Support the news
By David C. Holzman
Early afternoon found us downshifting into low as the grade abruptly steepened. Soon we were rising high above the coastal plains, towards Stevens Pass, elev. 4061 feet.
Yet the unexpected ease of pedaling my 30-pound, 1972 Peugeot bicycle, with 20 pounds of gear in the panniers up the Cascades made that day, July 16, 1975 (the beginning of a cross-country trek from Seattle to Boston) unusually memorable. Long after the trip was over, I would dream of cycling up mountains, with the same euphoric feeling as when dreaming of flight.
What a contrast to the previous summer’s trip, a 500-mile loop from Watertown to Burlington, VT, and back. On Day One I’d knocked off, exhausted, at midday, after struggling 50 miles over six hours, gaining a mere thousand feet of altitude.
At the end of that 10-day haul, I rode back to the Bicycle Repair Collective on Broadway in Cambridge (now the Broadway Bicycle School), where I’d learned bicycle mechanics, to check out the bike. It’s normal for a bicycle chain to stretch with use. Twelve chain links should measure 12 inches, but an extra eighth of an inch is no big deal. Mine was stretched half an inch.
I was perturbed. I’d bought and installed the chain just before the trip, and I was sure the it must have been defective to have stretched so far. But the mechanic on duty was having none of it. He claimed I’d pedaled too slowly. What???!
How could this mechanic have any idea how fast I’d been pedaling? He hadn’t been riding with me! That, he said, was simple: had I been riding with proper cadence, I wouldn’t have stretched the chain half an inch in a mere 500 miles.
Besides stretching the chain, the slow pedaling apparently was putting my knee joints at greater risk for several maladies: patellar chondro-malacia (or what some doctors call patellofemoral syndrome), which can range from minor inflammation to damage to the cartilage on the underside of the kneecap; patellar tendonitis; bursitis; and even arthritis. Another potential knee injury is ileo-tibial band syndrome. In that case, the pain is on the outside of the knee.
Pedaling slowly and pushing hard increases the sheer stress you put on the bearing surfaces of your knee joint, where the cartilage of your kneecap slides along the cartilage of your femur as the joint flexes. (The femur and tibia also articulate, but for cyclists, the weak point in the joint is generally the cartilage of the kneecap.)
But Vijay Jotwani, MD, of Houston Methodist Orthopedics and Sports Medicine, says that such injuries are unlikely unless there’s a muscle imbalance or biomechanical abnormality. “A muscle imbalance refers to the variation in strength or coordination of one muscle group that opposes another,” says Jotwani. “For example, for patellofemoral syndrome, the outside part of the quadricep muscle (vastus lateralis) may be stronger than the inside part (vastus medialis), which then pulls the kneecap to the outside when the entire quadriceps contracts.”
Biomechanical abnormalities are more likely to be problems for women, says Jotwani. Their wider hips can result in a slight outward angle at the knee in an unbent leg. Pedaling pressure can then pull the kneecap slightly out of its groove. Jotwani says that various leg weight-lifting exercises can mitigate these problems.
An improperly fitting bicycle, and a too-low seat can also raise the risk of knee injury, says Greg Cloutier, MPH, Project Manager for the Human Performance and Exercise Science Lab at Northeastern University.
Frequently I see cyclists grimacing as they bear down upon the pedals, and I wonder if they think the bulkier, stronger muscles they build this way will make them faster cyclists. If so, they are wrong. While a modicum of muscle is necessary, the thing that enables one to climb steadily, or pedal all day, is power.
Strength and power are two different things. Strength is force, which is what you need to lift weights, or what a boa constrictor needs to squeeze the life out of its prey. More strength means you can lift more weight, but without more power, you’ll quickly reach a limit on the number of lifts you can do.
Power is the amount of energy you can burn steadily as you exercise. It’s analogous to the size of the stream of water your faucet can produce. More power means you can ride faster, and that you can ride steadily up steeper hills.
While more muscle fibers make you stronger, power output comes from tiny organelles called mitochondria that reside within each muscle cell (they’re also inside the rest of your cells). The mitochondria take the energy contained in the chemical bonds of sugar molecules and turn that into adenosine triphosphate, a compound that they can convert to muscle power. When you begin cycling with a fast cadence, your muscle cells respond by manufacturing more mitochondria, and that boosts your power output.
(A cyclist can also boost power artificially, by taking Epogen®, the synthetic form of the hormone, erythropoietin (aka EPO). EPO, which raises the concentration of red blood cells, is one of the substances that got Lance Armstrong into trouble for doping. Alternatively, one can simply cycle at high altitude, as I did on a bicycle trip in Colorado in 1984, ascending five 12,000-plus foot passes over a week’s time. When I returned to sea level, I shattered my record for the 40-mile round trip from my home in Washington, D.C., to Mount Vernon and back.)
The mechanic explained to me that — ideally — one should pedal at 60-90 RPMs to keep joints and chain free of undue strain. Others suggest an even faster cadence, and Cloutier says good cyclists average 80-100 RPMs (while using only 40-70 percent of their maximum strength). The mechanic—whose name I’ve forgotten after all these decades—told me I would find pedaling easier once I got used to the faster cadence. I immediately began doing as he had suggested. It was hard, at first, to maintain that fast cadence. But it quickly got easier, and then it became automatic. Then I forgot about it, until that marvelous day when I felt like I was pedaling into the sky.
David C. Holzman writes from Lexington, Mass., on science, medicine, energy, environment, and cars. He is Journal Highlights editor for the American Society for Microbiology and won a Plain Language/Clear Communication Award in 2011 from the National Institutes of Health. His last piece for CommonHealth was on his own sedation-free colonoscopy.
This program aired on August 13, 2013. The audio for this program is not available.
Support the news