effects o f balance training on selected skills

Journal of Strength and Conditioning Research, 2006. 20(21, 422-428 2006 National Strength & Conditioning Association

EFFECTS OF BALANCE TRAINING ON SELECTEDSKILLSJAMES A. YAGGIE' AND BUIAN M. CAMPBELL^

'Applied Biomechatiks Laboratory, Department of Exercise and Nutritional Sciences, San Diego State University,San Diego, CA 92182; -Kinesiology Division, Bowling Green State University, Bowling Green, OH 43403.

ABSTRACT. Ya^gie, J.A., and B.M. Campbell. Effects of balancetraining on selected skills. J. Strength Cond. Res. 20(2):422^28.2006.The purpose of this study was to determine the effect ofa 4-week haiance training program on specified functional tasks.Thirty-six suhjects lage - 22.7 2.10 years; height = 168.30 9.55 cm: weight = 71.15 16.40 kg) were randomly placed intocontrol IC; n ^ 19) and experimental groups (Tx; ii = 17). TheTx group trained using a commercially available balance train-ing device (BOSU). Postural limits (displacement and sway) andfunctional task (time on ball, shuttle run, and vertical jump)were assessed during a pretest (Tl), a posttest (T2), and 2 weeksposttraining (T3). Multivariatf repeated measures analysis ( =0.05) revealed significant difTerences in time on hall, ^buttle run,total sway, and fore/aft displacement after the exerci.se inter-vention (T2). T3 assessment revealed that total sway and timeon ball remained controlled; however, no other measures wereretained. Balance training improved performance of selectedsport-related activities and postural control mea.sures, althoughit is unclear whether the effect of training would transfer togeneral functional enhancement.

KKY WOKU.S. core stability, exercise, proprioception, fitness

INTRODUCTIONompetitive and recreational sports are depen-dent on multiple components of training and thedevelopment of stren^h, power, and endurance(13, 15, 19). Balance training is a relatively re-

cent phenomenon in the fitness industry that has devel-oped into a primary point of interest for consumers andfitness professionals (5, 14, 16, 23). Balance is comprisedof the dynamic reactions of involuntary sensations andimpulses that maintain an upright stance and is neces-sary for most functional movements (7, 10, 17, 19). Suc-cess in athletic and recreational activities depends onboth balance and functional movements. The proper func-tion of al! active muscles and the velocities at which thesemuscular forces are applied are crucial (23). Many rec-reational activities require lateral, forward, and back-ward movements during which the center of gravity(COG) is often at the edge of the base of support (BOS)(23). To maintain balance, it is necessary to have a func-tional awareness of the BOS to better accommodate thechanging COG (6). The goal of balance training is to im-prove balance tbrough perturbation of the musculoskel-etal system that will facilitate neuromuscular capability,readiness, and reaction (5, 21, 33).

In recent years, several commercial products havebeen developed to enhance and improve proprioceptivetraining. The development of the Biomechanical AnklePlatform System (BAPS) board mirrored the uniaxial andmultiaxial boards that were designed for rehabilitative

purposes to increase proprioeeptive activity in injured an-kles (9, 29). Reebok's Core board was designed to increaseproprioception and core stability and was targeted forthose outside the commercial rehabilitative setting. TheKinesthetic Ahility Trainer (KAT) (18) and the BalanceMaster (12, 14, 27) are computerized mechanical plat-forms designed to enforce calculated perturbations andvisual stimulations to challenge the muscular and visualsystems.

The Both Sides Up balance trainer (BOSU; FitnessQuest, Canton, OH) is an apparatus that was designedfor balance training within the athletic and recreationallyactive population. The design of the BOSU provides a sol-id plastic base integrated with an inflatable rubber blad-der that resembles a halved Swiss ball. The BOSU has asolid surface facing down that provides an unstable sur-face on stable ground (Figure 1). Furthermore, it is de-signed to improve stability not only while tbe user main-tains an upright position, but also when the user is in ahorizontal position (i.e., during abdominal exercises).

Functional ability can be exemplified by tbe perfor-mance of a sport-related task (35). Tbese tasks requireappropriate control of the neuromuscular and musculo-skeletal systems, including the proprioceptive system. Itis presumed that balance training has the most profoundeffect on the somatosensory and proprioceptive controlsystems (2, 23, 25, 35); however, conventional means ofassessment must quantify the training effects gained byproprioceptive control, and not proprioception itselfThrough skill assessment, inferences regarding interven-tions may offer insight into the effects on the propriocep-tive system (23, 24, 32).

Several studies (2, 9, 23, 24, 32) have found that bal-ance training enhances proprioceptive control. Most ofthese studies have investigated subjects with chronicallyunstable or injured joints of the lower extremities com-pared witb untrained healthy subjects. Few investiga-tions bave examined the efTects of balance training innoninjured individuals (5, 14, 16, 33). Rozzi et al. (28)found that a 4-week balance training program was an ef-fective means of improving joint proprioception and sin-gle-leg standing ability in subjects with unimpaired an-kles. The limited usage of the noninjured population inthis context characterizes an underrepresentation ofhealthy, physically active individuals interested in sta-bility training.

The purpose of this study was to determine the influ-ence of a balance-training protocol, using the BOSU, ondynamic stance and functional performance in healthy,recreationally active individuals.

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BOSU BALANCE TRAINING 423

a). b).

FIGURE 1. Photographs of the Both Sides Up balanee trainer,la) Diameter of the base is 68 cm. (b) Approximate heightwben inflated is 25 cm.

METHODSExperimental Approach to the ProblemAll subjects completed a pretest (Tl), a posttest (T2), anda retention test (T3) designed to determine whether in-dividuals experienced a positive response from a balance-training program and whether they retained those posi-tive effects 2 weeks after training was terminated. Priorto the inception of training, postural sway, postural lim-its, vertical jump height, shuttle run time, and time onthe BOSU were assessed (Tl). Repeated assessmentswere performed following a 4-week training protocol (T2)and again following a 2-week suspension of training (T3).Previous research indicates that a 2-week cessation oftraining can result in a significant reduction of trainingeffects, related to physiological and neuromuscular im-plications of deconditioning (4).SubjectsThirty-six healthy reereationally active volunteers (meanage = 22.47 2.10 years; height = 168.30 9.55 cm;weight = 71.15 16.40 kg) participated in this investi-gation. In compliance with Institutional Review Boardprocedures, all subjects were required to read and signinformed consent documents. Subjects were screened viainterview and self-report regarding activity behavior andinjury status. Those participating in vigorous activity andcardiovascular training (3 to 5 times per week) and mus-culoskeletal resistance activity (2 to 3 times per week)were considered recreationally active. Subjects reportedhaving no lower extremity trauma within the 2 years pri-or to the investigation. All were free of known balancedisorders and were considered to he in good health, ac-cording to the Physical Activity Readiness Questionnaire(PAR-Q). Those with corrective lenses were encouragedto wear them for each testing and training session. Sub-jects were paired for gender and self-reported activity lev-el and were randomly assigned to BOSU-trained (Tx; n= 17) and untrained (C; n ^ 19) groups.ProceduresLimb Dominance and Postural Sway Atises.'iment. Prior topretesting, lower limb dominance was determined by hav-ing participants complete a ball-kick test and the step-uptest.

To assess postural sway parameters, the subjects wereinstructed to stand on an Advanced Medical Technolo-gies, Inc. (AMTI) force platform (Model OR-6; AdvancedMedical Technologies, Inc., Watertown, MA} using theirdominant leg with the nondominant leg flexed at a 45"angle at the knee joint and the arms placed across their

FIGURE 2. Schematic of sbuttle run.

chest. A visual target was placed approximately 3 m infront of the subjects as a focal point. Subjects were theninstructed to lean forward as far as possible without lift-ing any part of their foot off the platform, attempting tomaintain hip and knee extension at all times. Followinga familiarization trial, 3 15-second trials were performed,with the first 10 seconds standing upright and the last 5seconds leaning forward. Subjects were given 2 minutesof rest between trials. This method is similar to thosefound in the literature (3, 34).

Functional Tasks. Three functional tasks were used inthis investigation, balance on the BOSU (TOB), verticaljump (VJ), and shuttle run (SR). These assessments wereselected because of tbe specificity of the balance device(TOB) and the ability to assess the influence the trainingon power (VJ) and agility (SR).

Time on Ball. Subjects were instructed to stand on theBOSU using their dominant leg. Once comfortable, theywere asked to close their eyes and maintain that positionwithout falling or touching the ground or the BOSU withtheir nondominant leg. If the subject lost control of thatposture, the investigator stopped the watch and recordedthe time spent on the BOSU.

Shuttle Run. The shuttle run course used in this in-vestigation (Figure 2) was similar to that found in theliterature (34). The course included several directionalchanges and involved sprinting, backpedaling, sidestep-ping, and starting-and-stopping patterns. The time takento complete this running course was measured by the in-vestigator using digital timing pads placed at the startand finish (DT2819, Melbourne, FL). Subjects completedseveral practice trials to familiarize themselves with thecourse. Following the practice trials, 3 running trialswere performed by each subject with 2 minutes of restbetween each trial.

Vertical Jump. The vertical jump protocol used in thecurrent investigation has been described in the literature(34). Subjects performed a standing vertical jump withtheir preferred arm adjacent to the wall. The subjectsreached up with the selected hand, keeping their heels onthe floor and flrmly marked the wall by touching theinked flnger to the wall. The height was recorded.

Subjects were instructed on the proper form of a ver-tical jump. Each participant was allowed a countermove-ment prior to take off as long as a step approach was notused. The subjects were instructed to touch the wall withtheir inked hand at the peak of the jump. The distancebetween the standing reach and vertical jump marks wascalculated. The average from 3 vertical jump trials wascalculated and used for the analyses.

Training Procedure. The balance training on theBOSU began within 2 days following the pretest. The

424 YAGGIE AND CAMPBELL

a). b).

FIGURE 3. Example of exercise progresHion of ball stancewith la) unilateral stance on ball, and (b) unilateral stancewith trunk excursion on ball.

training protocol consisted of exercises progressing fromthe simplest to most complex sessions. The protocol thatwas used in the current investigation was a commerciallydeveloped training program that is provided with theBOSU at the point of sale (8). The prescribed protocolincluded activities that are consistent with exercises de-scrihed in the literature (2, 21, 23, 31).

The Tx group trained on the BOSU 3 times per weekfor approximately 20 minutes. Each week the suhjectswere presented with more difficult variations of exercisesto replace those already mastered. Mastery was definedas remaining on the BOSU for a period that was morethe 2 times longer than the previous session without fall-ing off or adding support. The selected exercises were de-signed to challenge one or more of the sensory systemsintegral in maintaining halance. Additions and modifi-cation to the battery of exercises included rotating thehead laterally, tilting the head upward, keeping the eyesopen or closed, and using the trunk excursion or lean(Figure 3).

All suhjects were asked to maintain a log to track theamount and intensity of elective activity during the test-ing period. Inclusion of each subject was hased on thefrequency of activity (3 to 5 sessions per week) and thenumber of average hours logged (1 to 3 hours per occur-rence). Those that cataloged the minimum hours withoutexceeding a maximum value (15 total hours per week)were included in the study. Activity included total timein participation of recreational activities and sports,strength and resistance training, exercises classes, flexi-bility training, and cardiovascular exercise. Initially,evenly numbered groups were recruited for the study;however, these criteria lead to the exclusion of data from4 subjects (C - 1; Tx - 3).

Instrumentation. Each subject's balance was assessedusing the AMTI force platform in conjunction withBalanceTrak software (Motion Analysis Corporation,Santa Rosa, CA) to detennine specific sway patterns. The

BalanceTrak software produced a trial duration of 15 sec-onds and sampled data at a rate of 200 Hz. The force platewas calibrated prior to data collection hefore each session.

Quiet Stance. Totai sway (TS), medial-lateral sway(MLS), fore-aft sway (FAS), fore-aft displacement (FAD),and medial-lateral displacement (MLD) were collected foreach suhject during each testing session (Tl, T2, and T3)and were compared across time and treatment.

Lean Test. During the unilateral forward lean test de-scribed by Blaszczyk et al. (3), voluntary MLD and FADof the center of foot pressure was estatalished while thesubject maintained a rigid body posture and leaned for-ward at the ankle joint. Correct body posture was verballyexplained, demonstrated, and observed by the investiga-tor prior to the testing sessions. The software calculatedthe excursion of the x and y values and determined themaximum FAD and MLD. Trials exhibiting incorrectleaning posture were discarded and not included in theanalysis.Statistical AnalysesSPSS for Windows (Version 13.0; SPSS, Inc., Chicago, IL)was used for statistical analyses. Data were recorded andcoded for gender and treatment group. A repeated mea-sures multivariate analysis of variance (MANOVA; a