Journal of Strength and Conditioning Research, 2007, 21(4), 1305-1309© 2007 National Strength & Conditioning Association

CORE STABILIZATION EXERCISES ENHANCE LACTATECLEARANCE FOLLOWING HIGH-INTENSITY EXERCISE

JAMES W. NAVALTA* AND STEPHEN P , HRNCIR

'Department of Physical Education and Recreation, Western Kentucky University, Bowling Green, Kentucky42101; '^English Department, Trinity High School, Trinity, Texas 75862.

ABSTRACT. Navalta, J.W., and S.P. Hrncir Jr. Core stabilizationexercises enhance lactate clearance following high-intensity ex-ercise. J. Strength Cond. Res. 21(4):1305-1309. 2007.—Dynamicactivities such as running, cycling, and swimming have beenshown to effectively reduce lactate in the postexercise period. Itis unknown whether core stabilization exercises performed fol-lowing an intense bout would exhibit a similar effect. Therefore.this study was designed to assess the extent of the lactate re-sponse with core stabilization exercises following high-intensityanaerobic exercise. Subjects (A - 12) reported twice for testing,and on both occasions baseline lactate was obtained after 5 min-utes of seated rest. Subjects then performed a 30-second Win-fjate anaerobic cycle test, immediately followed by a blood lac-tate sample. In the 5-minute postexercise period, subjects eitherrested quietly or performed core stabilization exercises. A finalblood lactate sample was obtained following the 5-minute inter-vention period. Analysis revealed a significant interaction (p -0.05). Lactate values were similar at rest (core - 1.4 ± 0.1, rest= 1.7 ± 0.2 mmol-L ') and immediately after exercise (core =4.9 ± 0.6, rest - 5.4 ± 0.4 mmol-L '). However, core stabiliza-tion exercises performed during the 5-minute postexercise peri-od reduced lactate values when compared to rest (5.9 ± 0.6 vs.7.6 ± 0.8 mmol-L '). The results of this study show that per-fonning core stabilization exercises during a recovery period sig-nificantly reduces lactate values. The reduction in lactate maybe due to removal via increased blood flow or enhanced uptakeinto the core musculature. Incorporation of core stability exer-cises into a cool-down period following muscular work may re-sult in benefits to both lactate clearance as well as enhancedpostural control.

KEY WORDS, lactic acid, trunk, lumbo-pelvic-hip complex

INTRODUCTION

^^^d t is well known that exercise at intensitiesJ I above the anaerobic threshold results in the ac-T I cumulation of lactic acid (1, 23). Lactate that

/"^^_^ has been accumulated during exercise isV. cleared primarily by muscle tissue. Hermansenand Vaage reported that glycogen synthesis at this sitemay be the primary mechanism for lactate removal (16),while Astrand et al. confirmed that approximately 50% ofthe lactate formed during intense exercise is convertedinto glycogen in the muscle during recovery (2). It is im-portant to note, however, that lactate is related only toacid-base disruptions and acidity and is a consequence ofworking muscle rather than the cause of acidosis (28).Indeed, the formation of lactate serves as an importantphysiological buffer that protects the muscle cell againstmetabolic acidosis and allows high-intensity exercise tobe extended for a period of time (28). Since muscle aci-dosis has been shown to inhibit oxidative phosphorylation(18), clearance of protons is important for continued mus-cular work.

It has been established that an active recovei*y follow-ing exercise serves to significantly reduce lactate and as-

sociated protons in the postexercise period compared torest (4, 5, 6, 29). Various modes of recovery exercise havebeen shown to decrease the lactate accumulated duringexercise. Denadai et al. found that running or swimmingas recovery modes significantly reduced lactate comparedto passive recovery after high-intensity exercise (9). Bo-nen and Belcastro observed greater decreases in lactatevalues when subjects performed continuous jogging or in-termittent jogging compared to a passive recovery (7).McLellan and Skinner found that lactate removal was en-hanced following cycle exercise when recovery was car-ried out just below the aerobic threshold (22), and Mo-nedero and Donne reported that recovery consisting ofboth cycling and massage was effective in reducing lacticacid buildup following a maximal effort exercise test (24).

The core musculature is considered to be all the mus-cles that have an attachment at the lumbo-pelvic-hip(LPH) complex. Training of these muscles typically fol-lows a progression from core stability (i.e., the ability tomaintain posture during an exercise) to core strength(i.e., improvement in functional contractility of the mus-culature) to core power exercises (i.e., the ability of thecore musculature to produce force that is transferred toother parts of the body during explosive movement). As afoundation, core training exercises involve little joint mo-tion and are designed primarily to improve intrinsic sta-bilization of the LPH complex before core strength orpower exercises are considered in a training program. In-creased ability to stabilize the LPH complex is thought toincrease the performance of various athletic and sport-related skills. Although core stability programs havefailed to show performance benefits in the limited liter-ature to date (32, 33), progi'ams have been successfulwhen aimed at decreasing low back pain or enhancingtrunk musculature (8, 19, 25). In addition, strength andconditioning coaches from all of the major professionalsports in this country have ranked core exercises amongthe top 5 most important exercises for the training oftheir athletes (10-12, 31).

Active recovery typically involves some form of whole-body exercise that allows muscles to metabolize lactateand thereby facilitates quicker removal compared to aresting recovery (4). It is unknown whether exercises in-volving little joint movement directed at the core mus-culature of the LPH complex would also significantly de-crease lactic acid buildup in the postexercise period.Therefore, the purpose of this study was to assess thelactate response to core stabilization exercises followinghigh-intensity anaerobic exercise.

METHODS

Experimental Approach to the ProblemTo examine what eHect activation of the core musculaturehad on lactate clearance, a controlled laboratory experi-

1305

1306 NAVALTA AND HRNCIR

FIGURE 1. Core stabilization exercise 1: supine position with knees bent followed by fle\aLiou of the hips. Consists of 2-secondconcentric phase, 2-second isometric phase, and 4-second eccentric phase.

ment was conducted. Male and female subjects performeda 30-second Wingate anaerobic test to facilitate a rise inlactate concentration, followed by a 5-minute interventionof either quiet rest or core stabilization exercises. Lactatemeasurements were taken at baseline, immediately afterthe Wingate anaerobic test, and following the 5-minutepostexercise intervention period, which was counterbal-anced among subjects.

Following the construct that core exercise programsprogress from stability to strength and then to power, thechosen activities in this study were classified as core sta-bility exercises. Specifically, these exercises involved littlejoint movement while focusing on the intrinsic core mus-culature to stabilize itself prior to or during movement.Core stability exercises were chosen for this study ratherthan strength or power exercises because these exercisesare done initially in core training programs. In addition,all subjects in the present study had the ability to per-form core stability exercises while maintaining properposture, whereas core strength or power exercises shouldbe executed by individuals with developed core muscula-ture who can functionally perform the exercises. Finally,core strength and power exercises are typically performedat higher intensities than core stability exercises, and theconsequences of these exercises to terms of lactate pro-duction was unknown.

Subjects

Twelve healthy subjects (n = 7 male, n = 5 female) vol-unteered to participate in the study. The mean age of sub-jects participating was 22 ± 1 (SE) years, height was 170± 3 cm, and weight was 85 ± 6 kg. All subjects wereactive (exercise >3 days per week) and included both in-dividuals who were not involved in collegiate athletics (fe-male ^ 2, male ^ 3) and those who were (female = 3Softball; male = 1 football, 1 baseball, 2 basketball). Pre-vious to participation, subjects provided written informedconsent that was approved by the university Human Sub-jects Committee.

Procedures

Participants reported to tbe Kinesiology Laboratory on 2occasions separated by at least 3 days. On both occasions,resting blood lactate measurements were obtained via fin-

ger stick using universal precautions following 5-10 min-utes of quiet sitting. Lactate concentrations were deter-mined with the use of an Accutrend Lactate analyzer(Roche Diagnostics, Mannheim, Germany). Approximate-ly 20-25 |xl of whole blood were applied to a test stripthat had been inserted into the analyzer. Once a hloodsample had been applied to the test strip, lactate wasmeasured via enzymatic determination and reflectancephotometry at 660-nm wavelength for 60 seconds.

After resting measurements were obtained, partici-pants were asked to perform the Wingate anaerobic pow-er test on a cycle ergometer (Monarch, Stockholm, Swe-den). The workload for males was determined by multi-plying body weight by 0.085 and for females multiplyingbody weight by 0.075. A finger-stick blood sample wasobtained immediately following the all-out 30-second cy-cle bout and again at 5 minutes postexercise.

Recovery

After the 30-second bout of exercise, subjects received in-structions regarding the postexercise period. On one oc-casion, participants were instructed to sit quietly duringthe postexercise period. On the other occasion, partici-pants performed core stabilization exercises. The order ofrecovery type performed during the postexercise periodwas counterbalanced among subjects. Exercises includedthe following.

Exercise 1. The subject began lying supine with palmsin the anatomical position and the knees bent at approx-imately 90°. From this initial position, the suhject poste-riorly rotated the pelvis and elevated the hips while theshoulders remained on the ground (Figure 1). The con-centric "pushing up" phase was completed in 2 seconds,and the subject held the position at the top in the iso-metric phase for 2 seconds and completed the eccentriclowering phase in 4 seconds.

Exercise 2. Initial position was lying on the fioor pronewith the arms in front of the body. Subjects then exter-nally rotated, retracted, and depressed the shoulder gir-dle while lifting the chest slightly off of the ground (Fig-ure 2). The concentric phase was completed in 2 seconds,the isometric phase was held for 2 seconds, and the ec-centric lowering phase was completed in 4 seconds.

Exercise 3. The subject assumed a prone position on

CORE EXERCISES AND LACTATE REDUCTION 1307

FIGURE 2. Core stabili/.aUuii (.XLivise 2: prone position with the arms in front of the body followed by external rotation, retrac-tion, and depression the shoulder girdle while lifting the chest off of the ground. Consists of 2-second concentric phase, 2-secondisometric phase, and 4-second eccentric phase.

FIGURE 3. Core stabilization exercise 3: prone position onforearms and toes. Position maintained for 8 seconds.

the forearms and toes that was maintained for 8 seconds(Figure 3). ' , ,.

Statistical Analyses

Statistical analyses were carried out using Statistica 5.1(Statsoft Inc., Tulsa, OK). Anaerobic power data were an-alyzed using i-tests for dependent samples. Lactate datawas analyzed using a 2 (gender) X 2 (recovery type) X 3(condition) repeated-measures analysis of variance withsignificance accepted at the p < 0.05 level. Tukey's HSDpost hoc analysis was performed to determine conditionsthat were statistically different from one another. Datawere also compared using Pearson product-moment cor-relation coefficients.

RESULTS

Analysis revealed a significant interaction between recov-ery intervention and condition {p = 0.009). Lactate valueswere similar at baseline (core = 1.4 ± 0.1 mmol-L', rest= 1.7 ± 0.2 mmol L ') and immediately after exercise(core = 4.9 ± 0.6 mmol-L ', rest = 5.4 ± 0.4 mmoLL').

14 -j

12 -

5 10-"5

e 8-

to 6 -

4-

2-

0

• Ffloiale Rest

o Feoule Core

• Male Rest

o Male Core

S-mtnPost

Post

Pre

I i

I iFIGURE 4. Individual lactate values of male and female sub-jects {N = 12) before (Pre). immediately after a 30-second Win-gate anaerobic test (Post), and following a postexercise inter-vention (5 minutes Post). Closed symbols represent lactate val-ues during the trial in which subjects sat quietly during thepostexercise period, whereas open symbols represent lactatevalues during the trial in which core stabilization exerciseswere performed in the postexercise period. An asterisk (*) indi-cates significant difference between interventions (p = 0.05).

However, core stabilization exercises performed duringthe 5-minute postexercise period significantly reducedlactate values when compared to rest (5.9 ± 0.6 mmol-L"^vs. 7.6 ± 0.8 mmol L ', p - 0.05; Figure 4). While maineffects were evident for recovery intervention (p <0.0001) and condition (p = 0.002), the effect of gender wasnot significant (p = 0.877).

Results of the Wingate anaerobic cycle tests are re-ported in Table 1. The peak power output (p - 0.5108)and average anaerobic capacity (p = 0.3691) measureswere not significantly different hetween trials in whicheither rest or core exercises were performed during the 5-minute postintervention. However, subjects displayed asignificant decline in power during performance of theWingate test in which core exercises were to he completedin the posttest intervention compared to rest (p = 0.0478).

Tbere was not a significant relationsbip between Win-

1308 NAVALTA AND HRNCIR

TABLE 1. Anaerobic measures of subjects (A = 12) who com-pleted the Wingate anaerobic power test in which the 5-minutepostintervention was rest (rest trial) or core exercise (core trial).Values are mean ± SE. An asterisk (*) indicates significant dif-ference between trials {p < 0.05).

Anaerobic Peak power Power declinecapacity (W) (W) (%)

Rest trialCore trial

479 ± 30466 ± 29

559 ± 38574 ± 39

29 ± 236 ± 3

gate peak power and lactate concentration 5 minutes fol-lowing the test {r = 0.3460, r = 0.1197, ;; = 0.0977).However, Wingate anaerobic power and lactate followingthe 5-minute intervention was significantly correlated (r= 0.4168, r' = 0.1737, p = 0.0428).

DISCUSSION

In exercising muscle, the formation of lactate serves as aphysiological buffer to protect the cell against metabolicacidosis by acting as a proton acceptor (28). In this re-spect, it is important to note that lactate measures are aconsequence of working muscle rather than the cause ofacidosis (28). Blood lactate concentration in this contextrepresents the net total of lactate production versus clear-ance. At higher levels of intensity, clearance is importantbecause accumulated protons and muscle acidosis havebeen shown to inhibit oxidative phosphorylation (18). Theresults reported here indicate that activation of the corestabilization muscles during a 5-minute recovery periodsignificantly decreases the concentration of lactate mea-sured in the venous blood when compared with rest. Al-though the present study was not designed to determinemechanisms of lactate clearance, a number of possible ex-planations exist.

The first explanation for reduced lactate concentrationfollowing high-intensity exercise may be an increase inblood flow to active muscles and subsequent metabolism.However, in a study performed on canine gastrocnemiusmuscle, Gladden et al. found that increased blood flow165% above normal did not have a significant effect onlactate uptake (14). Although blood flow rates were notmeasured in the current study, it is unlikely that the corestabilization exercises performed increased blood flow toa significant extent to facilitate lactate removal. The morelikely explanation for the increased clearance of lactateseen in the present study during the core exercise inter-vention relates to muscle fiber type. Although muscle fi-ber types vary greatly between individuals, a number ofinvestigators have found that the core musculature has apredominance of type I and type Ila fibers, which is con-sistent with the role of these muscles in maintaining pos-ture (15, 20, 26). It is known that these fiber types takeup lactate quicker (i.e., at lower concentrations) (27) andhave a greater capacity to oxidize lactate compared withglyeolytic type IIx muscle fibers (3). Given the oxidativenature of the core muscles and their role in maintainingposture, it is possible that the activation of these musclesfollowing high-intensity exercise facilitates lactate dis-posal during recovery.

In tbe present study, the core exercise interventiondecreased lactate concentration 22.4% compared to rest.Although the comparison of core exercise with other in-terventions that successfully reduce lactate following ex-ercise is difficult because of varying protocols used to el-evate lactate and the timing of blood sampling following

muscular work, selected studies will be presented. Afterhigh-intensity cycling, 10 minutes of low-intensity cyclerecovery reduced arterial lactate by 13.33% versus pas-sive recovery (4). Denadai et al. used both running andswimming to elevate lactate concentrations and observedlactate values after 1 minute of a passive recovery, swim-ming recovery, or running recovery (9). Running recoveryreduced lactate by 11.25% following swimming and 7.14%following running, while swimming recovery decreasedlactate by 12.5% after swimming and 1.19%' followingrunning (9). Lactate concentrations 5 minutes following a1-mile run were not different among various recovery in-terventions; however, 10 minutes after the bout, inter-mittent jogging reduced lactate by 14.93%, and continu-ous jogging decreased values by 34.19% compared to rest(7).

Previous studies incorporating core stability trainingprograms have failed to show improvement in perfor-mance measures (32, 33). Stanton et al. trained subjects2 times per week for 6 weeks using Swiss ball training,with each session lasting approximately 25 minutes (32).While core stability increased, there was no effect onVOamax, running economy, or running posture (32). Tseet al. trained subjects twice per week for 8 weeks, witheach session lasting between 30 and 40 minutes (33).While core strength increased with this training protocol,no improvement was observed during the performance ofa 2,000-m maximal rowing ergometer test (33). The lackof core stability training to affect performance variablesseems discouraging given the fact that many strengthand conditioning professionals consider core exercises animportant part of their programming (10-12, 31). Per-haps the discrepancy lies not in the core stability trainingprograms but in the performance variables being testedby investigators. In the present study, we found that per-forming core stability exercises following high-intensityexercise effectively reduces lactate concentration. Exer-cise training has been shown to eliminate lactate up to35'% faster following an 8-week program (29). Core sta-bility programs may have an effect on performance vari-ables associated witb the buildup of lactate, such as sub-maximal endurance exercise below the lactate thresholdor repeated exercise bouts in which lactate clearancewould confer an advantage. The assessment of core sta-bility training on these types of performance variableswarrants further investigation.

It should be noted that lactate values observed in thepresent study are somewhat lower than has previouslybeen reported in subjects following the Wingate anaerobiccycle test (20, 30). While the Wingate anaerobic test wasused in the present study merely to induce increases inconcentration rather than maximal lactate values, vari-ous explanations exist to explain the lower measureswhen compared to other studies. The most likely reasonfor low lactate values in the present study is that onlymodest power output was obtained during the Wingatetest. However, the subjects of Jordan et al. produced peakpower output more than double compared to the presentstudy, yet lactate measures were similar ranging from7.86-9.07 mmolL ' (17). The timing of blood samplingafter exercise also affects lactate measurement, as lactatemust diffuse from the muscle compartment into the blood.A common practice is to take blood lactate measures at 3minutes following muscular work (13, 17). Investigatorswishing to obtain peak lactate concentrations have drawnsamples at 3, 5, 7, 9, and 11 minutes postexercise (30) orhad subjects complete 3 successive Wingate cycle tests

CORE EXERCISES AND LACTATE REDUCTION 1309

(21). In the present study, a 5-minute postexercise samplewas chosen to allow subjects time in which to perform thecore stability exercises.

PRACTICAL APPLICATIONS

A variety of interventions have shown that dynamic ex-ercise is successful in reducing lactate concentration fol-lowing intense work. The present study shows for thefirst time that performing core exercises also has the abil-ity to reduce lactate in the postexercise period. Based onthe results of this study, core stability exercises per-formed during a cool-down period following activity wouldhelp facilitate lactate clearance in addition to the positivepostural effects associated with core training. As such,core stability training incorporated into the cool-down pe-riod may be warranted. Although further research isneeded, it is possible that core stability training, whichfocuses on type I and Ila muscle fibers of the trunk, couldfurther enhance lactate removal during or following mus-cular work. The practical application for endurance ath-letes or athletes who perform repetitive high-intensitybouts during competition should be an increased lactatethreshold or an enhanced ability to clear lactate betweenbouts. In addition, athletes who have time between train-ing drills could perform core stability exercises for thedual benefit of reducing lactate levels and enhancing thecore musculature. Finally, core stability training in spe-cial populations with functional limitations would resultnot only in better postural control for these individualsbut also in the ability to carry out work at higher func-tional capacities and for longer amounts of time beforelactate buildup begins to inhihit muscular activity.

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Address correspondence to James W. Navalta. james.navalta@wku.edu.