SANTA CRUZ—The suggested daily exercise regimen for humans is only a fraction of what it should be to offset heart disease concerns, according to Terrie M. Williams, a UC Santa Cruz professor who published research findings this month in the research journal Physiology.
“Scientists have said that exercise is important for the human mammalian heart,” said Williams, an Ecology & Evolutionary Biology Department professor who has spent three decades studying mammalian hearts. “The question has been how much exercise is necessary.”
Williams, who has monitored heart rates of mountain lions on treadmills, 95,000-pound whales and Maverick’s big wave surfers, says humans suffer from heart disease three times more often than other mammals.
“I’m hoping people realize that the American Medical Association recommendations are just a fraction of what humans should be considering in their exercise programs,” Williams said.
In an email from the Antarctic where she is currently studying Weddell seal heart rates, Williams said other mammals are not only more active on a daily basis, they experience a highly variable intensity.
In humans, that intensity was effectively tracked in the top-speed heart rates of big wave surfers Sarah and Mike Gerhardt who duct-taped heart monitors to their chests at one point so researchers could monitor their physiological experience while they paddled out and rode Maverick’s winter waves.
“We were really surprised that our heart rates were maxed the whole time,” said Sarah Gerhardt, a chemistry professor at Monterey Peninsula College and the first woman to surf Maverick’s. “That was surprising. It just goes to show what an amazing thrill and challenge it is to be surfing at a place like Maverick’s.”
The studies of surfers’ hearts, which included O’Neill pro surfers at Steamers Lane, helped document how the psychological component of fear influences the heart.
“The heart of a Maverick’s surfer is like the heart of a cheetah on steroids,” Williams said. “This combination of head and heart is becoming more and more important as a greater population partakes in extreme sports,” Williams said.
The ongoing study of mammalian hearts includes manatees, beluga whales and narwhals. Williams also is studying the effects of noise on cardiovascular function. O’Neill built a custom wetsuit for holding heart rate equipment onto dolphins and will be customizing a heart rate wetsuit vest for beluga whales in an aquarium in Vancouver, British Columbia.
“For the less athletically inclined individuals among us, these studies on wild mammals and extreme athletes should inspire a heightened awareness of the importance of a natural level of daily activity for heart health,” Williams says in her article. “Given the longevity and cardiac health of many species of wild mammals, perhaps it is time for humans to adopt a wilder daily exercise plan.”
Williams, who recently competed in an ironman race in Idaho, said just how much exercise we need depends on our own health.
“However, a good rule of thumb for me is at least an hour of exercise five days per week, remembering that rest is also critical for allowing the muscles to repair and grow.” Just as important is varying high and low intensity days. “Mixing up endurance and sprint activities builds muscle and the cardiovascular system that supports it.”
“The heart has an amazing capacity to work under extreme conditions. We need to recognize that it is a muscle that needs to be kept in condition. You don’t have to be an extreme surfer, but your heart would appreciate a little loving through exercise.”
Most people should get more exercise. Here is some heart trivia to contemplate during your next workout:
• One of the highest prolonged heart-rate levels ever recorded was for a professional big-wave surfer riding the monstrous swells at Maverick’s: more than 180 beats per minute for three hours, with peaks of 200 beats per minute during rides.
• Dogs and cats are opposites in terms of aerobic capacity and maximum heart rate, and humans are more like dogs, adapted for endurance exercise (chasing down prey), while cats are built for the short bursts of speed used in stalk-and-pounce hunting. This difference is reflected in heart size relative to total body mass (larger hearts in dogs and humans, smaller hearts in cats).
• The hearts of marathon runners are 10 to 33 percent larger than those of more sedentary people.
• Heart disease is exceedingly rare in wild animals, but it is the leading cause of death in humans worldwide. There are many plausible explanations for this, but one factor stands out above all others: the difference in daily activity levels.
• The mammalian dive response, automatically triggered by cold water contacting the face, involves an immediate slowing of heart rate and constriction of peripheral blood vessels to maximize blood and oxygen in the core. The mammalian exercise response has the opposite effect, increasing heart rate and metabolism. Thus, marine mammals chasing prey at depth have to balance opposing cardiovascular demands, and Williams found they can experience cardiac arrhythmias during dives.
• Heart rate can be controlled, and not just by meditating yogis. A California sea lion was trained to lower its heart rate on command while sitting out of water.
Co-authors of the study include: Penni Bengtson, local race director; Diana L. Steller, Moss Landing Marine Laboratories; Donald A. Croll, UCSC professor; and Randall W. Davis, Texas A&M University professor. The Physiology article can be found at: http://physiologyonline.physiology.org.
This article first appeared in the Santa Cruz Sentinel.