I attended the annual conference of the International Association of Nigerian Physical Therapists expecting to learn about laser therapy. Professor Chukuka Enwemeka, one of the world’s leading authorities on photobiomodulation, opened the lecture with a refreshing sense of humor. To him, photobiomodulation was simply light. He gently stripped away the scientific jargon and traced humanity’s use of light from ancient healing practices to today’s ability to harness specific wavelengths for different clinical purposes. Like many in the audience, I expected to hear about light, pain, wound healing, and rehabilitation, all of which he expertly covered. What I did not expect was to leave that lecture on laser therapy thinking about metabolism.
Professor Enwemeka began with the electromagnetic spectrum. Human vision, he reminded us, occupies only a tiny portion of reality, roughly between 400 and 700 nanometers. Beyond that narrow window lie ultraviolet radiation, infrared radiation, microwaves, radio waves, X-rays, and gamma rays. I had known these facts for years. What I had never truly appreciated was the enormity of everything that exists beyond what the human eye can perceive. For example, I was surprised to learn that some electromagnetic wavelengths extend for hundreds or even thousands of kilometers. That simple fact expanded my imagination.
Given the enormity of the physical world beyond our senses, it becomes clear that nature does not divide the universe into the visible and the invisible. The electromagnetic spectrum exists as one continuous reality whether we can perceive it or not. The visible portion occupies only a tiny neighborhood within a much larger landscape. Nature does not owe us an explanation for what lies beyond our perception. The universe is not hiding from us. It simply operates according to physical laws that existed long before humans evolved eyes capable of detecting visible light. Science does not invent those realities but patiently discovers what has always been there.
What awakened my metabolic instinct was Professor Enwemeka’s statement that everyone in the room was continuously emitting infrared radiation. I looked around and noticed more than a few surprised faces among the physical therapists listening attentively to a lecture on laser therapy. Ironically, every one of us was already participating in the physics of light. We were not merely learning electromagnetic radiation for healing and pain relief. We had been interacting with it at every moment of our lives simply because we were alive.
The professor brought the lecture full circle when he mentioned the physicists’ expression that matter is “frozen light.” Whether taken literally or as a metaphor, it immediately sent my thoughts toward metabolism. Glucose, fats, and proteins, the three major macronutrients, are all forms of matter that sustain life. Plants capture light energy and use it to drive the flow of high energy electrons that convert carbon dioxide and water into glucose. From that single starting point, biology builds fats, proteins, and countless other molecules that eventually become the food we eat. On our planet, the molecules that sustain life ultimately owe their existence to sunlight stored as chemical energy. In a very real sense, every meal carries the imprint of sunlight.
That realization raised another question. If light helped build the very molecules that sustain us, what becomes of that energy after we eat? Metabolism does not simply make ATP. It also produces heat. Enzymes, cells, tissues, and organs all depend on maintaining a remarkably narrow temperature range, making continuous heat removal just as important as continuous energy production.
What I had not anticipated was encountering the very same physical reality from an entirely different intellectual direction. Professor Enwemeka approached the body through optics, physics, and rehabilitation. His question was how different wavelengths of light interact with living tissues to influence healing. My own metabolic drift during the lecture followed a different path, prompted by the physical reality his lecture had brought into sharper focus.
That realization stayed with me long after the lecture had ended. It reminded me that physical laws are not organized into different disciplines. Physics does not stop where physiology begins. Chemistry does not end where rehabilitation starts, and biology does not exempt itself from the laws of thermodynamics. Nature recognizes no such boundaries. The same physical laws govern light, matter, metabolism, healing, and every living cell.
Sherlock Holmes once observed, “There is nothing more deceptive than an obvious fact.” For years I assumed that quotation belonged only to detective stories. Sitting in that lecture hall, I realized it describes physiology remarkably well. The most obvious biological processes are often the ones we stop noticing because they have accompanied us every second of our lives. Gravity, breathing, blood circulation, heat production, and infrared radiation become almost invisible precisely because of their constancy.
We rarely think about heat leaving our bodies because, under ordinary circumstances, it happens so successfully. Every second, we radiate heat into the surrounding world without the slightest awareness. It is one of physiology’s silent triumphs. A fever and heat stroke immediately bring the normally invisible heat dissipation into consciousness. Then, without warning, emergency medicine often begins where ordinary physiology can no longer remain invisible. In everyday life, we become aware of warmth, flushed skin, sweating, chills, and rising body temperature. Almost instinctively we loosen our clothing, switch on a fan, seek shade, turn on the air conditioner, or apply cool towels.
None of these actions creates a new physiological process. They simply assist the body’s own mechanisms of heat dissipation. By increasing airflow, lowering environmental temperature, exposing more skin, or promoting evaporation, we help the body continue exporting the heat it has been generating all along. The body has not suddenly begun producing heat. It has become less successful at getting rid of it. That was the larger lesson I carried home from the conference.
I arrived hoping to learn how light can influence healing. I left reminded that healing itself takes place inside a body that obeys the same physical laws governing the rest of the universe. Professor Enwemeka’s lecture illuminated one side of that reality through optics, physics, and rehabilitation. As I listened, it prompted me to reflect on the same physical principles governing metabolism, thermodynamics, and physiology.
We are biological infrared emitters. Every second of every day, our cells transform stored chemical energy into biological work and heat. Much of that heat then leaves our bodies as invisible infrared radiation. Nature is not divided into optics, chemistry, physiology, metabolism, thermodynamics, or rehabilitation. Neither does it divide the universe into the visible and the invisible. Those divisions arise from the limits of our perception, but nature remains the same, and our task is to be curious and humble enough to discover what has always been there.
Mukaila Kareem is a doctor of physiotherapy and founder of metabolichealthliteracy.com
