Squat or ScrumTruk: which is best for quadriceps training for athletes?
Bruce Ross of MyoQuip describes an alternative to the squat that rugby players and other athletes may consider for developing their quadriceps strength.
McLaughlin et al. (1978) suggests that there are deficiencies in the squat as an exercise for developing quadriceps strength. I suggest that the ScrumTruk may be a more efficient apparatus for this purpose.
McLaughlin and his colleagues investigated torques and joint forces generated during the parallel squat by studying nationally-ranked and world-class powerlifters competing at the U.S. Senior National A.A.U. Powerlifting Championships. Although now very dated, the study is important given that, as with other complex joint movements, the study of the kinetics of the squat exercise has been virtually neglected. The research involved a cinematographic analysis in calculating joint forces and muscular torques for the shank, thigh and trunk, i.e. at the ankle, knee and hip joints, respectively.
Subjects were classified as world-class, high-skilled or less-skilled. This delineation of ability was used to isolate trends in technique. It was assumed that the most-skilled subjects "would exhibit efficient patterns of performance," so that they were, in effect, used as a reference group in assessing the performance of those in the other subgroups.
By comparing the techniques of lifters in each group, the researchers hoped to identify possible general trends in performance for individuals unskilled in the squat.
Technique differences between highly-skilled and less-skilled lifters
McLaughlin (1975) and McLaughlin et al. (1977)[1,2] had found that less-skilled subjects "leaned forward more and moved the knees frontward to a greater extent during the descent, and ... moved the hips backwards more in the early ascent while also increasing trunk lean." The degree of forward lean during the lift appears to increase the torque for the trunk extensors and reduce those of the thigh extensors.
McLaughlin et al. (1978) confirmed these findings. One of its major observations was "a general trend for the high-skilled subjects to exhibit more extensor-dominant thigh torques than the less skilled." In particular, the three world-class subjects had the greatest extensor-dominant thigh torques.
For trunk torque, it was noted that it "increased linearly the more a subject's trunk angle decreased." The angle referred to was that between the trunk and the horizontal at the hip joint.
McLaughlin et al. (1977) found the mean trunk angles to be smaller for less-skilled subjects than for the high-skilled. The most recent study verified the related trend for less-skilled subjects to exhibit greater trunk torques than more highly-skilled subjects. "It would appear from the data that high-skilled subjects attempt to minimize the trunk torque and do so largely by reducing forward trunk lean."
It was noted that among the subjects, the then world super heavyweight champion maintained the greatest trunk angle of all subjects and, despite his much greater bar load, had a lower trunk torque than many smaller, less-skilled subjects.
It was suggested that the magnitudes for trunk torque affect the magnitude and dominance of the thigh torque values. As mentioned above, the high-skilled subjects demonstrate larger trunk angles, lower trunk torques, and more extensor-dominant thigh torques. "The high-skilled subjects strive to use the leg extensors to a greater extent than do less skilled subjects. This greater emphasis on the leg extensors is obtained by a minimization of the trunk torques by the high-skilled subjects (achieved by maintaining more erect trunk positions)."
Implications of the study results
Although the parallel squat has been regarded as primarily a leg-extensor activity, the results of this study show that trunk extensors play a very significant and even a dominant role. The muscular torques for the trunk extensors were found to be greater than the thigh and shank torques across a wide range of trunk-angle positions. The authors conclude that the general recommendation of the squat as one of the primary exercises for developing quadriceps needs to be altered in light of their findings. Those recommending the exercise primarily for quadriceps development should either ensure that a high trunk angle is maintained or suggest other exercises that more directly involve the quadriceps. In practice, of course, given the observed tendency of inexperienced lifters to move their hips back and lean forward more when coping with heavy loads, it is unlikely that the squat is an effective exercise for the development of the quadriceps group.
Is the ScrumTruk a useful alternative?
At the low point of the squat movement, the exerciser has completed the eccentric or lowering phase and is switching to the concentric or rising phase. This is occurring in a region of high mechanical disadvantage. At this point, the injunction to keep the hips forward and the trunk near upright is unlikely to be followed if an inexperienced lifter is struggling with a near-limit weight and worries about the implications of failure. The corresponding scenario with the ScrumTruk involves the exerciser allowing the push truck to roll back towards them in the eccentric phase then generating the shove for the concentric or pushing phase. If they are not confident about coping with the weight, they can allow the push truck to come to rest against the bumper stops. They do not need a spotter to take some of the load. Even more importantly, the horizontal trunk position adopted with the ScrumTruk is intuitive, comfortable and involves no strain on the lumbar spine. Athletes find no difficulty in maintaining a horizontal trunk throughout a set of repetitions. Figures 1 and 2 provide a comparison of the orientation of the trunk relative to the direction of weight force for the squat and ScrumTruk, respectively. In Figure 1, it is evident that there is quite a long moment arm from the fulcrum point at the hip joint to the vertical line of force from the weight bar. This moment arm increases as the trunk angle decreases and the hips are moved back. Figure 1 Vertical weight force with the Squat Figure 2 Horizontal weight force with ScrumTruk, the exerciser in Figure 2 is in the typical starting point for pushing the ScrumTruk. The included angles for both hip and knee joints are 90°. It can be seen that the moment arm from the hip joint to the horizontal weight force is negligible.
Range of movement
In scrummaging the conventional range of movement in terms of included angles for both hip and knee joints is 90° to 140°. This relationship is readily replicated using the ScrumTruk. Further, when the exercise range is extended to "lock-out" or full extension, hip and knee joints move in unison from 90° to 180°. Thus, the hip and knee extensors share more or less equally the distribution of the load, with the result that the quadriceps group, as knee extensors, are fully engaged.
As noted, there is a tendency with the squat for excessive trunk lean. To the extent that this occurs, at the lowest point of the squat, the included angle at the hip joint is significantly less than that at the knee joint. Consequently, rising to "lock-out" or 180° extension involves a much greater range of angular movement for the trunk than the thighs. Crucially, observation of actual lifters suggests that much of this greater relative movement tends to occur when the lifter is moving from a horizontal thigh position through the "sticking point," which McLaughlin and his colleagues estimated at around 30° above horizontal. Thus the trunk extensors, principally the gluteus maximus, bear the bulk of the serious loading while the quadriceps is not fully taxed.
Given that the ScrumTruk is a very recent invention that is just coming out of the development stage, there have not yet been any systematic studies of its operation or effects. However, the most common observation from players in Sydney University Football Club's Elite Development Squad who have been making extensive use of the ScrumTruk in out-of-season training is a very definite "pump" or "burn" in the quadriceps when performing heavy sets. When queried, they report no similar effect from the squat which they are simultaneously performing.
For rugby players, who usually have an inexpert technique in the squat, the ScrumTruk appears to be a much more efficient vehicle for developing and strengthening the quadriceps. Given its ease, comfort and efficiency of use, the ScrumTruk is likely to offer similar advantages over the squat for athletes in other sports or other people pursuing strength and fitness. Its use is certainly indicated where there is a history of back or knee problems or where the person's limb geometry makes it difficult to maintain good form in the squat.
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About the Author
Bruce Ross is a retired academic who has been President of Sydney University Sport for the past 14 years. He has a background in rugby, both playing and coaching, and in strength development. His company, MyoQuip Pty Ltd is focussed on identifying and exploiting areas where current strength-increasing technology is inadequate or non-existent.