Gertjan Ettema

The Physiology of World Class Sprint Skiers

The present study investigated the physiological characteristics of eight world‐class (WC) and eight national‐class (NC) Norwegian sprint cross country skiers. To measure the physiological response and treadmill performance, the skiers performed a submaximal test, a peak aerobic capacity (VO2peak) test, and a peak treadmill speed (Vpeak) test in the skating G3 technique. Moreover, the skiers were tested for G3 acceleration outdoors on asphalt and maximal strength in the lab. The standard of sprint skating performance level on snow was determined by International Ski Federation points, and the training distribution was quantified. WC skiers showed 8% higher VO2peak and twice as long a VO2 plateau time at the VO2peak test, and a higher gross efficiency at the submaximal test (all P<0.05). Furthermore, WC skiers showed 8% higher Vpeak (P<0.05), but did not differ from NC skiers in acceleration and maximal strength. WC skiers performed more low‐ and moderate‐intensity endurance training and speed training (both P<0.05). The current results show that aerobic capacity, efficiency, and high speed capacity differentiate WC and NC sprint skiers and it is suggested that these variables determine sprint skiing performance.

VELOCITY SPECIFICITY IN EARLY-PHASE SPRINT TRAINING

A comparison of resistance running, normal sprint running, and supramaximal running was performed. Nineteen young, generally well-trained subjects were divided into 3 training groups: resistance, normal, and supramaximal groups. Resistance and supramaximal training was done using a towing device, providing extra resistance or propulsion forces, resulting in running speed differences of about 3.3% (supramaximal) and 8.5% (resistance), compared to normal sprinting. The training period was 6 weeks, with 3 training sessions per week (5 sprint-runs over 22 m). Running times were measured using photocells, and average step length and cadence were recorded by digital video. A small (0.5%) but significant (p < 0.05) overall pre-post difference was found in running velocity, but the 3 groups changed differently over the running conditions. All individual subjects improved sprinting velocity most on the trained form, at 1–2% (p < 0.001), and thus, the principle of velocity specificity in sprint training was supported. This indicates that to obtain short-distance sprinting improvement in a short period of time, one may prefer normal sprinting over other training forms.

INFLUENCE OF INSTRUCTION ON VELOCITY AND ACCURACY OF OVERARM THROWING

This study investigated the influence of instruction on the ball velocity and accuracy of a goal-directed overarm throw. 9 experienced Norwegian male team handball players executed a throwing task randomly seven times under 5 different instructions varying from emphasizing speed to accuracy. When instructions increasingly emphasized accuracy, velocity decreased. However, accuracy did not improve when subjects were instructed to focus on it. A possible explanation for this finding could lie in the specific subject group. The subjects were highly experienced team handball players with an average of 12 years in the sport. Thus, the accuracy they demonstrated at high velocity might actually be already extremely high and difficult to improve upon when reducing throwing velocity. Further, the velocity of throwing when instruction emphasized accuracy was approximately 85% of the maximal velocity, indicating that experienced team handball players are trained to throw accurately at relatively high velocity.

A comparison between novices and experts of the velocity-accuracy trade-off in overarm throwing.

Expert team-handball players do not show the typical trade-off between speed and accuracy in overarm throwing. Van den Tillaar and Ettema (2003a) attributed this result to the uniqueness of the training experience of this group. The purpose of this study was to test their hypothesis by comparing experts with novices on overarm throwing by manipulating the goal of the task using different instructions. No trade-off between speed and accuracy was found for novices (n = 13; M age = 22.7 yr., SD = 2.2) or experts (n = 9; M age = 24 yr., SD = 2.2): accuracy did not change by instruction. Furthermore, the linear velocities of the ball and endpoints of body segments and their timing were affected by instruction in a similar fashion in both groups. This finding indicates that training experience is not related to speed-accuracy tradeoff in overarm throwing.

INSTRUCTIONS EMPHASIZING VELOCITY, ACCURACY, OR BOTH IN PERFORMANCE AND KINEMATICS OF OVERARM THROWING BY EXPERIENCED TEAM HANDBALL PLAYERS

On motor tasks like the overarm throw, velocity and accuracy are two important parameters of performance that may be incompatible and require different strategies in the execution of the motor task. The purpose was to investigate the effects of instruction (emphasizing velocity, accuracy, or both) on performance and kinematics of overarm throwing. Results for 9 experienced male team handball players (M age = 24 ± 2.2 yr.) showed type of instruction affected the maximal ball velocity. The difference in ball velocity reflected the significant difference in maximal linear velocity of the wrist, elbow, and hip segments together with their absolute timing before ball release. The subjects did not seem to change their throwing technique, i.e., the relative timing of movement initiation of the different body segments.

Is there a proximal-to-distal sequence in overarm throwing in team handball?

Abstract Research examining the proximal-to-distal sequencing of segments of the body involved in overarm throwing has been equivocal: some studies have found support for the concept while others have not. The aim of the present study, therefore, was to determine if there is a proximal-to-distal sequence in the timing of the movements of joints and the distal endpoints of segments in overarm throwing. The three-dimensional kinematics of a penalty throw in experienced team handball players (n = 11) were recorded and analysed with regard to the timing of events. We analysed the timing of the maximal velocity of the distal endpoints of six segments and the maximal angular velocity in 11 joints, as well as the initiation of these joint movements. A temporal proximal-to-distal sequence was observed only for the initiation of the joint movements. No such sequence was found for maximal velocity of the joints and distal endpoints of segments.

Effect of Physical Fatigue on Motor Control at Different Skill Levels

The purpose of this experiment was to explore the effect of fatigue on motor coordination, and of prospective adjustment strategies to compensate for fatigue in a multijoint movement. Two male groups (N = 8) participated in the experiment: Highly skilled table tennis players (M age = 27 yr., SD = 2.3, n = 4) and Recreational table tennis players (M age = 25.9 yr., SD = 0.04, n = 4). The task was an attacking forehand drive towards a scaled target on the opposite side of the net. The Highly skilled players adjusted their movement patterns and preserved the task requirements in terms of spatial accuracy under the condition of fatigue by using opportunistic movement coordination. The Recreational players did not adjust their forehand drive, and spatial accuracy deteriorated. The current results support the notion that expertise enhances potential to adjust motor coordination strategies as a reaction to induced physical fatigue.

A Comparison of Successful and Unsuccessful Attempts in Maximal Bench Pressing

PURPOSE This study was designed to compare the differences in EMG and kinematics between successful and unsuccessful attempts in bench pressing at one repetition maximum (1RM) in recreational weight-trained subjects. We hypothesized that failure occurs during the sticking period (the period during which there is a temporary reduction in movement velocity). METHODS Eleven male subjects (age = 21.9 +/- 1.8 yr, mass = 80.0 +/- 11.2 kg, height = 1.79 +/- 0.08 m) with at least 1 yr of bench press training experience participated in this study. They performed attempts at 1RM and 1RM + 2.5 kg in bench press during which kinematics and muscle activity were recorded. One successful attempt and one unsuccessful attempt were used for further analysis. RESULTS Both attempts showed the same sticking period, but only half of the failures occurred during that period. The main differences in the kinematics occurred during the sticking period. Muscle activity, in contrast, showed the same pattern in both attempts and only differed during the downward and the start of the upward movement of the lift. CONCLUSIONS The sticking period occurs in both successful and unsuccessful attempts in maximal bench press. However, failure does not always occur during the sticking period.

The “sticking period” in a maximum bench press

Abstract The purpose of this study was to examine muscle activity and three-dimensional kinematics in the ascending phase of a successful one-repetition maximum attempt in bench press for 12 recreational weight-training athletes, with special attention to the sticking period. The sticking period was defined as the first period of deceleration of the upward movement (i.e. from the highest barbell velocity until the first local lowest barbell velocity). All participants showed a sticking period during the upward movement that started about 0.2 s after the initial upward movement, and lasted about 0.9 s. Electromyography revealed that the muscle activity of the prime movers changed significantly from the pre-sticking to the sticking and post-sticking periods. A possible mechanism for the existence of the sticking period is the diminishing potentiation of the contractile elements during the upward movement together with the limited activity of the pectoral and deltoid muscles during this period.

Gender differences in endurance performance by elite cross-country skiers are influenced by the contribution from poling

Greater gender differences have been found in exercise modes where the upper body is involved. Therefore, the present study investigated the influence of poling on gender differences in endurance performance by elite cross‐country skiers. Initially, the performance of eight male and eight female sprint skiers was compared during four different types of exercise involving different degrees of poling: double poling (DP), G3 skating, and diagonal stride (DIA) techniques during treadmill roller skiing, and treadmill running (RUN). Thereafter, DP was examined for physiological and kinematic parameters. The relative gender differences associated with the DP, G3, DIA and RUN performances were approximately 20%, 17%, 14%, and 12%, respectively. Thus, the type of exercise exerted an overall effect on the relative gender differences (P < 0.05). In connection with DP, the men achieved 63%, 16%, and 8% higher VO2peak than the women in absolute terms and with normalization for total and fat‐free body mass (all P < 0.05). The DP VO2peak in percentage of VO2max in RUN was higher in men (P < 0.05). The gender difference in DP peak cycle length was 23% (P < 0.05). In conclusion, the present investigation demonstrates that the gender difference in performance by elite sprint skiers is enhanced when the contribution from poling increases.