Kenneth W. Rundell

Kinematics of cross-country ski racing.

This study investigated the evolution of skiing velocity, cycle length, and cycle rate in elite and subelite skiers during cross-country ski races. Senior male cross-country skiers engaged respectively in a 30-km skating race (N = 34) or a 50-km classical race (N = 27) were videotaped as they skied two different sections of 30 m, a 7 degrees uphill, and a flat section. In the skating race, most skiers used the offset technique on uphill and the 2-skate on flat, while the preferred techniques during the classical race were the diagonal stride for uphill and double-poling on flat. Results demonstrated that faster skiers had longer cycle lengths than slower skiers except for the flat sections of the classical race. Cycle rate was not different between skiers of different performance levels in any circumstances or races. Decreased velocity observed during the second half of the skating race was almost entirely due to a decrease in cycle length. We conclude that slower athletes should emphasize extending cycle length during their technical training. Therefore, skiers should place an emphasis on strength and power training to increase their kick and pole pushes and enhance cycle length.

Evidence for restricted muscle blood flow during speed skating.

INTRODUCTION We have previously hypothesized restricted muscle blood flow during speed skating, secondary to the high intramuscular forces intrinsic to the unique posture assumed by speed skaters and to the prolonged duty cycle of the skating stroke. METHODS To test this hypothesis, we studied speed skaters (N = 10) during submaximal and maximal cycling and in-line skating, in both low (knee angle = 107 degrees) and high (knee angle = 112 degrees) skating positions (CE vs SkL vs SkH). Supportive experiments evaluated muscle desaturation and lactate accumulation during on-ice speed skating and muscle desaturation during static exercise at different joint positions. RESULTS Consistent with the hypothesis were reductions during skating in VO2peak (4.28 vs 3.83 vs 4.26 L x min(-1)), the VO2 at 4 mmol x L(-1) blood lactate (3.38 vs 1.93 vs 3.31 L x min(-1)), and cardiac output during maximal exercise (33.2 vs 25.3 vs 25.6 L x min(-1)). The reduction in maximal cardiac output was not attributable to differences in HRmax (197 vs 192 vs 193 b x min(-1)) but to a reduction in SVmax (172 vs 135 vs 134 mL x beat(-1)). The reduction in SV appeared to be related to an increased calculated systemic vascular resistance (354 vs 483 vs 453 dynes x s(-1) x cm(-1)). During maximal skating there was also a greater % O2 desaturation of the vastus lateralis based on near infrared spectrophotometry (50.3 vs 74.9 vs 60.4% of maximal desaturation during cuff ischemia). The results were supported by greater desaturation with smaller knee angles during static exercise and by greater desaturation and accelerated blood lactate accumulation during on-ice speed skating in the low vs high position. The results of this study support the hypothesis that physiological responses during speed skating are dominated by restriction of blood flow, attributable either to high intramuscular forces, the long duty cycle of the skating stroke, or both.

Physiological characteristics and performance of top U.S. biathletes.

Success in biathlon involves skiing fast and shooting accurately. The purpose of this study was to determine whether physiological laboratory test results relate to success in biathlon. Tests included treadmill run and double-pole lactate profile and VO2peak tests, and a double-pole peak power test (UBP). 1993 National Points Rank (NR), racing ski time (ST), and shooting percentage (SP) from 1993 World Team Trials and laboratory test results (1993; N = 11 males, 10 females) were examined. Of athletes tested, six males and six females were top 10 U.S. ranked. Significance was identified between NR and ST (males, r = -0.88; females, r = -0.91). NR and SP were related for females (r = 0.75). Maximum run time during the VO2peak test was the only parameter related to NR (r = 0.72) or ST (r = -0.80) for males. Significance was identified for an uphill 1 km on snow double-pole time trial to NR (r = -0.84) and SP (r = -0.79) (subgroup; N = 8 males). For females, NR was related to running VO2peak (r = 0.81) and UBP (r = 0.95). Double-pole and running VO2peak were related to SP for women. This study suggests that SP is more important to NR for females than for males, and gender-specific tests might better predict success in elite biathlon skiers.

Effect of slope variation and skating technique on velocity in cross-country skiing

The purpose of the present study was to investigate the effect of slope variations upon the maximal velocity attainable by cross-country ski racers using three skating techniques (V-1, V-2, and Gunde). Nine (2 females, 7 males) junior ski racers (16.0 +/- 0.4 yr of age, mean +/- SEM) exhibiting strong technical skills participated in the study. The subjects were required to skate at maximal velocity over five different courses (length 120-200 m) with mean slopes of -1, 0, 6, 9, and 12%. Video analysis was used to determine skiing velocity, cycle length, and cycle rate. Heart rate was monitored to verify intensity of exertion. Results indicated that intensities were similar to those observed while racing. Velocities for the three techniques were not different for -1, 0, and 6% slopes. However V-1 was significantly faster (P < 0.01) at 9% and 12% inclines. Velocity was highly correlated to cycle length (P < 0.01) but unrelated to cycle rate. Cycle length was significantly different between techniques (P < 0.01) and varied across slopes. Cycle rate was significantly different between techniques (P < 0.01) but did not vary across slopes. Thus, our results indicate that any of the three techniques is adequate on flat and rolling terrain, but V-1 should be used at slopes of 9% and above. It is also concluded that during short trials skied at maximal velocity, skiing velocity is highly dependent on cycle length and independent of cycle rate.

Treadmill roller ski test predicts biathlon roller ski race results of elite U.S. biathlon women

This study evaluated ski-specific laboratory testing and the relationship of test parameters to biathlon race performance. Since the ski skating technique used exclusively during biathlon racing requires a large upper body contribution, treadmill roller ski test parameters may provide relevant information for ski-specific training and ski performance. Seven top U.S. female biathlon skiers performed lactate threshold and VO2 peak tests running (TR) and roller skiing (skating technique, RS) on a motor driven treadmill. In addition, a constant workload (14 km.h(-1), 6% grade) roller ski test to exhaustion at race pace (ET) on a motor driven treadmill, and a short-term double pole power test (DP) were also performed. Results indicate that lactate threshold VO2 and HR were significantly lower during RS than TR, DP power (w.kg(-1)) was related to RS VO2 peak (r = 0.90), but not to TR parameters. ET time to exhaustion was related to gross efficiency during ET (r = -0.86), RS VO2 peak (r = 0.80) and DP HR (% peak HR, r = 0.80). These results suggest that ski-specific laboratory testing provides better insight to ski performance than treadmill run testing.

Effect of kinematic variables on performance in women during a cross-country ski race

The purpose of this study was to investigate the relationship of uphill cycle velocity, cycle length, and cycle rate in top U.S. female skiers during a multiple lap cross-country ski skating race. Eighteen female cross-country skiers served as subjects at the United States Womens 10-km Freestyle 1995 National Championships. The course consisted of two laps of the same 5-km loop. The selected filming section was an 11-12% uphill grade approximately 400 m long located at the 2.5- and 7.5-km mark. The video sector was approximately 12 m long at the conclusion of the climb. During the climb, the skating technique used by all skiers was the V-1. The results demonstrated that cycle length is positively related to cycle velocity during uphill ski skating and ultimately translates to faster race times by female cross-country ski racers. Lap 2 cycle velocity and cycle length demonstrated the strongest relationship to lap time and total race time. Moreover, cycle rate was not related to cycle velocity or lap race times and was not different between successful and less successful skiers. The slower climbing velocity noted during the latter half of the 10-km race was a consequence of a decreased cycle length and not cycle rate. This suggests that the degree of physical conditioning could be a factor in the ability to maintain cycle length and thus uphill cycle velocity.

Effects of drafting during short-track speed skating.

Short-track speed skating involves pack-style racing where five to seven skaters may be on the ice at once. Since average speed for a 3000-m event may exceed 35 km.h-1, drafting may be beneficial. However, the short (111 m) oval track could limit effective drafting space, and high forces required in cornering may compromise potential benefits. We evaluated heart rate (HR)-lactate (LA) responses and post-drafting 3-lap sprint performance using 18 National Team and developmental skaters. Two 4-min trials, one drafting and one leading at 8.8 m.s-1, were performed. In addition, six skaters performed three 3-lap sprints, rested, immediately after a 4-min drafting trial at 9.2 m.s-1, and immediately after an unaided 4-min trial at 9.2 m.s-1. Results demonstrated lower HR and LA responses during drafting (174.0 +/- 9.0 and 5.56 +/- 2.18 vs 180.4 +/- 8.7 and 7.75, P < 0.05) at 8.8 m.s-1. After 4-min trials at 9.2 m.s-1, HR deltas were 6 bpm, lactate values were 9.00 +/- 1.84 and 5.22 +/- 1.18 for unaided and drafting, respectively. Sprint performance was better following drafting (33.46 +/- 1.19 vs 34.03 s, P < 0.05). HR and LA deltas during the 8.8 m.s-1 trials ranged from 0.8 to 12.4 and -0.18 to 5.37, respectively, indicating that some skaters were more effective drafters than others. These results suggest that drafting could be an important strategy in short-track speed skating, and drafting technique should be emphasized in training.