Circuit training for endurance athletes

A series of workouts designed to increase both strength and fitness

Back in the 1970s, people began to realize that both 'aerobic' and strength workouts were important for fitness, and that created a dilemma. Who had enough time to carry out five or so aerobic sessions per week - and also three or four strength workouts? In a fast-paced society, people wanted 'McTraining' (e.g. training which was quick and easy and could do everything - knocking down the risk of heart disease but also producing ripply muscles).

Thus, circuit training was born. Circuit workouts were modest in length (you could complete most of them in less than an hour), and they were said to be good for both your cardiovascular system and muscles. Suddenly, training time could be cut in half - without cutting back on the benefits of working out. You didn't have to be a runty runner or cyclist with small strips of sinews - or just a muscle-bound lifter with a fat-filled heart. You could be buff - AND aerobically fit. That was very appealing, and scientific research backed up the idea that circuit training was a good idea. Late in the 1970s, researchers at the National Athletic Health Institute in the United States asked 20 men and 20 women to complete some simple workouts which contained three circuits and 10 exercises per circuit. The exercises were performed on a Universal Gym and included the following: bench presses, inclined sit-ups, leg presses, lat pulls, back arches, shoulder presses, leg extensions, arm curls, leg flexions, and upright rows. All subjects performed 15 to 18 repetitions of each exercise in 30 seconds, using a resistance equal to 40 per cent of their individual one-repetition maximum (1-RM) values (e.g., 40 per cent of the greatest weight they could lift once, but not more than once).

The subjects in this NAHI study took 15-second breaks as they moved from one exercise to another, making the work-rest ratio 30:15 (or 2:1). Of course, the near-continuous nature of their activity, moving fairly rapidly from exercise to exercise with only a small respite, was supposed to keep heart rate and oxygen consumption high and thereby create aerobic benefits for the workout, in addition to the obvious strength-related ones. In these early circuits, there was no actual running or cycling involved; participants simply moved from one resistance exercise to another.

Slicing away body fat

The NAHI research clearly showed how beneficial circuit training could be. Male participants averaged more than 75 per cent of max heart rate while conducting the circuits, while females exercised at over 80 per cent of max. In addition, the men burned 204 calories doing the three circuits, not bad for 15 actual minutes of activity (30 thirty-second work intervals). That of course would add up to over 800 calories for an hour of work; one would have to run about seven miles in the same time frame to achieve the same caloric effect. The researchers estimated that carrying out this simple, short workout just three times a week would carve away four pounds of body fat within a year.

A separate study carried out by the same group of scientists determined that circuit training produced a number of other desirable effects. In this second piece of research, subjects carried out the circuit workout described above three times a week for a total of 10 weeks (the only change was that resistance increased from 40 to 55 per cent of 1-RM in some cases).

After 10 weeks, lean body weight increased for both male and female subjects, and the females significantly reduced percent body fat. On average, men and women gained about three pounds of muscle and lost about two pounds of fat. Both men and women achieved reductions in skin-fold thickness (another indication of fat loss), and both sexes increased the girths of their flexed biceps muscles. Both also increased overall muscular strength.

On the aerobic end of the spectrum, although neither the men or women had engaged in any running during the circuit training, both improved endurance while running on the treadmill by about 5 to 6 per cent at the end of 10 weeks. In addition, the women improved VO2max by 11 per cent (surprisingly enough, this is about the same average gain in VO2max achieved by individuals who take part in a 10-week aerobic-jogging programme). Another study detected a 9-per cent increase in treadmill endurance time after 20 weeks of circuit training, and two other investigations linked circuit training with enhancement of VO2max. Circuit training was off to a great start!

Adding running to the mix

In the early 1980s, researchers at the Institute for Aerobics Research in Dallas took notice of the rave reviews that circuit training was getting and planned a unique and outstanding piece of circuit research. 36 females and 41 males took part in this investigation, which involved working out for 12 weeks. One group of participants carried out a circuit session similar to the one described above (with three circuits of 10 exercises per workout) three times per week. A second group of people served as controls, and a third collection of subjects carried out the really interesting workouts - a combination of the regular circuits with running.

While the first group (the conventional circuit trainers) rested for about 15 seconds between their exercises (to allow time to move from one station to the other), the third group's members ran for about 30 seconds on an indoor track between exercises. This was the first study which really looked at the effects of a combination of running and strengthening activities within circuit workouts, comparing this combo with circuits which included only resistance work. The actual circuit, carried out by both the strength-only and strength-plus-running groups, consisted of the following exercises: squats, shoulder presses, knee flexions, bench presses, leg presses, elbow flexions, back hyperextensions, elbow extensions, sit-ups, and vertical flies. Each exercise was performed for 30 seconds (usually permitting 12 to 15 reps) at 40 per cent of 1-RM, followed by 15 seconds of rest for the strength-only group and 30 seconds of running for the strength-plus-running individuals, after which the next exercise commenced. The running itself was fairly modest in nature, averaging about 189 metres per minute (8:30 per mile pace).

The results

How did the groups fare after 12 weeks? Not a single person was injured during the training; indeed, low injury rates are one of the most attractive features of circuit training. Since the amount of running is moderate, there are few overuse injuries; since the resistance is modest, there is usually little risk of severe muscle strain or back injury. After 12 weeks, both the strength-only (SO) and strength-plus-running (SPR) groups lost the same amount of weight, trimmed away a similar amount of body fat, and added equivalent amounts of muscle tissue. Both groups also improved bench-press and leg-press strength to a similar extent.

On the aerobic end of things, the SO people, even though they didn't run at all, were able to increase endurance while running on the treadmill by about 12 per cent. However, the SPR subjects spiked treadmill endurance by 19 per cent. Similarly, SO individuals moved VO2max upward by 12.5 per cent, while SPR athletes advanced VO2max by 17 per cent. Those gains in the SPR group are pretty terrific: when you think about it, SPR group members were really only running for 15 minutes (10 reps x 30 seconds x 3 circuits) three times a week, in addition to their three 15-minute bouts of resistance training, yet they made great gains. The advances are even more impressive when one remembers that the subjects were not running hard during the running portions of their circuits; higher intensities of running would have no doubt produced even greater improvements.

Yet even those individuals who did no running at all made progress with their VO2max values and treadmill endurance times. Why is that so? For one thing, they improved muscular strength, and greater muscular strength tends to decrease muscular fatigue during exercise, allowing individuals to exercise longer, including when they are taking a VO2max test. If you last longer on a VO2max test, you move up to higher levels of exertion (with greater treadmill speeds or inclinations) and therefore to higher levels of oxygen consumption.

In addition, the continuous nature of circuit training tends to keep heart rate and oxygen consumption high throughout the workout. You are always doing something, so the muscles keep using oxygen to furnish the necessary fuel, and the heart keeps pumping oxygen to the muscles. High heart rates and oxygen-consumption rates during workouts tend to heighten VO2max. Interestingly enough, studies have shown that blood (and therefore oxygen) flow through muscles is greatest when one is working at between 30 and 60 per cent of 1-RM. Below 30 per cent, activity is so light that heart rate does not increase appreciably; above 60 per cent, muscular contractions are strong enough to constrict blood vessels within the muscles. Thus, the choice of 40 to 55 per cent of 1-RM in the studies we've described was probably optimal, and the lesson of course is that if you want your circuit training to improve you aerobically, you should not consistently use very heavy weights.

An unjustified slump

Strangely enough, despite all the physiological positives associated with circuit training in this early research, the popularity of circuit training has been on a steady decline for the last 15 years or so. Today, runners, cyclists, and swimmers tend to carry out straight running (or cycling or swimming) workouts and separate resistance sessions - or even avoid strength work altogether. One reason for this is that endurance athletes aren't sure exactly which strengthening exercises to include in their circuits, but in addition circuit work is often considered a throwback to the 70s and 80s. It no longer seems to be an up-to-date, cool thing to do.

That is unfortunate, because circuit training improves strength, which lowers the risk of injury, helps to improve efficiency of movement, and can be the prelude to considerably more powerful running, cycling, or swimming. In addition, circuit work can heighten VO2max, especially if one replaces the rather wimpy intervals used in the research studies with more intense effort. And circuit training can also heighten lactate threshold, the best predictor of endurance performance, as key research has shown. In case you haven't noticed, that means that circuit training can improve all five key variables which are important for endurance success - strength, power, economy, VO2max, and lactate threshold.

Try this workout

But what kind of circuits should you use? There are an almost infinite number of possibilities, but the following circuit workout will boost your fitness dramatically:

Warm up with 10 to 15 minutes of easy jogging, swimming or cycling, and then perform the following exercises in order. Move quickly from exercise to exercise, but don't perform the exercises themselves too quickly (don't sacrifice good form just to get them done in a hurry). The idea is to do each exercise methodically and efficiently - and then almost immediately start on the next one.

1. Run 400 metres at current 5-K race pace (if you're a swimmer, swim 100 metres at high intensity; if you're a cyclist pedal for 1600 metres at a high rate of speed)
2. Do 5 chin-ups
3. Complete 36 ab crunches
4. Perform 15 squat thrusts with jumps (burpees)
5. Do 15 press-ups
6. Complete 30 body-weight squats (fast)
7. Run 400 metres at 5-K pace again (if you're a swimmer or cyclist, see step 1)
8. Do 12 squat and dumbbell presses (with 10-pound dumbbells)
9. Complete 10 feet-elevated press-ups
10. Perform 36 low-back extensions
11. Do 15 bench dips
12. Complete 15 lunges with each leg
13. Run 400 metres at 5-K pace
14. Repeat steps 2-13 one more time (for two circuits in all), and then cool down with about 15 minutes of light jogging, swimming, or cycling.

It's tougher than it looks

Burpees? Press-ups? Feet-elevated press-ups? What do these exertions have to do with running, cycling, or swimming? John Q. Public tends to think that press-ups are good only for strengthening the arms and shoulders, but they are actually whole-body exercises, because they force the core muscles in the hips, abdominal, and low-back areas to support and stabilize the body while the trunk is moving up and down. And if you don't think that burpees work your whole body, try reeling off 15 of them right after you have run 400 metres hard and completed several chin-ups and a mess of ab crunches! The workout looks easy, but most endurance athletes find it to be far from that when they actually try it. We don't want to add to the toughness by leaving you confused about how to do the exercises, so here are explanations for the least familiar ones:

To carry out body-weight squats, stand with erect posture and your feet directly below your shoulders. Then, go into a squatting position, so that your thighs are roughly parallel with the ground. As you do so, it's okay to let your upper body incline forward a bit. Return to the standing position, and you have concluded one 'rep'. To perform ab crunches, lie on your back with your knees bent and your feet flat on the ground. Cross your arms over your chest and then use your ab muscles to lift your torso up and ahead as far as possible. Slowly return your shoulders to the ground to complete one rep.

Presses and dips

To complete squat & dumbbell presses, do the body-weight squats (as described above), but hold dumbbells in your hands - directly in front of your shoulders. Your hands should be turned inward, so that the palm sides of your hands are facing each other (the grip on each dumbbell will make a straight line directly forward from your shoulder). Once you've returned to the standing position from the squat, 'press' the dumbbells directly overhead, straightening your arms in the process. After you return the dumbbells to shoulder position, you have completed one rep.

Feet-elevated press-ups are normal press-ups, except that your feet are elevated (on a bench, chair, or wall). To perform bench dips, seat yourself on a bench or chair, with your hands at your sides. Your hands should be gripping the front edge of the bench or seat. While keeping your hands in the same position, slide forward off the chair and put your feet as far forward as possible, so that all your body weight is supported only by your hands and the heels of your extended feet. Then, simply lower your bum to the floor (or almost to the floor), and bring yourself back up again to complete one rep.

To do low-back extensions, lie on your stomach, with your arms by your sides and your hands extended toward your feet, with palms touching the floor. Contract the muscles at the back of your neck, so that you are gazing forward and upward. That's the basic starting position! A rep is simply a contraction of your low-back muscles, lifting your trunk well off the ground, followed by a slow easing of your torso back to the floor.

Of course, lunges are just exaggerated steps. You start with erect posture and feet under your shoulders and simply step forward with one foot. After this forward foot makes contact with the ground, you go into a squatting position, so that the thigh of the forward foot becomes almost parallel with the ground (it's okay to let your upper body incline forward slightly as you do so). Return to the starting position (feet back under shoulders, erect posture), and you've completed one rep with one leg.

Moving up

The way to progress with this circuit workout is to gradually increase the number of reps of the exercises, expand the number of circuits, and/or augment the distance of the running, cycling, or swimming intervals within the circuits. For example, I often have runners I am coaching start with two circuits with 400-metre intervals (they do two such workouts spaced a few days apart), move up to two workouts with 600-metre intervals, two with 800-metre reps, two with 1200s, and then two with one-mile intervals (all of these workouts contain two circuits, except for the one-mile interval session, which contains just one circuit). They then double back, and use the 400s and 600s in workouts which contain three circuits. All of this occurs over about a six-week period which is designed to increase general strength (while simultaneously advancing lactate threshold and VO2max). During this time frame, the number of reps of the various exercises increases by about 5 to 10 percent from week to week. Following the six weeks, a week of lighter training is carried out before moving on to a different type of strength work.

These circuit workouts are great for the beginning of the training year, when endurance athletes are attempting to improve general strength. They can also be used as 'tests' throughout the training cycle. If you struggle with the exercises, then you know your strength needs shoring up; if you have trouble with the running (or cycling or swimming) segments, then you know that your running (cycling or swimming) fitness is sub-par. The circuits also work particularly well during tapering periods prior to races, because they tend to 'put a cap' on both running capacity and overall strength. They are particularly effective before a marathon, because they give marathon runners confidence that they can run well in the face of fatigue.

Okay, now try this one

Once your fitness and strength have increased so much that the above circuit sessions are no longer challenging, you can then move on to a more challenging circuit workout, as follows (it is written for runners but can be adapted easily for swimming and cycling)

arm up with two miles of easy running, and then perform the following exercises in order. Move quickly from exercise to exercise, but don't perform the exercises themselves overly quickly (don't sacrifice good form just to get them done in a hurry). The idea is to do each exercise methodically and efficiently - and then almost immediately start on the next one.

1. Run 400 metres at 5-K race pace
2. Complete 8 high-bench step-ups with jumps
3. Do 6 plyometric press-ups
4. Perform 3 series of the 6-way lunge with arm drop
5. Complete 8 + 8 reps of the hanging scissors plus double-knee raise
6. Do 12 one-leg squats with hops
7. Perform 8 prone trunk extensions with arm raises
8. Run 400 metres at 5-K race pace
9. Repeat steps 2-8 once more (for two circuits in all), and then cool down with 2 miles of easy ambling.

How to do them

Here are the explanations of the exercises: To complete the high-bench step-ups with jumps, begin from a standing position on top of a bench which is approximately knee high, with your body weight on your left foot and your weight shifted toward the left heel. The right foot should be free and held slightly behind the body. Lower your body in a controlled manner until the heel of the right foot touches the ground, but support all of your weight on your left foot. Return to (and through) the starting position by driving down with the left heel and straightening your left leg as quickly as possible, so that you actually jump vertically and leave the surface of the bench. Upon landing from the jump (hopefully in the same spot from which you took off), lower your body again in a controlled manner until your right foot touches the ground. Repeat for the prescribed number of repetitions, and then switch over to the right leg. Maintain absolutely upright body posture with your trunk throughout the entire movement, with your hands held at your sides (with or without dumbbells). Please note that the bench used for this exercise must be very sturdy, with no wobble or instability. Failure to perform this exercise on a stable surface could result in disaster!

The high-bench step up with jump helps to develop muscular power, primarily in the hips, quadriceps, and hamstrings. These muscles are largely responsible for the propulsive force needed for running fast - particularly on hilly terrain. To carry out the plyometric (aka 'clapping') press-ups, assume the standard press-up position on the floor. Your upper body should be supported with your hands on the floor - shoulder-width apart. Your arms are fully extended, and your legs and feet are supported by your toes, which are hip-width apart. To begin the exercise, lower your chest toward the floor by bending your elbows while keeping your trunk and hips extended and 'rigid.' When your chest is one to two inches from the floor, rapidly straighten your arms and push your body upward as fast as possible. As your arms reach full extension, release your hand contact with the floor and clap your hands together very quickly, before returning your hands to the floor in the same position that they were in before the clap. Repeat this action (lowering, rapid extension, clap, land on hands) for the prescribed number of repetitions.

The plyometric push-up helps to develop upper-body power as well as stabilizing strength in the core muscles (abs, obliques, and low-backs). These muscles work together to stabilize the upper body during running, improving running economy.

Lunges

To do the 6-way lunges with arm drops, stand with your feet parallel and hip-width apart. Your arms should be bent at the elbows with your hands in front of your shoulders. Step forward with your right foot into a long-lunge position and lean your upper body forward approximately 45 degrees at the waist. Drop your hands on either side of your right knee as your right foot makes contact with the ground. Quickly extend your right knee and return your body to the original, full-standing position. Repeat with your left leg.

From the full standing position, step directly to your right with your right foot into a lateral-lunge position. Your upper body should face to the right and lean forward over your right leg at approximately a 45-degree angle. Again, drop your hands on either side of your right knee as your right foot makes contact with the ground. Your left foot should remain pointing straight ahead. Quickly extend your right knee and return your body to the original, full-standing position. Repeat with your left leg moving to the left.

Then, from the original standing position, step diagonally and to the rear with your right leg into a backward-lateral lunge position. Your upper body should face to the right-rear (about '4-o'clock') position, and it should lean forward over your right leg at about 45 degrees. Again, drop your hands on either side of your right knee as your right foot makes contact with the ground. Your left foot should remain pointing straight ahead. Quickly extend your right knee and return your body to the original position. Repeat with your left leg, moving it to the left-rear ('8-o'clock') position.

Repeat the entire series of movements (forward right leg, forward left leg, right-side right leg, left-side left leg, back-and-right right leg, back-and-left left leg) the prescribed number of times. The 6-way lunge stretches and strengthens the hamstring muscles in all three key planes of motion (sagittal, frontal, and transverse). Strong and flexible hamstrings stabilize the knee during running and help provide the propulsive force required for powerful strides.

Scissors and raises

To carry out the hanging scissors + double-knee raises, begin by hanging from a bar or overhead support. The height of the bar should allow you to hang with your body fully extended, without your feet touching the ground. Raise your right knee vertically (with the knee bent as in a running stride) as high as you can while simultaneously pushing your left foot and leg behind you (with the left leg almost completely straight). Next, quickly reverse your legs so that your left knee swings forward and upward (with the knee bent as in a running stride) and your right foot and leg move downward and backward behind you (with the right leg nearly straight). Repeat this 'scissor' action for the prescribed number of repetitions before moving onto the second part of the exercise - the double-knee raise:

To perform the double-knee raises, return to a straight, hanging position. Simultaneously raise both legs up as high as you can towards your chest - with both knees bent. Then, lower both legs together slowly to the starting position, before repeating the raising and lowering action for the prescribed number of repetitions. The hanging scissors and double-knee raises strengthen the hip-flexor, abdominal, and oblique muscles. These muscles function together to stabilize the trunk during running.

Squats

To do the one-leg squats with hops, stand with your left foot forward and your right foot back, with your feet about one shin-length apart (your feet should be hip-width apart from side to side). Place the toes of your right foot on a step or block which is about six to eight inches high. Most of your body weight should be directed through the heel of your left, forward foot. Bend your left leg and lower your body until the left knee reaches an angle of about 90 degrees between the thigh and lower part of the leg. Hop upward with your left foot while maintaining contact with the step or block with your right foot. Upon landing, immediately descend into another squat and again hop upward while maintaining contact with the step or block with your right foot. Be sure to maintain upright posture with your upper body and hold your hands at your sides throughout the squatting and hopping movement. Complete the prescribed total number of hops with your left leg before switching to the right. Note: make certain you perform these one-leg hops only on an aerobics floor, wooden gym floor, grass surface, soft dirt, rubberized track, or any other resilient surface which offers some 'give'. Hopping repeatedly on concrete or asphalt may increase your risk of overuse injuries to the lower part of your leg. The one-leg squats with hops develop both coordination and muscular power, particularly in the muscles of the shin, calf, and foot. These are the muscles that undergo significant strain during fast-paced running.

Extensions

To complete the prone trunk extensions with overhead arm raises, begin by lying face down on the floor with your legs straight and your arms extended straight forward (they would be 'overhead' if you were standing up). Slowly raise your chest, shoulders, and arms up toward the ceiling as high as you can, keeping your toes in contact with the floor at all times. Then, slowly lower your chest, shoulders, and arms down to the floor, but do not rest on the floor - maintain some muscle tension throughout your back for the entire exercise. Slowly repeat this up-and-down action for the prescribed number of repetitions. The prone trunk extensions strengthen the muscles of the upper and lower back. These muscles coordinate with the abdominals and obliques to stabilize the trunk during all running activities.

If you plan your training on a yearly cycle, a great time for this advanced circuit workout would be mid-year, after you have already completed 'blocks' of general, special, and specific strength training (general strength includes whole-body exercises similar to those in the basic circuit; special strengthening focuses on exertions which mimic the biomechanics of running, cycling, or swimming; specific training incorporates hill work and running or cycling with a weighted vest for runners or cyclists; it involves swimming against resistance for swimmers). It is also a great general-strengthening routine for those who have mastered - or need a break from - the basic circuit workout. As was the case with the basic session, the advanced circuit efforts can be made more difficult over time by increasing the reps of the exercises, the lengths of the running, cycling, or swimming intervals, and the number of circuits per workout.

Owen Anderson

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