EVALUATION OF THE SKY KING CALF ISOLATOR
PURPOSE: The purpose of this study was to investigate the effectiveness of the Sky King Calf Isolator in increasing calf girth, calf strength, vertical jumping ability, balance, and agility
PROCEDURES: Subjects for this study were 26 males between the ages of 15 and 28 years. All subjects were physically active and a number of them were participating in team or individual sports (e.g. cross-country, track, football, basketball, golf, soccer, and baseball). Descriptive characteristics of the subject are presented in Table 1.
For pre and post-testing, each subject was measured for calf girth, calf strength, vertical jump height, balance, flexibility, and agility. Calf girth was measured with a spring loaded tape measure on both legs at the maximal protrusion of the calf musculature.
Calf strength was measured using a free weight hip sled. After several warm-up sets, the sled was progressively loaded until the subject was unable to fully plantar flex the ankle. Vertical jump height was measured with a Vertex machine using a two foot take-off. Low-back and hamstring flexibility was measured using a standard sit-and -reach test.
Agility was determined using the Barrow zig-zag run, where the subjects ran or side-stepped through a series of cones.
Balance was measured using two version of the Bass stick test. Lengthwise balance required the subject to balance on each foot with the ball and heel of the foot on a 1X1X12 inch block of wood. Cross-wise balance was determined similarly, except the subject stood with just the ball of the foot resting on the block.
Training took place 3-4 days per week for 8 weeks. The number of sessions completed by each subject over the 8 week period averaged 26 sessions.
Each subject was instructed on the proper use of the Calf Isolator and demonstrated correct performance of each of the training exercises. Each subject was given a Calf Isolator and trained on their own at home. Each subject was called once per week by a research assistant to verify that they were following the training protocol and to answer any questions.
The protocol recommended by the manufacturer was followed by each subject. The first set of exercises was performed with the feet pointed straight up and down.
The subjects completed 3 sets of 10 repetitions of flexion and dorsiflexion, with 30 seconds of rest between sets. Next, the subjects completed 3, 30 second contractions, with 60 seconds of rest in between repetitions.
The second and third sets of exercises were identical to the first set, except set two was conducted with the toes pointed in, and the third set was conducted with the toes pointed outward.
STATISTICAL ANALYSIS: Comparison between groups from pre to posttesting was analyzed with a two-way ANOVA with repeated measures. Specific differences between means were made using Tukey's post-hoc tests.