Feel like you're "doing your duty" by spending hours on the treadmill, but not getting the weight-loss or fat-burning results you expected? It's called the miracle of adaptation, or the SAID principle: Specific Adaptation to Imposed Demands.
It works like this: When you first started your aerobic exercise, it probably didn't take long for you to feel winded. But if you stayed with it, your heart and lungs got stronger, allowing you to go longer distances. At the same time, your metabolism got more efficient at using your body fat for energy. As your energy utilization improved, your body required less energy to do the same amount of cardio. So you ended up burning less and less fat, even though you were diligently spending the same amount of time on the treadmill.
At some point, you can't help but feel like your hard work is not paying off.
"I've talked to so many people who tell me that when they first started working out, they were doing great, but that after a while they got discouraged because they weren't seeing the changes they expected," says trainer, coach and fitness consultant Charlie LePari of LePari's Sports & Fitness in Medford. "I ask them when was the last time they changed their workout routine, and they look at me like, 'What do you mean?' I tell them, 'Well, that's your problem.' "
Science has long marveled at the body's ability to adapt to physical stress. Adaptation is why your muscles grow, your bone density increases and your joints, tendons and ligaments get stronger from weight training. The same adaptation process happens with cardio demands.
Yet this amazing capacity can also work against us because the body's ability to adapt to ever-increasing demands can cause our progress to plateau if we don't vary our workout routines.
"Once your body adapts to things, it becomes routine," LePari says. "But there are so many ways to change things up. Whether you add more weight or add some reps or change the order of your exercises, just doing little things can make a big difference."
Many fitness professionals advocate interval training, which uses short bursts of explosive energy, as a way to shake things loose and get the body's attention. It is a known metabolism booster, whereas steady aerobic exercise, such as walking on a treadmill, does not cause a post-exercise increase in metabolic rate. Yes, you are burning calories while exercising, but once you are through with your walk — or swim or jog — your metabolism quickly returns to normal.
"During interval training, you're not really burning much fat, but the idea of promoting and stimulating lean muscle mass has profound effects on your fat-burning processes because when you have more metabolically active tissue, even when you're sleeping, you're burning more calories," explains Andy Baxter, owner of Baxter Fitness Solutions for Fifty and Beyond in Ashland.
The right amount of resistance training combined with an intense interval training session can keep your metabolism revved up for 24 to 42 hours after exercising — even while you're sleeping.
Interval training is also valued in the medical community. "Within reason, it's good even for cardiac patients and diabetics," explains Baxter. "Recently, they found that seven minutes of interval training a week, in 30-second bouts, produced a 23-percent increase in insulin sensitivity in the diabetic population. When they discontinued the program and continued to monitor these clinically obese diabetics, they found that the insulin sensitivity just rode that metabolic wave for 10 more days before it started to come back down."
No matter what method you use to keep yourself inspired, avoiding monotony is critical.
"Exercise can be extremely boring, so you need to switch it up just so you don't go nuts," LePari adds. "Sometimes just going from inside, like a gym, to the outside can keep people excited about their workouts. I take people to the park or a track, and we do a boot camp-like program. You can do a sprint, some pushups, sit-ups and jumping jacks.
"You'd be surprised what you can do in a half-hour and get a really great workout. People get excited because it's something different. And the body works the same way."