The Effectiveness of Traditional and Sling Exercise Strength Training in Women

THE EFFECTIVENESS OF TRADITIONAL AND SLING EXERCISE STRENGTH TRAINING IN WOMEN

BETHANY D. DANNELLY,SARAH C. OTEY,TED CROY,BLAIN HARRISON,COREY A. RYNDERS, JAY N. HERTEL, AND ARTHUR WELTMAN Department of Human Services, Curry School of Education, University of Virginia, Charlottesville, Virginia

ABSTRACT improved sling exercise push-ups supports previous ﬁndings Dannelly, BD, Otey, SC, Croy, T, Harrison, B, Rynders, CA, suggesting functional superiority of CKCE.

Hertel, JN and Weltman, A. The effectiveness of traditional and KEY WORDS closed-kinetic chain, open-kinetic chain, Redcord, sling exercise strength training in women. J Strength Cond Res 1RM, isokinetic dynamometry, balance 25(2): 464–471, 2011—Strength training often combines closed-kinetic-chain exercises (CKCEs) and open kinetic-chain INTRODUCTION exercises (OKCEs). The CKCE may be more effective for trength training programs typically combine improving performance in lower-body training. Recently, we closed- and open-kinetic-chain exercises to im- reported upper-body CKCE (using a commercially available prove overall strength. Open-kinetic-chain exer- system of ropes and slings, Redcord AS, Staubo, Norway) was cises (OKCEs) are performed with the terminal as effective as OKCE training for strength gains and that CKCE S segment, typically the hand or foot, free to move with the load was more effective than OKCE for improving throwing applied to the distal portion of the limb such as in the bench performance. To our knowledge the effectiveness of a strength press orlegextensionexercise.These exercisesareusuallynon– training program that uses exclusively CKCE is unknown. In this weight bearing, with the movement occurring at the elbow or study, we examined the effectiveness of CKCE vs. OKCE knee joint (6,13). Closed-kinetic-chain exercises (CKCEs) are strength training programs in women enrolled in an introductory exercises performed where the hand (for arm movement) or strength training program. Twenty-six participants were ran- foot (for leg movement) is fixed and cannot move, such as domized to OKCE (traditional exercises) or CKCE (sling-based a squat or push-up. The hand or foot remains in constant exercises). Participants completed 6 sets per week for 13 contact with the surface, usually the ground or the base of a machine. These exercises are typically weight-bearing weeks. Pre and posttraining evaluations included the following: exercises, where exercisers use their own body weight with or 1 repetition maximum (1RM) leg and bench press; sling exer- without external weight. The CKCEs tend to work more than cise push-ups; isokinetic dynamometry; lateral step-down test; 1 muscle group and joint simultaneously (6,13). and the Star Excursion Balance Test. Both groups significantly Several studies have shown that CKCEs may be more improved bench press (by an average of 4–6 kg) and leg press effective than OKCEs in improving performance-related (by an average of 23–35 kg) (p , 0.001). There was a sig- measures in lower-body training (1,3). For example, lower- nificant group 3 time interaction (p , 0.001) for sling exercise body CKCE training is more effective than OKCE training push-ups (OKCE pre = 5.5 6 8.6, OKCE post = 6.1 6 8.2, for improving vertical jump performance (1,3,13). Further, CKCE pre = 6.8 6 6.0, CKCE post = 16.9 6 6.6). Isokinetic CKCEs are commonly prescribed for athletes, possibly measures of knee extension, knee flexion, shoulder internal because they result in less anterior and posterior tibiofemoral rotation, and shoulder external rotation increased (improve- shear force than lower-body OKCEs do (6,10,16). Studies ments ranged from 2.7 to 27.7%), with no group differences. also have shown that lower-body CKCE generate muscular co-contraction, which provides greater joint stability than Both OKCE and CKCE strength training elicited similar OKCE (7,16). changes in balance. We conclude that CKCE training is Studies conducted on upper-body strength training have equally as effective as OKCE training during the initial phases of shown that CKCEs are typically limited by body weight as a strength training program in women. The fact that only CKCE a source of resistance so low repetition, high-intensity strength training can be difficult to execute (4,11). Thus, Address correspondence to Arthur Weltman, [email protected]. OKCEs are commonly employed in upper-body strength 25(2)/464–471 programs. Despite these perceived limitations, it has been Journal of Strength and Conditioning Research shown that CKCEs can be effective for upper-body training Ó 2011 National Strength and Conditioning Association (4,11). Similar to the lower-body exercises, upper-body 464 Journalthe of Strength and Conditioning ResearchTM

CKCEs elicit muscular co-contractions, thus providing basic weight training techniques and safety guidelines. Three dynamic joint stability, which does not occur with OKCEs subjects withdrew from the study. Two subjects dropped (11,13). A recent study from our laboratory found that the course, and 1 subject was unable to complete the study substituting 4 upper-body CKCEs was as effective as OKCE because of work-related conflicts. Three additional subjects training in producing maximal strength gains in collegiate were unable to complete all aspects of performance testing softball players (13); however, only CKCE training signifi- because of pre-existing orthopedic injuries, but measures cantly improved throwing velocity. Based on these findings, they were able to complete are included (resulting in n =23to it is reasonable to conclude that CKCE training can be n = 26, depending on the variable tested). incorporated into upper-body strength training without sacrificing gains in maximal strength or performance criteria. Procedures Although some studies have shown that CKCE training may Performance Testing. Pre and posttraining testing consisted of be as or more effective than OKCE training, to our isokinetic concentric phase PT for knee flexion and extension knowledge, no data exist on the effectiveness of a strength and for shoulder internal and external rotation; isokinetic training program that uses CKCEs exclusively (1,3,6,7,10,11, concentric phase PP for knee flexion and extension and for 13,16). The use of CKCE may have particular utility for shoulder internal and external rotation; 1RM bench press and individuals who may be intimidated by traditional weight 1RM leg press; lateral step-down test; SEBT; and maximum training settings. sling exercise push-ups. For example, women beginning a weight training program are often uncomfortable in a typical weight room setting and Isokinetic Strength Testing. Isokinetic strength testing was as such may choose not to engage in this important activity performed using a Biodex System 3 multijoint dynamometer (8). In this study, we compared a sling-based CKCE training (Shirley, NY, USA). All subjects performed 3 sets of 5 trials program to an OKCE training program in a group of women of each exercise with 90 seconds between sets. Verbal enrolled in an introductory strength training program. We encouragement was given for each repetition and testing was hypothesized that after training, both CKCE training and preceded with 10–15 practice repetitions to familiarize the OKCE training would increase 1 repetition maximum (1RM) subject with the isokinetic device. Concentric internal rota- bench and leg press, and Biodex peak torque (PT) and power tion and external rotation tests intraclass correlation to a similar degree. We also hypothesized that performance coefficients [ICCs] = 0.81 and 0.74 for internal and external on CKCE and dynamic balance would improve more with rotation, respectively) were conducted at 180° s21 through CKCE training because of specificity of training and the extra a65° arc of motion, with the seatback angle set at 85°.The demands CKCE place on core stability. tested extremity was abducted approximately 25°, and shoulder flexed slightly to place the shoulder in the scapular METHODS plane for testing. Dynamometer and seat height were adjusted such that the humerus was in line with the rotor, Experimental Approach to the Problem as recommended by the manufacturer. The isokinetic knee This study included 1 independent variable with 2 levels (pre- flexion and extension test (ICCs = 0.91 and 0.92 for flexion and post-13 weeks of strength training) and 13 dependent and extension, respectively) was also performed at 180° s21 variables. The independent variable was the type of training in from full knee extension (0°) to approximately 85–90° of which the subject engaged (CKCE or OKCE). Dependent flexion for 3 sets of 5 test repetitions with a 90-second rest variables included isokinetic concentric phase PT for knee period between sets. The seatback angle was set at 85°, and flexion and extension and for shoulder internal and external the hips were in 90° of flexion. Values from the 3 sets were rotation; isokinetic concentric phase peak power (PP) for averaged to find PT and power values for each subject. knee flexion and extension and for shoulder internal and external rotation; 1RM bench press and 1RM leg press; lateral 1RM Testing. The 1RM testing was performed using the step-down test; Star Excursion Balance Test (SEBT); and National Strength and Conditioning Association 1RM pro- maximum sling exercise push-ups. tocol (2). Participants began the 1RM bench press and leg press assessments by warming up with repetitions on the Subjects bench press on 45-lb bars and free weights (York Barbell, The study was approved by the university’s institutional York, PA, USA) and repetitions on the leg press machine review board. Twenty-nine female undergraduate students at (Hammer Strength, Schiller Park, IL, USA). The goal was to the University of Virginia were recruited from Lifetime build to the 1RM load by approximately the fifth set. For the Physical Activity weight training classes (mean age = 19.6 6 bench press, a successful repetition was scored if the weight 1.11 years, mean weight = 60.5 6 7.2 kg, mean height = was lowered to the chest and raised to full arm extension 166.4 6 5.9 cm). All participants were enrolled in an intro- without subject losing foot, hip, back, or shoulder contact ductory strength training class and provided written informed with the bench or the floor, and no help was provided by the consent. Participants had 1 week (2 or 3 sessions) to learn spotter. For the leg press, a successful repetition was scored if

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the weight was lowered such that the knees created a 90° Lateral Step-Down Test. The quality of movement during the angle and raised to full leg extension without the subject lateral step-down test was assessed by a trained investigator losing back or shoulder contact with the machine and using a scale designed for this purpose. Each participant was without help from the spotter. Three failed repetitions at asked to stand on single-leg support with hands on the waist, a given weight or voluntary termination ended each test. knee straight, and weight-bearing foot on the edge of

Figure 1. Examples of open-kinetic-chain (OKCE) and closed-kinetic-chain (CKCE) pairs used in training intervention.

466 Journalthe of Strength and Conditioning ResearchTM

a 20-cm-high step. The contralateral leg was held, fully Participants were asked to stand on 1 leg with their toe at the extended, over the floor adjacent to the step. The participant base of the upper part of the ‘‘Y.’’ While maintaining this was then asked to bend the tested knee until the contralateral single-leg stance, the participant was asked to reach with leg lightly touched the floor and then re-extend the knee to the free leg in the specified direction (5,9). Reach was the start position. This was repeated for 3 repetitions. The measured in centimeters, and each participant completed investigator faced the subject and scored the test based on 3 trials. Measurements from the 3 trials were averaged and 5 criteria, described in detail elsewhere (12): (a) Arm strategy, normalized to subject leg length. Reach was also measured (b) Trunk movement, (c) Pelvis plane, (d) Knee position, on the opposite foot in all 3 planes of movement. and (e) Maintenance of steady unilateral stance. A point was added for an unsuccessful execution of each of the 5 criteria Sling Exercise Push-Ups. Sling exercise push-ups were during any of the 3 repetitions. Each subject received a score performed with a Redcord minitrainer (Kilsund, Norway). between 0 and 6. Handles were approximately 10 cm above the ground with participants positioned on their knees. An investigator Star Excursion Balance Test. The anterior, posteromedial, and instructed each participant in proper push-up form and posterolateral components of the SEBT were conducted by counted the number of successful repetitions. A repetition a trained investigator using a ‘‘Y’’ that was taped the floor was considered successful if the subject lowered her chest to (ICCs range from 0.85 to 0.96 depending on movement). the height of her hands while maintaining core stability and

TABLE 1. Mean (6SD) pre and posttraining results for OKCE and CKCE training (n = 13 for OKCE, n = 13 for CKCE).*†

Parameter OKCE pre OKCE post CKCE pre CKCE post

Leg press (kg) 54.6 (26.9) 90.4 (30.6)‡ 85.1 (32.3) 108.2 (41.9)‡ Bench (kg) 30.9 (4.4) 36.5 (7.3)‡ 34.8 (6.8) 38.7 (6.3)‡ Sling push-ups§ 5.5 (8.6) 6.1 (8.2) 6.8 (6.0) 16.9 (6.6)‡ Torque knee ﬂex (NÁm) 49.4 (10.5) 53.9 (12.5)‡ 47.9 (8.3) 53.7 (14.4)‡ Torque knee ext (NÁm) 68.9 (15.0) 74.4 (14.3)‡ 71.4 (18.5) 73.4 (20.6)‡ Torque shoulder IR (NÁm) 19.2 (5.5) 22.1 (5.5)‡ 20.4 (6.0) 23.6 (7.9)‡ Torque shoulder ER (NÁm) 9.4 (2.6) 10.0 (3.1) 10.9 (3.3) 11.5 (3.6) Power knee ﬂex (W) 89.7 (17.1) 99.9 (16.1)‡ 88.3 (14.5) 103.7 (22.8)‡ Power knee ext (W) 129.1 (18.0) 143.3 (13.1)‡ 136.7 (26.3) 146.1 (32.7)‡ Power shoulder IR (W) 26.4 (10.0) 33.7 (9.2)‡ 30.4 (9.7) 37.2 (12.4)‡ Power shoulder ER (W) 12.1 (4.7) 13.2 (4.3)‡ 14.8 (4.7) 16.9 (7.6)‡ Lateral step-down (L) 2.4 (1.6) 1.3 (1.5)‡ 1.8 (1.0) 1.3 (0.9)‡ Lateral step-down (R) 2.0 (0.9) 1.3 (1.3)‡ 1.6 (1.1) 1.4 (1.2)‡ Anterior SEBT (R) 0.8 (0.05) 0.7 (0.09) 0.7 (0.06) 0.7 (0.06) Posteromedial SEBT (R) 0.8 (0.07) 0.9 (0.1) 0.8 (0.1) 0.9 (0.07) Posterolateral SEBT (R) 0.8 (0.1) 0.8 (0.1) 0.8 (0.1) 0.8 (0.08) Anterior SEBT (L) 0.7 (0.06) 0.7 (0.09) 0.7 (0.06) 0.7 (0.07) Posteromedial SEBT (L) 0.8 (0.09) 0.9 (0.1)‡ 0.8 (0.1) 0.9 (0.8)‡ Posterolateral SEBT (L) 0.8 (0.1) 0.8 (0.08)‡ 0.8 (0.1) 0.9 (0.08)‡

*OKCE pre = open-kinetic-chain group pretraining test; OKCE post = open-kinetic-chain posttraining test; CKCE pre = closed- kinetic-chain pretraining test; CKCE post = closed-kinetic-chain posttraining test; leg press = 1 repetition maximum leg press (lbs); bench = 1 repetition maximum bench press (lbs); sling push-ups = maximum sling push-ups; torque knee flex = peak torque knee flexion (NÁm); torque knee ext = peak torque knee extension (NÁm); torque shoulder IR = peak torque shoulder internal rotation (NÁm); torque shoulder ER = peak torque shoulder external rotation (NÁm); power knee flex = peak power knee flexion (W); power knee ext = peak power knee extension (W); power shoulder IR = peak power shoulder internal rotation (W); power shoulder ER = peak power shoulder external rotation (W); lateral step-down (L) = left leg lateral step-down test; lateral step-down (R) = right leg lateral step-down test; anterior SEBT (R) = right leg anterior star excursion balance test; posteromedial SEBT (R) = right leg posteromedial direction star excursion balance test; posterolateral SEBT (R) = right leg posterolateral direction star excursion balance test; anterior SEBT (L) = left leg anterior direction star excursion balance test; posteromedial SEBT (L) = left leg posteromedial direction star excursion balance test; posterolateral SEBT (L) = left leg posterolateral direction star excursion balance test; ANOVA = analysis of variance. †For the following variables, n was slightly different: n = 8 for CKCE lateral step-down; n = 10 for OKCE lateral step-down; n =11 for OKCE bench and OKCE sling push-ups; n = 12 for OKCE leg press, OKCE torque knee extension and flexion, and OKCE power knee extension and flexion, CKCE bench press, CKCE sling push-ups, CKCE shoulder internal and external rotation average torque, and CKCE shoulder internal and external rotation peak power. ‡ANOVA analyses revealed the following: Significantly greater than pre-testing score, p , 0.05. §Significant group 3 time interaction, p , 0.05.

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posture. Failure to maintain proper form or failure to con- 0.05 level. When baseline differences between groups were tinuously progress from 1 repetition to the next terminated observed, analysis of covariance results were used with the the test. baseline scores as the covariate. The Tukey–Kramer post hoc tests were used to locate differences. Training Intervention. Participants were randomized to 1 of RESULTS 2 training intervention groups: OKCE training and CKCE training. Participants completed 6 sets of strength training Table 1 shows mean (SD) pre and posttraining data for exercises per week for 13 weeks. Based on course enrollment the selected performance parameters. Both the OKCE and and time, some participants completed 3 sessions per week, CKCE conditions had significant (p , 0.05) and similar performing 2 sets during each session, whereas others improvements on most performance measures. The OKCE completed 2 sessions per week, performing 3 sets during group improved 1RM leg press by 35.7 kg, with a 23.0-kg each session. Investigators supervised all exercise sessions. increase in the CKCE group (group 3 time interaction, The duration, relative intensity, and volume of each set were p = 0.13). The OKCE group improved 1RM bench press by the same for both treatment groups. All participants were 5.6 kg, with an 4.0-kg increase in the CKCE group (group 3 instructed to refrain from strength training outside of time interaction, p = 0.36). treatment sessions. Figures 2 and 3 show the individual responses for 1RM leg The CKCE group completed a full-body strength training and bench press, respectively. There was a significant program with Redcord minitrainers hung from ceiling beams, group 3 time interaction (p = 0.003) for sling exercise which consists of ropes with slings and handles that can be push-ups. The CKCE group improved by 148.5%, with an adjusted. Exercise intensity was controlled by adjusting observed mean 11% increase in the OKCE group. Individual handle height relative to the floor, foot height, and leg and responses are shown in Figure 4. hand position relative to the rope fulcrum. Although there For most Biodex measures, including PT and PP, there was some trial and error in the determination of relative were significant increases seen in both groups posttraining intensity of major pull and press lifts, all subjects realized their full capabilities within the first full week of training. By keeping the handles elevated, subjects could complete exercises with intensity and volume comparable with those in the OKCE group. The OKCE group trained with free weights, dumbbells (York Barbell, York, PA, USA), and machines (Hammer Strength, Schiller Park, IL, USA). Exercise intensity and volume were adjusted relative to a subject’s 1RM for major press and pull lifts. Intensity for exercises was determined by subject familiarity and proper form. Examples of commonly selected OKCE and their CKCE analogs, in italics, are shown: (a) Barbell flat bench press/ bilateral push-ups, (b) Cable seated row/bilateral inverted row, (c) Dumbbell biceps curl/biceps curl, (d) Triceps pulldown/ triceps extension, (e) Shoulder extension/shoulder extension, (f) Pullover/Pullover, (g) Hip abduction/hip abduction, (h) Hip adduction/hip adduction, (i) Leg extension/leg extension-prone bridge, and (j) Leg curl/leg curl–supine bridge–leg press. Figure 1 provides visual examples of OKCE–CKCE exercise pairs.

Statistical Analyses Statistical calculations were performed using Statview version 5.0.1 (SAS Institute, Cary, NC, USA). A 2-factor analysis of

variance (ANOVA) with repeated measures was executed Figure 2. Pre to posttraining individual changes (dashed lines) and group with the treatment group (CKCE or OKCE) as the indepen- mean change 6 SEM (bold line) in the 1 repetition maximum (1RM) leg dent variable. The dependent variables were the outcome press of closed- and open-kinetic-chain training subjects (n = 25). OKCE = open-kinetic-chain subjects; CKCE = closed-kinetic-chain subjects; measures for the various performance tests. Thus, there was pre = pretraining 1RM leg press; post = posttraining 1RM leg press. A 1 between-subjects factor (training group) and 1 within- signiﬁcant increase over time was observed (p , 0.001). subjects factor (time). The threshold for signiﬁcance was set at 468 Journalthe of Strength and Conditioning ResearchTM

Figure 4. Pre to posttraining individual changes (dashed lines) and group Figure 3. Pre to posttraining individual changes (dashed lines) and group mean change 6 SEM (bold line) in sling exercise push-ups of closed- and mean change 6 SEM (bold line) in the 1 repetition maximum (1RM) open-kinetic-chain training subjects (n = 23). OKCE = open-kinetic-chain bench press of closed- and open-kinetic-chain training subjects (n = 23). subjects; CKCE = closed-kinetic-chain subjects; pre = pretraining sling OKCE = open-kinetic-chain subjects; CKCE = closed-kinetic-chain exercise push-ups; post = posttraining sling exercise push-ups. A subjects; pre = pretraining 1RM bench press; post = posttraining 1RM signiﬁcant group 3 time interaction was observed (p , 0.001). bench press. A signiﬁcant increase over time was observed (p , 0.001).

for knee extension (p = 0.002 [PT], p = 0.003 [PP]), knee a group 3 time interaction, with CKCE eliciting more flexion (p = 0.003 [PT], p , 0.001 [PP]), and shoulder improvement than OKCE (p = 0.085 [LL], p = 0.12 [RL]). internal rotation (p , 0.001 [PT], p , 0.001 [PP]). Shoulder external rotation did not have a significant group effect DISCUSSION (p = 0.25 [PT], p = 0.08 [PP]). There were no significant This study compared the effectiveness of CKCE training and differences between groups. OKCE training on several strength and balance measures in There was a significant improvement in lateral step-down women initiating a strength training program. The major performance posttraining with no significant differences findings of this study were as follows: (a) both OKCE and between groups in both the right and left legs (p , 0.001). CKCE strength training were equally effective for improving Strength training had little overall effect on anterior, traditional measures of strength (e.g., 1 RM, isokinetic power) posteromedial, and posterolateral direction performance on (Table 1, Figures 2 and 3); (b) only CKCE exercise improved the SEBT. For both the right and left legs, there was not sling exercise push-ups indicating both specificity of training a significant difference between pre and posttraining and functional training superiority of CKCE exercise (Table performance on the anterior direction of the SEBT (p = 1, Figure 4); and (c) both OKCE and CKCE strength training 0.16 [RL], p = 0.90 [LL]). For the right leg, there was also no elicited similar changes on balance with the exception of the significant difference between pre and posttraining perform- posterolateral direction measure, where posterolateral meas- ances on the posteromedial direction (p = 0.10), but for the urements trended toward a group x time interaction, with left leg, there was an increase in the posteromedial direction CKCE eliciting more improvement than OKCE (Table 1). (p = 0.003). For the right leg in the posterolateral direction, The similar improvements in strength between the overall improvement approached significance (p = 0.067), conditions suggest that solely using CKCE training is equally whereas there was a significant increase in reach in the as effective as OKCE training during the initial phases of posterolateral direction for the left leg (p = 0.023). strength training. Previous studies have also found that CKCE Additionally, posterolateral measurements trended toward training elicits strength and performance gains similar to or

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better than OKCE training (1,3,7,13,16). For example, lower- training appears to develop functional strength more so body CKCE training has been shown to be more effective than OKCE training, which is beneficial for both perfor- than OKCE training for improving vertical jump performance and everyday living. mance (1,3,13), and CKCE training generates muscular co- This study shows similar changes in balance for CKCE and contraction, resulting in greater joint stability (7,16). Another OKCE training on the SEBT, with the exception of the study found that substituting 4 upper-body CKCE was as posterolateral direction. Both strength training methods effective as OKCE training in producing maximal strength resulted in a significant improvement for left leg balance in gains (13). To our knowledge, this is the first study to the posteromedial direction and marginally significant examine the effectiveness of a strength training program that improvements for right leg balance in the posteromedial uses CKCEs exclusively. direction. There was no significant change in balance in It is interesting to note that the changes observed in the anterior direction in both legs. The improvement in the strength outcomes after training were similar between groups, posteromedial direction was expected. Movement in the despite the fact that the Redcord group had higher initial posteromedial direction is a functional movement and strength values after random assignment. One could recruits both the quadriceps and hamstrings; thus, strength hypothesize that individuals who were less strong to begin training is expected to improve performance on this measure would be more likely to experience great change in strength (5). The lack of change in anterior balance was not expected. with training (14). It is possible that if subjects started with The anterior component of the SEBT is mostly quadriceps similar initial strength values, we might have observed greater dependent, demonstrated by significant quadriceps electro- improvements with CKCEs, similar to what has been myographic activation during this task (5). Thus, with observed in previous studies (1,3,6,7,10,11,13,16). strength training, specifically quadriceps strength training, These findings have important implications for women performance on the anterior component of the SEBT has initiating a weight training program, showing that CKCEs been shown to improve (5). We do not have an explanation can be substituted for OKCEs without a detrimental effect at this time for the lack of training effect for both the CKCE on strength. Women initiating weight training programs are and OKCE training groups. often hesitant to begin an OKCE program because of Our hypothesis that performance on balance measures intimidation and fear of a weight room (8). These women would improve more with CKCE training was supported in may be more inclined to undertake a CKCE training program the posterolateral direction on the SEBT. Our hypothesis was that can be conducted outside of a weight room. Further, based on the idea that the extra demands CKCEs place on a CKCE that uses a Redcord device are beneficial because it core stability would help with balance performance. Given removes several barriers to strength training. The Redcord the rotational component of the posterolateral direction, it is device is a convenient and effective strength training device possible that the CKCEs facilitated more recruitment that is portable, and time efficient, which eliminates the time strategies and core stabilization, allowing for more controlled factor that is a barrier for many people trying to consistently pelvic rotation (5). It is reasonable to hypothesize that CKCE strength train (15). training develops better joint coupling at the hip and knee Our hypothesis that performance on CKCE would than OKCE training, allowing for more stable pelvic rotation improve more with CKCE training was supported. The and core stabilization during the SEBT. In conclusion, both significant group 3 time interaction for sling exercise push- CKCE training and OKCE training for 13 weeks significantly ups shows that specificity of training impacts performance. improved overall strength and balance in women beginning The subjects in the CKCE training group used inherently weight training. unstable sling-based equipment, which likely activated both core and stabilizing muscles to a greater extent, and led to an PRACTICAL APPLICATIONS improvement in performance. In a recent study from our On the basis of the current data, it can be concluded that laboratory (13), we investigated the relationship between CKCE training is equally as effective as OKCE training in strength training method and throwing velocity. That study eliciting improvements during the initial phases of a strength reported that subjects in the CKCE training group training program in women starting a strength training significantly improved throwing velocity compared to the program. The fact that only CKCEs improved sling exercise subjects in the OKCE training group, despite similar push-ups supports previous findings suggesting functional improvements in maximal strength. The instability of the superiority of CKCEs. Further, women beginning strength sling-based training method again likely enhanced activation training are often hesitant to begin an OKCE program of the musculature involved in the torso and shoulder because of intimidation and fear of a weight room. These stabilization. The activation of these muscles along with women may be more inclined to undertake a CKCE training more time spent on the eccentric portion of a given exercise program that can be conducted outside of a weight room and could have contributed to the improvement in throwing can substitute CKCEs for OKCEs without a detrimental effect velocity (13). Through core activation and activation of on strength. Although only beginners were examined, data smaller stabilizing muscles, CKCE sling-based strength from this study and data from previous studies indicate that 470 Journalthe of Strength and Conditioning ResearchTM

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