Posted: January 14, 2005

Science of Sport: Is Contrast Training For You?

By Owen Anderson, Ph. D. (copyright © 2003-2005)

When athletes carry out strength-training workouts designed to improve their power, they often utilize relatively light resistances, since such resistances permit more explosive movements. However, they also often combine light loads with heavy loads within their power workouts, because heavy resistance seems to create a greater activation and preparation for maximal effort in subsequent explosive movements (1). Some exercise experts have claimed that the power gains associated with the utilization of a combination of heavy and light resistance can be three times greater, compared with conventional programs which use only light or only heavy resistance (2).

Controlled scientific research suggests that the gains in power associated with heavy-light combinations are a bit more subdued, but nonetheless real. In one study, athletes achieved a statistically significant 2.8-% increase in explosive, jump-squat height after performing a set of relatively heavy-resistance half-squats, compared with doing the jump squats without the preceding high-load half-squats (3). Researchers suggested that this difference occurred because the heavy squats produced a "potentiation" effect which allowed muscles to contract more quickly and forcefully. This response was believed to be particularly noticeable in fast-twitch motor units - collections of muscle cells with an intrinsic ability to shorten at high rates of speed.

Supporting work carried out by noted German scientist Dietmar Schmidtbleicher (4) found that three maximal voluntary contractions of the quadriceps muscles led to a 3.3-% upswing in counter-movement jump height for both male and female athletes (counter-movement jumps are efforts in which an athlete first goes into a crouching position and then springs upward as high as possible). In Schmidtbleicher's investigation, drop-jump height also improved after maximal quadriceps work (drop jumps are performed by jumping down from a platform and then springing up explosively), and explosive force and movement velocity were greater during bench throws after upper-body maximal voluntary contractions. Note that this positive effect of prior heavy exertion on subsequent power, although real, is somewhat counter-intuitive. One might expect that maximal or near-maximal contractions against heavy resistance would induce some level of fatigue that would subsequently retard explosive movements, but instead well-controlled high-load work often seems to facilitate subsequent powerful actions.

Although there has been fairly general agreement that combining high-resistance work with lighter, quicker movements during training produces optimal gains in power (compared with utilizing only the quicker motions), there has been debate about exactly how the two types of strength training should be combined within workouts. There are basically two schools of thought: Followers of "complex training" believe that various sets of groups (complexes) of exercises should be performed in a manner in which several sets of heavy-resistance exercise are followed by a number of sets of lighter-resistance exertion. As an alternative, proponents of "contrast training" suggest that heavy and light exercises should be alternated, set for set, with a lightning-quick, light-resistance set always following a heavy one.

To see which form of training produces higher-quality workouts, scientists at the School of Human Movement and Sports Science at the University of Ballarat and the Performance Enhancement Center at the Queensland Academy of Sport in Australia recently carried out an intriguing study with 11 female athletes (age 19 to 31) in which three different types of weight-training session were conducted (5). The 11 athletes ordinarily strength-trained for about five hours each week, along with a supplementary 15 weekly hours of training in either hockey or softball (the athletes were all national- or international-level hockey or softball players); all of the subjects had strength-trained regularly, in an attempt to enhance both strength and power, for more than two years prior to the study. The 11 females were well-accustomed to performing the two exercises, half-squats and jump squats, which were an integral part of the investigation.

The half-squats were performed on a Smith machine, with the down-position (squat-position) knee angle set at 90 degrees and the intensity fixed at 3RM (i. e., the three-repetition maximum, the maximal amount of weight which could be squatted successfully three - and only three - times). This 3-R-M resistance averaged 120.5 kg for the 11 athletes.

In contrast, the jump squats were completed with a modified Smith machine positioned over a force plate. This Smith machine was three meters high and thus permitted safe completion of the jumps. The bar of the machine was fixed so that it could move only vertically, and a (light) resistance of just 30% of the 1-R-M half-squat (or about 32% of the 3-R-M half-squat resistance) was utilized as the load, primarily because it had been previously found to produce maximal mechanical power outputs (6); this load averaged 38 kilograms. The athletes had to keep the Smith-machine bar in contact with their shoulders at all times; any failure to do so was considered a false trial. Once again, a knee angle of 90 degrees was selected for the farthest-down (squat) position. The explosive jump for height was undertaken from this stationary, squat position, with the knees flexed at the chosen angle of 90 degrees; thus, the jump itself involved a purely concentric action of the quads, which helped to control the influence of muscle pre-stretch on performance. Four reps of jump-squats were performed per set. Naturally, the half-squats at 3RM were considered to be the heavy-load exercise, while the jump squats at 32% of 3RM represented the explosive exertion.

As mentioned, three different workouts were conducted. In a "traditional" workout, the 11 female athletes completed three sets of light-load exercise (the jump squats) and then three sets of heavy-load work (half-squats); this is considered to be traditional, because athletes often move from lighter to heavier loads over the course of a workout. In a second, "complex" workout, all sets of the heavy-load half-squats were performed before the three sets of explosive jump squats were completed. Finally, in the "contrast" session, a set of the heavy half squats was alternated with a set of the lighter jump squats until three sets of each exercise had been performed. Uniform, thorough warm-ups which included stationary cycling, light static stretching, and submaximal half-squats preceded each type of workout.

As it turned out, the complex workout produced the worst jump squats during the first set of jump squatting, compared to the traditional and contrast sessions. This may have been due to a fatigue effect associated with the completion of the prior three sets of heavy-load, 3-R-M half-squats. As mentioned, heavy-load exercise may facilitate explosive movements, but it can not do so if the heavy-load work is extensive enough to induce significant muscular fatigue. In a related study carried out by noted former-Soviet-Union strength-training guru Y. Verkhoshansky (7), novice track-and-field athletes who utilized heavy loads before carrying out "speed-strength" exercises achieved less improvement in explosive strength over the course of a 12-week training program, compared with athletes who put the explosive work before the heavy loads.

Interestingly enough, the difference in power performance during the different squat-training methods depended on the Australian athletes' strength levels, so the 11 subjects were "median-split" (with the median athlete "thrown out") into two groups, with the five athletes with the highest 1-R-M values in one group and the five females with the lowest 1-RMs in the other. 1RM for the low-strength group averaged 116 kg, while 1RM for the high-strength athletes settled at 139 kilograms. After this split was performed, statistical analysis revealed that the higher-strength group achieved a greater improvement in jump-squat performance during the contrast workout, compared with the traditional method (no such difference was observed in the lower-strength athletes). Basically, the higher-strength group achieved a 2-percent increase in maximal force and a 4-percent upswelling in peak power during squat jumping with the contrast training method, compared with the conventional technique, even though in the conventional workout all of the squat jumping was performed before any potentially fatiguing heavy-load training could occur. Notably, the lower strength group tended to fare worse with the contrast workout, producing about 1-percent less maximal force and peak power, compared with the traditional session. The Australian researchers concluded that contrast training is advantageous for increasing power output in athletes with relatively high strength levels.

This is a reasonable conclusion. In a separate study, stronger subjects had greater gains in jump-squat performance after completing one set of heavy (5-R-M) squats, compared with weaker individuals (8), and in a very interesting investigation, highly trained athletes displayed a significant neuromuscular potentiation response after heavy-load exertion, whereas less-well-trained physical-education students did not (4). It is not clear whether the higher response observed in better-trained athletes is a consequence of the fact that they have heightened fatigue resistance during initial heavy-load exercise - or simply reflects the fact that they have more responsive neuromuscular systems which become more "fired up" by the vital, high-intensity work (i. e., their potentiation effect is greater).

Overall, there was a trend for performance during the jump squats to decrease over the course of each type of workout; however, the contrast technique tended to have the smallest decrement in performance, possibly because the potentiation effect mentioned above counterbalanced increased fatigue over the course of the contrast workout. Because contrast training worked well with the strong athletes but not the simpering ones, the Australian researchers suggested that athletes should develop a very advanced strength base before undertaking the contrast method of power development.

If such a base were indeed developed, what might a contrast workout actually look like for an athlete attempting to develop power? For an athlete who runs in his/her sport and wants to improve raw running speed, explosive sprints, jumps, hops, bounds, and high-intensity drills might be alternated with heavy-load exercises such as half-squats, partial squats, bench step-ups, and so on, using a barbell to provide resistance. In a similar vein, very fast intervals on flat ground might be alternated with short, steep, hill-climbing. For a cyclist, the explosive sprints and movements could be alternated with high-load leg presses and bicycle leg swings carried out with elastic stretch cords with very high resistance.

Interestingly enough, it is not known how long the potentiation effect actually lasts. For example, if an athlete completed a set of 4-R-M squats, would the resulting potentiation hang around for just one subsequent set of explosive activities, or might it last for several sets of different explosive routines? An understanding of the "window of potentiation" is lacking, and indeed this window might vary significantly from athlete to athlete. The research in this area is incomplete, but it is clear that it might be advantageous - as long as the potentiation window is fairly broad - to limit the total number of heavy-load moves within an overall contrast workout (to curtail the chance that fatigue resulting from heavy-load work would reduce the quality of the highly desired explosive movements). For now, athletes will have to experiment with their workouts to determine which combination of heavy- and light-load exercise seems to work best.

It is also very interesting to note that submaximal contractions of less than 85% of 1RM probably do not induce potentiation of the neuromuscular system. Thus, if one is attempting to construct a contrast workout in order to enhance power development, it is very important that quite-high resistances be used for the slower, heavy-load interludes. Squatting at just 80% of max, for example, might only give fatigue a boost without potentiating anything. It is also thought that the heavy contractions must be sustained for several seconds at a time in order for potentiation to occur.

Note that the contrast-technique results have profound implications not just for workouts but also for warm-ups which precede competitive efforts. If the competitive effort involves explosive movement, it is clear that the inclusion of heavy-load exercise within the warm-up will be far more beneficial to a strong, experienced athlete than a traditional warm-up of lower intensity which only attempts to activate the cardiovascular system and "warm up" the muscles in a more moderate way. Indeed, several studies have already shown that warming up with a heavy load produces enhanced "acute" efforts (short-duration efforts which involve a quick burst of activity). For example, the use of a preparatory heavy load augments explosive countermovement jump height (8), drop-jump height (also 8), standing-long-jump-performance (9), general jumping ability, and throwing speed.

References

(1) Soviet Sports Review, Vol. 21, pp. 120-124, 1986
(2) Explosive Power and Strength: Complex Training for Maximum Results. Champaign, IL: Human Kinetics Publishers, 1996
(3) Journal of Strength and Conditioning Research, Vol. 12, pp. 82-84, 1998
(4) New Studies in Athletics, Vol. 11, pp. 67-81, 1996
(5) Journal of Strength and Conditioning Research, Vol. 16(4), pp. 530-538, 2002
(6) Medicine and Science in Sports and Exercise, Vol. 25, pp. 1279-1286, 1993
(7) Soviet Sports Review, Vol. 18, pp. 166-170, 1983
(8) Journal of Strength and Conditioning Research, Vol. 12, pp. 82-84, 1998
(9) Medicine and Science in Sports and Exercise, Vol. 28, p. S189, 1996

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