Posted: March 31, 2005

Science of Sport: Much More Than Diddley-Squat

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

Weightlifters do it all the time. Downhill skiers rely on it for control and stability. Soccer, basketball, and hockey players like it. Even a few endurance runners, the ones who complete strength-training workouts on a regular basis, enjoy carrying it out.

It's squatting - the performance of weight-bearing "knee bends," usually while supporting a weight on the shoulders. Squatting is sometimes considered to be the premier strength-training movement for athletes who run in their sports, since squatting engages the major muscle groups in the legs and requires simultaneous flexion at the hip, knee, and ankle, as is the case with each ground contact during running. It is also sometimes argued that squats, when performed properly, may help athletes achieve greater thoracic expansion, boosting ventilation capacity.

But are squats really so great for athletes who run? Well, there really is evidence that squatting can improve maximal running speed. In research carried out at the Human Performance Laboratory at the NSW Academy of Sport in Sydney, Australia, athletes were divided into two groups, one of which performed squatting exercises while the other served as a control. At the end of the training period, squatting subjects improved performance during a 40-meter, all-out sprint by 2.2 percent and bolstered power output during a maximal, six-second bicycling test by 9 percent, while control individuals failed to improve at all (1).

There is also evidence that squatting is a strong exercise for upgrading sport-specific strength. In a study carried out at the Department of Rehabilitation Medicine at Goteborg University in Sweden, 24 healthy subjects carried out either barbell-squat or knee-extension exercises twice a week for six weeks. All 24 athletes were tested prior to training and at the completion of the six-week training period. A three-rep-maximum barbell squat and a vertical jumping test were utilized to monitor the effectiveness of training (2).

Naturally, you would expect the squatters to improve their three-rep-max squatting to a greater extent, compared with the knee extenders, since the squatters were actually using the squatting movement during their training. Not surprisingly, the squat-group members improved their three-rep-max squatting by 23 kilograms (31 percent), considerably above the 12-kilo (13-percent) gain attained by the knee-extension specialists.

The vertical jump was the sport-relevant movement in this study, and squatters upped max vertical jump by 10 percent, while the knee-extension athletes could not jump even a fraction of a centimeter higher after their six weeks of training. The wise Swedish researchers attributed the superiority of squatting over extension to "neural adaptation," i. e., to the fact that the test movement (jumping) more closely paralleled the actual training movements of squatting, compared with extending the leg at the knee (remember that knee extensions are carried out in a seated position, with the quads working in virtual isolation from the other muscles in the leg). As a result, the "lessons learned" by the nervous system in coordinating and controlling the training squats could be more easily carried over to the jumping tests.

Research carried out at Middlesex Hospital in London adds further evidence that squatting is a good exercise for improving sport-specific strength and performance. In the Middlesex investigation, 20 healthy female athletes performed strength tests for their quadriceps muscles during open-chain kinetic exercise (leg extensions) and for their hip, knee, and ankle extensors during closed-chain exertion (squats). If your long-term memory is temporarily failing you, remember that in closed-chain exercise the distal segment of the body (in this case, the foot) is fixed to a supporting surface (either stationary or moving), while in open-chain exercise the distal segment is not attached to a support structure. The sports-relevant movements in this study were vertical jumping and long-jumping, both of which were assessed using an opto-electric motion-analysis system (3).

The system revealed that squatting (closed-chain) strength was very highly correlated with vertical- and long-jump performances, while leg-extension (open-chain) strength demonstrated very little correlation with vertical- and long-jump ability. In other words, if you want to be able to jump high or leap far in your sporting activity, you would be wise to focus very heavily on squat training, since it correlates very well with both attributes. Although it wasn't specifically investigated in this study, it is likely that squatting strength would be correlated with stride length in runners. Even though open-chain exercises like knee extensions also activate the quads, the strength gained is specific to the open-chain activity and carries over poorly to the closed-chain actions associated with real sporting activities (running as fast as possible, leaping over a hurdle in track events, bounding over obstacles during cross-country running, crossing the barrier in a steeplechase, jumping as high as possible while playing basketball or volleyball, or vaulting over an opponent in a rugby scrum.

Now that you are convinced that squatting is a great exercise, it is good to begin your squatting adventures conservatively with a barbell which checks in at about 25 percent of your body weight. If this feels a bit heavy, there is no problem: Simply use a lighter (or no) bar, as it is important to focus on technique for the first few workouts. If the bar feels too light, feel free to add a reasonable amount of weight.

With the bar resting in a stand, slide underneath it and place it on your trapezius muscles at the bottom back of your neck, a little higher than your posterior deltoids. Grasp the bar in both hands with a comfortable grip, and pull your elbows backward.

Now, take in a nice, deep breath and hold your breath (to prevent your chest from "collapsing" anteriorly). You may lean your upper body forward a little bit, using a slight, anterior pelvic tilt. Contract your abdominal muscles strongly, look straight ahead, and remove the bar from its support.

Step back one or two steps, and stop with your feet basically parallel (it's OK to have your toes pointed outward slightly, if you wish). Your feet should be about shoulder-width apart. As you squat, keep the descent under control, and avoid "rounding" your back (keep the line formed by your back straight at all times, even if your back is tilted slightly forward). Once your thighs are parallel with the floor, gradually straighten your legs until you are in the standing, beginning position again (completing one squat). Breathe out at the end of the movement.

Squatting does a superb job of strengthening your quads, glutes, hamstrings, adductors, abs, and erector muscles of your spine. As you know, these muscles are essential for control and force production during running.

Some notes about this critical movement:

(A) If you feel your upper body is tilting forward too far when you squat, try placing a small block of wood under your heels. This should help you stabilize your upper body and also forces your quads to work a bit harder.

(B) If the bar feels uncomfortable on your "traps," lower it a bit onto your posterior deltoids. This will also make your back a stronger "lever" and will make it easier to squat with heavier weight. In either case, make sure to pull your elbows backward.

(C) If you wish, it's fine to perform squats with a frame guide; this helps eliminate excessive forward tilt of the torso and also calls on the quads to do more work.

(D) Don't let your knees move inward (toward the midline of your body) as you squat.

(E) To make your glutes do more work, continue the squat below the thighs-horizontal position (for a deeper squat), but do this only if you experience no discomfort in your knees. Make certain you avoid the common tendency to round the back as you do this.

For your first workout, start with just one set of eight to 10 reps with light to medium resistance. Over time, increase the number of sets to three, and gradually upgrade the amount of resistance you are using. Increasing the speed with which you carry out your squats - without sacrificing coordination - is also an important progression. In a recent study carried out at the Department of Health Sciences in the Sargent College of Allied Health Professions at Boston University, two groups of young women squatted repeatedly with either a slow tempo (two seconds for ascending, two seconds for descending) or a fast cadence (one second up and one second down). Both groups completed three warm-up sets and three eight-repetition maximum sets, three times per week for seven weeks (4).

The women were tested at the beginning and end of the study using force-platform and video analysis of their vertical jumping, long jumping, and maximum squatting; they also underwent isometric and isokinetic quadriceps-muscle testing at speeds ranging from 25 to 125 degrees per second. As it turned out, the fast-squat group was superior to the slow squatters in a number of variables, including peak velocity of the knee and absolute power. The bottom line is that you can not expect to reach your full power potential simply by working your muscles at slow rates of movement, even if mega-resistances are utilized. Power doesn't magically descend on you as a reward for hard work; it must be developed via a combination of training using heavy resistance and training which places a premium on quick, coordinated movements. Once you have become a good squatter, a good strategy would be to carry out three sets of squats per workout, with the first two squats involving relatively high resistance (and fairly slow movement) and the last set utilizing lighter resistance and explosive motion. This is "contrast training," the advantages of which were described in a recent issue of Running Research News (5).

It is often stated that varying the position of the feet during squatting can target specific muscles within the quadriceps groups, but this is actually not the case. For example, one study determined that widening the squatting stance did not change the ratio of vastus-medialis/vastus-lateralis activation, as is popularly believed (6). Another investigation carried out at the University of Pittsburgh found that turning the feet outward by 30 degrees from the straight-ahead position had no impact on muscle-activity patterns in either the quads or hamstrings during squatting (7). Instead of worrying about adopting a wide stance or turning your feet in or out, you should simply place your feet in a comfortable position which seems to offer you the most stability as you perform your squats.

If you have damaged an anterior-cruciate ligament (ACL) in one of your knees or if you have undergone ACL reconstruction surgery, can you still squat? Naturally, you would want to be prudent in such cases, but the scientific evidence clearly shows that squatting produces less shearing forces on the ACL, compared with traditional, open-kinetic-chain exercises such as knee extensions on an exercise machine (8). While this might seem counterintuitive, bear in mind that squatting involves simultaneous co-contraction of the quads and hamstrings, which tends to stabilize the tibia and to thus reduce stress on the ACL. In addition, the squat is a weight-bearing exercise which tends to compress the knee joints, lowering tension and side-to-side movement of the ACL. Finally, contraction of the primary calf muscle (the gastrocnemius) during the squat also stabilizes the tibia and reduces forward shear forces.

It is important to remember that quad activation is enhanced by squat depth. For example, just increasing the flexion angle of the knee from 30 to 60 degrees as one squats with a vertical upper body generally quadruples the tension in the quads (9), and the greatest level of quad activation may occur at about 90 to 100 degrees of knee flexion (10). It is also true that quadriceps activation far outstrips the development of tension in the hamstrings during squatting. For example, the amount of muscular tension in the quads is approximately 14 times greater, compared to the hamstrings, when the upper body is in a vertical position and the knee-flexion angle is 30 degrees; when the knee is flexed to 60 degrees, the tension in the quads is roughly 13 times greater (9).

Strength specialists sometimes contend that flexing the trunk (inclining it forward) during squatting improves the activation of the hamstrings and gluteal (butt) muscles, and this is indeed the case. For example, altering the trunk-flexion angle from 0 degrees (the straight-up position) to 30 degrees can spike hamstring tension eightfold when the knee-flexion angle is 30 degrees and can double the tension when the knees are flexed to 60 degrees (9).

This forward leaning will slightly reduce activation of the quads, of course. And - the danger of the forward lean is that it may augment shearing forces on the vertebrae in the spinal column. This has been documented in research carried out at the University of Bristol in the United Kingdom, in which 21 men and 18 women lifted objects from the ground while either squatting with straight backs or else stooping with relatively straight legs and flexed torsos (11). The Bristol researchers also varied the mass of the objects and the speed of movement utilized to pick up the weighted structures. Spinal compressive forces were assessed by measuring the peak extensor moments generated by the back muscles and connective tissues during the lifts. Extensor moments were calculated from EMG activity of the erector spinae muscles in the lower back, using corrections for muscle length, contraction velocity, and electro-mechanical delay. The bending forces ("bending torques") acting on the intervertebral discs and ligaments were quantified by comparing dynamic measurements of lumbar flexion with the normalized bending properties of cadaveric lumbar spines.

The measurements made by the Bristol scientists showed that lifting with the trunk flexed actually reduced compressive forces acting on the spine by about 10 percent, compared with straight-back squat lifting. This is not bad, since there is some concern about the compressive forces acting on the spine during squat activity. Some research has suggested, for example, that the compressive forces acting on the lumbar portion of the spine during squats carried out with a loaded barbell can be equal to six to 10 times body weight, possibly increasing the risk of a ruptured disc or even a vertebral stress fracture.

However, the bad news was that trunk-flexed lifting increased the bending torque - the kind of force most likely to cause one vertebra to slip over another and induce spondylolisthesis - by about 75 percent! Thus, adding trunk flexion to your squatting actions may better activate your hams and glutes and slightly reduce spinal compression, but it probably increases the chances of sustaining the kind of injury (vertebral displacement) associated with high bending forces.

While we are on the topic of spinal safety, we should mention that good abdominal strength probably also helps to protect the spine during squatting. In addition, holding one's breath while squatting (as recommended above) increases intra-abdominal pressure and is likely to stabilize the spine. This has actually been verified in research carried out at Auburn University and the University of Oregon in which balloon catheters were inserted into the recta of skilled weightlifters to monitor intra-abdominal pressure during the performance of squats (12). In this investigation, increased intra-abdominal pressure reduced back-muscle forces by 15 percent and lowered spinal compressive forces by 21 percent.

Although squatting is a great exercise, it does have some limitations. It is clear that squatting is not a magnificent exercise for maximally strengthening the hamstrings, for example, since tension development in the hammies during squats is low, compared with the quads. That being said, however, squatting is certainly good for functional strengthening of the hams, since it forces the 'strings to work in a coordinated way with all the other muscles in the legs while the lower appendages are in a weight-bearing position.

It is also true that if hypertrophy of your quads is what you want, squats are not the best way to go. Studies have shown, for example, that about 60 percent of the maximum volitional contraction of the quads is achieved during squatting activity, compared with 82 percent during leg-extension exercises (13). Since maximal bulk-ups depend on max activation of a muscle, leg extensions might do a better job of fattening up sinews, compared with squats.

When performed carefully and correctly, however, squatting is a relatively safe activity which can dramatically improve your functional leg-muscle strength, jumping ability, and running speed. Endurance runners would be wise to perform squatting exercises regularly and to progress from two- to one-leg squatting during the strengthening phases of their overall training cycles, before they move on to hill training and explosive work. ©

References

(1) "The Ability of Tests of Muscular Function to Reflect Training-Induced Changes in Performance," Journal of Sport Science, Vol. 15-2 (April), pp. 191-200, 1997
(2) "Weight Training of the Thigh Muscles Using Closed- vs. Open-Kinetic-Chain Exercises: A Comparison of Performance Enhancement," J Orthop Sports Phys Therapy, Vol. 27-1 (January), pp. 3-8, 1998
(3) "The Relationship between Open and Closed Kinetic Chain Strength of the Lower Limb and Jumping Performance," J Orthop Sports Phys Therapy, Vol. 27-6 (June), pp. 430-435, 1998
(4) "Early Phase Differential Effects of Slow and Fast Barbell Squat Training," American Journal of Sports Medicine, Vol. 26-2, pp. 221-230, 1998
(5) "Special Advantages of Contrast Training," Running Research News, Vol. 19-1, pp. 1, 6-8, 2003
(6) "EMG Analysis of the Vastus Medialis/Vastus Lateralis Muscles Utilizing the Unloaded Narrow- and Wide-Stance Squats," Journal of Sport Rehabilitation, Vol. 7, pp. 236-247, 1998
(7) "Electromyographic Analysis of the Squat Performed in Self-Selected Lower Extremity Neutral Rotation and 30 Degrees of Lower Extremity Turn-Out from the Self-Selected Neutral Position," Journal of Orthopaedic and Sports Physical Therapy, Vol. 25-5, pp. 307-315, 1997
(8) "The Benefits and Controversy of the Parallel Squat in Strength Training and Rehabilitation," National Strength & Conditioning Association Journal, Vol. 22-3, pp. 30-37, 2000
(9) "Biomechanical Analysis of Rehabilitation in the Standing Position," American Journal of Sports Medicine, Vol. 19, pp. 605-611, 1991
(10) "A Comparison of Tibiofemoral Joint Forces and Electromyographic Activity during Open and Closed Kinetic Chain Exercises," American Journal of Sports Medicine, Vol. 24, pp. 518-527, 1996
(11) "Bending and Compressive Stresses Acting on the Lumbar Spine during Lifting Activities," Journal of Biomechanics, Vol. 27-10, pp. 1237-1248, 1994
(12) "Biomechanics of the Squat Exercise Using a Modified Center of Mass Bar," Medicine and Science in Sports and Exercise, Vol. 18-4, pp. 469-478, 1986

To learn about Owen-Anderson's running camps in California, please send a note to Owen at owen@rrnews.com.

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