Skating performance in ice hockey when using a flared skate blade design

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This is an Author's Revised Manuscript of an article whose final and definitive form 1

has been published in the journal Cold Regions Science and Technology in January 2

2012 [copyright Elsevier] 3

To cite this paper: 4

Peter Federolf, Benno Nigg (2012): Skating performance in ice hockey when using a 5

flared skate blade design. Cold Regions Science and Technology 70, p. 12-18. 6

http://dx.doi.org/10.1016/j.coldregions.2011.08.009 7

http://dx.doi.org/10.1016/j.coldregions.2011.08.009

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Original Research 8

Skating Performance in Ice Hockey when using a Flared Skate Blade Design 9

Peter Federolf a,b, Benno Nigg a 10

a Human Performance Laboratory, University of Calgary, Calgary, Canada 11

b Norwegian School of Sport Sciences, Oslo, Norway 12

13

Corresponding author: Peter Federolf 14

Address: Human Performance Laboratory, University of Calgary, 2500 University 15

Drive NW., Calgary, Alberta, T2N 1N4, Canada 16

Phone: (403) 220-7003 17

Fax: (403) 284-3553 18

Email: [email protected] 19

20

21

22

mailto:[email protected]

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ABSTRACT 23

In ice hockey the skating speed and the agility of the players depend on the 24

interaction between the skate blade and the ice. A skate blade design that flares 25

outward towards the bottom of the blade changes the geometry of the blade-ice 26

contact. A previous study showed reduced blade-ice friction with flared blades set 27

vertically on the ice and mechanical considerations of the blade-ice penetration 28

suggest that flared blades might also improve the lateral grip on the ice in turns or 29

during push-off. However, skating is a complex motion depending on multifaceted 30

blade-ice interaction mechanisms and on the skaters’ individual technique. A 31

modification of the blade design may thus not cause the desired effect in actual 32

skating or may be uncomfortable for the players. The purpose of this study was 33

therefore to test if a flared blade design measurably improves skating performance of 34

ice hockey players in selected skating tests. Twelve experienced players of a 35

university ice hockey team volunteered for a glide turn test and a straight skating test. 36

In both tests, each subject performed five trials on the flared and on the standard 37

skate blade. The run times were used to quantify skating performance. In straight 38

skating, acceleration and maximum speed were assessed. After the tests, the 39

players’ subjective opinions about the two blades were evaluated using a visual 40

analog scale. The statistical analysis used effect sizes to test for blade effects on the 41

run times within subjects and two-way repeated measures ANOVAs to test for group 42

effects. The subjects performed on average 1.3%, 0.9%, and 1.3% faster on the 43

flared blades in the glide turn test, in the acceleration and the maximum speed of the 44

straight skating test, respectively. The blade effect was statistically significant 45

(p=0.016, p=0.049, p=0.007), however, the individual results suggested that not all 46

subjects benefited from the modified blade design. This might indicate that some 47

adaptation of the players’ skating technique to the blade condition was necessary. 48

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The results of this study show that relative simple modifications on ice hockey 49

equipment can lead to measurable improvements in skating performance. Further 50

research into the mechanics of the blade-ice interaction and new designs for skate 51

blades may therefore be able to further improve selected performance variables in 52

ice hockey. 53

54

Key Words: blade-ice interaction processes; cutting of ice; winter sports; sports 55

engineering; friction 56

57

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INTRODUCTION 58

In many countries ice hockey is one of the most popular winter sports. The 59

performance and success of ice hockey players depend on many factors, including 60

skating performance. Consequently, subject-specific factors, such as muscle strength 61

or anaerobic capacity, and training procedures to improve the players’ skating skills 62

have been studied in many research projects (Behm et al., 2005; Bracko, 2001; 63

Bracko and Fellingham, 1997; Bracko and George, 2001; Brocherie et al., 2005; 64

Cornish et al., 2006; Ebben et al., 2004; Geithner et al., 2006; Green et al., 2006; 65

Hoff et al., 2005; Manners, 2004; Mascaro et al. 1992). Technological innovations in 66

the skating equipment may also have the potential to substantially affect skating 67

performance, however, this topic has not received equal scientific attention. 68

Equipment-related research in ice hockey has predominantly focused on injury 69

prevention and protective gear such as helmets and mouth guards (Biasca et al., 70

2002; Knapik et al. 2007; Sherbondy et al., 2006; Spyrou et al., 2000; Stevens et al., 71

2006) or focused on performance improvement in shooting by studying the effects of 72

different hockey stick constructions on puck speed (Pearsall et al., 1999; Worobets et 73

al., 2006; Wu et al., 2003). 74

The interaction of the skate blade and the ice and how it may be affected by a 75

modification of the skate blade design have received little interest by scientists or 76

engineers. Consequently, the design of skate blades has not changed over several 77

decades. In the development of new designs of ice hockey skate blades two 78

interaction mechanisms between ice and blades need to be considered because they 79

limit the players’ speed and agility: a) friction and b) the lateral grip on the ice for 80

example when turning or when pushing-off from the blade. Low friction is particular 81

important during the gliding phase of the step cycle when the blade is set vertically on 82

the ice. Some blade properties that are thought or known to affect ice friction are the 83

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width of the blade (Federolf et al., 2008), the hollow (Figure 1) that is created when 84

sharpening the blade (Federolf, 2010; Morrison et al., 2005), the rocker radius and 85

centre, the blade temperature, the blade material and the surface treatment. The 86

lateral grip on the ice is crucial for skating performance because it prevents the skate 87

from slipping sidewise when the blade is inclined. Slippage would not allow the 88

athlete to push off with the same force, it would increase the radius of a turn, it would 89

increase frictional energy losses, and it would impede the player’s movement control. 90

The blade’s lateral grip on the ice depends on the penetration of the blade’s edge into 91

the ice (Figure 2). If the blade is inclined, this penetration process may be considered 92

as a cutting or machining process at a negative rake angle (Lieu and Mote, 1984; 93

Tada and Hirano, 1999). In analogy to observations in cutting and machining of other 94

materials one may speculate that smaller edge angles on the blade (called “wedge 95

angle” in metal cutting) or larger relief angles (Figure 2) might improve the 96

penetration of the blade into the ice and thus provide a better lateral grip. A flared 97

skate blade design (Figure 1), as presented by the company CT Edge Inc. 98

(Vancouver, Canada), features smaller edge angles and increases the relief angle 99

when the blade is inclined (Figure 2). This new blade design was developed with the 100

aim of improving the lateral grip on the ice (US patent 6,830,251). In friction tests with 101

the blades mounted on a test sled such that the blades were vertical on the ice, this 102

design also showed blade-ice friction coefficients that were approximately 20-23% 103

smaller than those of traditional blades (Federolf et al., 2008). 104

However, ice skating is a complex motion depending not only on the multifaceted 105

blade-ice interaction mechanisms, but also on the individual skating technique, on the 106

balance and control of the skaters, and possibly on other factors. A new blade design 107

with the purpose of improving ice friction and the blades lateral grip on the ice may 108

therefore not have the desired effects and may even be detrimental, for example, if 109

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the players have difficulties in adapting to the new design. It is therefore critical to test 110

new blade designs in practical, game-like situations with real ice hockey players. 111

The purpose of this study was to test if skilled ice hockey players measurably 112

improve their skating performance when skating on a flared skate blade design. As 113

performance variables the runtimes in a straight skating test and in a glide turn test 114

were selected. In the straight skating test acceleration and maximum speed were 115

also compared between blade conditions. In addition, it was investigated if the 116

players felt comfortable with the new blade and how they characterized the difference 117

they felt between the blade designs. 118

METHODS 119

Test Subjects 120

Twelve members of the University of Calgary men’s ice hockey team volunteered for 121

this study (Table 1). All subjects participating in this study were verbally informed of 122

the procedures, and all subjects gave informed written consent prior to the tests. The 123

study was approved by the University of Calgary Ethics Committee. Each subject was 124

a member of the University of Calgary men’s CIS - ice hockey team and had between 125

18 and 20 years of skating experience. 126

Skate Blades 127

Two skate blade types were selected for this study: standard blades, as owned and 128

previously used by the subjects, and the new flared skate blade, which had outward 129

blade angles measuring eight degrees (Figure 1). In all other dimensions, i.e. length, 130

height, and width at the blade holder, the two blade types were equal. All skates were 131

sharpened equally, with a “rocker/radius” (longitudinal curvature of the blade) of 3.35 132

m (11 feet), and a “hollow” depth (height of the transverse curvature of the blade) of 133

0.08 mm (0.032 inches). To create the same hollow depth on the wider flared blades, 134

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the sharpening stone had to be dressed with a larger radius. This was done 135

according to the guidelines provided by the manufacturer of the flared blades (CT 136

Edge Inc.). The quality of the blade sharpening was checked with a rocker template 137

and a “Quick Square” manufactured by Maximum EdgeTM, which had been modified 138

(with permission of the manufacturer) to accommodate the wider bottom of the new 139

blade design. 140

The test blades were mounted on the subjects’ own hockey skates. In some subjects 141

the rocker or hollow were changed from the ones they normally used to the rocker 142

and hollow tested in this study. These changes were done at the beginning of the 143

subjects’ ice hockey season (beginning of the semester). At the same time old blades 144

were replaced. This gave the subjects approximately 2 months to adjust to changes 145

in blade sharpening or to a new standard blade. Five weeks before the performance 146

tests were conducted, the subjects’ blades were exchanged with the flared blade 147

design to allow the subjects to become accustomed to the new skate blades. During 148

the semester the subjects performed a daily 2-hours ice hockey practice (Monday to 149

Friday) and on the weekends they participated in the games of the Canadian 150

Interuniversity Sport (CIS) league. In the CIS-games they could chose their standard 151

blade or the new blade, however, after two weeks practicing with the flared blades all 152

subjects chose to play on the flared blade. 153

Performance Tests 154

Each subject completed two performance tests in which five trials per blade condition 155

were recorded. Run times were measured using photocells (Brower Timing Systems, 156

South Draper, UT, USA). The first test was a glide turn test in which the subjects 157

skated around four pylons set 14 m apart, including two tight right turns and two tight 158

left turns (Figure 3a). The performance variable assessed in this test was the entire 159

run time of the glide turn test. Up to 3 players were tested on the same day, but after 160

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10-12 trials on the same ice, the entire set-up was moved to fresh ice in order to 161

minimize the effect of damaged ice. 162

The second test was a straight skating test over 45 m at maximum speed (Figure 3b). 163

Three performance variables were evaluated: The run time for straight skating was 164

measured between 0 and 40 m. Acceleration was quantified using the section times 165

between 0 and 10 m. Maximum speed was measured between 30 m and 40 m. The 166

finish line for the test subjects was set at 45 m to prevent subjects from slowing down 167

too early. In the maximum speed test up to 5 players were tested on the same day. 168

Maximum speed test and glide turn test were conducted on separate days. 169

In each test, the subjects performed five trials with each blade type. An experienced 170

skate technician exchanged the blades. Exchange of the blades required a break of 171

approximately 5 min per pair of skates in which the subjects rested on the bench. For 172

most subjects the blades were exchanged after 5 trials (one exchange). However, 173

since several subjects were tested at the same time, some subjects had their blade 174

changed after 3 and 8 trials or after 4 and 9 trials (two exchanges) in order to reduce 175

the break necessary for changing the blades. Before the first set of trials and after 176

the break required for exchanging the test blades, subjects were asked to warm up 177

and to get accustomed to the blade condition. The subjects could decide themselves 178

how long they needed. Typically the subjects felt ready for the test runs after skating 179

two or three laps on the rink. Half of the subjects started with the new blade design; 180

the other half started on standard blades. Subjects were randomly assigned to each 181

group and were not informed which blade they were skating on. However, in skating 182

the subjects seemed to recognize the blade condition immediately. Hence, blinded 183

test conditions were not present. 184

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Trials in which the subject slipped were omitted and repeated. Slips occurred rarely 185

on both blade types. A statistical analysis of the number of slips was therefore not 186

possible. 187

The tests were carried out during the Canadian university hockey season in an indoor 188

ice rink (Olympic ice pad), with the subjects in good physical condition. Each subject 189

had to complete each test on the same day, but they were allowed to recover 190

between repetitions with rest periods as long as the subjects felt they needed. 191

Subjective Assessment of the Test Blades 192

Immediately after the final test session (in which the subjects had skated on both 193

blade types), the subjects completed a questionnaire to assess if they felt a 194

difference between the new blade design compared to their standard blades. By this 195

time, the subjects had had on average five weeks to get accustomed to the new 196

flared blades. The questionnaire used a 10 cm visual analogue scale (VAS) (Figure 197

4). Task-specific assessments were given for (a) glide turn, (b) cross-over turn, (c) 198

changing direction, (d) stopping, and (e) “glidability.” Overall assessment of the 199

blades was addressed by the questions: (f) “which blades did you overall prefer?”, 200

and (g) “which blades would you purchase?” In addition to the filling out the 201

questionnaire, all subjects were encouraged to write down any observations they 202

made when skating on the new or on the standard blade. 203

Test Design and Statistics 204

When analyzing if the blade condition affects the subject’s run time two factors may 205

confound the conclusions: a) fatigue and b) the order in which the blades were 206

tested. Fatigue would cause a trend towards slower run times with increasing trial 207

number. The order in which the blades were tested could be significant, for example, 208

if players needed more time to adapt to the new blade after having the blade 209

changed. In order to minimize the effects that both confounding variables might have 210

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on the results of the comparison between the test blades, subjects were randomly 211

assigned to two equal sized sub-groups: players who started testing with the 212

standard blade (group 1) and players who started on the new flared blade (group 2). 213

It was hypothesised that if fatigue or order effects were present, then they would 214

cancel out when mean values of the whole test group were compared. 215

To identify effects in the whole group of subjects, a 2-way repeated measures 216

ANOVA was performed on the subjects’ mean run times per blade condition. The 217

blade condition was treated as a within subjects effect, the order in which the blades 218

were tested was considered a between subjects effect. In addition, the differences 219

between the mean values and the effect sizes, quantified by Cohen’s d, were 220

determined for each individual subject. Cohen’s d was calculated using the pooled 221

variance. A value of d > 0.8 was considered a large effect (Cohen, 1992). 222

This procedure was used for all performance variables tested in this study. All 223

statistical analyses were conducted with SPSS 16.0 for Windows, (SPSS Inc., 224

Chicago, Il, USA). The level of statistical significance was set at α ≤ 0.05 for all tests. 225

RESULTS 226

Skating Performance 227

The individual run times in the straight skating test (0 m to 40 m) and in the glide turn 228

test are listed in Tables 2 and 3, respectively. In the glide turn test (Table 4) subjects 229

were on average 1.3% faster when wearing the flared blade design. The blade effect 230

was statistically significant. The order in which the blades were tested did not affect 231

the test result. 232

In the straight skating test (Table 5) subjects were on average 1.0% faster when 233

skating on the new blades. The statistical analysis showed that the blade condition 234

had a significant effect on the subjects’ run times, however, the interaction 235

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blade*order was also statistically significant: Subjects who started the tests on the 236

new blade (group 2) tended to skate faster on the new blade compared to skating on 237

the standard blade (up to 3.8% faster). Subjects who started on the standard blades 238

(group 1) showed little difference in their skating times (between +/- 0.8 % time 239

difference). Similar results were found for the acceleration section (Table 6) and the 240

maximum speed section (Table 7) of the straight skating test. The overall 241

improvements with the new blade were 0.9% and 1.3% for acceleration and 242

maximum speed, respectively. In both cases the blade effect and the interaction 243

blade*order were statistically significant. 244

The effect sizes calculated for the individual subjects suggested that not all subjects 245

benefitted from the new blade. Seven of the twelve subjects showed a large blade 246

effect in the glide turn test, five of the twelve subjects in the straight skating test. 247

However, large effect sizes were only found when subjects performed better with the 248

flared blade. It was also observed that large effects seemed to appear not in the 249

same subjects when comparing the glide turn test and the straight skating test. 250

Differences in the Subjective Assessment of the Test Blades 251

All subjects preferred the new blade design to standard skate blades (Figure 5). For 252

specific tasks, the lowest preference ratings for the new blades were given for 253

stopping. The highest preference rating was indicated for both glide turns and for the 254

overall rating. All 12 subjects stated that, having the choice between the two blade 255

types, they would purchase the new blade design. The players made 18 written 256

comments comparing the skating characteristics of the new blades with the standard 257

blades. Seventeen of these statements were positive about the new blades, while 258

one comment was critical of them. 259

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DISCUSSION 260

In all four performance variables tested in this study the subjects skated on average 261

between 0.9% and 1.3% faster on the flared blade. These differences were 262

statistically significant. This suggests that the flared blade design with its smaller 263

edge angle and larger relief angle did improve aspects of the blade-ice interaction. 264

These improvements were substantial enough that they might be of practical 265

relevance in specific situations of a game. For example, when two players chase the 266

puck over a distance of 30m (half the length of an ice hockey rink) the skater on the 267

flared blade would be about 39 cm ahead (assuming that both start from zero velocity 268

and reach the same maximum speed as observed in the straight skating test). 269

Moreover, all subjects in this study indicated that they felt a difference between the 270

two blade types and all subjects preferred the flared blade to standard skate blades 271

(Figure 5). This subjective evaluation might be affected by a placebo effect, however, 272

the subjects’ preference of the flared blades and their comments were in line with the 273

expected differences in the blade-ice interaction mechanisms. For example, several 274

of the subjects’ written comments reported that improved friction was noticeable by 275

the subjects, for example, “way better glide,” “glide is amazing,” or “glide is noticeably 276

different.” This suggest that the reduced friction, which had been reported earlier 277

(Federolf et al., 2008), did contribute to an improved skating performance in a way 278

that was noticeable for the players. 279

The improved performance in the glide turn test and several subjective observations 280

of the subjects suggest that the flared blade also provided a better lateral grip on the 281

ice. The subjects stated, for example, “new blades allowed tighter turns,” “new blades 282

felt sharper,” “more power when pushing off,” or “fewer ice chips.” The manufacturer 283

of the blade suggested that due to the sharper edges, the new blades might 284

penetrate deeper into the ice when the blades are inclined. Another hypothesis may 285

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be that the side angle of the flared blade increased the relief angle and thus reduced 286

the likelihood of contact between ice and the side surface of an inclined blade. In 287

skating, the blade inclination changes constantly. If an increase of the blade 288

inclination would decrease the relief angle to zero then it might cause pressure 289

between the blades side face and the ice (Figure 2). This could potentially affect the 290

blade’s grip on the ice. 291

A third effect that may have affected the test results might be improved balance due 292

to a wider support area. The new blade angles outward near the bottom of the blade 293

increasing the width of the blade by about 50%. This may have given the subjects 294

improved stability. This hypothesis was inferred from the written statements of the 295

subjects in this study, who reported “felt more comfortable and confident on the new 296

blade,” “far better balance straight leg,” or “more stability.” 297

While the results of this study suggest that there might be functional differences 298

between the blade designs, several results also suggested that not all subjects were 299

able to equally benefit from such functional differences: in each test several subjects 300

showed large effect sizes, however, there were also a number of subjects whose 301

effect sizes did not suggest that the blade design affected their performance. 302

Moreover, the two skaters with the best improvement in the straight line run times (9 303

and 12) showed poor or no improvements in the glide turn times. Conversely, the two 304

skaters with the best improvement in the glide turn run times (2 and 6) had poor or no 305

improvements in the straight line run times. These results suggest that the individual 306

performance on the different blade types might depend on the subjects’ ability to 307

adapt their skating technique to the specific blade design. For example, one might 308

hypothesize that improved lateral grip of one blade design might only be effective if 309

the players trust this improved grip enough and actually increase the (turning) forces 310

exerted to the blade-ice contact. Better glide might be most effective if the skaters are 311

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able to keep the blades vertically on the ice, which requires a fine-tuned balancing. 312

The ability of the subjects to adapt their skating in one or the other task might differ 313

and might explain the subject specific improvements. Moreover, the test design 314

required the subjects to adapt their skating technique within a few minutes to a 315

different blade condition after their blades were exchanged. If a subject needed more 316

time to adapt, then this might affect his performance. It is possible that in the straight 317

skating tests not all subjects had sufficient time to fine-tune their skating to the blade 318

condition. This may have lead to a significant interaction effect between the blade 319

condition and the testing order. 320

Limitations of this study 321

Testing with human subjects has the advantage that the results are of high practical 322

relevance, however, it has the disadvantage that many factors which are difficult to 323

control may have an influence on the results. In this study, potential effects due to 324

subject fatiguing or due to the order in which the blades were tested were specifically 325

addressed in the design of the study: equal number of subjects started their tests with 326

either blade condition and the subjects were randomly assigned to these groups. 327

However, other factors which were not explicitly controlled in this study may also 328

affect the subjects’ runtimes. For example, all test blades in this study were 329

sharpened with the same rocker and the same hollow. This improved comparability of 330

the test results, however, it also required some subjects to adapt to sharpening 331

characteristics that they normally did not use. Since there were indications that 332

adaptation effects might have played a role this additional uncertainty may constitute 333

a confounding effect. 334

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CONCLUSIONS AND OUTLOOK 335

The flared skate blade design tested in this study allowed several subjects to skate 336

substantially faster in the straight skating and glide turn tests. The mean differences 337

(between 0.9% and 1.3%) were large enough that ice hockey players might have an 338

advantage in their game. However, the individual results showed that not all subjects 339

benefited from the modified blade design. 340

The results of this study show that relative simple modifications on ice hockey 341

equipment can lead to measurable improvements in skating performance of at least 342

some players. Further research into the mechanics of the blade-ice interaction and 343

into new designs for skate blades may be able to further improve selected 344

performance variables in ice hockey. One focus area for such research could be 345

further studies investigating blade-ice friction. Studies investigating what factors 346

influence the blades’ lateral grip on the ice would be particularly useful, since 347

theoretical concepts of the how an ice hockey blade cuts into the ice are scarce and 348

a validation of such models are widely missing. 349

ACKNOWLEDGEMENTS 350

Robert Mills and skate technician Jamie Wilson were responsible for coordinating 351

with subjects, sharpening skate blades, exchanging blades on the subjects’ skates, 352

and assisted in all measurements. Support from the Calgary Olympic Oval and the 353

participation of the University of Calgary Dinos men’s ice hockey team is gratefully 354

acknowledged. Dr. Tak Shing Fung helped with the statistical analysis. 355

The study was financially supported by CT Edge Inc. of Vancouver, Canada and the 356

Da Vinci Foundation, Calgary, Canada. 357

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CONFLICT OF INTEREST STATEMENT 358

The company CT Edge of Vancouver, Canada, has funded this study and provided 359

the flared blades used in this study. The company CT Edge did not influence the 360

design, data analysis, interpretation, or manuscript writing of this study. 361

None of the authors has financial or personal relationships with the company CT 362

Edge. 363

364

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effects of stick construction and player skill. Sports Engineering 6, 31-40. 433

434

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TABLES 435

Table 1: Subject statistics of the participants in this study. 436

437

438

439

440

441

442

ID age

[years] height

[m] weight

[kg]

1 24 1.83 83.9 2 22 1.75 86.2 3 22 1.88 86.2 4 22 1.78 72.6 5 22 1.83 97.5 6 22 1.83 83.9 7 22 1.85 83.9 8 24 1.80 90.7 9 24 1.85 84.8

10 23 1.85 83.9 11 22 1.92 99.8 12 22 1.91 94.4

mean 22.6 1.84 87.3 SD 0.9 0.05 7.3

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Table 2: Individual run times in the straight skating test in the order they were 443

collected 444

ID

order 1: ST first 2: CT first

trial 1 [s]

trial 2 [s]

trial 3 [s]

trial 4 [s]

trial 5 [s]

trial 6 [s]

trial 7 [s]

trial 8 [s]

trial 9 [s]

trial 10 [s]

2 1 5.49 5.52 5.53 5.55 5.63 5.61 5.59 5.62 5.63 5.76 3 1 5.56 5.64 5.61 5.71 5.48 5.56 5.55 5.66 5.63 5.72 4 1 5.12 5.1 5.13 5.12 5.1 5.1 5.16 5.12 5.17 5.17 6 1 5.52 5.44 5.44 5.46 5.64 5.47 5.58 5.45 5.51 5.38 7 1 5.49 5.47 5.45 5.42 5.51 5.49 5.46 5.57 5.51 5.48

11 1 5.25 5.31 5.26 5.21 5.28 5.35 5.28 5.21 5.15 5.25 1 2 5.35 5.34 5.29 5.36 5.36 5.43 5.42 5.4 5.38 5.57 5 2 5.52 5.47 5.57 5.52 5.62 5.57 5.62 5.56 5.57 5.70 8 2 5.17 5.12 5.02 5.32 5.34 5.15 5.19 5.33 5.37 5.42 9 2 5.15 5.3 5.25 5.2 5.23 5.38 5.39 5.38 5.42 5.47

10 2 5.17 5.18 5.06 5.07 5.06 5.36 5.19 5.2 5.31 5.25 12 2 5.24 5.15 5.19 5.25 5.26 5.5 5.49 5.41 5.29 5.43

ID = subject number, order indicates which blade condition was tested first, for each 445

trial the run time and the test blade is listed: ST = standard blade, CT = CT EdgeTM 446

blade, run times obtained with the CT blades were shaded 447

448

- 23 -

Table 3: Individual run times [s] in the glide turn test in the order they were 449

collected 450

ID

order 1: ST first 2: CT first

trial 1 [s]

trial 2 [s]

trial 3 [s]

trial 4 [s]

trial 5 [s]

trial 6 [s]

trial 7 [s]

trial 8 [s]

trial 9 [s]

trial 10 [s]

1 1 12.75 12.96 13.07 13.18 13.65 12.75 12.71 12.84 12.92 12.95 3 1 13.15 13.09 13.39 13.02 13.03 13.25 13.03 12.97 12.96 13.12 5 1 13.38 13.47 13.47 13.33 13.40 13.19 13.06 13.16 13.11 12.88 8 1 13.24 13.44 13.48 13.39 13.24 13.19 13.04 13.13 13.10 13.31

10 1 12.26 13.43 12.86 12.64 12.77 12.46 12.68 12.82 12.92 12.76 12 1 13.47 13.50 13.48 13.49 13.78 13.53 13.58 13.67 13.56 13.64 2 2 13.15 13.28 13.25 13.17 13.58 13.58 13.74 13.88 13.75 13.78 4 2 12.65 12.58 12.59 12.76 12.67 12.88 12.76 12.83 12.66 12.66 6 2 12.92 12.85 13.04 12.78 13.28 13.73 13.51 13.47 13.49 13.13 7 2 13.35 13.36 13.24 13.37 13.43 13.76 13.31 13.32 13.32 13.69 9 2 12.69 12.35 14.12 12.93 12.86 12.70 12.94 12.89 12.88 12.77

11 2 13.87 13.89 13.81 13.53 13.63 13.87 13.69 13.72 13.95 13.77

ID = subject number, order indicates which blade condition was tested first, for each 451

trial the run time and the test blade is listed: ST = standard blade, CT = CT EdgeTM 452

blade, run times obtained with the CT blades were shaded 453

454

455

- 24 -

Table 4: Mean values, standard deviation σ, and relative difference in the subjects’ 456

run times in the glide turn test. Negative values in the relative difference indicate that 457

the subject was faster wearing flared blades, positive values indicate that the subject 458

was faster wearing standard blades. 459

MEAN RUN TIMES IN THE GLIDE TURN TEST

ID order 1: ST first 2: CT first

Standard blades Flared blades difference

[%] Effect size

mean [s]

σ [s]

mean [s]

σ [s]

Cohen’s d

1 1 13.12 0.34 12.83 0.10 -2.2% 1.2

2 2 13.75 0.11 13.29 0.17 -3.3% 3.2

3 1 13.14 0.16 13.06 0.11 -0.6% 0.6

4 2 12.78 0.08 12.63 0.04 -1.2% 2.4

5 1 13.41 0.06 13.08 0.12 -2.5% 3.5

6 2 13.47 0.22 12.97 0.20 -3.7% 2.4

7 2 13.48 0.23 13.35 0.07 -1.0% 0.8

8 1 13.36 0.11 13.15 0.10 -1.5% 2.0

9 2 12.84 0.10 12.99 0.67 1.2% 0.3

10 1 12.79 0.42 12.73 0.17 -0.5% 0.2

11 2 13.80 0.11 13.75 0.16 -0.4% 0.4

12 1 13.54 0.13 13.60 0.06 0.4% 0.6

mean difference in run time: -1.3%

Two-way ANOVA for repeated measures: blade effects (within subjects): F(1,10)=8.297, p=0.016 order effects (between subjects): F(1,10)=0.297, p=0.753 order*blade effects (within subjects): F(1,10)=0.104, p=0.598

460

461

- 25 -


run times in the straight skating test. Negative values in the relative difference 463

indicate that the subject was faster wearing flared blades, positive values indicate 464

that the subject was faster wearing standard blades. 465

MEAN RUN TIMES IN THE STRAIGHT SKATING TEST



[%] Effect size

mean [s]

σ [s]

mean [s]

σ [s]

Cohen’s d

1 2 5.39 0.03 5.39 0.11 -0.1% 0.0

2 1 5.57 0.11 5.62 0.02 0.8% 0.6

3 1 5.60 0.09 5.62 0.07 0.4% 0.2

4 1 5.14 0.03 5.12 0.02 -0.4% 0.8

5 2 5.59 0.03 5.56 0.09 -0.6% 0.4

6 1 5.50 0.08 5.48 0.07 -0.4% 0.3

7 1 5.47 0.03 5.50 0.04 0.6% 0.8

8 2 5.29 0.12 5.19 0.14 -1.9% 0.8

9 2 5.41 0.04 5.23 0.06 -3.4% 3.5

10 2 5.26 0.07 5.11 0.06 -2.9% 2.3

11 1 5.26 0.04 5.25 0.07 -0.3% 0.2

12 2 5.42 0.08 5.22 0.05 -3.8% 3.0


Two-way ANOVA for repeated measures: blade effects (within subjects): F(1,10)=8.273, p=0.016 order effects (between subjects): F(1,10)=0.854, p=0.377 order*blade effects (within subjects): F(1,10)= 11.207, p=0.007

466

467

- 26 -


acceleration times. Negative values in the relative difference indicate that the subject 469

was faster wearing flared blades, positive values indicate that the subject was faster 470

wearing standard blades. 471

MEAN ACCELERATION TIMES (0-10M)



[%] Effect size

mean [s]

σ [s]

mean [s]

σ [s]

Cohen’s d

1 2 1.86 0.03 1.86 0.07 0.0% 0.0

2 1 1.96 0.03 1.97 0.02 0.6% 0.4

3 1 1.92 0.09 1.93 0.05 0.2% 0.1

4 1 1.73 0.01 1.74 0.03 0.8% 0.4

5 2 1.97 0.03 1.96 0.04 -0.7% 0.3

6 1 1.88 0.06 1.90 0.07 1.2% 0.3

7 1 1.81 0.03 1.82 0.06 0.7% 0.2

8 2 1.83 0.07 1.79 0.07 -2.1% 0.6

9 2 1.79 0.03 1.76 0.02 -2.1% 1.2

10 2 1.76 0.08 1.69 0.05 -3.8% 1.0

11 1 1.79 0.04 1.77 0.06 -1.1% 0.4

12 2 1.82 0.05 1.74 0.03 -4.2% 1.9



472

473

- 27 -


maximum speed. Negative values in the relative difference indicate that the subject 475

was faster wearing flared blades, positive values indicate that the subject was faster 476

wearing standard blades. 477

MEAN SPEED IN THE MAXIMUM SPEED SECTION (30-40M)



[%] Effect size

mean [m/s]

σ [m/s]

mean [m/s]

σ [m/s]

Cohen’s d

1 2 9.20 0.28 9.23 0.13 -0.3% 0.1

2 1 9.18 0.23 9.09 0.15 0.9% 0.5

3 1 8.91 0.10 8.82 0.09 1.1% 0.9

4 1 9.62 0.11 9.62 0.07 0.0% 0.0

5 2 8.93 0.06 9.09 0.15 -1.8% 1.4

6 1 9.03 0.07 9.11 0.04 -0.9% 1.4

7 1 8.87 0.04 8.80 0.12 0.7% 0.8

8 2 9.35 0.21 9.61 0.33 -2.7% 0.9

9 2 8.90 0.09 9.40 0.15 -5.7% 4.0

10 2 9.19 0.11 9.53 0.21 -3.6% 2.0

11 1 9.26 0.09 9.26 0.17 0.0% 0.0

12 2 9.03 0.10 9.36 0.10 -3.7% 3.3

mean difference in speed: -1.3%


478

479

- 28 -

Figure Captions 480

Figure 1 Schematic illustration (not to scale) of the cross-sectional shapes of a 481

standard blade (STD) and of the new flared skate blade design 482

developed by CT Edge Inc. (CT). The “blade angle”, the “edges” of the 483

blade, and the “hollow” at the running surface of the blade, which is 484

created by sharpening, are indicated in the illustration. 485

Figure 2 Schematic illustration of the rake angle, edge angle and relief angle of a 486

standard blade (black) and a flared blade (white broken line). Note: the 487

relative width of the flared blade as compared to the standard blade is in 488

this schematic not to scale. 489

Figure 3 Schematic illustrations of the test set-ups used to determine skating 490

performance: (a) set-up used to determine acceleration (0 – 10 m), 491

maximum speed (30 – 40 m), and total run time (0 – 40 m); (b) set-up of 492

the glide turn test. 493

Figure 4 Visual Analog Scale (VAS) used to assess the subject’s opinion about 494

the different blade types. A mark at the left end indicated that the subject 495

preferred the standard blade to 100%, a mark in the middle (0) indicated 496

no preference, and a mark at the right end indicated preference of the 497

new blade design (“CT Edge”) to 100%. 498

Figure 5 Averages of the feedback of the 12 subjects when asked “which blade do 499

you prefer?” The thick black bar indicates the mean value. The gray box 500

indicates the standard deviation of the subjects’ ratings. 501

502

503

504

- 29 -

505

506

507

STD CT

hollow

blade

angle

edge

- 30 -

508

Ice

+ -

Skate

blade

edge

angle

relief

angle

rake angle

- 31 -

509

510

- 32 -

511

512

513

standard 0 new blade

- 33 -

514

515

516

Glide Turn

Cross-over Turn

Changing Direction

Stopping

Glidability

Overall Preference

new 0 standard

0

0

0

new standard

new standard

new standard

standard

new standard

0

0

new

Skating performance in ice hockey when using a flared skate blade design

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