1. Anatomy & Kinesiology.
2. THE FUNCTION OF THE MID-TORSO IN SPORT ACTIVITIES
Most sports encompass relatively large movements of the trunk. Since the trunk segment has a large mass, great demands are exerted on the trunk musculature, particularly if the trunk movements are to be performed with high accelerations. Also the trunk has a critical role in the maintenance of stability and balance when performing movements with the extremities.
Sporting activities requiring running or jumping place pressure on the lumbo-pelvic region (that includes the 4th and 5th lumbar vertebra), the pelvis and the hips as this region becomes the hub of weight bearing. The superior forces (from torso, head and arms) meet the inferior forces transmitted from the ground through the lower extremity.
No part of the body is more vulnerable to tissue strains and sprains. This point is the center of all body movements and efficient body movements (as required in sprinting) can be critical in maintaining the stability of an anatomically correct body position, that of the Abdominal muscle groups, erector spinae (making up the mid-torso region) and the gluteus maximus (Porterfield 1985).
A study by Comerford, et al. (1991) analyzed the mid-torso muscle groups to see which group had the greatest impact on lumbo-pelvic stabilization. Results indicated that oblique muscle groups were the most important for this stabilization (especially from pelvic rotation forces) as found in high-speed sprint movements.
To assist in sprint acceleration, powerful arm drive will allow for a more rapid and powerful leg extension. The limitation with this technique is that large rotational forces can be placed upon the mid-torso musculature. If there is inadequate stability in this region, rotation of the pelvis will occur to counteract shoulder rotation resulting in poor technique and inefficient force application; therefore a slower athlete will be the result.
At an elite level, upper body strength is emphasized in sprint athletes out with a concurrent development of mid-torso strength to allow efficient usage of this additional strength during high-speed sprinting movements.
The naturally occurring wide pelvis of the mature female also leads to the above problem and mid-torso strength is absolutely vital if the coach wishes to maximize efficient technique at maximal speed in his/her female sprint athletes. Hip rotation is required to maximize stride length, but if excessive, then poor technique will result and if combined with a poor pelvic tilt, then major inefficiencies will result, leading to either poor performance, injuries or both.
Apart from resistance to rotational forces, there must be support of the pelvis to minimize excessive anterior pelvic tilt. An excessive anterior tilt indicates poorly toned mid-torso musculature and this can increase the lordotic curve (lower back arch) in the lumbar region. This can increase the strain on the facet joints in the vertebral column and can result in the iliopsoas going into spasm to protect the lower core from injury.
Also increased pressure on the neural plexus from the lumbar region can result in nerve irritation (e.g. sciatic nerve) which can then affect the optimal functioning of lower limb musculature that can have deleterious effects if maximal effort work (e.g., 100% sprinting) is performed (such as hamstring strains).
Excessive anterior tilt of the pelvis can limit hip range of motion leading to excessive hip extension and limited hip flexion. This technical position limits stride length and increases ground contact time (which is undesirable for increases in speed performance) due to the athlete's center of gravity being lower than required for maximal sprinting speed.
The demands of sprinting require the abdominals to function in a way that leads to optimal torsional stabilization during explosive contractile sequences, matching the needs of performing up to 5 strides per second (such as that which occurs in an elite sprint race). During sprinting at this rate, the lower limb velocity can reach 80km/h; therefore the stresses placed upon the pelvic stabilizers are extreme and can only be accommodated for with extremely well-developed abdominal (including oblique) musculature (Francis 1992).
3. WAYS OF DEVELOPING THE MID-TORSO REGION
The development of a strong mid-torso should be the goal of all speed/power athletes and the preferred procedures for maximizing strength in this region is by the common sit-up. Kinesiologically, the sit-up and its many variations are the ideal exercises to develop the vertebral flexor and rotational muscles (namely the RA, EO & IO).
The mid-torso musculature consists of postural muscles with a high percentage of slow-twitch muscle fibers. Their function is to be able to hold contractions for long periods to maximize trunk stability (Nordel and Frankel 1989, p. 104).
To best condition this region, variations on the sit-up can be used. To maximize abdominal development and minimize stress placed upon the lower back, exercises should be performed slowly (1-4 seconds per repetition) while working on all muscle groups in the mid-torso region.
These exercises should also be performed through a range of motion that minimizes lower back strain, and maximal control is required. When compared to the stress placed upon the lumbar region when standing (assume this is measured as 100%), the full sit-up (Figure 5), even with knees bent and feet flat on the floor, creates a stress equal to 200%.
This load can be decreased if the sit-up is only partial (first 30' from floor) and lessened even more if a reverse sit-up is performed (pelvis lifted off the floor) (Figure 6).
The reverse curl has been shown to increase the activation on the EO and IO as well as the RA (Nordin & Frankel 1989, p. 202). A modification to maximize load and minimize stress upon the lumbar region is to perform a partial crunch as well as a reverse sit-up concurrently (Figure 7) and hold each maximal contraction for four seconds. This minimizes the use of assistant muscle groups and quickly fatigues the musculature targeted in only 5-15 repetitions.
Sit-ups performed fast and or with the feet supported have:
- The relative contribution of the hip flexors increasing while the relative contribution of the abdominal muscles decreasing (Sevier 1969).
- Increased stress placed upon the lumbar region of the spine.
- Decreased load on the abdominal musculature due to increased momentum from the upper body.
The major limitation of the sit-up is the functional application of mid-torso strength transferable from a sit-up routine to the pelvic stabilization required under the stresses of a sprint or any high-speed movement performance. Personal observation of a variety of athletes has highlighted that even the development of very strong mid-torso regions from situps and squat type activities do not automatically transfer to the pelvic and mid-torso positions required to maximize sprinting performance.
Many athletes are strong enough through their mid-torso region but have not developed correct motor patterns to be able to stabilize the body while having rapid upper and lower limb movements (e.g., arm and leg movements in sprinting). To develop the specific strength qualities or transfer mid-torso strength to the required strength positions can be achieved both in a weight room and the field/court/ track situation.
WEIGHT ROOM MID-TORSO TRAINING
The best adaptation in the mid-torso musculature results from slow isotonic training in combination with isometric training in a range of nonspecific and sprinting-specific body positions.
Once the athlete can perform acceptable slow isotonic (with movement) mid-torso exercises, more sprint specific positioning can be introduced that requires the athlete to place his hips in the necessary posterior tilt position while placing stress upon the mid-torso musculature. Examples of these exercises are:
- Abdominal hollowing (Figure 8)
- Isometric prone (Figure 9)
- Single leg raise with lumbar support (Figure 10).
To perform abdominal hollowing the athlete can be either in a supine position or standing. The technique is to contract the abdominals "INWARDS" as hard as possible while maintaining normal rib cage positioning. This can be assisted by placing a finger into the belly button and try to push the abdominal wall inwards while maximally contracting. The athlete should continue to breath as normally as possible throughout the exercise; each contraction can be held for up to 60 seconds.
To perform an Isometric prone exercise the athlete begins on elbows and knees and then takes the knees off the ground while trying to maximally contract the abdominal musculature upwards. If any stress is felt on the lower back, this is an indication that the abdominal wall is not being totally contracted. This position should be held 15-60 seconds depending upon the condition of the athlete.
Single leg raise with lumbar support
To perform a single leg raise with lumbar support, the athlete places the tips of his fingers under the lower back and maximally contracts the back against the fingers. Then one leg at a time is slowly lowered (up to 10 seconds per leg) while maintaining a constant pressure on the fingers. As soon as the pressure decreases, this indicates that the abdominal musculature is beginning to fail and the hip flexors have been activated. At this point if the pressure cannot be regained, the athlete either finishes that repetition or brings the leg slowly back to the starting position until lower back pressure can be regained and then continues the repetition.
These are still "PASSIVE" isometric exercises (done slowly) that once a high competency is reached can be followed by "ACTIVE" isometric exercises that are highly sprint specific.
Examples of these exercises are:
- Rapid hip extension/hip flexion (Figure 11)
- Modified Russian Twist with/ without arm swing. The 'MRT' is accomplished while reclining with the buttocks on a raised, fixed seat and with the toes/feet hooked under a rigid padded bar. In this position, the back, shoulders and head are not supported. Then twist at the waist while swinging an arm in the direction of the rotation. (Figure 12)
ON TRACK/FIELD MID-TORSO TRAINING
The weight room training is purely a precursor to what must be achieved at the "on field" situation. This is where true application of the strength gain can be both assessed and true transfer can be completed.
This goal can be achieved in two parts.
- The correct body positioning can be further applied by several "running drills" that are aimed at correct running form (which usually means correct body posture through the mid-torso).
The "A", modified single leg "A", "B", heel flick and high knee drills (Figure 13) are all aimed at increasing the tilting and rotational stresses that are placed upon the mid-torso musculature. These drills can be done slowly at first and progressively sped up as the athlete's ability to hold the correct position improves.
The modified single leg "A" places high levels of stress upon the mid-torso region to hold the pelvis in place while the athletes perform very explosive hip flexion and extension movements in a single leg form.
- The most specific transfer to sprinting is to have the athlete sprint while concentrating on the positioning drilled previously. Sprints should be less than maximal at first, progressing only as the athlete is able to maintain the correct running position. As soon as pelvic stability decreases, the drill should be stopped.
External resistance to increase learning can be in the form of a towing device that the athletes place around their mid-torso and the pressure on this region through each repetition reinforces the control required and increases the level of control as the athlete is having to work harder to maintain good body position under this increased resistance. (Figure 14)
It is important that the resistive load be small enough so that the athlete is able to maintain proper sprint acceleration posture. Bending forward at the waist should be avoided.
In summary, the mid-torso is the link between the upper and lower body and must allow the transfer of strength movements and allow powerful movements of both the upper and lower body to complement each other. The best way to achieve this is to develop mid-torso strength through traditional ways (situps) but ensure functional strength (by more specific mid-torso training methods) is being attained throughout the athlete's training year.