Force variability during isometric wrist flexion in highly skilled and sedentary individuals

The association of expertness in specific motor activities with a higher ability to sustain a constant application of force, regardless of muscle length, has been hypothesized. Ten highly skilled (HS group) young tennis and handball athletes and 10 sedentary (S group) individuals performed maximal and submaximal (5, 10, 20, 50, and 75% of the MVC) isometric wrist flexions on an isokinetic dynamometer (Kin-Com, Chattanooga). The wrist joint was fixed at five different angles (230, 210, 180, 150, and 1300). For each position the percentages of the maximal isometric force were calculated and participants were asked to maintain the respective force level for 5 s. Electromyographic (EMG) activation of the Flexor Carpi Ulnaris and Extensor Digitorum muscles was recorded using bipolar surface electrodes. No significant differences were observed in maximal isometric strength between HS and S groups. Participants of HS group showed significantly (P < 0.05) smaller force coefficient of variability (CV) and SD values at all submaximal levels of MVC at all wrist angles. The CV and SD values remained unaltered regardless of wrist angle. No difference in normalized agonist and antagonist EMG activity was observed between the two groups. It is concluded that long-term practice could be associated with decreased isometric force variability independently from muscular length and coactivation of the antagonist muscles

Amazon, syjuntatant - lotta : Om frivilligdeltagandet inom Riksförbundet Sveriges lottakårer mellan 1960- och 1970-talen

This thesis on the Swedish voluntary women’s defence organisation Riksförbundet Sveriges lottakårer (SLK), studies how the board and the members of SLK discussed the problems and the meaning of voluntary defence work during the 1960s and 1970s. Furthermore the thesis aims to engage with previous research and give an explanation to why people may be interested in voluntary defence. Views varied greatly within SLK: some meant that the voluntary grounds of participation gave a sense of elite status to the organisation; however others saw voluntary work as untenable, since more women at the time had both work and family obligations. Another issue was professionalisation versus socialisation. While some members wanted to see a centralisation and professionalisation of the organisation, others found it more important to safeguard the social functions and independence of the local corps unit. The results suggest that gender structures as well as individual agency create multiple reasons and meanings behind voluntary defence work

Amazon, syjuntatant - lotta : Om frivilligdeltagandet inom Riksförbundet Sveriges lottakårer mellan 1960- och 1970-talen

This thesis on the Swedish voluntary women’s defence organisation Riksförbundet Sveriges lottakårer (SLK), studies how the board and the members of SLK discussed the problems and the meaning of voluntary defence work during the 1960s and 1970s. Furthermore the thesis aims to engage with previous research and give an explanation to why people may be interested in voluntary defence. Views varied greatly within SLK: some meant that the voluntary grounds of participation gave a sense of elite status to the organisation; however others saw voluntary work as untenable, since more women at the time had both work and family obligations. Another issue was professionalisation versus socialisation. While some members wanted to see a centralisation and professionalisation of the organisation, others found it more important to safeguard the social functions and independence of the local corps unit. The results suggest that gender structures as well as individual agency create multiple reasons and meanings behind voluntary defence work

A biomechanical approach of lower limbs laterality in tennis - an examination of its change through training

The aim of the present study was to investigate the influence of the phenomenon of “laterality” in a wide spectrum of parameters of the physical condition of the lower limbs in tennis, as well as to study the influence of 3 different methods on the same parameters, through examining variations in performance. The sample consisted of 64 sport science students at Serres, aged between 21.05 ± 1.33. Data were collected by means of laboratory measurements in the Department’s Laboratory of Biomechanics. Initially, their dominant and non-dominant side was examined and ascertained during lateral movement with side steps. Based on a specific measurement protocol which included: a) jumping attempts, b) races, c) strength tests, d) reaction to a visual stimulus and e) a speed check of cycle ergometer, the performance of both sides was registered when they were brought into action either one at time or both simultaneously. Following recommendations by Baumann, a single axis dynamometer (AMD Co. Ltd., typ LC 4204-K600, 1-D, Load cell) was used to assess all the vertical jumps, performances in body side displacements and in reaction speed to optical stimulus. The dynamometer was placed in parallel with the ground on which there was a special steel platform. To assess the maximal isometric strength of the lower limbs (Fmaxiso), a second identical dynamometer was used, placed vertically on the ground, on a special closed device to facilitate its transfer. To assess the maximal speed on a cycle-ergometer (UEmax), a MONARK Ergomedic cycle-ergometer (814E, classe A, din 32932) was used without an additional brake resistance. The speed at the distance of 11.885 m. was measured (a) using two photocell fences consisted of two bands with two pairs of photocells each, and (b) with an automatic digital timer with minimal time measurement set to 0.01 sec. Then, the subjects were divided into 4 subgroups (3 experimental groups and one control group). The training protocols that were applied to improve the non-dominant side, included jumping exercises for group A, tennis-specific racing exercises for group B, and an equal combination (50 % - 50 %) of the two previous types of exercise for group C. The volume of the training load during each training session comprised of 4 exercises from a program of six exercises in total, that were executed in various combinations across training sessions. Each exercise was repeated between 6 and 8 times in two sets in each training session. There was an interval of two minutes between sets. There was also a time break of 3 to 4 minutes between each type of exercise. To examine the influence of the various training methods the tests used were the Paired t-test, and the one-way ANOVA followed by the Scheffee post-hoc test. It was concluded, that the training of group A was as a whole more efficient in dealing with laterality, followed by group C, and then by group B. The non-dominant limb performances were improved as follows: The time of the body side displacement at 4.115 m. and the sprint time at 11.885 m. were decreased. Also, the height of the vertical jump and the speed at the cycle ergometer test were increased. Finally, the reaction time at the optical stimulus was decreased while the maximal isometric strength was increased. The practical application of the research results would be particularly useful in diagnosing laterality and would mainly contribute to the improvement speed and strength of lower limbs in tennis.Σκοπός της παρούσας έρευνας ήταν να διερευνηθεί η επιρροή του φαινομένου της «πλευρικότητας» σε ένα ευρύ φάσμα παραμέτρων της φυσικής κατάστασης των κάτω άκρων στην Αντισφαίριση, καθώς και να μελετηθεί η επίδραση τριών διαφορετικών μεθόδων προπόνησης, μέσω των μεταβολών στις επιδόσεις σε αυτές τις παραμέτρους. Το δείγμα απετέλεσαν 64 φοιτητές του Τ.Ε.Φ.Α.Α. Σερρών του Α.Π.Θ., ηλικίας 21,05 ± 1,33 χρόνων και τα δεδομένα τους συλλέχθηκαν μέσω εργαστηριακών μετρήσεων στο Εργαστήριο Βιομηχανικής του. Αρχικά ελέγχθηκαν και εξακριβώθηκαν η κυρίαρχη και η μη-κυρίαρχη πλευρά κατά την πλευρική μετακίνηση με πλάγια βήματα side steps. Με βάση ειδικό πρωτόκολλο μετρήσεων που περιελάμβανε: α) αλτικές δοκιμασίες, β) δρομικές δοκιμασίες, γ) δοκιμασίες δύναμης, δ) αντίδραση σε οπτικό ερέθισμα και ε) έλεγχο της ταχύτητας στο εργοποδήλατο, καταγράφηκε η επίδοση και των δύο πλευρών, όταν αυτές ενεργοποιούνταν μεμονωμένα ή και ταυτόχρονα. Για τη μέτρηση όλων των κατακόρυφων αλμάτων, των επιδόσεων στις πλάγιες μετακινήσεις και στην ταχύτητα αντίδρασης σε οπτικό ερέθισμα χρησιμοποιήθηκε ένα μονοαξονικό δυναμόμετρο (AMD Co. Ltd., typ LC 4204-K600, 1-D, Load cell) κατά Baumann, τοποθετημένο παράλληλα με το έδαφος, στο οποίο υπήρχε προσαρτημένο ειδικό χαλύβδινο δάπεδο. Ένα δεύτερο πανομοιότυπο δυναμόμετρο, προσαρτημένο σε ειδική κλειστή (για την εύκολη μεταφορά της) συσκευή και τοποθετημένο κάθετα στο έδαφος, χρησιμοποιήθηκε για τη μέτρηση της μέγιστης ισομετρικής δύναμης (Fmaxiso) των κάτω άκρων. Ένα εργοποδήλατο τύπου MONARK Ergomedic (814E, classe A, din 32932) χρησιμοποιήθηκε για τη διεξαγωγή μέτρησης της μέγιστης ταχύτη­τας σε εργοποδήλατο (ΤΕmax), χωρίς επιπλέον αντίσταση πέδησης. Η ταχύτητα στην απόσταση των 11,885 μέτρων μετρήθηκε α) με δύο φράκτες φωτοκυττάρων (Autonics Beam Sensor BL5M), αποτελούμενους από δύο δέσμες με δύο ζεύγη φωτοκύτταρα η κάθε μια και β) με ένα αυ­τόματο ψηφιακό χρονόμετρο (Saint Wien Digital Timer Type H5K), με ελάχιστο χρόνο μέτρησης το 0,01 sec. Κατόπιν, οι δοκιμαζόμενοι χωρίστηκαν σε τέσσερις υποομάδες (τρεις πειραματικές ομάδες και μια ομάδα ελέγχου). Τα προπονητικά προγράμματα που εφαρμόστηκαν για τη βελτίωση της μη-κυρίαρχης πλευράς περιελάμβαναν για την α’ ομάδα αλτικές ασκήσεις, για τη β’ ομάδα ειδικές δρομικές ασκήσεις της Αντισφαίρισης και για τη γ’ ομάδα έναν συνδυασμό των προηγούμενων περιεχομένων σε αναλογία 50 % - 50 %. Ο όγκος της επιβάρυνσης στη διάρκεια της κάθε προπόνησης περιελάμβανε 4 ασκήσεις από ένα πρόγραμμα 6 συνολικά ασκήσεων, οι οποίες εκτελούνταν εκ περιτροπής. Κάθε άσκηση επαναλαμβανόταν 6 - 8 φορές, σε 2 σειρές. Μεταξύ των σειρών υπήρχε διάλειμμα 2 λεπτών και στην αλλαγή της άσκησης διάλειμμα 3 - 4 λεπτών. Για τον έλεγχο της επίδρασης των διαφορετικών προπονητικών μεθόδων εφαρμόστηκαν το Paired T-test και το one way ANOVA, με Scheffee test. Από τα αποτελέσματα διαπιστώθηκε πως η προπόνηση της α’ ομάδας ήταν συνολικά σημαντικά αποτελεσματικότερη στην αντιμετώπιση της πλευρικότητας, ακολουθούμενη από την ομάδα γ’ και κατόπιν την ομάδα β’. Οι επιδόσεις του μη-κυρίαρχου σκέλους βελτιώθηκαν ως εξής: Συντομεύθηκε ο χρόνος στην πλευρική μετακίνηση στα 4,115 m και στο σπριντ των 11,885 m, αυξήθηκε το ύψος του άλματος και η ταχύτητα στη δοκιμασία στο εργοποδήλατο, μειώθηκε ο χρόνος αντίδρασης στο οπτικό ερέθισμα και τέλος αυξήθηκε η μέγιστη ισομετρική δύναμη. Η πρακτική εφαρμογή των αποτελεσμάτων της έρευνας θα ήταν ιδιαίτερα χρήσιμη στη διάγνωση της πλευρικότητας και θα συνέβαλλε κυρίως στη βελτίωση της επίδοσης σε παραμέτρους της φυσικής κατάστασης, που αφορούν την ταχύτητα και τη δύναμη των κάτω άκρων στο άθλημα της Αντισφαίρισης

Force Steadiness during Submaximal Isometric Plantar and Dorsiflexion in Resistance Training: Experienced vs Non-experienced Individuals

The purpose of this study was to determine differences in force steadiness during submaximal plantar flexion (PF) and dorsiflexion (DF) of the dominant leg between individuals experienced and not experienced in resistance training. Forty males aged 18-32 were divided in two groups based on their experience in resistance training (experienced – not experienced). Evaluation of maximal voluntary isometric force was carried out on a Humac-Norm isokinetic dynamometer. The measurement of the maximal voluntary contraction (MVC) was measured in 3 isometric attempts. Then, the stability measurement of 10%, 30%, 50% and 70% of the MVC was assessed. The duration of the isometric contraction was 10 seconds but only 6 seconds were analyzed. T-test for independent samples and ANOVA was applied for the statistical analysis. The results showed that the individuals with more experience in resistance training presented a significantly higher MVC and force steadiness of the plantar and dorsiflexors muscles, compared with the individuals with less experience (p < 0.05). In conclusion, the years of practice with resistance training appear to have a beneficial effect on force steadiness