, by learning how a participant has been struggling to walk for years or is trying to move better so that they can finally enjoy their retirement. Occasionally, they use the window to see me, sharing their own time in graduate school, filled with research and collaborations to nourish our collective scientific community. Every day I feel lucky to research people.

What is the most important piece of equipment for your research, what does it do and what question did it help you address?

Two tools were critical to the research in this paper. The first was optical motion capture and the second was indirect calorimetry. We use optical motion capture to track the movement of markers placed on body landmarks. Optical motion capture is what you might see in movies or video games to track the motion of objects. A series of cameras, measuring reflected infrared light, triangulate the position of an object with incredible precision. These cameras are equipped with shutter speeds so fast, they can track the motion of an object to ten thousandths of a second (i.e. a resolution high enough to capture the virtually instantaneous barrage of a mantis shrimp, with a few frames left to spare!).

Indirect calorimetry was used to determine the energy spent (metabolic cost) within each walking condition. Our calorimeter works well for aerobic activities that primarily metabolize oxygen. Thus, the intensity of the activity needs to be somewhat low. We measure gas flow between two conditions to test whether the participant has altered their O₂ consumption. We use the measured CO₂, with established formulae, to determine metabolic rate. Depending on the conditions, gas flow can be a surrogate for metabolic rate because our muscles consume oxygen while contracting. While a true calorimeter might be more accurate in determining energy exchange, they usually require the complete ignition of a substrate to heat a container of water by 1°C, which is not practical for use with our living participants!