1,721,091 research outputs found
Five-meter rope-climbing: a commando-specific power test of the upper limbs
No full textTo examine the concurrent validity and absolute and relative reliabilities of a commando-specific power test
Unilateral static and dynamic hamstrings stretching increases contralateral hip flexion range of motion
No full textStatic (SS) and dynamic stretching (DS) can lead to subsequent performance impairments or enhancement with the stretched limb. Crossover or non-local muscle fatigue (NLMF) refers to unilateral fatigue-induced impairments in a contralateral or non-exercised muscle. Whereas there are conflicting findings in the NLMF literature, there are few studies examining the effect of an acute bout of SS or DS on contralateral flexibility, torque or power. Fourteen highly trained subjects (means ± standard deviations: 18 ± 2 years; 179·4 ± 4·6 cm; 70·5 ± 6·3 kg; %body fat: 10·7 ± 2·5%) were tested before and following separate sessions of eight repetitions of 30 s of unilateral hip flexion SS or DS. Pre- and postintervention testing at 1 and 10 min included hip flexor range of motion (ROM), isokinetic leg flexion torque and power at 60°.s(-1) and 300°.s(-1) of the stretched and contralateral limbs. The stretched limb had a 6·3% (P = 0·01; ES: 0·91) ROM increase with DS at 10 min. The contralateral non-stretched hip flexors experienced ROM increases with SS of 5·7% (P = 0·02; ES: 0·68) from pretest to 1 min post-test, whereas DS showed 7·1% (P<0·0001; ES: 1·09) and 8·4% (P = 0·005; ES: 0·89) increases, respectively. There were no relative differences in ROM changes between conditions or limbs nor any stretch-induced changes in isokinetic torque or power. In conclusion, unilateral SS and DS augment contralateral limb ROM likely through an increased stretch tolerance
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The role of instability with resistance training
No full textThere are many instances in daily life and sport in which force must be exerted when an individual performing the task is in an unstable condition. Instability can decrease the externally-measured force output of a muscle while maintaining high muscle activation. The high muscle activation of limbs and trunk when unstable can be attributed to the increased stabilization functions. The increased stress associated with instability has been postulated to promote greater neuromuscular adaptations, such as decreased co-contractions, improved coordination, and confidence in performing a skill. In addition, high muscle activation with less stress on joints and muscles could also be beneficial for general musculoskeletal health and rehabilitation. However, the lower force output may be detrimental to absolute strength gains when resistance training. Furthermore, other studies have reported increased co-contractions with unstable training. The positive effects of instability resistance training on sports performance have yet to be quantified. The examination of the literature suggests that when implementing a resistance training program for musculoskeletal health or rehabilitation, both stable and unstable exercises should be included to ensure an emphasis on both higher force (stable) and balance (unstable) stressors to the neuromuscular system.Peer reviewedFinal article publishedtrunk musclescocontractionsmuscle activationstrengthbalanc
Maintenance of EMG activity and loss of force output with instability
No full textSwiss Balls used as a platform for training provide an unstable environment for force production. The objective of this study was to measure differences in force output and electromyographic (EMG) activity of the pectoralis major, anterior deltoid, triceps, latissimus dorsi, and rectus abdominus for isometric and dynamic contractions under stable and unstable conditions. Ten healthy male subjects performed a chest press while supported on a bench or a ball. Unstable isometric maximum force output was 59.6% less than under stable conditions. However, there were no significant differences in overall EMG activity between the stable and unstable protocols. Greater EMG activity was detected with concentric vs. eccentric or isometric contractions. The decreased balance associated with resistance training on an unstable surface may force limb musculature to play a greater role in joint stability. The diminished force output suggests that the overload stresses required for strength training necessitate the inclusion of resistance training on stable surfaces. ABSTRACT FROM AUTHORPeer reviewedFinal article publishedmuscle activationSwiss ballresistance trainingdynamicisometri
Trunk muscle activity increases with unstable squat movements
No full textThe objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p < 0.05). Increased EMG activity of these muscles may be attributed to their postural and stabilization role. Furthermore, EMG activity was higher during concentric contractions compared to eccentric contractions. Performing squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL). ABSTRACT FROM AUTHORPeer reviewedFinal article publishedelectromyographystabilizersresistance trainingeccentricconcentri
The impact of instability resistance training on balance and stability
No full textThe most predominant literature regarding balance has emphasised the physiological mechanisms controlling stability. Topics range from extrinsic factors (environment) to intrinsic factors (i.e. muscle coordination, vestibular response). Balance is achieved through an interaction of central anticipatory and reflexive actions as well as the active and passive restraints imposed by the muscular system. However, less research has attempted to document the effects of balance on performance measures (i.e. force, power). Furthermore, short- and long-term adaptations to unstable environments need more substantial research. While force and other performance measures can be adversely affected by a lack of balance, the transferability of instability training to activities of daily living and sport is not precisely known. The applicability of instability and resistance training using unstable platforms or implements may have strong relevance in a rehabilitative or athletic setting. Therefore, a comprehensive review of the literature in this area may possibly be of benefit to practitioners who deal with the general population, athletes or persons debilitated by balance and/or stability disabilities.Peer reviewedFinal article publishedResistance TrainingMaximal Voluntary ContractionRectus FemorisRectus AbdominusBalance Trainin
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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