Specific Fitness Profiles through Analysis of the Correlation between Anaerobic Power, Maximal Strength, and Isokinetic Strength in Korean National Snowboarders

Research Subjects

The subjects of this study were 89 male and female snowboarders from the Korean National team (22.17 ± 4.82 yrs., 170.19 ± 16.17 cm, 74.61 ± 11.01 kg) whose physical characteristics and physical strengths have been measured regularly from 2013-2019. The physical characteristics of the subjects who participated in this study are shown in Table 1.

Measuring Methods

Body Composition. For body composition, we measured the snowboarders’ height (cm), body mass (kg), body fat percentage (% fat), weight with empty stomachs (kg), and body mass index (kg/m²) (Yoon et al., 2017) using bioelectrical impedance analysis and the InBody 720 multiple frequency bioelectrical impedance analysis device (Inbody Co., Ltd., Seoul, Korea).

Anaerobic Power. For anaerobic power, we measured the snowboarders’ peak power (w/kg), mean power (w/kg), and power-drop rate (%) using a 30-second Wingate test with a Monark Model 824E flywheel ergometer (Monark Exercise AB, Vansbro, Sweden) and a Brachumera Sport arm ergometer (Lode BV, Groningen, The Netherlands). To measure the variable of anaerobic power, we defined peak power (w/kg) as the maximum value of the sectional record for five seconds in 30 seconds of exercise time during the evaluation and defined mean power (w/kg) as an average of the sum of the average value of each five seconds. The participants performed a warm-up exercise using the cycle ergometer for three minutes at 60 rpm and 100 w, and this was measured for 30 minutes, with the tension set at 7.5% (4.41 J) relative to the body weight. The evaluation after the warm-up exercise started with an oral signal (“start”) following an oral count synchronized with a dial tone generated by a computer five seconds prior to the measurement (Kim, Song, & Min, 2016).

Maximal Strength. We measured the snowboarders’ maximal strength with an ACE 2000 multifunction exerciser (Ariel Dynamics Inc., Trabuco Canyon, California, USA), capturing the maximal weight each person could lift with a bench press and squat. After ten minutes of warm-up with active stretching, the athletes performed 8–10 rep. at 40–60% of the strength of one-repetition maximum (1RM). We measured this until the athletes could repeat the repetition with a weight increase of 5–10% for each set with a 3–5-minute break between sets (Grooten, Puttemans, & Larsson, 2002). The athletes were asked to stand upright, straighten their ankles and arms, grasp the handle of the measuring instrument, and bend their anterior scalene at about 30° to measure their back-muscle strength; this was done only once.

Isokinetic Strength. We measured the snowboarders’ isokinetic strength using a Humac^® Norm™ isokinetic measuring device (Computer Sports Medicine Inc., Stoughton, Massachusetts, USA). We measured the snowboarders’ knee-muscle strength at the angular velocity of 60°/sec and trunk strength at 30°/sec. First we measured the trunk strength followed by a sufficient break before measuring knee muscle strength. To measure their trunk strength, we adjusted the height of the foothold based on where the extension of the iliac crest on each athlete’s waist met the spine. We firmly fixed the femur and placed the scapula pad in the center of the scapula. The athletes’ upper bodies were completely fixed by connecting both linkages of the chest pads to the scapula pad. We asked them to grasp the handle in front of their chests with both hands. After we matched the driveshaft and the superior bone, we took the measurements while the athletes performed the actions of bending and elongating the waist joints, setting the operating range from 0° to 90° for elongation. To measure the athletes’ knee-muscle strength, we asked them to sit in the measurement chair. Then, we adjusted the table and backrest until the center point of the knee joint matched the rotation axis of the dynamometer. To ensure that no external force was applied on body parts other than the knee joints during the flexion and extension actions, we adjusted for their leg length, and then fixed their thighs and torsos in place with straps. We set the range of operation from 0°–90° of the extension and toll measurements while they conducted flexion and extension actions for each load velocity. During the measurements, they performed warm-up exercises for the extension and flexion movements three times to minimize any sense of unfamiliarity with or rejection of the equipment and maximize the performance. We calculated the peak torque (% BW) values after the athletes performed three flexion and extension actions with maximum force in both parts. We calculated the resulting values separately for the dominant and nondominant groups (Kim et al., 2016).

Data Processing Methodology

We analyzed all the data gathered using the software Windows SPSS Statistics Version 23.0 (Armonk, New York, USA: IBM Corp.), using skewness and kurtosis to analyze the data and confirm its normal distribution. We calculated the athletes’ body composition in mean (M) and standard deviation (SD). We conducted an independent t-test to examine the differences in body composition and professional body strength of male and female snowboarders. In addition, we used binary logistic regression to test the relationship among isokinetic strength, anaerobic power, and maximal strength. The statistical significance level was set at α = 0.05 for all items.

Trunk Strength, Anaerobic Power, and Maximal Strength

The results of the logistic regression analysis performed to examine the relationship among national snowboarders’ isokinetic trunk strength, anaerobic power, and maximal strength are shown in table 2. We separated the values into different three groups: males, females and total population. We found significant differences for both the males and the females in the flexor and extensor muscles in trunk strength of the lower body: (1) average power (flex/ex ratio total: β = .354, p = .006; flexor muscle total: β = .761, p < .001; extensor muscle total: β = .863, p < .001; (2) peak power (flex/ex ratio total: β = .422, p = .001; flexor muscle total: β = .659, p < .001, extensor muscle total: β = .835, p < .001.), and (3) power drop rate (flex/ex ratio total: β = .385, p = .003; extensor muscle total: β = .345, p = .007) in. However, we found no significant differences in the power-drop rate in the flexion muscles for either men or women. We found statistically significant differences in the flexor muscle, extensor muscle, and the ratio between flexor and extensor muscles for trunk strength for bench press which was the maximal strength (flex/ex ratio total: β = .254, p = .048; flexor muscle total: β = .352, p = .005; extensor muscle total: β = .449, p < .001); squat (flexor muscle total: β = .649, p < .001; extensor muscle total: β = .751, p < .001); and back strength (flex/ex ratio total: β = .399, p = .002; flexor muscle total: β = .652, p < .001; extensor muscle total: β = .841, p < .001.). However, for squat, there were no significant differences in the flex/ex ratio in either males or females.

Trunk Strength and Isokinetic Strength

The results of logistic regression analysis performed to examine the relationship between national snowboarders’ isokinetic trunk strength and lower body knee muscle strength are shown in table 3. We separated the values into three different groups: men, women, and the total population. For all the groups, we found significant differences in the total values for trunk strength, lower-body (knee) isokinetic strength, dominant flexor muscle trunk strength, trunk flexor and extensor strength, and the ratio between knee flexor and extensor strength (flex/ex ratio total: β = .267, p = .038; flexor muscle total: β = .717, p < .001; extensor muscle total: β = .822, p < .001); extensor muscle (flex/ex ratio total: β = .307, p = .016; flexor muscle total: β = .571, p < .001; and extensor muscle total: β = .724, p < .001). We also found significant differences in the total values of the nondominant flexor muscle (flexor muscle total: β = .749, p < .001; extensor muscle total: β = .834, p < .001); and extensor muscle (flex/ex ratio total: β = .360, p = .004; flexor muscle total: β = .569, p < .001; and extensor muscle total: β = .776, p < .001). However, no significant differences were shown in nondominant flexion PT in the nondominant for either males or females.