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Six commonly prescribed trunk- strengthening exercises were performed by 120 subjects (40

subjects in each of the following age groups: 18–30 years, 31–40 years, 41–50 years). Ultrasound imaging was used to measure the thickness of the transversus abdominis (TrA) and internal oblique (IO) muscles during the resting and contracted states of each exercise. The average thickness of the muscles while in the contracted position was divided by the thickness values in the resting position for each exercise, based on two performances of each exercise. The aim was to characterise changes in muscle thickness in the TrA and IO muscles during common trunk-strengthening exercises, and to determine whether these changes differ based on age.

Results: For both muscles, the trunk exercise- by-age interaction effect and the main

CHANGES IN DEEP ABDOMINAL MUSCLE THICKNESS DURING COMMON TRUNK- STRENGTHENING EXERCISES USING ULTRASOUND IMAGING. Teyhen DS, Rieger JL, Westrick RB, et al. Journal of Orthopaedic and Sports Physical Therapy 2008;38:596–605.

effects for age were not significant. A

significant main effect for trunk exercise for both muscles was found. Horizontal side- support and abdominal crunch exercises resulted in the greatest change in muscle thickness for both muscles. The abdominal drawing-in manoeuvre and quadruped opposite upper- and lower-extremity lift exercises resulted in changes in TrA muscle thickness, with minimal changes in IO muscle.

sportEX comment Changes in TrA and

IO muscle thickness differed across six commonly

prescribed trunk-strengthening

SIGNIFICANT EFFECT OF GENDER ON HAMSTRING-TO-QUADRICEPS STRENGTH RATIO AND STATIC BALANCE IN PREPUBESCENT CHILDREN FROM 7 TO 12 YEARS OF AGE. Holm I. Vøllestad N. American Journal of Sports Medicine 2008;36:2007–2013.

A total of 368 children aged 7–12 years participated in the study. They performed isokinetic

concentric hamstring and quadriceps muscle strength measurements at 60°/s and 240°/s and a static balance test using the KAT 2000™.

Results: Gender had a significant effect on both the hamstring/quadriceps (HQ) ratios and static

STRETCHING POSITIONS FOR THE POSTERIOR CAPSULE OF THE GLENOHUMERAL JOINT STRAIN MEASUREMENT USING CADAVER

SPECIMENS. Izumi T, Aoki M,

Muraki T, et al. American Journal of Sports Medicine 2008;36:2014–2022.

Using eight fresh-frozen cadaver shoulders (average age 82.4 years), eight stretching positions for the posterior capsule were simulated by passive internal rotation. The following stretching positions were adopted: 0°, 30°, 60° and 90° of elevation in the scapular plane; 60° of flexion; 60° of abduction; 30° of

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extension; and 60° of flexion and horizontal adduction. Strain was measured in the upper, middle and lower parts of the capsule. Results: With internal rotation, the mean strain on the upper capsule was 3.02% at 0° of elevation and 3.35% at 30° of extension. Strain on the middle capsule at 0° and 30° elevation was 0.78% and 4.77%, respectively; on the lower capsule, it was 5.65% and 2.24% at 30° and 60° of elevation, respectively, and 2.88% at 30° of extension. Increases in strains of the upper, middle and lower capsule with internal rotation at 0°, 30° and 60° of elevation were statistically significant. Other shoulder positions demonstrated no positive strain values.

balance. Except in the 7-year-old participants, boys showed significantly higher HQ ratios than the girls in every age group, indicating that the hamstring muscles in girls were relatively weak when compared with the quadriceps muscles. There was also a gender effect on the balance index, with better balance in girls than in boys.

sportEX comment There is a significant gender

difference in HQ ratios and static balance in children aged 8–12 years. Because many children start their sporting careers at an early age, prevention programmes including hamstring strength training should be prescribed at an earlier age than recommended in previously published studies.

sportEX comment These are cadaver studies, which

don’t always translate into real life. Based on the results, however, large strains on the posterior capsule of the shoulder were obtained at a stretching position of 30° of elevation in the scapular plane with internal rotation for the middle and lower capsule, while a stretching position of 30° of extension with internal rotation was effective for the upper and lower capsule; therefore, it is necessary to change the angles in order to ensure that all of the capsule is targeted.

exercises among healthy subjects without lower back pain. These differences did not vary by age. This information may be useful for informing exercise prescription.

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