Lower Body Characteristics [.pdf]
Calf strength and hip flexibility both play important roles in vertical jumping ability. Baechle and Earle (2000) define flexibility as the range of motion about a body joint. Moscov, Lacourse, Garhammer, and Whiting (1994) further define flexibility as either static or dynamic. Static flexibility refers to the maximum range of motion at a joint during a slow graded movement and is limited by one or more connective-tissue structures, including the joint capsule, muscle, tendon, and skin. Dynamic flexibility refers to the maximum range of motion of a joint during a ballistic movement. Dynamic flexibility has been a valid indicator of success in ballistic sport activities (Moscov et al. 1994).
Moscov et al. (1994) investigated three groups of ballet dancers; advanced level, intermediate level, and beginner level to determine whether there were differences in static and dynamic hip flexibility, leg power and leg strength. The test administered for leg strength was the one repetition maximum on the leg press machine. To determine leg power a vertical jump test was performed. Static hip flexibility was measured by summing hip range of motion during flexion and hyperextension. Dynamic hip flexibility was determined while each dancer performed a jete, which is a springing step from one foot to the other in which the leading unsupported leg is thrust into the direction of the leap. Joint markers were placed on the greater trochanter, lateral epicondyle and medial epicondyle to facilitate video analysis of the angle of interest (Moscov et al. 1994).
The dancers completed a warm up and then performed three exercises: plie, tendu, and grand battement, each requiring 2-3 min. of work. Each exercise was completed on both sides of the body. Next, the dancers performed the vertical jump protocol. Three jumps were completed with the standing reach protocol. Lastly, they performed the one repetition maximum on the leg press. The order of exercises went from the least fatiguing to the most fatiguing. This was so the vertical jump scores were not skewed by the intensity of the leg press 1 repetition maximum (Moscov et al. 1994).
Moscov et al (1994) showed that there were no significant differences between the three ability levels for dynamic hip flexibility, leg power, and leg strength. However, there was a significant difference in static hip flexibility between the advanced group and the beginner group. Static hip flexibility between advanced level dancers and beginners was related to the extent of ballet training. In contrast, the extent of ballet training did not appear to effect dynamic flexibility. Moscov et al. (1994) noted that dancers devoted a large portion of time trying to improve static hip flexibility but there appeared to be no justification for this if the primary goal was to improve dynamic hip flexibility. There were no differences in leg strength and leg power between the groups. This was due to the inadequate overload of training. The load was not great enough to elicit an increase in leg strength and therefore leg power. There appeared to be no relationship between the amount of hip flexibility a dancer has to vertical jump height (Moscov et al. 1994).
Common assumptions that the greater range of motion athletes have in their joints; a greater level of performance will result. Lee, Etnyre, Poindexter, Sokol, and Toon (1989) investigated the 1986 United Stated National Olympic Festival Volleyball team. They compared hip flexibility to jumping height of 24 men and 22 women. Vertical jump was measured using the Vertec jump measuring device. The athletes performed a standing vertical jump and an approach vertical jump. A stainless steel goniometer was used to measure hip flexion. Hip flexion measurement was taken while subjects were lying supine with the right leg maximally flexed and both knees fully extended (Lee et al. 1989).
Lee et al. (1989) showed that there was a strong relationship between the two jumping measures for both the men and the women. A significant and positive correlation was calculated between the approach vertical jump and hip flexibility in the men. For women significant and negative correlations were found between standing vertical jump and hip flexibility and approach vertical jump and hip flexibility (Lee et al. 1989). The researchers showed that a positive correlation supported that increased hip flexibility was related to greater jumping height in men. The opposite occurred for the women. The women with the least flexibility in their hips jumped the highest. Clarity as to why this occurred is unknown. The only possibility the researchers could determine was, that the anatomical differences between men and women in the hip joint. The increased flexibility in the hip joint benefited the men more so than the women. The women on average had greater hip flexibility than the men (Lee et al. 1989).
Brown, Gorman, DiBrezzo, and Fort (1988) conducted a study measuring the improvement in lower body explosive power after a six- week training using three modes. The three modes were selected to represent different portions of the wholistic athletic training model. The three modes were static training, performed one 30 sec. static effort combining hip an knee extension using electronic, digital strength apparatus. The second mode was dynamic training. The group performed three sets of 8-12 repetitions on a leg press machine with two min. rest in between sets. The resistance was set to near fatiguing levels. The third group was the motivational vertical jump, the subjects were motivated to attain their maximal jump for 10 successive repetitions. Subjects also underwent a goniometric test, which measured hip flexibility as part of their assessment.
The researchers showed significant increases in anaerobic power for the dynamic and motivational vertical jump groups (Brown et al. 1988). There was little relationship between flexibility and anaerobic power. Therefore, the researchers Brown et al. (1988), Lee et al. (1989), and Moscov et al. (1994) had similar findings. Hip flexibility had little if not any relationship to vertical jump with the exception of Lee et al. (1989) men had a relationship between hip flexibility and vertical jump, the women did not.
The calf muscle (gastrocnemius) plays a major role in jumping ability. Stern (1991) stated that because the ankle is a hinge joint, the ankle allows movement from a maximum dorsiflexion of 20 degrees through neutral to a near maximum plantar flexion of 50 degrees. Because of this, the ankle allows the calf muscle work when fully contracted and not transfer the stress to the bones. The calf is mostly composed of type II muscle fibers (fast twitch). The calf flexes the knee and plantar flexes the ankle. When the knee is bent the contractability is less in the calf and the soleus muscle is responsible for extending the foot. The soleus is made up of mostly type I (slow twitch) muscle fibers (Stern, 1991).
Signorile, Duque, Cole, and Zink (2002) compared the muscle utilization patterns of two major muscles in the triceps surea group during performance of multiple high speed constant resistance exercise performances. The two muscles were the soleus and the gastrocnemius. The gastrocnemius was divided into the lateral head and the medial head. The researchers also examined the antagonist muscle group called the tibialis anterior. Signorile et al. (2002) stated: The muscles of the triceps surae group differ in their structure, anatomical position, function, and fiber type characteristics. There differences may dictate different utilization patterns among the muscles in the group. Structurally, the gastrocnemius is a bipennate muscle, whereas the soleus is a fusiform muscle. Anatomically the medial and lateral heads of the gastrocnemius have their origins on the posterior surfaces of the medial and lateral femoral epicondyles, respectively. In contrast, the origin of the soleus is along the upper two thirds of the posterior surfaces of the tibia and fibula. However, both muscles share a common insertion on the posterior surface of the calcaneus via the Achilles tendon (p. 434).
Signorile et al. (2002) stated that because of the position of these muscles, they shared the common action of plantar flexing the foot. The gastrocnemius also helps in the action of flexing the knee because it passes across the knee joint. Therefore, when the knee is bent, the gastrocnemius is less effective when plantar flexing the foot when the knee is bent as compared to when the knee is extended (Signorile et al. 2002).
Since the gastrocnenius has two heads; lateral and medial, they too have different functions. The medial head is of larger size and the origin is closer to the midline of the knee joint and slightly more dorsal that the lateral head. The lateral head has more sarcomeres than the medial head, and therefore the two have different length-force relationships (Signorile et al. 2002). The lateral head is comprised of 49% slow twitch muscle fibers and the soleus is comprised at approximately 80%. Therefore, the gastrocnenius can produce faster and more explosive movements. The soleus is more endurance oriented and can sustain low intensity, long duration activities (Signorile et al. 2002). Signorile et al. (2002) had 11 subjects perform three sets of 50 isotonic plantar flexions on a Biodex dynamometer using three different knee angles. The knee angles were 90, 135, and 180 degrees. Both the root mean square amplitude and the integrated signal of electromyography (EMG) were analyzed to quantify the level of activity in the muscles. The EMG reflects motor unit recruitment, firing rate, firing duration, and propagation velocity (Signorile et al. 2002).
Signorile et al. (2002) showed that there were significant differences among the muscles at the different angles. At 90 and 135 degress the tibialis anterior produced a lower level of electrical activity than the other muscles. At 180 degrees the medial head produced significantly higher root mean square amplitude EMG values than the soleus and the tibialis anterior, but the lateral head was not significantly different. Among the different knee angles there were no significant differences for either the tibialis anterior of the lateral head. There were significant differences for the soleus and the medial head (Signorile et al. 2002). The soleus produced less activity at 180 degrees than at 90 and 135 degrees and the medial head produced greater activity at 180 degrees than at 90 and 135 degrees. The researchers showed similar findings with the integrated signal EMG. Signorile et al. (2002) stated: The results of the EMG analysis of the medial head, lateral head, and soleus muscles reveal notable differences in muscle utilization patterns because of the knee angle. Because the lateral head and the medial head cross both the knee and the ankle joints, their length and relative tension during plantar flexion would be affected by the changes in knee angle (p. 438).
The soleus has little effect on the knee angle because of its origin. Therefore, the only impact that might be expected due to the change of knee angles would be with the lateral and medial heads of the gastrocnemius (Signorile et al. 2002). Taking this information and using it practically, one would say to train the gastrocnemius with the knee angle at 180 degrees and to train the soleus with a knee angle at 90 degrees (Signorile et al. 2002).
The information provided by Signorile (2002) helps further understand the research performed by Fukashiro and Komi (1987). They examined the joint movement and the mechanical power of the lower limb during three types of vertical jumps. The three jumps were a maximal vertical jump from a squatting position, a maximal vertical jump from an erect position with a countermovement, and repetitive submaximal hopping in place with preferred frequency. The jumps were filmed with a 16 mm cine-camera from a side view. The vertical ground reaction forces were taken for analysis. After analyzing the three jumps, the countermovement jump represented a large amount of force in sequence from the hip, then the knee, and then the ankle. The squat jump was similar to the countermovement but to a lesser degree at the hip. The order of force application was the same as the countermovement jump. The hopping was very different from the squat and countermovement jumps. The largest force came from the ankle, next was the knee, and the smallest was the hip joint. Fukashiro and Komi (1987) showed that the movements in the squat jump and the countermovement jump depended primarily on the hip extensors, whereas the hopping movement depended on the ankle plantar flexors (soleus, gastrocnemius, tibialis posterior, peroneus group, flexor digitorum longus, and flexor hallucis longus). The mechanics of the hop signify the last phase of the vertical jump. The researchers, Signorile et al. (2002) and Fukashiro and Komi (1987), and Stern (1991) illustrate that the calf muscles play a big role in vertical jumping ability.