| 61. |
- Parker, James, 1980-, et al.
(författare)
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Differences in kinematics and driver performance in elite female and male golfers
- 2022
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Ingår i: Sports Biomechanics. - Abingdon : Routledge. - 1476-3141 .- 1752-6116. ; 21:6, s. 731-747
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare swing kinematic differences between women and men and investigate which variables predict clubhead speed (CHS) and carry distance (CD) whilst accounting for individual variation. Methods: Swing kinematics and driver performance data were collected on 20 (10 women) elite golfers (HCP 0.7 ± 1.4). We used Bayesian T-test for between sex comparison of swing kinematics and Bayesian Analysis of covariance (ANCOVA) to produce general linear models for CHS and carry distance for elite female and male golfers separately. Results: There was strong evidence that the driver performance variables CHS and CD were decreased in women compared to men, and two kinematic variables; time to arm peak speed downswing and angular wrist peak speed were slower in women. The ANCOVAs identified very strong to overwhelming evidence that participant as a fixed factor was a determinant of CHS for both women and men but was not a determinant of CD. Conclusion: when looking to enhance driver performance among high-level golfers, coaches should be aware that variables that determine CHS and CD differ among women and men and if the aim is to improve CHS coaches should not forget the importance of individual swing characteristics. © 2019 Parker, Hellström & Olsson. Published by Informa UK Limited, trading as Taylor & Francis Group.
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| 62. |
- Parker, James, 1980-, et al.
(författare)
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Effects of 8 Weeks of Isokinetic Training on Power, Golf Kinematics, and Club Head Speed In Elite Golfers
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Elite competitive golfers commonly use physical conditioning as a way of improving playing results. Multiple studies have investigated the use of different training methods for improving performance but few studies have investigated the use of isokinetic power training as a way of improving swing kinematics and/or club head speed (CHS). The specific objective of the study was to investigate if eight weeks of isokinetic power training was more effective than traditional power training in improving swing kinematics and CHS.Methods: 20 competitive elite golfers (handicap better than -3.1), 13 men and 7 women, (age 22±2 years) were tested for lower body power (countermovement jump and loaded vertical squat jump 20,40 & 60kg), rotational power (seated upper body rotational power at 10% of body weight; bw) and golf swing kinematics (pelvis, thorax and lead arm peak rotational velocities using electromagnetic motion capture system; Polhemus Inc. USA ) and club head speed (doppler-radar launch monitor system; Flightscope, South Africa), Participants were split into a control (CTL) group (n=10) who continued with the regular strength and power training and an intervention (IK) group (n=10) performing isokinetic power training in the isokinetic 1080Quantum system (1080Motion, Sweden) during 8 weeks. The intervention focused on barbell squat (22kg at 0.5 ms-1) and standing rotation (10% body weight at 1 ms-1).Statistical analysis: a 2 (between; groups) x 2 (within; time) ANOVA assessed any differences in power, club and swing kinematics.Results: Statistically significant improvements were observed in both the IK and CTL group for rotational power (p<0.001), CHS (p=0.025), and peak arm speed (p=0.001). There were no significant differences in countermovement jump height, peak power during squats, peak pelvis speed, or peak thorax speed following the intervention period.Discussion: After 8 weeks of power training, both rotational power and peak arm speed improved as did the performance measure of CHS in both the IK and CTL group. However no significant changes were found between the two groups. In conclusion, there was no evidence suggesting that isokinetic training, as performed in this study, is neither detrimental, nor more effective, than traditional strength training when it comes to increasing CHS in golf performance.
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| 63. |
- Parker, James, 1980-, et al.
(författare)
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Effects of nine weeks isokinetic training on power, golf kinematics, and driver performance in pre-elite golfers
- 2017
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Ingår i: BMC Sports Science, Medicine and Rehabilitation. - London : BioMed Central. - 2052-1847. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundIt has previously been shown that isotonic strength training can improve driver performance among golfers, though few studies have investigated effects of strength training on swing kinematics together with driver performance. In this study we investigated whether isokinetic rotational training could improve driver performance and swing kinematic variables amongst elite golfers.MethodsTwenty competitive pre-elite golfers (handicap better than −3.0), 13 men and 7 women, were split into two groups, one group received the isokinetic power training (IK) alongside their normal isotonic pre-season strength-training and the other group continued with their normal isotonic pre-season strength-training regime (IT). The IK group completed 12 sessions of isokinetic power training on a standing rotation exercise (10% body weight at 1 m/s) and barbell squat (25 kg plus 10% body weight at 0.5 m/s). The IT group continued with their normal isotonic pre-season strength-training regime. Participants were tested for rotational power, lower body power, golf swing kinematics, and driver performance before and after a nine-week training period.ResultsAfter the nine-week training period both the IK and the IT groups increased their dominant side rotational force and power (effect sizes between 0.50–0.96) and magnitude based inference indicated that IK had a likely (> 80%) more beneficial increase in dominant side rotational force and power. For swing kinematics, IK had a likely (> 80%) more beneficial improvement in lead arm speed and acceleration compared to the IT group. For driver performance, IK had a possible (65%) beneficial effect on ball speed and likely (78%) beneficial effect on carry distance when compared to IT, whereas neither of the groups improved club head speed.ConclusionIn the present study on pre-elite golfers we found that 9 weeks of isokinetic training increased seated rotational force and power, peak arm speed and arm acceleration, ball speed, and carry distance more compared to isotonic training. Even though isokinetic training did not increase CHS, it did result in greater carry distance. © The Author(s). 2017
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| 64. |
- Parker, James, 1980-, et al.
(författare)
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Relationships between golf swing kinematics and driver performance in elite golfers
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Swing kinematics and driver performance are considered important factors in golf performance. In golf research clubhead speed (CHS) is commonly used as the driver performance measure, whereas carry distance (CD) is less investigated and together with final ball position determine the success of a drive. The aim of this study was to investigate which kinematic factors of the pelvis, thorax, and lead arm explain CHS and/or CD. Swing kinematics data on 15 elite golfers were collected using an electromagnetic 3-D system and a doppler-radar launch monitor system. Variables that emerged as important for both CHS and CD were: reduced pelvis rotation top of backswing (TOB); reduced X-factor TOB; and more thorax lateral bend TOB, along with greater thorax peak speed during the downswing. Variables that were distinctive for the CHS model were mainly during the downswing: greater X-factor stretch; and higher pelvis peak speed. Finally, factors distinctive to the regression model for CD were: reduced thorax rotation; and greater thorax lateral bend. Implications from the results suggest whilst greater peak pelvis speed and x-factor stretch effect CHS they do not significantly influence CD. Likewise, the variables unique to CD do not significantly influence CHS but may be a technical attributes which allow for more optimal clubhead delivery leading to improved CD.
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| 65. |
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| 66. |
- Ražanskas, Petras, et al.
(författare)
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Predicting physiological parameters in fatiguing bicycling exercises using muscle activation timing
- 2017
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Ingår i: Biomedical Signal Processing and Control. - Amsterdam : Elsevier. - 1746-8094 .- 1746-8108. ; 35, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- This article is concerned with a novel technique for prediction of blood lactate concentration level and oxygen uptake rate from multi-channel surface electromyography (sEMG) signals. The approach is built on predictive models exploiting a set of novel time-domain variables computed from sEMG signals. Signals from three muscles of each leg, namely, vastus lateralis, rectus femoris, and semitendinosus were used in this study. The feature set includes parameters reflecting asymmetry between legs, phase shifts between activation of different muscles, active time percentages, and sEMG amplitude. Prediction ability of both linear and non-linear (random forests-based) models was explored. The random forests models showed very good prediction accuracy and attained the coefficient of determination R2 = 0.962 for lactate concentration level and R2 = 0.980 for oxygen uptake rate. The linear models showed lower prediction accuracy. Comparable results were obtained also when sEMG amplitude data were removed from the training sets. A feature elimination algorithm allowed to build accurate random forests (R2 > 0.9) using just six (lactate concentration level) or four (oxygen uptake rate) time-domain variables. Models created to predict blood lactate concentration rate relied on variables reflecting interaction between front and back leg muscles, while parameters computed from front muscles and interactions between two legs were the most important variables for models created to predict oxygen uptake rate.© 2017 Elsevier Ltd.
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| 67. |
- Rodríguez-Varela, Ricardo, et al.
(författare)
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The genetic history of Scandinavia from the Roman Iron Age to the present
- 2023
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Ingår i: Cell. - : Elsevier. - 0092-8674 .- 1097-4172. ; 186:1, s. 32-46
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a 2,000-year genetic transect through Scandinavia spanning the Iron Age to the present, based on 48 new and 249 published ancient genomes and genotypes from 16,638 modern individuals. We find regional variation in the timing and magnitude of gene flow from three sources: the eastern Baltic, the British-Irish Isles, and southern Europe. British-Irish ancestry was widespread in Scandinavia from the Viking period, whereas eastern Baltic ancestry is more localized to Gotland and central Sweden. In some regions, a drop in current levels of external ancestry suggests that ancient immigrants contributed proportionately less to the modern Scandinavian gene pool than indicated by the ancestry of genomes from the Viking and Medieval periods. Finally, we show that a north-south genetic cline that characterizes modern Scandinavians is mainly due to the differential levels of Uralic ancestry and that this cline existed in the Viking Age and possibly earlier.
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| 68. |
- Stelzer, J E, et al.
(författare)
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Expression of cardiac troponin T with COOH-terminal truncation accelerates cross-bridge interaction kinetics in mouse myocardium
- 2004
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - Bethesda : American Physiological Society. - 0363-6135 .- 1522-1539. ; 287:4, s. H1756-H1761
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Tidskriftsartikel (refereegranskat)abstract
- Transgenic mice expressing an allele of cardiac troponin T (cTnT) with a COOH-terminal truncation (cTnTtrunc) exhibit severe diastolic and mild systolic dysfunction. We tested the hypothesis that contractile dysfunction in myocardium expressing low levels of cTnTtrunc (i.e., <5%) is due to slowed cross-bridge kinetics and reduced thin filament activation as a consequence of reduced cross-bridge binding. We measured the Ca2+ sensitivity of force development [pCa for half-maximal tension generation (pCa50)] and the rate constant of force redevelopment ( ktr) in cTnTtrunc and wild-type (WT) skinned myocardium both in the absence and in the presence of a strong-binding, non-force-generating derivative of myosin subfragment-1 (NEM-S1). Compared with WT mice, cTnTtrunc mice exhibited greater pCa50, reduced steepness of the force-pCa relationship [Hill coefficient ( nH)], and faster ktr at submaximal Ca2+ concentration ([Ca2+]), i.e., reduced activation dependence of ktr. Treatment with NEM-S1 elicited similar increases in pCa50 and similar reductions in nH in WT and cTnTtrunc myocardium but elicited greater increases in ktr at submaximal activation in cTnTtrunc myocardium. Contrary to our initial hypothesis, cTnTtrunc appears to enhance thin filament activation in myocardium, which is manifested as significant increases in Ca2+-activated force and the rate of cross-bridge attachment at submaximal [Ca2+]. Although these mechanisms would not be expected to depress systolic function per se in cTnTtrunc hearts, they would account for slowed rates of myocardial relaxation during early diastole.
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| 69. |
- Strålsjö, L, et al.
(författare)
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Total folate content and retention in rosehips (Rosa ssp.) after drying.
- 2003
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 51:15, s. 4291-4295
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Tidskriftsartikel (refereegranskat)abstract
- Folate concentrations in rosehips and commercial rosehip products and factors affecting folate retention during drying were investigated. On the basis of the raw material studied during 3 years, rosehips were shown to be a rich folate source, 400-600 g/100 g based on dry matter and 160-185 g/100 g based on the fresh weight (edible part). Rosehips are not often consumed fresh; therefore, drying to produce stable semimanufactures is a crucial step. The degradation of folate was shown to be dependent on the drying time until the water activity was below 0.75. The required drying time was reduced by cutting the rosehips in slices and to some extent also by increasing the temperature. Retention of folate and ascorbic acid was affected by the same factors, and high content of ascorbic acid could provide a possible protection for folate degradation.
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| 70. |
- Sundström, Tomas, et al.
(författare)
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Five Weeks of Plyometric Training Improve Vertical Jump Height in Female Handball Players During In-Season
- 2010
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Ingår i: Nordic Conference 2010. - Odense : University of Southern Denmark. ; , s. 112-113
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Konferensbidrag (refereegranskat)abstract
- Introduction: Handball is a sport requiring many different physical qualities in order to perform well, one of which is good jumping ability. For handball players available time to enhance power during in-season is often restricted due to an already high training load emphasizing other aspects of the sport than jumping ability. Therefore, one aim of this study was to examine if a small amount of additional plyometric training during in-season, combining drop jumps and box jumps, could give significant improvements in vertical jump height in female handball players after five weeks of training. Generally, vertical jump height is evaluated with two-legged tests, however, the question arises if the tests are relevant in sports that predominantly use several steps and one-leg jumps such as handball. A second aim of this study was thus to develop, evaluate and validate a handball-specific test performed on one leg.Methods: Two Swedish female handball-teams playing in the third division were recruited. Players from one team made up the intervention-group (n = 9) and players from the other team functioned as the control-group (n = 4). Plyometric training was added to the regular handball training session twice per week during five weeks, lasting approximately 15 minutes per session, consisting of two sets of eight repetitions of drop jumps and box jumps respectively, while the control-group continued their training as normal. Jumping performance was evaluated through the squat jump test (SJ), countermovement jump test (CMJ) and the handball-specific one leg jump test (OLJ) developed for this study in order to offer a more sport-specific evaluation tool when testing sports that predominantely jump on one leg.Results: The intervention-group improved their jumping height significantly with 2,7 cm in the SJ, 3,6cm in the CMJ and 3,6 cm in the OLJ (p < 0,01 for all). The control-group had an opposite trend with diminishing results in all three jumps, -1,5 cm in the SJ (p < 0,05), -1,7 cm in the CMJ (p < 0,05) and -0,9 cm in the OLJ (not significant). The one-legged jump test (OLJ) correlated well with both SJ (r= 0,79, p <0,01 ), and CMJ (r=0,75, p < 0,01).Discussion: The present study found significant improvements in jumping height after only five weeks of plyometric training for female handball players. Interestingly, the intervention-group improved to the same extent in both the one and the two-leg jumps test, which might be explained by the accumulation of handball specific training drills performed on one-leg, together with the two-legged plyometric exercises. The same assumption could also explain why the control-group showed no change in the one-leg jump test between the pre and post-tests, but displayed significant lower scores in the two-legged jumping tests after 5 weeks with only regular handball training.Conclusion: The improvements seen in this study with a small amount of additional plyometric training is relevant for coaches that need to provide gains in jumping performance during in-season when there is not a lot of time for additional training. Moreover, an evaluation test needs to be as specific as possible to the performance in the sport. The one-leg vertical jump test, developed in this study, could be a first step to a future handball-test that better resembles the jumping performance in handball than already established two-leg jumping tests.
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