Physique and body composition

Height was measured nearest 0.1cm using an anthropometer, and body weight, BMI and body fat were measured for body composition using Inbody 720 (Biospace, Korea). After first measuring body weight and height, players were told to stand on foot plate electrodes, grab electrodes on both hands, open their arms to about 30° and away from their body, and stand still during measurement.

Measurement of physical fitness

Muscular strength

Back muscle strength was measured using back muscle dynamometer (TKK-1270, Takei, Japan) by making the subjects stand with knees and arms open while grabbing the handle, straightening the waist and then bending the waist forward by about 30 degrees to exert maximal force in perpendicular direction. This procedure was repeated twice and higher value was recorded. Grip was measured using grip dynamometer (TKK-1270, Takei, Japan) by making the subjects exert maximal force after adjusting the adjustment screw so that the second joint of the index finger is almost at a right angle. Left and right sides were alternately measured twice, and higher value was recorded.

Leg strength was measured using isokinetic muscle strength measuring device (Humac Norm, CSMI, USA). Leg strength was measured at angular speed of 60°/sec and trunk strength was measured at angular speed of 30°/sec. After adjustment of posture, players were given sufficient explanation on the measurement method before repeating warm-up exercise several times and measuring. Leg strength was measured first, and trunk strength was measured after taking enough rest. After repeating flexion and extension of the two parts three times at maximum force, peak torque (%BW) of flexion and extension was calculated.

Muscle endurance for sit-up, number of sit-ups done in a minute was recorded by bending knees to right angle and counting the number of times in which two elbows touch the knees and return to starting position.

Power

For Sargent jump, highest distance was recorded using Sargent jump meter (TKK-1220, Takei, Japan) after the subjects jumped in place. Standing long jump measured distance jumped from a take-off board. Both Sargent jump and standing long jump were done twice to record higher values.

Anaerobic power

Peak power (w/kg), mean power (w/kg) and power drop rate (%) were measured by 30-second Wingate test using bicycle ergometer (Monark 824E, Sweden). Warm-up exercise was done by lightly pedaling for less than 3 minutes on the bicycle ergometer. The bicycle ergometer exercise was done with full strength for 30 seconds when the subjects were given a ‘start’ signal.

Cardiorespiratory endurance

Maximum oxygen uptake was measured by maximum exercise load test using respiratory gas analyzer (Quinton, USA). KISS protocol developed by Korea Institute of Sport Science was used as the measurement protocol. Starting on a 6% slope at speed of 80m/min, speed was increased by 20m/min at every 2 minutes and measurement was done until all subjects were out. Maximum oxygen uptake was determined by maximum value of oxygen uptake.

20m shuttle run was measured by running 20m distance according to sound source. Running ended upon second time at which the subjects failed to reach the destination before the signal sound, and the number of repetitions was recorded.

Pulmonary function was measured using Chestgraph HI-101(Chest M.I Inc, Japan) by making the subjects stand up, take a deep breath with the mouth piece on the mouth, and fully breathe air out of the lungs. Measurement was repeated twice, and higher value was recorded.

Flexibility

Sitting trunk flexion was measured using sitting trunk flexion meter (Welltek, Korea) by making the subjects sit with legs straight and bend the upper body forward as much as possible without bending the knees.

Trunk extension was measured using trunk extension meter (TKK-1860, Takei, Japan). During measurement, an assistant grabbed both ankles of the subjects and the subjects put both hands on their waist while lying face down, lift the upper body as much as possible, and maintaining lifted posture for 1 second or longer with the chin lifted. Linear distance from the chin to the floor was measured. Both sitting trunk flexion and trunk extension were measured twice, and higher values were recorded in cm.

Statistics

For data analysis of the study results, SPSS 21.0 was used to calculate mean and standard deviation of all measurement items. Independent t-test was performed to find the differences in body composition, basic physical fitness and professional physical fitness between forwards and defenders. Statistical significance level was p<0.05 for all analyses.

Muscular strength

The results of examining physical fitness attributes of the Korean national women’s ice hockey players and comparing muscular strength factor between forwards and defenders are as presented in <Table 2>.

Mean leg strength of right flexion was 119.8 ± 18.28%BW, and it was significantly higher (p<0.05) in forwards (M=126.1%) than defenders (M=112.3%BW).

Mean leg strength of right extension of the national team was 246.8 ± 31.40%, and it was significantly higher (p<0.05) in forwards (M=258.5% BW) than defenders (M= 234.2% BW). Mean leg strength of left flexion and left extension was 118.6 ± 18.56% BW and 237.85 ± 28.19%, respectively. There was no significant difference between forwards and defenders.

Mean back strength of the national team was 97.7 ± 12.35kg and mean left and right grips were 34.5 ± 4.16kg and 34.5 ± 4.16kg, respectively. There was no significant difference in back strength and grip between forwards and defenders.

Mean trunk strength of flexion and extension was 244.2 ± 45.57% and 339.6 ± 80.44%, respectively. Mean sit-up count was 48.7 ± 9.13 times. There was no significant difference in both trunk strength and sit-up between forwards and defenders.

Power

The results of examining physical fitness attributes of the Korean national women’s ice hockey players and comparing power factor between forwards and defenders are as presented in <Table 2>.

Mean Sargent jump of the national team was 44.4 ± 4.61cm and mean standing long jump was 197.8 ± 11.6cm. There was no significant difference in Sargent jump between forwards and defenders.

Peak power of the national team was 9.52 ± 0.734W/kg, mean power was 6.55 ± 0.529W/kg, and power drop rate was 58.0 ± 6.08%. There was no significant difference in peak power, mean power and power drop rate between forwards and defenders.

Cardiorespiratory endurance

The results of examining physical fitness attributes of the Korean national women’s ice hockey players and comparing cardiorespiratory factor between forwards and defenders are as presented in <Table 2>.

Mean maximum oxygen uptake of the national team was 50.79 ± 4.20 ml/kg/min, and it was significantly higher (p<0.05) in forwards (M=52.80 ml/kg/min) than defenders (M=48.21ml/kg/min).

Mean 20m shuttle run of the national team was 64.2 ± 12.9 times, and it was significantly higher (p<0.05) in forwards (M=69 times) than defenders (M=62.6 times).

Mean vital capacity of the national team was 3,170.2 ± 394.9cc, and mean one-second capacity was 2,937.8 ± 331.4cc. There was no significant difference in vital capacity and one-second capacity between forwards(3210.8 ± 421.5) and defenders(3093.6 ± 411.9).

Flexibility

Flexibility factor between forwards and defenders are as presented in <Table 2>.

Mean sitting trunk flexion of the national team was 26.8 ± 6.00 and trunk extension was 54.7±8.88cm. There was no significant difference in both sitting trunk flexion (25.2 ± 7.08 vs 28.4 ± 2.62) and trunk extension (53.4 ± 9.84 vs 54.2 ± 5.34) between forwards and defenders.

strength

Muscular strength is divided into absolute muscular strength and relative muscular strength, and both absolute and relative muscular strengths are important in ice hockey. Absolute muscular strength provides strength to move and withstand body contact with other players. Relative muscular strength provides strength for quickness, speed and agility (Twist, 2007; Twist & Rhodes, 1993b). Since body checking is not permitted in women’s ice hockey, relative muscular strength for speed and agility is more important (Twist, 2007). Leg strength of right flexion and right extension of the Korean national women’s ice hockey team was significantly higher in forwards than defenders. There was no significant difference in left flexion and left extension. A study of Ha & Kim (2013) on male ice hockey players reported that isokinetic leg strength of right flexion and right extension is significantly higher in defenders than forwards. Muscular strength of lower body is needed for sudden stop, quick direction change, and high-speed turn during skating. In women’s ice hockey, forwards showed higher relative muscular strength because they are required to show faster skating speed, wider range of activity and quick direction change compared to defenders.

Muscular strength of upper body is needed for accurate handling of puck and maintenance of shooting posture. In addition, core muscular strength greatly helps balance, stabilization, power and delivery of strength from lower limbs to upper limbs during game (Twist, 2007). There was no significant difference in back strength, grip, trunk strength (flexion, extension) and sit-up of the national team between forwards and defenders. However, according to studies of Burr et al. (2008) and Vescovi et al. (2006) conducted on men’s ice hockey, both muscular strength and muscular endurance of upper body were significantly higher in defenders than forwards. Whereas defenders need high muscular strength of upper body to push forwards away from the goal post using muscular strengths of upper body and lower body because of ice checking in men’s ice hockey, there is no difference between forwards and defenders in women’s ice hockey because body checking is not permitted. Although muscle hypertrophy is not the main focus of training in ice hockey, as sufficient muscle mass is important in all aspects and can reduce risk of injuries (Twist & Rhodes, 1993b), training that focuses on increasing muscle mass can be important during off-season (Moller & Bracko, 2004). On the one hand, since excessive muscle can affect skating speed and agility and increase of body weight from increase of muscle can consume greater energy for movement, deceleration and direction change (Bompa & Haff, 2009), muscle mass should only be increased by appropriate amount.

Power

Muscular strength is important in ice hockey, but muscular power is more essential (Moeller & Bracko, 2004; Twist & Rhodes, 1993b). Ability to make fast speed is the most important part of ice hockey game (Twist & Rhodes, 1993b), and power is an important factor of acceleration (Bompa & Haff, 2009). There was no significant difference in power variables like Sargent jump, standing long jump, peak power and mean power between forwards and defenders. Studies of Ransdell et al. (2013) and Vescovi et al. (2006) reported that there is no significant difference in muscular power between forwards and defenders. However, a study of Burr et al. (2008) on male ice hockey players reported that peak power and standing long jump of defenders are significantly higher than forwards. There is no difference in power between forwards and defenders because both forwards and defenders are required to respond to various situations and repeatedly exhibit explosive performance during three 20-minute game periods on ice.

Comparing the Korean national team with global players, Sargent jump of the Korean national team was lower than elite players of the U.S national team and 13 other nations and higher than college teams of Canada and NCAA Division III teams <Table 4>. Standing long jump was lower than top and middle-ranking elite players of the U.S national team and 13 other nations but higher than low-ranking players <Table 4>. Ransdell et al. (2013) reported that players of top-ranking nations showed about 6-12% higher power of lower body compared to players of low-ranking nations. To improve athletic performance of the Korean national team, it would be necessary to increase power of lower body to the same level as high-ranking nations. Exercises such as maximum muscular strength, plyometric, power clean and snatch should be continuously done to improve power of lower body. In addition, the Korean national team was found to have lower power drop rate compared to players of NCAA Division III. Power drop rate is an indicator used to check power endurance, and lower power drop rate indicates higher power endurance. Ice hockey game consistently requires high power, and players need to have enough power endurance to able to respond to various situations and repeatedly exhibit explosive strength during 60 minutes of game time (Twist & Rhodes, 1993b). As power drop rate of the Korean national team was relatively low, lactic acid resistance training that can improve power endurance would be necessary.

Cardiorespiratory endurance

It is estimated that 31% of energy required in ice hockey is supplied by aerobic system (Moeller & Bracko, 2004). High level of aerobic ability is important because it increases endurance needed for actions continuously repeated for 60 minutes (Twist, 2007; Bracko, 2001). Maximum oxygen uptake and shuttle run, variables of aerobic power, were significantly higher in forwards than defenders (p<0.05). Whereas aerobic ability of forwards was higher than defenders in a study of Twist & Rhodes (1993a), aerobic ability of forwards was significantly lower than defenders in studies of Ha & Kim (2013) and Burr et al. (2008). The reason why aerobic ability was higher in forwards than defenders is probably because of repeated speed actions during game, quick recovery during short time of substitution, and consistent agility and speed training.

Comparing maximum oxygen uptake of the Korean team with global players, it was higher than high, middle and low-ranking elite players of 13 nations and higher than college teams of Canada <Table 3>. The Korean national team showed higher level of aerobic ability compared to global players, suggesting that its aerobic ability is well trained. On the one hand, Carey, Pliego & Raymond (2007) proposed that there is minimal aerobic ability required to improve recovery in women’s ice hockey, and they reported that higher aerobic ability does not provide additional recovery. In addition, since intensive interval training develops aerobic ability, they suggested that there is no need to include a separate aerobic program in training. As the Korean national team currently has relatively excellent level of aerobic ability, no separate training program is necessary for aerobic ability.

Flexibility

Flexibility is important because of unexpected movement from reaction in sports. Joints must be able to pass all motions to reduce risk of injuries (Twist, 2007). Especially, flexibility of the hip, inguinal region and thighs increases skating speed and efficiency and decreases risk of injuries (Moller & Bracko, 2004; Twist & Rhodes, 1993b). There was no significant difference in flexibility variables like sitting trunk flexion and trunk extension between forwards and defenders. A study of Burr et al. (2008) also reported that there was no significant difference in flexibility between forwards and defenders. Crouching posture maintained throughout game time refers to a state in which hamstring muscles are not completely extended and causes excessive contraction of hamstrings. Since excessive contraction of hamstrings can hinder skating speed and power, flexibility of hamstrings is particularly important (Twist & Rhodes, 1993b). Also, when players cannot fully straighten their hind leg while skating, poor skating speed and skate mechanic can restrict flexibility of other body parts. Players must maintain flexibility through regular stretching (Twist & Rhodes, 1993b). It would be desirable for the Korean national team to maintain current flexibility.