1. Energy Expenditure (cal/kg)
Energetics Among Collegiate Ice Hockey Players
Karyn Schmaltz Mentor: Dr. Cara Ocobock, Grand Valley State University
Materials and methods
Total energy expenditure (TEE) was measured for collegiate ice hockey players (N=20), 10 males (5 forwards, 5 defense) and 10 females (5 forwards, 5 defense) for one men’s game and one women’s game.
An ActiTrainer unit (heart rate monitor and accelerometer unit) was placed on each player for the each 60-minute intercollegiate game. We measured the players body fat percentage, muscle mass, height and weight. We used sex specific published equations (Hiilloskorpi et al. 2003) to calculate energy expenditure using the heart rate data. Energy expenditure was calculated in calories and calories per kilogram, to take into account differences in body mass. The summary of calories per kilogram are found in Table 2.
Figures were generated using Microsoft© Excel© All statistical analyses were performed using IBM© SPSS© Version 21. Metabolic costs are reported in kcal/kg to control for differences in mass among the subjects. For statistical analysis, the sex and position variables were combined, creating a transformed variable such that there were four iterations: male forwards, male defensemen, female forwards, and female defensemen. Mauchly’s test for sphericity was performed to ensure the variance of the differences between the metabolic costs of each period was equal. A test of within-subjects effects was performed to determine if there were any significant interactions between time and the sex-position transformed variable. Confidence intervals for the costs of each period of hockey play among the four transformed variable iterations were reported. A one-way ANOVA was performed to determine if there was a difference in total game play cost between the four transformed variable iterations; however, the number of subjects was not high enough to detect a difference if one exists.
Photo 1. Placing heart rate monitors on players
Results
Table 2. Energy Expenditure by period for sex and position.
Objective
The purpose of this experiment is to determine the energy expenditure of ice hockey players during a game period and how shift energetics change throughout a game.
Sex-Position
Mass (kg)
Height (inches)
Body Fat Percentage
Skeletal Muscle Mass (kg)
Female Forwards
68.1 ± 9.7
65.7 ± 2.7
28.86 ± 4.41
24.1 ± 2.2
Female Defense
65.1 ± 8.2
66.4 ± 1.7
27.72 ± 1.52
23.1 ± 2.5
Male Forwards
84.7 ± 5.2
70.5 ± .7
21.48 ± 3.67
35.4 ± 1.7
Male Defense
86.4 ± 8.0
70.7 ± .9
21.1 ± 4.13
34.7 ± 1.9
Table 1. Physical Attributes and Body Composition.
Hypotheses
Forwards exert more energy per period on average than defensemen.
Players exert more energy in the later periods than during the earlier periods.
Time
Sex-Position
Energy Expenditure (cal/kg)
Confidence Interval
Period 1
Lower Bound
Upper Bound
Male Forward
4.15 ± .59
3.282
5.020
Male Defense
4.25 ± .62
3.385
5.123
Female Forward
3.96 ± 1.27
3.086
4.825
Female Defense
4.25 ± 1.0
3.382
5.120
Total
4.15 ± .85
Period 2
4.87 ± .77
4.101
5.633
5.0 ± .59
4.236
5.768
3.86 ± 1.14
3.096
4.629
4.50 ± .60
3.735
5.267
4.56 ± .87
Period 3
5.52 ± .99
4.769
6.263
5.12 ± .85
4.372
5.865
3.77 ± .82
3.019
4.513
3.99 ± .31
3.248
4.742
4.59 ± 1.05
Total Game
4.85 ± .81
4.79 ± .687
3.86 ± 1.11
4.25 ± .637
Graph 1. Summary of female energy expenditure (calories) for periods 1-3 and total game.
Background
Defensemen and forwards in ice hockey anthropometrically differ. Previous research has shown that forwards are on average shorter and weigh less than defensemen. Defensemen are taller, heavier, and have more muscle and fat mass than forwards (Agre, 1998; Vescovi et al. 2006; Green et al. 1976; Burr et al. 2008). One reason that defensemen maintain a higher fat mass is because fat protects the body from checks and defensemen tend to give more body checks (Montgomery, 1998). Forwards need to be leaner and lighter to maneuver around the larger defensemen to maintain puck control and get scoring opportunities (Burr et al. 2008).
For both positions, the shift length changes from the beginning to the end of the game. On average, shift lengths increase from the 1st to the 3rd period (Green et al. 1976). This change in shift length can be attributed to the fatigue of the players toward the end of the game, which causes each shift to be more energetically demanding and results in less distance covered in a shift (Green et al. 1976). Shifts become less productive (less distance covered) toward the end of the game. The distance covered in a shift was recorded using time motion analysis and overall the distance from the 1st period to the 3rd period dropped by 5.2% (Green et al. 1976).
Previous research on ice hockey players has included anthropometric measurements, shift energetics, and aerobic capacity between forwards and defensemen.
T-tests were performed to compare mass, body fat percentage, and skeletal muscle mass between the positions for both male and females.
Mass difference between positions for both males and females was not significantly different (T-test, p>0.63 in both cases).
Body fat percentage between positions for both males and females was not significantly different (T-test, p>0.66 in both cases).
Skeletal muscle mass between positions for both males and females were not significantly different (T-test, p>0.60).
A summary of the physical attributes and body composition results can be found in Table 1.
The test for Sphericity Assumed indicated a significant interaction between period of play and the transformed sex-position variable (p<0.001).
Graph 2. Summary of male energy expenditure (calories) for periods 1-3 and total game.
Key Finding:
The confidence intervals indicated that there is a significant difference in metabolic costs only in the third period of play. During the third period, female forwards and female defensemen used significantly fewer calories than male forwards (Table 2).
Summary and Discussion
The difference between female forwards and defense from male forwards may have arisen because of game strategy. In the women’s game, the team being tested was winning by a large margin, so their opponents may have given up and played at a lower intensity in the third period. The males being tested were also winning their game in the third period, but the opponents were not letting up in intensity of the game.
There is a small pool of similar studies about other collegiate sports. Schmidt (2010) conducted a study on female collegiate gymnasts and found they expended an average of 634 calories extra on practice days. This is less than the average female hockey player who expended an average of 784 calories per game. A study by Ousely-Pahnke et. al. (2001) found that during a 2 hour collegiate swim practice, female swimmers expended 732 ± 132 calories. This is close to the amount of calories female hockey players expended during the game, but less than the average 1232 calories expended by the men.
Literature cited
Agre, J.C. (1988). Professional ice hockey players: physiologic, anthropometric, and musculoskeletal characteristics. Archives Of Physical Medicine And Rehabilitation. 3,
Burr, J. F., Jamnik, R. K., Baker, J., Macphearson, A., Gledhill, N., McGuire, E. J. (2008). Relationship of physical fitness test results and hockey playing potential in elite level ice hockey players. Journal of Strength and Conditioning Research, 22,
Fornetti, W.C., Pivarnik, J. M., Foley, J. M., Feitchner, J. J. (1999). Reliability and validity of body composition measures in female athletes. Journal of Applied Physiology, 87,
Geithner, C. A., Lee, A. M., Bracko, M. R. (2006). Physical and performance differences among forwards, defensemen, and goalies in elite women’s ice hockey. Journal of Strength and Conditioning Research, 20,
Green, H., Bishop, P., Houston, M., McKillop, R. Norman, R., Stothart, P. (1976). Time-motion and physiological assessment of ice hockey players. Journal of Applied Physiology, 40,
Hiilloskorpi, H. K., Pasanen, M. E., Fogelholm, M. G., Laukkenan, R. M., Mantaari, A. T. (2003). The use of heart rate to predict energy expenditure from low to high activity levels. International Journal of Sports Medicine, 5 , 24.
Ousley-Pahnke, L. Black, D.R., Gretebeck, R. J. (2001). Dietary intake and energy expenditure of female collegiate swimmers during decreased training prior to competition. Journal of American Dietetic Associaiton (3)101, doi: /S (01)
USA Hockey Incorporated (2013). The official rules of ice hockey. Colorado Springs, CO.
Vescovi, J. D., Murray, T. M., VanHeest, J. L. (2006). Positional performance profiling of elite ice hockey players. International Journal of Sports Physiology and Performance, 1,
Acknowledgments
This project has been approved by Grand Valley State University’s HRRC { }. Thank you to the Office of Undergraduate Research and Scholarship for funding. Thank you to the Statistics Counseling Center for assistance in statistical analysis.