Responsibility is patient. Fitness isn’t. Skip town for a while on vacation or business, tossing some of your usual cares to the wind, and what happens?

Responsibility welcomes you home with a firm embrace. But turn your back on fitness and it wanders away, responding in kind. Oh, it can come back…on its own schedule, with a lot of coaxing. My 25 years as a personal trainer suggests to me that it’s better not to lose it in the first place.

The first time I put the rod to use was to catch peacock bass in the canals that run through the city of Miami. Peacock bass are native to the Amazon River basin but, hey, this is the age of globalization, and the fish are able to make it to another continent. But that experience was more of a stunt; you don’t take up fly-fishing to cruise the canals of South Florida. Your art will take you to far more beguiling spheres.

When you’re away from home, the drudgery of exercise often plays second fiddle to fun and relaxation, and that’s only natural. After all, vacation is vacation, right? It’s my belief that more travelers would happily take time to exercise if the endeavor seemed less overwhelming and more portable. Many believe that fitness is all or nothing, that their whole exercise routine must travel with them, intact. And for some people-triathletes and marathoners in particular-it does.

Others begin or end their vacation days in full, state-of-the-art spas and health clubs, now mainstream amenities in many larger hotels. I support this dedication.

But for the rest of us, and even for the obsessed, fitness can, and perhaps should, be compressed into a smaller package. Exercise must serve the exerciser.

Not only is it possible to slip a “full gym” (rubber cables and a jump rope) into a small piece of luggage, but workouts can be equally compact. Even the most activity-laden itineraries can be punctuated with brief and infrequent exercise sessions. Compact workouts of just a half hour, say, Wednesday and Saturday, preserve strength and endurance. That’s great, right? Exercising while away, no longer a burden, is happily anticipated. Of course, there’s a catch: Quality replaces quantity.

Fitness carries momentum, not unlike a car rolling in neutral. Once pushed and moving, sharp, periodic nudges keep it going. Likewise, strength and endurance developed through longer workouts remain if occasional jolts of effort are applied. Fewer workouts, but mostly short, hard sessions, become the size 12 boot on the bumper of that car. Less is more, especially when you’re on vacation.

Brief, intense efforts quickly stimulate great physical development. No coincidence, then, that exquisite physiques turn up among anaerobic athletes.

Hard work begets a hard body! But that’s old news. And to keep things in perspective, even as studies continue to show that anaerobic activity-typically intense bursts of a few seconds to sustained efforts of nearly two minutes, followed by relatively long recovery-produces fast, dramatic results, it’s not a panacea. It’s merely one piece of the fi tness puzzle.

Regardless, heavy exertion can yield the payoff of the often-disparaged edict “no pain, no gain.” This so-called pain is an inevitable sensation of intense exercise.

Fortunately, duration decreases as intensity increases (nature is charitable), and extended recovery time lets you catch your breath. Precise, repeated, 1:3 work/rest ratios of particular exercise programs reflect this dynamic.

Most of us can handle grueling, 30-second efforts if we’re allowed to back off for a minute and a half in between. Sandwich five of these intervals between a 10-minute warm-up and cool-down, and you have an extremely effective, compact workout. Swim, bike, run, walk, climb stairs, jump rope, lift weights…it’s all good.

But quality training is undermined by the recreational mindset. Recreational exercisers tend to go too hard on easy days, and vice versa. Why? Because, easy feels useless-and hard hurts. The truth is, easy to low moderate exercise is exceptionally potent, building a foundation for hard effort later. Intense workouts, only maximized following a period of lower-level training, quickly peak the capacity of the athlete. Tepid, in-between workouts produce mediocre results. Notice: Starbucks doesn’t sell room-temperature coffee.

Make no mistake, intervals are tough. Good physical condition is a must. Here, the normal caveat surfaces: Before beginning any exercise regimen-in particular a strenuous one-see your physician. It’s in your interest to determine whether the extreme exertion of intervals will help. For many people, low-intensity exercise is the ticket to better health.

Inevitably, following an extended vacation, that bear hug of responsibility greets us at the door. Relaxed or wrung out from travel, handling the squeeze is easier when you haven’t lost your training edge. The following suggested workouts turn potentially fickle fitness into a faithful friend.

PIECE DE RESISTANCE GEOFF’S “SUPER SEVEN”

If you pack rubber cables and a jump rope:

Tip: Intensity is the name of the game. Use medium-tension cables, doubling them to increase load. Use a slow exercise pace for the main set. An honest, 5-4-3-2-1-pause-1-2-3-4-5 gives you about three reps in 30 seconds. However, I think eight reps, about 90 seconds’ worth, are required for this workout. Avoid fully extending knees and elbows at the top of each movement.

Warm-up: Walk, jog or jump rope for five minutes. Next, use the cables for three smooth, quickly paced sets of eight reps of upright rows, squats, standing rows, alternating lunges and overhead presses. Jump rope for 30 seconds between sets.

Main set: Do eight S-L-O-W reps of single leg squats, keeping body weight over the ball of your foot. Then, do eight S-LO-W reps of single arm rows with the cables. Finally, do a set of eight S-L-O-W pushups. If needed, loop the cables over your back, and hold the ends beneath each hand. Stretching the cables at the top of each movement adds load. Keep ‘em honest! Rest for a minute and repeat.

Cool-down: Use the cables for three smooth, moderately paced sets of eight reps of upright rows, squats, standing rows, alternating lunges and overhead presses. Then stretch muscles of the hip, spine and shoulder joints for five minutes. Use gentle traction to fl ex and extend muscles.