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  • 1.
    Andersson, Helena
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Krustrup, Peter
    Elite football on artificial turf versus natural grass: movement patterns, technical standards, and player impressions.2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 26, no 2, p. 113-22Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to examine the movement patterns, ball skills, and the impressions of Swedish elite football players during competitive games on artificial turf and natural grass. Time - motion analyses (36 observations) and technical analyses (16 team observations) were performed and 72 male and 21 female players completed a questionnaire. No differences were observed between artificial turf and natural grass in terms of total distance covered (mean 10.19 km, s = 0.19 vs. 10.33 km, s = 0.23), high-intensity running (1.86 km, s = 0.10 vs. 1.87 km, s = 0.14), number of sprints (21, s = 1 vs. 22, s = 2), standing tackles (10, s = 1 vs. 11, s = 1) or headers per game (8, s = 1 vs. 8, s = 1), whereas there were fewer sliding tackles (P < 0.05) on artificial turf than natural grass (2.1, s = 0.5 vs. 4.3, s = 0.6). There were more short passes (218, s = 14 vs. 167, s = 12) and midfield-to-midfield passes (148, s = 11 vs. 107, s = 8) (both P < 0.05) on artificial turf than natural grass. On a scale of 0-10, where 0 = "better than", 5 = "equal to", and 10 = "worse than", the male players reported a negative overall impression (8.3, s = 0.2), poorer ball control (7.3, s = 0.3), and greater physical effort (7.2, s = 0.2) on artificial turf than natural grass. In conclusion, the running activities and technical standard were similar during games on artificial turf and natural grass. However, fewer sliding tackles and more short passes were performed during games on artificial turf. The observed change in playing style could partly explain the male players' negative impression of artificial turf.

  • 2. Aujla, Imogen J
    et al.
    Nordin-Bates, Sanna M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Sport Psychology research group.
    Redding, Emma
    Multidisciplinary predictors of adherence to contemporary dance training: findings from the UK Centres for Advanced Training.2015In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 33, no 15, p. 1564-73Article in journal (Refereed)
    Abstract [en]

    Little is known about the predictors of adherence in a dance context. The aim of this study was to investigate adherence to a dance talent programme using a multidisciplinary set of variables representing psychological correlates of adherence, maturation and physical factors relating to dance talent. Psychological (passion, motivational climate perceptions, eating attitudes), physical competence (vertical jump height, handgrip strength, hamstring flexibility, external hip rotation, aerobic fitness), and maturation-related (age of menarche) variables were gathered from female students enrolled on a dance talent programme. Participation behaviour (adherence/dropout) was collected from the talent programme's records approximately two years later. Logistic regression analysis of 287 participants revealed that greater levels of harmonious passion predicted greater likelihood of adherence to the programme, and greater ego-involving motivational climate perceptions predicted less likelihood of adherence. Neither measures of physical competence nor maturation distinguished adhering from dropout participants. Overall, the results of this study indicate that psychological factors are more important than physical competence and maturation in the participation behaviour of young talented dancers.

  • 3.
    Cardinale, Daniele A.
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Björn Ekblom's research group.
    Hyperoxia for performance and training.2018In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, no 13, p. 1515-1522Article in journal (Refereed)
    Abstract [en]

    Recent technological developments have made it possible to use hyperoxia as an enhancement aid during training. Athletes wearing a mask can breathe a higher fraction of oxygen from a stationary or portable apparatus while exercising. A large body of evidence indicates that the oxygen transport capacity, lactate metabolism, power output and work tolerance (endurance) are improved when breathing hyperoxia. The physiological mechanisms underlying these performance improvements, although still not fully elucidated, are based on higher oxygen delivery and reduced central fatigue. Although much is known about the acute effects of hyperoxia, the effect of hyperoxic-supplemented endurance training on performance and the mechanisms beneath training adaptations are not very well understood, especially in well-trained endurance athletes. The few studies on the physiological effects of hyperoxia training have been conducted with conflicting results, discussed in this paper. Potential detrimental effects have not yet been shown experimentally and warrant further investigation.

  • 4.
    Enqvist, Jonas K
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Mattsson, C Mikael
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Johansson, Patrik H
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Brink-Elfegoun, Thibault
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Bakkman, Linda
    Swedish School of Sport and Health Sciences, GIH.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Energy turnover during 24 hours and 6 days of adventure racing.2010In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 28, no 9, p. 947-955Article in journal (Refereed)
    Abstract [en]

    Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake ([Vdot]O(2)) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and [Vdot]O(2) were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 +/- 2,390 kcal (750 +/- 100 kcal . h(-1)) and 80,000 +/- 18,000 kcal (500 +/- 100 kcal . h(-1)) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 +/- 1,160 kcal, resulting in an energy deficit of 9,590 +/- 770 kcal. Body mass decreased in Study 1 (-2.3 +/- 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (-2.3 +/- 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.

  • 5.
    Gray, Stuart R
    et al.
    Strathclyde inst of pharmacy and biomedical sciences, university of strathclyde, Glasgow UK.
    Söderlund, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Ferguson, Richard A
    ATP and phosphocreatine utilization in single human muscle fibres during the development of maximal power output at elevated muscle temperatures.2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 26, no 7, p. 701-7Article in journal (Refereed)
    Abstract [en]

    In this study, we examined the effect of muscle temperature (Tm) on adenosine triphosphate (ATP) and phosphocreatine utilization in single muscle fibres during the development of maximal power output in humans. Six male participants performed a 6-s maximal sprint on a friction-braked cycle ergometer under both normal (Tm = 34.3 degrees C, s = 0.6) and elevated (T(m) = 37.3 degrees C, s = 0.2) muscle temperature conditions. During the elevated condition, muscle temperature of the legs was raised, passively, by hot water immersion followed by wrapping in electrically heated blankets. Muscle biopsies were taken from the vastus lateralis before and immediately after exercise. Freeze-dried single fibres were dissected, characterized according to myosin heavy chain composition, and analysed for ATP and phosphocreatine content. Single fibres were classified as: type I, IIA, IIAX25 (1 - 25% IIX isoform), IIAX50 (26 - 50% IIX), IIAX75 (51 - 75% IIX), or IIAX100 (76 - 100% IIX). Maximal power output and pedal rate were both greater (P < 0.05) during the elevated condition by 258 W (s = 110) and 22 rev . min(-1) (s = 6), respectively. In both conditions, phosphocreatine content decreased significantly in all fibre types, with a greater decrease during the elevated condition in type IIA fibres (P < 0.01). Adenosine triphosphate content was also reduced to a greater (P < 0.01) extent in type IIA fibres during the elevated condition. The results of the present study indicate that after passive elevation of muscle temperature, there was a greater decrease in ATP and phosphocreatine content in type IIA fibres than in the normal trial, which contributed to the higher maximal power output.

  • 6.
    Hellström, John
    et al.
    Örebro universitet.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Isberg, Leif
    Örebro universitet.
    Drive for dough. PGA Tour golfers' tee shot functional accuracy, distance and hole score.2014In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 32, no 5, p. 462-9Article in journal (Refereed)
    Abstract [en]

    A player's ability to score low is critical to the tournament outcome in golf. The relationships of round scores to fairways hit in regulation or striking distance on two holes per round have been investigated before with some disagreement. The purpose is therefore to examine the relationships of par-4 and par-5 hole scores to tee shot functional accuracy and distance, measured as lie of the ball and penalty, and striking distance or distance to the pin for the second shot. Such information is possible to collect without interviewing players. The best US Professional Golfers' Association Tour players' statistics during a season are used, provided by the Professional Golfers' Association Tour and ShotLink. Distance was measured with laser equipment. The results include significant (P < 0.05) correlations between score and striking distance or distance to pin, when hitting rough but not fairway on par-4s and when hitting fairway and rough on par-5s. It is therefore relevant, for performance, to consider the type of fairway miss as well as the striking distance in relation to the par and length of the hole. The findings can be considered when making gap and needs profiles, and when making tactical decisions for tee shots on different types of holes.

  • 7. Holmberg, Hans-Christer
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Reliability and validity of a new double poling ergometer for cross-country skiers.2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 26, no 2, p. 171-9Article in journal (Refereed)
    Abstract [en]

    Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50-70% higher than that at the flywheel. There was a high test-retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W x kg(-1)) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.

  • 8. Holmberg, Hans-Christer
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Reliabilty and validity of new double poling ergometer for cross-country skiers2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 26, no 2, p. 171-179Article in journal (Refereed)
    Abstract [en]

    Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50 – 70% higher than that at the flywheel. There was a high test – retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W · kg−1) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.

  • 9. Karlsen, Jon
    et al.
    Smith, Gerald
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The stroke has a minor influence on direction consistencyin golf putting among elite players2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 3, p. 243-250Article in journal (Refereed)
    Abstract [en]

    In the golf instructional literature, the putting stroke is typically given higher priority than green reading and aiming. The main purpose of this study was to assess the importance of the putting stroke for direction consistency in golf putting. Kinematic stroke parameters were recorded from 71 elite golf players (mean handicap = 1.8, s = 4.2) on 1301 putts from about 4 m. Of the different factors deciding stroke direction consistency, face angle was found to be the most important (80%), followed by putter path (17%) and impact point (3%). This suggests that improvements in consistency of putter path and impact point will have very little effect on overall putting direction consistency and should not be prioritized in the training of elite players. In addition, mean stroke direction variability for an elite player (European Tour) was found to be 0.39°, which is good enough to hole about 95% of all 4-m putts. In practice, however, top professionals in tournaments only hole about 17% of 4-m putts. We conclude that the putting stroke of elite golfers has a relatively minor influence on direction consistency.

  • 10. Karlsen, Jon
    et al.
    Smith, Gerald
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The stroke has only a minor influence on direction consistency in golf putting among elite players.2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 26, no 3, p. 243-50Article in journal (Refereed)
    Abstract [en]

    In the golf instructional literature, the putting stroke is typically given higher priority than green reading and aiming. The main purpose of this study was to assess the importance of the putting stroke for direction consistency in golf putting. Kinematic stroke parameters were recorded from 71 elite golf players (mean handicap = 1.8, s = 4.2) on 1301 putts from about 4 m. Of the different factors deciding stroke direction consistency, face angle was found to be the most important (80%), followed by putter path (17%) and impact point (3%). This suggests that improvements in consistency of putter path and impact point will have very little effect on overall putting direction consistency and should not be prioritized in the training of elite players. In addition, mean stroke direction variability for an elite player (European Tour) was found to be 0.39 degrees, which is good enough to hole about 95% of all 4-m putts. In practice, however, top professionals in tournaments only hole about 17% of 4-m putts. We conclude that the putting stroke of elite golfers has a relatively minor influence on direction consistency.

  • 11. Lees, A
    et al.
    Nolan, Lee
    Liverpool John Moores University.
    The biomechanics of soccer: a review.1998In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 16, no 3, p. 211-34Article in journal (Refereed)
    Abstract [en]

    This review considers the biomechanical factors that are relevant to success in the game of soccer. Three broad areas are covered: (1) the technical performance of soccer skills; (2) the equipment used in playing the game; and (3) the causative mechanisms of specific soccer injuries. Kicking is the most widely studied soccer skill. Although there are many types of kick, the variant most widely reported in the literature is the maximum velocity instep kick of a stationary ball. In contrast, several other skills, such as throwing-in and goalkeeping, have received little attention; some, for example passing and trapping the ball, tackling, falling behaviour, jumping, running, sprinting, starting, stopping and changing direction, have not been the subject of any detailed biomechanical investigation. The items of equipment reviewed are boots, the ball, artificial and natural turf surfaces and shin guards. Little of the research conducted by equipment manufacturers is in the public domain; this part of the review therefore concentrates on the mechanical responses of equipment, player-equipment interaction, and the effects of equipment on player performance and protection. Although the equipment has mechanical characteristics that can be reasonably well quantified, the player-equipment interaction is more difficult to establish; this makes its efficacy for performance or protection difficult to predict. Some soccer injuries may be attributable to the equipment used. The soccer boot has a poor protective capability, but careful design can have a minor influence on reducing the severity of ankle inversion injuries. Performance requirements limit the scope for reducing these injuries; alternative methods for providing ankle stability are necessary. Artificial surfaces result in injury profiles different from those on natural turf pitches. There is a tendency for fewer serious injuries, but more minor injuries, on artificial turf than on natural turf pitches. Players adapt to surface types over a period of several games. Therefore, changing from one surface to another is a major aetiological factor in surface-related injuries. Heading the ball could lead to long-term brain damage. Simulation studies suggest the importance of ball mass, ball speed and player mass in affecting the severity of impact. Careful instruction and skill development, together with the correct equipment, is necessary for young players. Most applications of biomechanical techniques to soccer have been descriptive experimental studies. Biomechanical modelling techniques have helped in the understanding of the underlying mechanisms of performance, although their use has been limited. It is concluded that there are still many features of the game of soccer that are amenable to biomechanical treatment, and many opportunities for biomechanists to make a contribution to the science of soccer.

  • 12. Li, Xiao
    et al.
    Wang, Shi-Jun
    Tan, Shing Cheng
    Chew, Pey Ling
    Liu, Lihong
    Wang, Li
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Wen, Li
    Ma, Lihong
    The A55T and K153R polymorphisms of MSTN gene are associated with the strength training-induced muscle hypertrophy among Han Chinese men.2014In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 32, no 9, p. 883-91Article in journal (Refereed)
    Abstract [en]

    Myostatin, encoded by the MSTN gene, is a strong regulator of skeletal muscle growth. The present study aimed to investigate whether the A55T and K153R polymorphisms of MSTN were associated with the strength training-induced muscle hypertrophy among Han Chinese men. A total of 94 healthy, untrained men were recruited for an 8-week strength training programme. The thicknesses of biceps and quadriceps, along with anthropometric measurements of the participants, were assessed before and after the programme. The MSTN polymorphisms were subsequently genotyped employing polymerase chain reaction-restriction fragment length polymorphism technique and confirmed by DNA sequencing. One-way analysis of variance was used to compare the pre- and post-training measurements between carriers of different polymorphic genotypes. Our results indicated that individuals with AT + TT genotype of the A55T polymorphism showed a significant increase in the thickness of biceps (0.292 ± 0.210 cm, P = 0.03), but not quadriceps (0.254 ± 0.198 cm, P = 0.07), compared to carriers of AA genotype. For the K153R polymorphism, the increases in the thicknesses of both biceps (0.300 ± 0.131 cm) and quadriceps (0.421 ± 0.281 cm) were significantly higher among individuals with KR than those with KK genotypes (P < 0.01 for both muscles). The results obtained therefore suggested a possible association between the two polymorphisms and the strength training-induced muscle hypertrophy among men of Han Chinese ethnicity.

  • 13.
    Lundqvist, Carolina
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Sport Psychology research group.
    Hassmén, Peter
    Competitive State Anxiety Inventory-2: Evaluating the Swedish version by confirmatory factor analyses2005In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 23, no 7, p. 727-736Article in journal (Refereed)
    Abstract [en]

    The Competitive State Anxiety Inventory-2 (CSAI-2) is one of the most frequently used instruments when assessing competitive state anxiety in sport psychology research. However, doubts have been expressed about the factorial validity of both the English and the Greek versions of the scale. Hence, a revised version of the inventory (CSAI-2R) has recently been suggested to be more psychometrically sound (Cox et al., 2003). In the present study, the aim was to evaluate the psychometric properties of the Swedish version of the CSAI-2 using confirmatory factor analyses. A total of 969 athletes (571 men and 398 women) competing in 26 different sports completed the Swedish version of the CSAI-2. Three different factor structures were evaluated: the original three-factor model (with cognitive anxiety, somatic anxiety and self-confidence), a two-factor model in which self-confidence was excluded, and a three-factor model containing 17 items (CSAI-2R). The results revealed that only the 17-item model displayed an acceptable fit to the data. Although some doubts remain about the amount of variance that can be attributed to error variance in the subscales, the results suggest that it is better to use the CSAI-2R rather than the original CSAI-2.

  • 14.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Csergö, Sandor
    Gullstrand, Lennart
    Tveit, Per
    Refsnes, Per Egil
    Work-time profile, blood lactate concentration and rating of perceived exertion in the 1998 Greco-Roman Wrestling World Championship.2002In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 20, no 11, p. 939-45Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to examine work-time profiles, blood lactate concentrations and perceived exertion among Greco-Roman wrestlers in the 1998 World Championship. Forty-two senior wrestlers from nine nations were studied in 94 matches. Each match was recorded with a video camera (Panasonic AG 455, film rate: 25 Hz) and analysed for duration of work (wrestling) and rest (interrupt) periods. Blood lactate concentration was determined with an electrochemical device (Analox P-LM5) and a rating of perceived exertion scale (Borg) was used to estimate general exertion and exertion in the extremity and trunk muscles. The mean duration of the matches was 427 s (range 324-535 s), with mean durations of work and rest of 317 and 110 s, respectively. The mean periods of work and rest were 37.2 and 13.8 s, respectively. Mean blood lactate concentration was 14.8 mmol x 1(-1) (range 6.9-20.6). The difference in mean blood lactate concentration between the first- and final-round matches was not significant (P > 0.05). Blood lactate concentration was significantly higher (P < 0.04) in matches of long duration than in those of short duration. The mean general rating of perceived exertion for all matches was 13.8 according to the scale used. Most of the wrestlers (53.3%) perceived exertion to be highest in the flexors of the forearm, followed by the deltoids (17.4%) and the biceps brachii muscles (12.0%). In addition to a relatively high rating of perceived exertion in the arm muscles, this indicates a high specific load on the flexor muscles of the forearm.

  • 15.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Haugen, Per
    Knee angular displacement and extensor muscle activity in telemark skiing and in ski-specific strength exercises.2004In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 22, no 4, p. 357-64Article in journal (Refereed)
    Abstract [en]

    Much of the training of competitive telemark skiers is performed as dry-land exercises. The specificity of these exercises is important for optimizing the training effect. Our aim here was to study the activation of the knee extensor musculature and knee angular displacement during competitive telemark skiing and during dry-land strength training exercises to determine the specificity of the latter. Specificity was analysed with respect to angular amplitude, angular velocity, muscle action and electromyographic (EMG) activity. Five male telemark skiers of national and international standard volunteered to participate in the study, which consisted of two parts: (1) skiing a telemark ski course and (2) specific dry-land strength training exercises for telemark skiing (telemark jumps and barbell squats). The angular displacement of the right knee joint was recorded with an electrogoniometer. A tape pressure sensor was used to measure pressure between the sole of the foot and the bottom of the right ski boot. Electromyographic activity in the right vastus lateralis was recorded with surface electrodes. The EMG activity recorded during maximum countermovement jumps was used to normalize the EMG activity during telemark skiing, telemark jumps and barbell squats. The results showed that knee angular displacement during telemark skiing and dry-land telemark jumps had four distinct phases: a flexion (F1) and extension (E1) phase during the thrust phase of the outside ski/leg in the turn/jump and a flexion (F2) and extension (E2) phase when the leg was on the inside of the turn/jump. The vastus lateralis muscle was activated during F1 and E1 in the thrust phase during telemark skiing and telemark jumps. The overall net knee angular amplitude was significantly greater (P < 0.05) for telemark jumps than for telemark skiing. Barbell squats showed a knee angular amplitude significantly greater than that in telemark skiing (P < 0.05). The mean knee angular velocity of the F1 and E1 phases during telemark skiing was about 0.47 rad x s(-1); during barbell squats, it was about 1.22 rad x s(-1). The angular velocity during telemark jumps was 2.34 and 1.59 rad x s(-1) in the F1 and E1 phase, respectively. The normalized activation level of the EMG bursts during telemark skiing, telemark jumps and barbell squats was 70-80%. In conclusion, the muscle action and level of activation in the vastus lateralis during the F1 and E1 phases were similar during telemark skiing and dry-land exercises. However, the dry-land exercises showed a larger knee extension and flexion amplitude and angular velocity compared with telemark skiing. It appears that an adjustment of knee angular velocity during barbell squats and an adjustment of knee angle amplitude during both telemark jumps and barbell squats will improve specificity during training.

  • 16.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsen, Jon
    A new device for evaluating distance and directional performance of golf putters.2006In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 24, no 2, p. 143-7Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to construct and evaluate the reliability of an apparatus for testing golf putters with respect to distance and direction deviation at different impact points on the clubface. An apparatus was constructed based on the pendulum principle that allowed putter golf clubs to swing at different speeds. The mean speed of the club head before ball impact, and of the ball after impact, was calculated from time measurements with photocells. A pin profile rig was used to determine the directional deviation of the golf ball. Three different putters were used in the study, two that are commercially available (toe-heel weighted and mallet types) and one specially made (wing-type) putter. The points of impact were the sweet spot (as indicated by the manufacturer's aim line), and 1, 2 and 3 cm to the left and right of the sweet spot. Calculation of club head speed before impact, and of ball speed after impact (proportional to distance), showed errors < or = 0.5% of interval duration. The variability in ball impacts was tested by measuring time and direction deviations during 50 impacts on the same ball. The mean duration (+/- s) after ball impact in the test interval (1.16 m long) was 206 (0.8) ms and the standard deviation in the perpendicular spreading of the balls in relation to the direction of the test interval was 0.005 m. A test-retest of one putter on two consecutive days after remounting of the putter on the test apparatus showed less than 1% difference in distance deviation. We conclude that the test apparatus enables a precise recording of distance and direction deviation in golf putters as well as comparisons between different putters. The apparatus and set-up can be used in the laboratory as well as outdoors on the putting green.

  • 17.
    Nolan, Lee
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lees, Adrian
    The influence of lower limb amputation level on the approach in the amputee long jump.2007In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 25, no 4, p. 393-401Article in journal (Refereed)
    Abstract [en]

    In this study, we investigated the adjustments to posture, kinematic and temporal characteristics of performance made by lower limb amputees during the last few strides in preparation for long jump take-off. Six male unilateral trans-femoral and seven male unilateral trans-tibial amputees competing in a World Championships final were filmed in the sagittal plane using a 100-Hz digital video camera positioned so that the last three strides to take-off were visible. After digitizing using a nine-segment model, a range of kinematic variables were computed to define technique characteristics. Both the trans-femoral and trans-tibial athletes appeared to achieve their reduction in centre of mass during the flight phase between strides, and did so mainly by extending the flight time by increasing stride length, achieved by a greater flexion of the hip joint of the touch-down leg. The trans-tibial athletes appeared to adopt a technique similar to that previously reported for able-bodied athletes. They lowered their centre of mass most on their second last stride (-1.6% of body height compared with -1.4% on the last stride) and used a flexed knee at take-off on the last stride, but they were less able to control their downward velocity at touch-down (-0.4 m x s(-1)). Both this and their restricted approach speed (8.9 m x s(-1) at touch-down), rather than technique limitations, influenced their jump performance. The trans-femoral athletes lowered their centre of mass most on the last stride (-2.3% of body height compared with -1.6% on the second last stride) and, as they were unable to flex their prosthetic knee sufficiently, achieved this by abducting their prosthetic leg during the support phase, which led to a large downward velocity at touch-down (-0.6 m x s(-1)). This, combined with their slower approach velocity (7.1 m x s(-1) at touch-down), restricted their performance.

  • 18. Reilly, Thomas
    et al.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    The use of recovery methods post-exercise.2005In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 23, no 6, p. 619-27Article in journal (Refereed)
    Abstract [en]

    Competitive soccer engages many of the body's systems to a major extent. The musculoskeletal, nervous, immune and metabolic systems are stressed to a point where recovery strategies post-exercise become influential in preparing for the next match. Intense activity at a 7-day training camp causes participants to experience lowered concentrations of non-killer cells and T-helper cells. Two consecutive games in 24 h produce disturbances in the testosterone-cortisol ratio. When competitive schedules are congested, the recovery process should be optimized for performance capabilities to be restored to normal as soon as possible. There is evidence that glycogen stores are reduced near to depletion at the end of a soccer game and that a diet high in carbohydrates can aid recovery. Water alone is not the best means of restoring body fluids, since carbohydrate-electrolyte drinks display better intestinal absorption and reduce urine output. Some relief from muscle soreness may be achieved by means of a warm-down. Deep-water running regimens can replace conventional physical training in the days after competition. Massage, cryotherapy and alternative therapies have not been shown to be consistently effective. It is concluded that optimizing recovery post-exercise depends on a combination of factors that incorporate a consideration of individual differences and lifestyle factors. The procedures to facilitate recovery processes should start immediately the game or training finishes. Match administrators and tournament planners should consider the stressful consequences for players in periods of congested fixtures and alleviate the physiological strain as far as possible by allowing 72 h between competitive games. This frequency of competition is unlikely to be sustainable in the long term.

  • 19. Rosenbloom, Christine A
    et al.
    Loucks, Anne B
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Special populations: the female player and the youth player.2006In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 24, no 7, p. 783-93Article in journal (Refereed)
    Abstract [en]

    Females and youth are frequently described as "special" populations in football literature, but together these two populations outnumber male players. What makes females "special" is that they tend to eat less when training and competing than their male counterparts, leading to lower intakes of energy, carbohydrate, and some nutrients. Youth football players are special in regard to energy and nutrient requirements to promote growth and development, as well as to fuel sport. There is limited research on the dietary habits of these two populations, but the available literature suggests that many female and youth players need to increase carbohydrate intake, increase fluid intake, and develop dietary habits to sustain the demands of training and competition.

  • 20.
    Rosén, Johanna S
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Goosey-Tolfrey, Victoria L
    Loughborough University, UK.
    Mason, Barry S
    Loughborough University, UK.
    Hutchinson, Michael J
    Loughborough University, UK.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The impact of impairment on kinematic and kinetic variables in Va'a paddling: Towards a sport-specific evidence-based classification system for Para Va'a.2019In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 37, no 17, p. 1942-1950Article in journal (Refereed)
    Abstract [en]

    Para Va'a is a new Paralympic sport in which athletes with trunk and/or leg impairment compete over 200 m. The purpose of this study was to examine the impact of impairment on kinematic and kinetic variables during Va'a ergometer paddling. Ten able-bodied and 44 Para Va'a athletes with impairments affecting: trunk and legs (TL), legs bilaterally (BL) or leg unilaterally (UL) participated. Differences in stroke frequency, mean paddling force, and joint angles and correlation of the joint angles with paddling force were examined. Able-bodied demonstrated significantly greater paddling force as well as knee and ankle flexion ranges of movement (ROM) on the top hand paddling side compared to TL, BL and UL. Able-bodied, BL and UL demonstrated greater paddling force and trunk flexion compared to TL, and UL demonstrated larger bottom hand paddling side knee and ankle flexion ROM compared to BL. Significant positive correlations were observed for both male and female athletes between paddling force and all trunk flexion angles and ROM in the trunk and pelvis rotation and bottom hand paddling side hip, knee and ankle flexion. The results of this study are important for creating an evidence-based classification system for Para Va'a.

  • 21.
    Sandamas, Paul
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Gutierrez-Farewik, Elena M
    KTH, Karolinska institutet.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    The effect of a reduced first step width on starting block and first stance power and impulses during an athletic sprint start.2019In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 37, no 9, p. 1046-1054Article in journal (Refereed)
    Abstract [en]

    This study investigated how manipulating first step width affects 3D external force production, centre of mass (CoM) motion and performance in athletic sprinting. Eight male and 2 female competitive sprinters (100m PB: 11.03 ± 0.36 s male and 11.6 ± 0.45 s female) performed 10 maximal effort block starts. External force and three-dimensional kinematics were recorded in both the block and first stance phases. Five trials were performed with the athletes performing their preferred technique (Skating) and five trials with the athletes running inside a 0.3 m lane (Narrow). By reducing step width from a mean of 0.31 ± 0.06 m (Skating) to 0.19 ± 0.03 m (Narrow), reductions were found between the two styles in medial block and medial 1st stance impulses, 1st stance anterior toe-off velocity and mediolateral motion of the CoM. No differences were found in block time, step length, stance time, average net resultant force vector, net anteroposterior impulse nor normalised external power. Step width correlated positively with medial impulse but not with braking nor net anteroposterior impulse. Despite less medially directed forces and less mediolateral motion of the CoM in the Narrow trials, no immediate improvement to performance was found by restricting step width.

  • 22. Spurway, N C
    et al.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Noakes, T D
    Wagner, P D
    What limits VO2max?: A symposium held at the BASES Conference, 6 September 20102012In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 30, no 6, p. 517-531Article in journal (Refereed)
    Abstract [en]

    Three modern views about the factors limiting oxygen uptake in healthy humans are set against the original (early 1920s) concept of A. V. Hill and colleagues. The majority view for most of the intervening time has been that cardiac output is the essential limiting function. Among recent research in support of this contention is that, in quadrupeds, pericardiectomy, which allows greater diastolic filling, elevates maximum oxygen uptake; however, the relevance to bipedal exercise can be questioned. In any case, algebraic analyses of model systems indicate that all identifiable stages on the oxygen transport pathway, from pulmonary diffusion to oxidative phosphorylation in skeletal muscle mitochondria, materially influence maximum uptake. Thus, if a high cardiac output is to be of benefit, all the other steps must function better too. Nevertheless, these two viewpoints concur that the limit to maximum oxygen uptake is somatic. In contrast, there are strong indications that at altitudes where oxygen availability is about half that at sea level, cerebral oxygenation is a limiting factor, and some recent experiments raise the possibility that it might be a substantial influence at sea level also. Clearly, consensus cannot yet be reached on the question posed in the title.

  • 23. Thelwell, Richard C
    et al.
    Wagstaff, Christopher R D
    Chapman, Michael T
    Kenttä, Göran
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Sport Psychology research group.
    Examining coaches' perceptions of how their stress influences the coach-athlete relationship.2017In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 35, no 19, p. 1928-1939Article in journal (Refereed)
    Abstract [en]

    This study extends recent coach stress research by evaluating how coaches perceive their stress experiences to affect athletes, and the broader coach-athlete relationship. A total of 12 coaches working across a range of team sports at the elite level took part in semi-structured interviews to investigate the 3 study aims: how they perceive athletes to detect signals of coach stress; how they perceive their stress experiences to affect athletes; and, how effective they perceive themselves to be when experiencing stress. Following content analysis, data suggested that coaches perceived athletes able to detect when they were experiencing stress typically via communication, behavioural, and stylistic cues. Although coaches perceived their stress to have some positive effects on athletes, the overwhelming effects were negative and affected "performance and development", "psychological and emotional", and "behavioural and interaction" factors. Coaches also perceived themselves to be less effective when stressed, and this was reflected in their perceptions of competence, self-awareness, and coaching quality. An impactful finding is that coaches are aware of how a range of stress responses are expressed by themselves, and to how they affect athletes, and their coaching quality. Altogether, findings support the emerging view that coach stress affects their own, and athlete performance.

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