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.

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

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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