Research Review By Carson Boddicker©

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Date Posted:

April 2011

Study Title:

Effect of Core Stability Training on Throwing Velocity in Female Handball Players

Authors:

Saeterbakken AH, van den Tillar R, Seiler S

Author's Affiliations:

Faculty of Teacher Education and Sport, Sogn og Fjordane University College, Norway; Research Center for Sport, Health and Human Development, Villa Real, Portugal; and Institute of Public Health, Sport and Nutrition, University of Agder, Norway.

Publication Information:

Journal of Strength and Conditioning Research 2011; 25(3): 712-8.

Background Information:

In the athletic development and rehabilitation worlds, the term “core” is commonly used in reference to the torso and its active and passive components that transfer force between upper and lower extremities. In recent years, the training of “core stability” has become popular in various professional realms and has shown potential in cases of low back pain, reduction in lower extremity injury, and shoulder injury (1, 2, 3).

Unfortunately, in healthy populations, the use of core stability training has yet to be effectively supported by the literature. Stability training on Swiss balls is common, and these training interventions improve measures of core stability, however, increases in performance ability have not been demonstrated in swimming and running athletes (4, 5). Contrarily however, evidence shows that training in unstable “slings” can improve club head speed and kicking velocities in high level golfers and soccer players (9, 10).

Some evidence exists to support the use of resistance training modalities to improve throwing velocity in handball players and softball players at the division I level in interventions ranging between 6 and 9 weeks. In these studies, general improvement in velocity ranges between 1.4 and 6.9% (6, 7).

This study was performed with the intent of determining the impact of core stability training in unstable slings on the velocity of a handball throw. It could be theorized that any increase in velocity be attributed to improved rotational stability through the lumbo-pelvic-hip complex that ultimately leads to better energy transfer from the ground to the upper extremity and decelerative ability of the core (8).

Pertinent Results:

While no difference existed between control and experimental groups at pre-testing, the experimental group demonstrated a 4.9% increase in throwing velocity at the end of the training period. In the same period, the control group saw no statistical changes.

In the experimental time frame, all but one of the experimental group athletes was able to exercise at the highest level of training difficulty. The other athlete performed four of the six exercises at the highest difficulty level.

Clinical Application & Conclusions:

  • Incorporating closed-chain, functional core stabilization exercises may improve throwing velocity
  • Incorporating exercises with three dimensional stability, like sling based exercises, may be of more value in rotational sport athletes than traditional core stability exercises
  • The loading of core training exercises should not be confined to low-load, longer duration exercises if improved throwing velocities are desired. In the current study, athletes exercised in 4 to 6 RM load range
  • Proper training can lead to increased throwing velocities in 6 to 9 weeks
  • Progression should be employed, and in younger, inexperienced athletes, this progression can be done with reasonable speed as the neuromuscular system will adapt.

Study Methods:

Group Selection:

Two groups were formed (a sling-based exercise group and a control group) from a group of 28 female handball players. The exercise group had 16 athletes (average age: 16y) and the control group consisted of 12 athletes, who met certain entry criteria.

To be included, athletes went through an extensive assessment process and were required to be currently free of injury, training for competitive handball concurrently, and a minimum of five years of team handball experience. Subjects played at the two highest levels of handball and had an average of eight total years of handball experience.

The experiment was conducted over six weeks during the competitive season in which athletes competed weekly. To control for confounding variables, athletes self-reported total training times and distribution. Average training time in all groups was 11.9 hours weekly. Training distribution was generally 5:1 of sport skill practice to general training modes. Both groups performed identical strength training programs including push-ups, sit ups, squat jumps, and dips. In an effort to maintain this average training load, the experimental group replaced two skill sessions with the sling training protocol.

Testing Protocols:

To establish a pre-test throwing velocity, a familiarization protocol was undertaken to eliminate learning curve improvement following a 15 minute general warm up of jogging and throwing drills. Each athlete was then given ten attempts of a standing 7.0 meter throw with 60 seconds between each throw. This test was completed one week prior to training intervention and one week following the completion to prevent fatigue factors. Velocities were captured using two photocell arrays along the flight path of the ball spaced by 3.0 meters.

Training Protocols:

The experimental group trained twice weekly for six consecutive weeks, with a minimum of 48 hours of rest between each session. Sessions lasted approximately 75 minutes and consisted of 6 exercises (5 in sling apparatus and 1 on a balance pillow) performed in the closed kinetic chain.

Four sets of 4 to 6 repetition maximum for each exercise were performed for each exercise with 1 to 2 minutes recovery between sets. The exercises were graded by three levels and were intensified by adding instability via balance pillow or by elongating the lever arm. Progression began at level one for the first four sessions before being intensified. After 8 sessions, those subjects capable of performing well at level two were advanced to the third stage.

Exercise Selection:

The authors selected a six exercise battery consisting of a supine abduction, a side-lying bridge with abduction, a dynamic crunch, all with the feet in the sling. Additionally, a sling “superman” exercise was performed, along with a single leg squat and a push up to tax the extremities and dynamic stability of the hip and shoulder girdle, respectively.

Statistical Analysis:

A minimum study population was determined to be six subjects via statistical power equation at p < 0.05 level with a power of 0.8. The throwing velocity was examined as the dependent variable.

Study Strengths / Weaknesses:

The study did a good job of ensuring that confounding variables were minimized with a detailed analysis of the self-reports. Skill acquisition was also accounted for as the control group had more skill practice, yet demonstrated no statistical improvement in throwing velocity over the course of the experiment. The significant length of playing experience required - 5 years - is a value as well as it eliminated the steep adaptation curve of new athletes.

The age of the athletes and gender may have played a role in the value of strength training as, generally, the female possesses less strength than male counterparts. Additionally, using subjects with an average age of 16 may result in improvements not applicable to older, elite handballers.

Additional References:

  1. Behm, DG and Anderson, KG. The role of instability with resistance training. J Strength Cond Res 2006; 20: 716–722.
  2. Richardson, CA, Snijders, C, Hides, JA, Damen, L, Pas, MS, and Storm, J. The relation between the transversus abdominis muscles, sacroiliac joint mechanics, and low back pain. Spine 2002; 27: 399–405.
  3. Leetun, DT, Ireland ML, Willson JD, Ballantyne BT, Davis IM. Core stability measures as risk factors for lower extremity injury in athletes. Med Sci Sports Exerc 2004; 36: 6.
  4. Schibek, JS, Guskiewicz, KM, Prentice, WE, Mays, S, and Davis, JM. The effect of core stabilization training on functional performance in swimming. J Athl Train 1999; 34: 27.
  5. Stanton,R,Reaburn,PR,andHumphries,B.Theeffectofshort-term Swiss ball training on core stability and running economy. J Strength Cond Res 2004; 18: 522–528.
  6. Prokopy,MP,Ingersoll,CD,Nordenschild,E,andKatch,FI.Closed- kinetic chain upper-body training improves throwing performance of NCAA division I softball players. J Strength Cond Res 2008; 22: 1790–1798.
  7. Ettema, G, Glosen, T, and van den Tillaar, R. Effect of specific resistance training on overarm throwing performance. Int J Sports Phys Perf 2008; 3: 164–175.
  8. Willardson, JM. Core stability training: Applications to sports conditioning programs. J Strength Cond Res 2007; 21: 979–985.
  9. Pedersen, JLS, Magnussen, R, Kuffel, E, and Seiler, S. Sling exercise training improves balance, kicking velocity and torso stabilization strength in elite soccer players. Med Sci Sports Exerc 2006; 38: 243.
  10. Seiler, S, Skaanes, PT, and Kirkesola, G. Effects of sling exercise training on maximal clubhead velocity in junior golfers. Med Sci Sports Exerc 2006; 38: 286.