April 2014

Cleat Smarts: Foot posture and injury risk in pitchers

4cs-iStock_000006258623MD-lrBy Luis A. Feigenbaum, PT, DPT, SCS, ATC, LAT, CSCS; Kathryn E. Roach, PT, PhD; Chris Vitolo PT, DPT; Victoria Bown, PT, DPT; Sabine Gempel, PT, DPT; Natalia Sikaczowski, PT, DPT; Kelly Stapf, PT, DPT; and Michelle Whitaker, PT, DPT

Injuries in baseball are fairly common, with an incidence of 5.8 injuries per 1000 athletic game exposures and 1.9 injuries per 1000 athletic practice exposures in the collegiate ranks.1 The amount of time lost due to injury is significantly higher in pitchers than in position players. Conte et al2 found that, over an 11-year span, pitchers constituted an average of 48.4% of the Major League Baseball disabled list reports (40.6% to 51.2%), representing 56.9% (46.8% to 62.5%) of the total disabled list days. Numerous articles have investigated the causes of shoulder and elbow pathology in baseball pitchers.3-17 Poor pitching mechanics, limitations in shoulder and hip range of motion, alterations of the lumbo-pelvic-hip complex, decreased balance, and abnormal foot postures have all been investigated as possible reasons pitchers are at risk of upper extremity injury.3-19

It is commonly accepted that force development in overhead throwers begins with the lower extremity exerting a force against the ground. The constant unilateral loading of the foot-arch complex against the ground that is inherent to the act of pitching may increase the likelihood that the pitcher will develop asymmetries that lead to increased injury risk. It is conceivable that prior injury to the musculoskeletal system, irrespective of anatomical location, may also lead to the development of asymmetries through compensatory actions during the full body act of pitching. The focus of this clinical commentary is to define and describe measurement of abnormal foot posture, its influence on balance, and clinical interventions as they relate to pitchers.

Foot arch posture measurement

A comprehensive evaluation of a pitcher, either pre- or post­injury, should include an assessment of foot arch posture, specifically, the medial longitudinal arch (MLA).20 The MLA is the primary shock-absorbing structure of the foot.20 Without this arched configuration, large forces at the foot would exceed the physiologic weight-bearing capabilities of the tarsal bones.20

Basmajian and Stecko21 found that only heavy loading of the foot elicited muscle activity about the foot. In their study, loads of 100 to 200 lbs were controlled by only the inert structures of the arch through their ligamentous and bony matrix. With loads of 400 lbs, increased muscular activity was noted, but some muscles continued to remain inactive.21 Therefore, it is essential that the inert tissues that maintain foot arch posture be uncompromised so heavy loads acting on the foot can be mitigated. Because pitching a baseball requires a transfer of body weight through from the stance limb to the lunge limb, the ability of the foot to absorb shock is important. The magnitude of load experienced by the arch during the pitching motion has yet to be investigated.

Clinical measurement of the MLA can be done using various methods that are considered both valid and reliable.22-33 Measurement of the MLA will be determined by the equipment and resources available, but can be evaluated simply through a standard goniometer measuring the longitudinal arch angle (LAA), through digital imaging, by assessing changes in dorsal arch and navicular height with the sit-to-stand test, and with the Foot Posture Index.22-33 Regardless of the measurement tool used, abnormal foot postures are classically described as either pes planus (flat foot) or pes cavus (high arch), while a normally arched foot is considered typical.

Research shows fatigue can also affect foot arch posture measurements. Headlee et al34 found the navicular drop, a measure of pronation and the integrity of the MLA in static stance, increased significantly after fatigue. This may be the result of the intrinsic foot muscles fatiguing, as these muscles help provide substantial support to the MLA in static stance. This change in navicular height occurred regardless of prefatigue arch measurements. Although it has yet to be investigated, it may be of interest to measure the MLA of pitchers throughout the course of a baseball season. Because professional baseball includes a six-week preseason, a 162-game regular season, and, potentially, a postseason of up to 19 games, repetitive unilateral loading of the lower limbs occurs throughout most of the calendar year (February through October), likely leading to some magnitude of fatigue.

In the Headlee et al34 study, navicular drop occurred within the confines of just one exercise session of 75 repetitions of isotonic toe flexion contractions of the intrinsic foot muscles using a custom pulley system. Because the drop in navicular height occurred during just one session of exercise, it is conceivable that the MLA would also drop within the confines of one baseball game, most especially for a starting pitcher, who is subjected to larger exposures due to higher pitch counts.

Variations in foot posture are thought to influence the function of the lower limb and may therefore influence a pitcher’s predisposition to overuse injur­ies.19 Recent findings indicate abnormal foot arch posture is significantly associated with a previous history of shoulder and elbow injuries requiring surgery in elite-level baseball pitchers.19 Additionally, foot contact measurements have been investigated during the pitching motion.10 These measurements have
included stride length, lead foot position, lead foot angle, pelvic range of motion angles, upper trunk angles, and lead knee flexion.10 Deviation in these measures is associated with a potential increase in the likelihood of shoulder or elbow overuse injury.

Foot posture and balance

Pitching, like walking gait, can be described as a controlled fall. Similar to walking gait, a significant amount of time during the pitching motion occurs in single-limb stance. Adequate balance is a prerequisite to maintaining effective single-limb stance. And, as such, it is conceivable to conclude that balance plays an important role in effectively sustaining body mechanics during pitching.

Figure 1. Phases of the pitching motion.

Figure 1. Phases of the pitching motion.

Proper balance requires the ability to maintain the center of gravity within the base of support (equipoise). Balance is the result of a number of body systems working together. Specifically, to achieve balance, the eyes (visual system), ears (vestibular system), and the body’s sense of where it is in space (proprioception) all need to be intact. Even if we assume the visual and vestibular systems are intact in a pitching population, changes in arch posture may have an effect on the proprioceptive system. Deviations in the normal structure of the MLA can produce unbalanced, functionally unstable conditions, as is the case with pes planus or pes cavus.21 Either a pronated foot witih pes planus or a supinated foot with pes cavus may cause abnormal ankle strategies, possibly leading to a loss of balance.35-36 These types of alterations to sensory input increase the risk of injury in athletes suffering from chronic ankle instability,35 and could have similar effects in baseball pitchers who have experienced structural changes to the arch.

Additional factors necessary for maintaining balance include neuromuscular control, normal strength, and adequate range of motion. Because the legs and trunk serve as the main force generators during pitching, it seems clear these forces would be reduced in the presence of poor balance. Proper interaction between the lower extremities and the core musculature also reduces the need for excessive contributions by the shoulder during the pitching motion.12 Reductions in additional stresses on the shoulder may prevent injury, leading to greater durability and health of the throwing arm.

Figure 2. Towel pick-up starting position (left) and ending position (right).

Figure 2. Towel pick-up starting position (left) and ending position (right).

Static and dynamic balance measures of the lower quarter can assess for proprioceptive deficits.37-39 The Star Excursion Balance Test (SEBT) includes dynamic lower extremity movements that require demands similar to those performed during pitching. Cote et al40 incorporated the SEBT as a measure of dynamic postural stability when comparing pronated and supinated foot types. Their primary findings were that foot type affected sway index during static postural stance and dynamic reach measures. Additionally, they found pronators had greater reach than supinators in the anterior and anteromedial directions, while supinators had greater reach in the posterior and posterolateral directions.40 The results are consistent with those of Olmsted et al,35 who found that athletes with chronic ankle instability had significantly less SEBT reach distance while standing on the injured limb compared with the uninvolved limb and compared with the reach distances of healthy individuals.

Muscle activation for the lower quarter has also been investigated during dynamic excursion reaches.41 Hertel et al41 found that different muscle groups tend to be activated with different reaches when individuals perform the SEBT. Vastus medialis oblique and vastus lateralis activity was greatest in the anterior reach directions. The hamstrings were most active in the posterior reach directions. When considered alongside the findings of Cote et al, this information may suggest that pronators are more quadriceps dominant during dynamic excursions, while supinators are hamstrings dominant.

Figure 3. Toe curl starting position (left) and ending position (right).

Figure 3. Toe curl starting position (left) and ending position (right).

The Y-Balance Test, which uses three of the eight SEBT directions, was recently used to assess dynamic balance in 30 high school and collegiate baseball players.42 The study demonstrated that players with previous ulnar collateral ligament tears scored significantly lower on the Y-Balance Test for both stance and lead lower extremities than their noninjured counterparts. This study furthers the argument that, in pitchers, there is a potential association between impaired balance and injuries to the upper extremity.

Balance demands during pitching

The pitching motion is divided into six phases (Figure 1).10,14 Each phase places increasing demands on balance as forces rapidly transfer from the stance limb to the lunge limb (Table 1). These forces are both acceleratory and deceleratory and occur in multiple planes of motion. Pitchers who can generate greater magnitudes of force in the direction of the pitch will produce greater ball velocities.4,8,9-12 In Major League Baseball, increased pitching velocities have been linked to increased risk of elbow injury.9-12

Foot arch posture and injuries in pitchers

Figure 4. Side bridge exercise.

Figure 4. Side bridge exercise.

Abnormal foot postures in pitchers have been associated with higher odds of injury to the upper extremity, severe enough to warrant surgery, than typical feet.19 Feigenbaum et al19 investigated elite-level baseball pitchers to see if there was an association between abnormal foot arch posture, measured with the LAA, and a previous history of shoulder and elbow surgery. The injuries that required surgery had to be associated with the act of pitching. It was shown that the odds of having undergone pitching-arm surgery in pitchers with either type of abnormal foot posture (pes planus or pes cavus) in the stance foot were 3.4 times higher than in pitchers with typical foot posture.

The odds ratio for pes planus on the stance foot was 3.7 and statistically significant, whereas for pes cavus the odds ratio was 3.2 and approaching significance.19 A pes planus foot lacks the stability of the inert tissues to maintain a proper arch. This condition likely limits the ability to effectively load the stance limb. This may be especially true during the wind-up phase, in which muscle loading occurs from the ground up. Additionally, the wind-up phase prepares the pitcher for correct body posture and balance.

Figure 5. Single-limb squat starting position (left) and ending position (right).

Figure 5. Single-limb squat starting position (left) and ending position (right).

The odds of having undergone pitching-arm surgery in pitchers with either type of abnormal foot posture (pes planus or pes cavus) in the lunge foot were 2.9 times higher than in pitchers with typical foot posture.19 The odds ratio for pitchers with a pes cavus lunge foot was 3.4 and approached statistical significance, while the odds ratio for pitchers with a pes planus lunge foot was 2.4 and was not statistically significant.19 Having an abnormal arch posture on the lunge leg may affect the ability to control acceleration and deceleration forces as the ball is released and through the transfer of body weight. In a study investigating runners with pes cavus, increased leg stiffness was noted during landing.43 Leg stiffness associated with a pes cavus foot may have implications related to the ability to absorb deceleration forces about the knee during the deceleration and follow-through phases of the pitching motion.

Because the study by Feigenbaum et al19 was retrospective, it was unable to determine if the presence of an abnormal arch height preceded the injury to the shoulder or elbow or if adaptations in the pitching motion lead to changes in foot posture. However, it is plausible that a once-injured shoulder can lead to alterations in muscle coordination, instability, hypermobility, or muscle imbalances throughout the trunk, lumbo-pelvic-hip complex, and lower quarter. These changes may then lead to the collapsing of the arch of the foot as a means of compensation to generate the forces required in the pitching action.

Interventions

Figure 6. Single-limb dead lift starting position (left) and ending position (right).

Figure 6. Single-limb dead lift starting position (left) and ending position (right).

There are several interventions that may help counteract the potentially negative effects of an abnormal foot arch posture for pitchers.44-48 These include foot orthoses, exercise, balance training, and antipronation taping. Note that these suggestions for intervention are not exclusive, but should be integrated into a comprehensive plan of care.

In-shoe foot orthoses and soft or semirigid ankle orthoses enhance muscular activity of the lower quarter, support the medial longitudinal arch, and improve balance.43-45,47 Hertel et al49 found that, in exercises such as the single-leg squat and lateral step-down, vastus medialis and gluteus maximus activity was enhanced with an off-the-shelf orthotic device, regardless of the posting or foot type. Sesma et al44 identified direction-specific improvements in dynamic reach with orthotic interventions. These improvements in dynamic balance were attributed to increased mechanical support of the MLA, leading to enhanced sensory receptor activity and neuromuscular facilitation.44 Because foot posture can change over time, we recommend orthotic fittings on a relatively frequent basis.50-51 However, we do not recommend the use of ankle orthoses in pitchers. Pitchers tend to dislike the feeling of an ankle brace due to a perception of stiffness and the constraint they feel during their delivery.

An additional consideration for pitchers is that they would likely need stiffer foot orthoses than the average person because of the intense nature of their sport. This would be especially true for their lunge limb, as there would be greater ground reaction forces occurring through the foot. Furthermore, because orthoses require a period of gradual adjustment (weeks to months), implementing their use in this population would best be tolerated during the offseason.

Figure 7. Weight-bearing pelvic drop starting position (left) and ending position (right).

Figure 7. Weight-bearing pelvic drop starting position (left) and ending position (right).

Muscle fatigue has been found to alter navicular height as well as decrease static and dynamic balance.34,52-53 Because fatigue of the foot intrinsic muscles can cause a drop in navicular height, clinicians should include exercises to potentially counteract this effect.34 Exercises that isolate the intrinsic muscles of the foot, such as towel pick-ups and toe curls, should facilitate improvement (Figures 2 and 3). To address fatigue-related balance impairments, an exercise program that focuses on lateral hip musculature, frontal plane strength, and muscular endurance should be initiated (Figures 4-7).52-54

Antipronation or augmented low Dye taping is a common treatment technique used by clinicians to address arch height. Biomechanically, antipronation taping has demonstrated increases in navicular and MLA height, reduced tibial internal rotation and calcaneal eversion, and altered plantar pressure patterns in static stance and dynamic activity (ie, walking, jogging, running) immediately after its application.48 Because there is immediate support after its application, augmented low Dye taping can be utilized before or during a game. This taping technique consists of the low Dye technique, involving spurs and ministirrups, with the addition of two calcaneal slings and three reverse figure sixes that are anchored on the distal third of the leg using a rigid 38-mm wide sports tape with zinc oxide adhesive.48

Luis A. Feigenbaum, PT, DPT, SCS, ATC, LAT, CSCS, is an instructor and chief of sports physical therapy in the Department of Physical Therapy at the University of Miami. Kathryn E. Roach, PT, PhD, is an associate professor and associate chair for research in the Department of Physical Therapy at the University of Miami. Chris Vitolo PT, DPT, is an instructor and clinic manager in University of Miami Hospital’s physical therapy program. Victoria Bown, PT, DPT; Sabine Gempel, PT, DPT; Natalia Sikaczowski, PT, DPT; Kelly Stapf, PT, DPT, and Michelle Whitaker, PT, DPT; are recent graduates of the University of Miami’s Department of Physical Therapy.

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