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May 28, 1998
Ken Pflugner
Vertical Power Co., Inc.
P.O. Box 56
South Bend, IN 46624-0056
Dear Ken,
Attached you will find the final report for the study
investigating the benefits consequent to training with the Sky King Calf Isolator. Once
you've had a chance to look at the report, please give me a call and we can discuss the
result.
I look forward to talking with you in the near future
and if you ever have any other research projects you would like done, please keep us in
mind.
[ Study Results
]
FINAL REPORT
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.
RESULTS: Results of
the study are presented in Tables 2 and 3. It can be seen that training with the Calf
Isolator resulted in a 79 lb. (11%) increase in calf strength in the training
group. There was no change in calf girth in either leg after the 8 weeks of training. Vertical
jump increased by an average of 1.5 inches in the training group. The largest increase in
vertical jump by a single subject was 3 inches. Sit-and-reach flexibility increased by
approximately 1 inch in the training group.
All of the agility and balance measures increased significantly in the training group
when compared to the control group. There was a 1 second decrease in the Barrow
test (agility). For the lengthwise balance test, there was a 14
second (61%) increase for the left foot and a 16 second (71%) increase
for the right foot. For the cross-wise balance tests, there was a 2.8
second (46%) increase for the left foot and 3.3 second (50%) increase
for the right foot. |
| DISCUSSION: Overall, training with Sky
King Calf Isolator resulted in very positive results. There was a highly
significant increase in calf strength which resulted in a number of positive
sports-related improvements in balance, agility, flexibility, and vertical jumping
ability. From your point of view the increase in vertical jump may not have met
your expectations. However, several subjects (3) increased their vertical jump by
2.5-3 inches, and it needs to be remembered that this study was only 8 weeks in
length. It is very possible that a greater training period would result in more
significant changes. |
The anecdotal comments by the subjects are very interesting. A
good number of the subjects reported that they felt quicker and could jump higher after
the study.
All in all I would say that the results of
this study were very positive and that the device has excellent potential for those
athletes who want to increase their performance.
Table 1.
Descriptive Characteristics of Subjects
| |
Control |
Experimental |
| Age (yr.) |
22.0 +/- 4.2 |
19.6 +/- 3.5 |
| Height (in.) |
69.2 +/- 3.5 |
70.6 +/- 2.8 |
| Weight (lbs.) |
171 +/- 28.1 |
165 +/- 31.1 |
Table 2.
Changes in Vertical Jump, Calf Strength, Calf Girth, and Flexibility
| |
Control |
Experimental |
| Pre-Vertical Jump (in.) |
22.5 +/- 2.1 |
22.0 +/- 2.9 |
| Post-Vertical Jump (in.) |
22.4 +/- 2.2 |
23.5 +/- 3.2* |
| |
|
|
| Pre-Calf (lbs.) |
718 +/- 142 |
704 +/- 91 |
| Post-Calf (lbs.) |
712 +/- 158 |
783 +/- 131* |
| |
|
|
| Pre-Calf Girth (in.) L |
14.9 +/- 1.3 |
14.6 +/- 0.9 |
| Post-Calf Girth (in.) L |
15.0 +/- 1.4 |
14.7 +/- 1.1 |
| |
|
|
| Pre-Calf Girth (in.) R |
14.9 +/- 1.3 |
14.7 +/- 0.8 |
| Pre-Calf Girth (in.) R |
14.8 +/- 1.4 |
14.8 +/- 0.9 |
| |
|
|
| Pre-Flexibility (in.) |
12.6 +/- 3.6 |
12.2 +/- 2.3 |
| Post-Flexibility (in.) |
12.7 +/- 3.7 |
13.3 +/- 2.2* |
*Change significantly greater than Control group (p.05).
Table 3. Changes
in Balance and Agility
| |
Control |
Experimental |
| Pre-Agility (sec.) |
22.1 +/- 1.7 |
21.2 +/- 1.2 |
| Post-Agility (sec.) |
21.8 +/- 1.5 |
20.1 +/- 1.5* |
| |
|
|
| Pre-Length Balance L (sec.) |
22.9 +/- 11.3 |
22.9 +/- 9.4 |
| Post-Length Balance L (sec.) |
25.1 +/- 12.2 |
36.9 +/- 15.9* |
| |
|
|
| Pre-Length Balance R (sec.) |
24.2 +/- 9.6 |
22.3 +/- 9.7 |
| Post-Length Balance R (sec.) |
28.4 +/- 13.2 |
38.2 +/- 13.4* |
| |
|
|
| Pre-Cross Balance L (sec.) |
6.5 +/- 3.6 |
6.0 +/- 3.3 |
| Post-Cross Balance L (sec.) |
6.3 +/- 3.5 |
8.8 +/- 6.4* |
| |
|
|
| Pre-Cross Balance L (sec.) |
6.9 +/- 4.3 |
6.5 +/- 4.1 |
| Post-Cross Balance L (sec.) |
6.6 +/- 3.7 |
9.8 +/- 6.6* |
*Change significantly greater than Control group (p.05).
|
