The Effect of a Plyometrics Program Intervention on Skating Speed in Junior Hockey Players

Abstract

Few studies have been conducted to examine the effects of plyometrics
on skating speed in junior hockey players. The present study was designed
to look at the effects of a 4-week, eight session, plyometric training
program intervention on skating speed. Six male subjects (18.8 ±
.98 years) that engaged in the training program completed pre and post
40 meter on-ice sprinting tests. The training group showed significant
time improvements (p<.05) in the 40 meter skating distance. The results
suggested that plyometric training has a positive effect on skating speed
in junior hockey players such that a reduction in on-ice sprinting times
is evident.

At the junior level, ice hockey can be characterized by intense bouts
of on-ice play lasting up to 90 seconds in duration. Games are made up
of three 20 minute periods with typically 12-15 minutes of rest in between
periods. Developing muscular strength, power, and speed, in addition to
training both the aerobic and anaerobic energy systems have become crucial
if players wish to advance to elite levels of hockey (Cox et al, 1995).
According to Montgomery (1988), a major difference between junior and
professional players is their upper and lower body muscular strength and
power. In addition, Greer et al (1992), reported that the fastest skating
speeds are seen at the professional level. Therefore, developing muscular
strength and speed should be emphasized in training programs for aspiring
junior players. Plyometrics are explosive movement exercises which aim
to improve both strength and speed abilities in athletes by training fast
twitch muscle fibers and increasing movement power output (Chu,1983, Gambetta,
1989, McNaughton,1988, McFarland, 1985).

Plyometrics may be defined as “jumping exercises that involve a
rapid deceleration of body mass followed immediately by rapid acceleration
of that body mass in an opposing direction”(Wathen,1993). These
jumping exercises force a rebound action known as the myostatic reflex,
that elicit the contraction of the both homonymous and synergist muscles
while inhibiting antagonist muscles in an effort to produce a fast response
to an applied stimulus (Chu,1984).The myostatic reflex contributes to
an increase in muscular force generation due to the effects of voluntary
contraction and the involuntary contraction resulting from the reflex
itself. The main objective of these hopping and bounding exercises is
to convert elastic energy generated by both the force of gravity and body
weight during eccentric or lengthening muscle contraction into an opposite
force during the concentric or shortening contraction. A lengthening or
eccentric contraction followed by a concentric contraction utilizes the
elastic energy stored in the that muscle during the stretching phase.
When released this elastic energy can make a substantial contribution
to the efficiency of the muscle contraction resulting in greater power
output (Koutedakis,1989). Muscle spindles located within the muscles react
to sudden stretch by sending signals to the spinal cord, resulting in
muscular contraction to resist the sudden stretch. Given the above information,
it is understood that plyometric training has the potential to assist
help athletes in increasing movement speed and power by developing quicker
reaction times.

Research investigating the effects of plyometrics on speed in ice hockey
players is somewhat limited. Rimmer and Sleivert (2000) conducted an eight
week study to determine the effects of a sprint-specific plyometrics program
on sprint performance. Results showed that the plyometric group significantly
reduced both there 10m and 40m sprint times. Polhemius et al (1980), looked
at the effects of weighted plyometric exercises had on conventional sprint
training practices in university level track athletes. Pre and post measures
of 40 meter sprint times revealed those participating in the additional
plyometric exercises, three times per week for six weeks in combination
with there conventional training programs, decreased their 40m sprint
times. Plyometric training in both studies was credited for improving
the sprinting acceleration phase due to a specificity training response,
where ground contact times decreased and force production rates increase.
We can therefore hypothesize that because ice contact times and stride
force production rates are also critical components in skating at top
speed, plyometric training should be able to address these to critical
components as it did in sprinters. If players are able to decrease contact
time with the ice while improving stride force production, the result
would be faster, more powerful skating ability, beneficial in all aspects
of the game. Therefore the purpose of this study is to determine the effect
of a four week, eight session plyometric program intervention on skating
speed in junior hockey players.

Methods

Participants

Six male participants from a local Jr.B hockey team volunteered to take
part in eight plyometric training sessions over the course of a four week
period. Prior to participation, all players completed a history profile
which contained medical and lifestyle questions, as well as written informed
consent before participating in the training study. Procedures of the
study were in compliance with guidelines established by the Research Ethics
Board at Brock University.

Table 1.

Participant Characteristics (Mean ± S.D.)
Variable Training Group (n=6)
Age (yrs) 18.8 ± .98
Height (cm) 177.16 ± 4.02
Weight (kg) 75 ± 5.78
Experience (yrs) 11.16 ± 1.32

Experimental Design

A quasi-experimental single group pre/post test design method was employed
by
the researcher. Subjects (n=6) participated in the same two microcycles
composed of in-step jumping patterns on four separate occasions, for a
total of eight sessions. Pre and post 40m on-ice sprint times were used
to determine the effectiveness of the plyometrics program intervention.

Training Intervention

Training sessions were conducted following on-ice practices twice a week.
Forty-eight hours of rest separated the training sessions. Each plyometric
training session was 20 minutes in duration and consisted of quick in-step
jumping patterns within a square quadrant. The plyometrics training protocol
followed was developed by Frappier Accleration™. All training sessions
were instructed and timed by the experimenter. Participants took turns
using the jumping quadrants which were created by placing masking tape
on the rubber flooring. These quadrants were composed of four boxes numbered
clockwise starting from one in the lower left box, and finishing with
four in the lower right box. Single leg and double leg jumping patterns
followed by participants were outlined in there personal tracking sheets,
and as stated earlier, were the same for everyone in the eight sessions.
The beginning and conclusion of each jumping pattern was initiated by
the experimenter who was holding a stopwatch and used a verbal cue. Encouragement
and motivation was provided throughout the training sessions by the experimenter.
Upon the completion of each pattern the exact number of foot contacts
achieved was recorded. (e.g., if the pattern was 1-2-3-4, one contact
was quantified when the subject returned to the original starting point
of the pattern). Participants typically engaged in the jumping patterns
from five to ten seconds depending on the drill protocol, and were given
rest when another subject was using the jumping quadrant. Foam blocks
were added to increase jumping difficulty throughout the 8 sessions. A
typical work-rest ratio seen in the training sessions was approximately
1:4.

Figure 1. Jumping quadrant utilized in the plyometric training
sessions

2 3
1 4

Results

A paired samples t-test was used to examine changes over time in skating
speed between the pre and post 40m on-ice sprint. Results revealed a statistically
significant effect such that the skaters on average reduced their times,
t (6) = 2.55 , p < .05. The mean value sprinting times for the six
participants from the pre test (6.625 sec ± .507) to post test
(6.46 sec ± .531) are represented in figure 2.

Figure 2. Group average comparison between pre
and post test on-ice 40m sprint times.

Discussion

This investigation was undertaken to examine the impact of a four week
plyometric training program on skating speed in junior level hockey players.
The results suggested that plyometric training has a positive effect on
skating speed in junior hockey players such that a reduction in on-ice
sprinting times is evident. The preliminary work of Rimmer and Slievert
(2000) and Polhemius et al (1980), provided the researcher with a foundation
for explaining the outcome of this training intervention by paralleling
and connecting the physiological and practical explanations given for
the reduction in track sprinting times offered by these two studies to
the principal investigation. It must be noted that although a significant
difference was found in the pre to post sprinting times of the skaters,
the results may be due to sampling error. Therefore we can not make a
confident inference that these findings are generalizable to all junior
level hockey players. As well, the principal researcher did not control
for any additional training that the participants may be engaged in outside
of the study, which may be seen as internal validity threat. However,
it was assumed that the majority of the training was consistent as all
players were on the same team. The results of this study should influence
the design of off-ice training programs by junior and professional hockey
league teams. Combining plyometric exercises with traditional training
protocols should improve skating speed ability, beneficial in all aspects
of ice hockey.

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