The effect of grunting on overhead throwing velocity in collegiate baseball pitchers

Introduction

Performance enhancement in sports is an area of great scientific interest and controversy in athletes of all ages. Investment in sports is large worldwide, with the global sports market being valued at approximately 488 billion U.S. dollars in 2018. ¹ Expenditures are not limited to professionals, as the pursuit of athletic success has seen the U.S. pour over $19 billion annually into the amateur youth sports industry. For a very small percentage of the population, success on the field can lead to college scholarships or lucrative professional playing opportunities. These spoils of athletic success have led to debates on the merits of performance enhancing drugs,^2,3 growth of in interest in sports science research, ⁴ and pursuit of the predictors of athletic performance. ⁵

Throwing velocity has been found to be an important contributor to success in overhead sports such as baseball, handball, cricket and water polo.^6,7 In fact, overhead throwing velocity has been found to be the best predictor of success in baseball pitchers. ⁸ As a result, throwing velocity is one of the most evaluated and desired measures of pitching performance. While the development of throwing has been studied since the 1930’s, ⁹ most recent research has focused on training interventions to effect ball velocity.^10–13 A systematic review by Myers et al. ¹⁴ identified various methods that demonstrated meaningful training effects on ball velocity in overhead athletes including isokinetic, resistance, plyometric, weighted ball and multimodal training. Many of the included velocity enhancement programs required training of 4-9 months and some demonstrated an increased injury risk.^13,15

Most studies focused on upper and lower extremity exercise, but those with the largest effect sizes also incorporated trunk exercise. Along with an individual’s throwing velocity, research demonstrates lumbopelvic control and trunk strength and stability are important predictors of pitching success at all levels of competition.^16–20 Conversely, poor core stability has been tied to increased injury rate of the upper and lower extremities in the overhead throwing population.^19,21,22 There is evidence that a large percentage of college pitchers may have poor lumbopelvic control. ²¹ Due to the trunk’s clear role in velocity enhancement, pitching performance and injury prevention, further exploration of novel means of incorporating the trunk into overhead throwing is warranted.

One such method of enhancing trunk muscle activation has been studied in tennis, a sport that shares some kinematic similarities with baseball in positions and movements of the trunk. ²³ Multiple studies have demonstrated that grunting, or vocal disinhibition, improves abdominal muscle activation and velocity and force production in the overhead serve and forehand strokes.^24–26 Similar forms of forced exhalation and vocalization, such as the ki-hap used in taekwondo, have been shown to improve upper extremity muscle force, corticospinal excitability and trunk muscle activation.^27–32 The trunk plays a key role in the kinetic chain of the baseball pitch, working with the legs to produce over half of the kinetic energy, which is transferred to the upper extremities during the acceleration phase of the throw.^14,33 Thus, it seems likely that the increased velocity found during grunting in the overhead tennis serve could also be produced during overhead baseball throwing.

The purpose of this study was to investigate the effect of grunting on overhead throwing velocity in baseball players. Velocity was measured when players completed overhead throws with and without grunting. We hypothesized that throwing velocity would be greater when players grunted. This study may help strength and conditioning professionals develop a simple and efficient method of enhancing throwing velocity in overhead athletes.

Materials and methods

Standing overhead throwing velocities were measured in collegiate baseball players using a radar gun in a randomized order of grunting and non-grunting conditions. The repeated measures design was chosen to eliminate the introduction of any possible confounding from subject, temporal or environmental variability. Randomization of grunting conditions was employed to control for practice effects.

Procedures

Subjects provided data regarding their age, height, weight, handedness, and experience with grunting while throwing. None of the subjects reported routinely grunting while throwing. Demographic data were collected prior to the subjects performing a self-selected warm-up. Each subject performed their own individualized warm-up to mimic their typical throwing conditions. Once the subject reported they were prepared to throw, they viewed a 30-second video clip on a laptop showing a professional pitcher grunting while throwing. Following this, the subject was read a script describing the desired technique and timing of the grunt. Subjects were instructed to perform an audible grunt during the acceleration phase of their throw, as research has shown rectus abdominus activation typically peaks just before ball release. ³⁴ Three practice grunt trials were performed using a standard-weight (5 oz/141.7 g) baseball and subjects received verbal feedback on the timing and technique of their grunts. Acceptable grunt volume was broadly defined as being audible to the researcher operating the radar gun, rather than strict use of a decibel meter. This was done to avoid the potential deleterious effects on throwing performance that could occur from shifting the participants’ focus internally on grunt performance, instead of maintaining an external focus on maximum throwing velocity. ³⁵

After warm-up, subjects were randomly assigned to 1 of 2 testing conditions. In condition 1, subjects completed three grunting throws followed by three non-grunting throws. In condition 2, subjects completed three non-grunting throws followed by three grunting throws. During the throws, subjects stood on a standard dirt pitching mound 10 inches above the rest of the playing field. Each subject performed their throws from the stretch position and was given a 15-second rest between each throw. Maximal ball velocity was measured using a calibrated radar gun (STALKER PRO II, Applied Concepts, Inc.; Texas, USA) specifically designed for baseball applications with an accuracy of ± 0.16 km⋅h⁻¹ and a speed range of 1.6-482.8 km⋅h⁻¹. The radar gun (calibrated before each subject) was held 0.3 m directly behind the catcher in a straight line with the subject and a height that allowed a clear view of the thrown ball’s path. The catcher’s glove was placed at the posterior corner of home plate, 18.4 m from the pitching rubber (Figure 1). Throws were only included in analysis if the catcher was able to catch the ball in a standard crouched position to control for throwing accuracy. Because the subjects warmed up before data collection, no subject made more than one uncatchable throw. Subjects were not given any feedback on throwing velocity until all trials were completed. Peak velocities of all throws at ball release were recorded, and the values for each condition were averaged and used for data analysis. Because our data were collected outdoors, we monitored weather conditions, ambient temperature and wind velocity during each subject’s trials to ensure environmental consistency.

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Figure 1.

Data collection setup.

Results

The average ambient temperature during data collection was 70° F (68–72° F) with wind speeds ranging from 1.60 to 8.05 km⋅hr⁻¹. Due to the brief amount of time required for each throw and calm winds, atmospheric conditions were consistent throughout each subject’s trials. Intraclass correlation coefficients for throwing velocity in the grunt and non-grunt trials were high (Table 1). ³⁷

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Table 1.

Test-retest reliability.

Type of measure	ICC	CI95	p
Ball velocity
Grunting	.807	.662–.904	<.001
Non-grunting	.882	.785–.943	<.001

ICC: intraclass correlation coefficients; CI: confidence intervals.

Results of the paired-samples t-test (Table 2) showed that subjects threw with an average of 3.6%, or 4.40 km⋅hr⁻¹ (95% CI, 3.30 to 5.50) greater velocity when grunting than without grunting (t(23) = 8.27, p <.001, d = 0.73). None of the subjects reported routinely grunting while throwing at intake and all experienced an increase in average throwing velocity when grunting, with gains ranging from .32 to 9.07 km ⋅ hr⁻¹. Age (r_p = .168, p = .432), height (r_p = .043, p = .841), weight (r_p = −.174, p = .417) and handedness (r_pb = .103, p = .632) had no significant relationship with the magnitude of change in velocity between throwing conditions.

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Table 2.

Overhand throwing velocity during grunting and non-grunting conditions.

	Overhand throwing velocity (km⋅hr–1)	CI95
Grunt	127.96 ± 5.82a
Non-grunt	123.56 ± 6.29a
Difference between conditions	4.40 km⋅hr−1b	.301–.501

^aData are mean ± SD.

^bp < .05.

Discussion

The findings of the current study demonstrate that overhead throwing velocity increased significantly when grunting. This effect is similar to a study by O’Connell et al. ²⁵ which found that grunting increased overhead serve velocity in tennis players by 4.91%. These increases in velocity could lead to significant performance gains in pitchers. Research by Whiteside et al. ⁸ found that every 1% increase in pitch speed produced a 2.3% improvement in fielding independent pitching (FIP), a key performance metric. Research suggests several possible mechanisms by which this increased velocity is being produced, including increased muscle activation, enhanced neuromotor excitability and improved efficiency of energy transfer through the kinetic chain.

Previous studies by Li and Laskin ³⁰ and Ikeda et al. ²⁹ demonstrated that forced exhalation significantly increased peak muscle forces in the finger flexors, shoulder adductors, elbow extensors and knee extensors, which are all active during the overhead throwing motion. ³⁴ These increases could be attributed to enhanced corticospinal tract excitability that occurs during forced exhalation. ³¹ In addition to its effect on the muscle forces of the extremities, grunting and forced exhalation has been shown to increase the peak muscle forces of key trunk stabilizers including the internal oblique, external oblique and transversus abdominis.^25,27,38 Motor control and stability of the trunk has been consistently linked to pitching performance^20,21 and injury risk.^16,19

As a key part of the kinetic chain, the trunk muscles initiate the transfer of energy to the upper extremity during the acceleration phase of overhead pitching, which lasts from maximal shoulder external rotation to ball release. ³³ During this phase, core muscle activation is high, moving the trunk from a hyperextended to flexed position ³⁹ and concluding with peak rectus abdominus force just before ball release. ³⁴ Previous research has suggested that having a relatively stiff trunk that efficiently transfers energy from the lower extremities may be more important than rotational power in producing throwing velocity. ⁴⁰ In particular, the transverse abdominus has been shown to play a critical role in trunk stability ⁴¹ and is the first abdominal muscle recruited during forced exhalation maneuvers like grunting. ²⁷ Considering the evidence, it seems likely that the increased throwing velocity observed in the present study could have resulted from a combined effect of increased muscle forces and more efficient transfer of forces from the lower extremities and trunk to the throwing arm.

There are limitations to this study. The volume of each grunt was not formally measured. Future study may determine if grunt volume is a significant factor in determining its effect on throwing velocity. Additionally, this study was performed on baseball players between the ages of 18 and 24 years, affecting its generalizability.

Additional considerations for future study may offer insight into the competitive advantage that is provided by grunting. Previous studies in tennis have suggested that grunting may effect an opponent’s anticipatory judgment of a shot’s trajectory due to distractive effects or mechanisms of multisensory integration.^42,43 As a result, grunting may provide the baseball pitcher an advantage of, not only enhanced throwing velocity, but also impairment of the batter’s ability to perceive pitch trajectory. In our study, we utilized a sample of collegiate-level pitchers. Further research is needed to determine if grunting is similarly beneficial for players of greater or lesser skill and pitching experience. However, the simplicity of instruction makes grunting a feasible method of velocity enhancement at most levels of play.