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COMPARISON OF THE EFFECTS OF ISOKINETIC VS ISOTONIC ECCENTRIC TRAINING ON MUSCLE STRENGTH AND MASS.
No full textIntroduction
Eccentric (ECC) training has been shown to induce higher improvements than concentric training on muscle strength and mass (Roig, 2009). The majority of the studies have used isokinetic (ISOK) dynamometers for investigating the acute and chronic effects of ECC training. However, isotonic (ISOT) devices are more commonly available in real sport setting. Aim of the study was to compare ISOK to ISOT ECC training by assessing the effects on muscle strength and mass.
Methods
Forty-nine healthy sport science students were randomly divided in 3 groups: isokinetic eccentric training (ISOK, n=14), isotonic eccentric training (ISOT, n=17) and control group (CON, n=18). Both training groups performed 50 ECC repetitions of knee extension at 120% of their maximal strength measured in concentric modality (1RM for ISOT and peak concentric torque for ISOK), for a total of 14 times in 6 weeks. Isometric maximal voluntary contraction (MVC), concentric and eccentric strength at 60 °/s, 1RM, and muscle mass (using DEXA) were measured pre and post training. All dependent variables were analyzed after log transformation using ANCOVA, entering the baseline values as covariate and factor “group” as independent variable.
Results
Compare to CON, the ISOK group showed higher 1RM (12%, CI95% 6 to 19%), concentric (15%, 8 to 22%), eccentric (35%, 25 to 45%) and isometric (25%, 18 to 34%) maximal strength (P<0.001). Compare to CON, ISOT showed higher 1RM (14%, 9 to 20%), concentric (17%, 11 to 24%), eccentric (25%, 16 to 34%) and isometric (22%, 15 to 29%) maximal strength (P<0.001). No differences between ISOK and ISOT were found in 1RM (2%, -3 to 7%), concentric (-2%, -4 to 8%) and isometric (-3%, -8 to 3%) maximal strength. Only eccentric strength was higher in the ISOK compare to the ISOT group (8%, 1 to 14%). No differences between groups were found in muscle mass (0.419<P<0.769).
Discussion
This study showed that ECC training using both ISOK and ISOT improved maximal strength in physically active people. The lack of muscle mass changes suggests that the increase in muscle strength waw mainly due to neural adaptations (Hortobagyi, 1996). ISOK showed higher improvement in ECC strength measured on the isokinetic dynamometer but this may be due to similarity between testing and training conditions. Nevertheless, considering ISOT devices are more easily available this training modality seems to be a good alternative to ECC training using isokinetic dynamometers.
References
Roig et al., 2009, Br J Sports Med 43(8): 556-68.
Hortobágyi et al., J Appl Physiol. 1996 Oct;81(4):1677-82
Effect of contraction modality on muscle strength and structure after resistance training and detraining
No full textIntroduction: Traditional resistance training involves both concentric and eccentric contraction, even if the latter has been shown to be more effective in total strength and muscle mass increment (Roig, 2009). However, often total training volume has been not considered. In addition, less is known about improvements retention after a detraining period. Therefore, aim of the study is to evaluate if muscle strength and structure changes are contraction dependent. In addition, we want to investigate if contraction modality can influence modifications retention after detraining.
Methods: Sixty healthy female sport science students were randomly allocated in eccentric only (E), concentric only (C), eccentric plus concentric training (E+C) or control group (CG). Training groups exercised isovolume unilateral isotonic leg extension for 8 weeks, while CG did not train. Isokinetic eccentric, concentric and isometric Maximal Voluntary Contraction (MVC), 1RM, vastus lateralis fascicle angle (FA), fascicle thickness (FT) and fascicle length(FL) and fat free mass (FFM) were recorded at baseline, 1 and 4 weeks after the end of training. Changes of dependent variables were detected using two- way repeated measures ANOVA.
Results: Significant two way interaction resulted in concentric (p<0,001), eccentric (p<0,001) and isometric (p<0.001) MVC, 1RM (p<0.001) and FA (p<0.05). FFM showed a strong tendency in two way interaction (p=0.058), while FT and FL did not displayed it. Post hoc analysis showed different strength coupling training-testing behavior both after training and detraining. FFM increased only in E after detraining (p<0.05). PA similarly increased in all training groups; FT incremented only in E (0.01) and C (0.05); Fascicle lengthened after detraining in E (p<0.01) and C (p<0.05).
Discussion: Effectiveness of resistance training depend both on volume and contraction modality. Confirming literature, high intensity resistance training showed muscle strength and improvement retention (Fatouros, 2005). Hence, even if high intensity isovolume resistance training improved total strength, contraction specific training- testing is a torque high lightening factor, with a superiority of eccentric training (Guilhem, 2012). Trainers and conditioners should keep in mind that a timeline adaptations knowledge resulted in a more effective training planning.
Fatouros, I. G., et al. (2005). Strength training and detraining effects on muscular strength, anaerobic power, and mobility of inactive older men are intensity dependent. British journal of sports medicine, 39(10)
Guilhem, G.,et al. (2012). Neuromuscular Adaptations to Isoload versus Isokinetic Eccentric Resistance Training. Medicine and science in sports and exercise.
Roig, M., et al.(2009). The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis. British journal of sports medicine, 43(8), 556–68
Repeated bout effect induced by eccentric isoinertial device.
No full textMuscle damage is proved to occur after eccentric training (Clarkson, 2002). Moreover, it confers protection to a subsequent session, i.e.: repeated bout effect (Nosaka 2001). A new technology (YoYo technology) has been developed in order to enhance negative phase using inertia (Tesch 1994). Aim of the study is evaluate if lengthening contraction enhanced by inertial flywheel squat will cause symptoms of muscle injury and following protection.
Twelve healthy males performed 100 maximal squat repetitions using inertial device. At baseline, after training and up to 4 days after CK blood concentration, Knee extensors strength, muscle soreness and jump performance were measured as markers of muscle damage. Same protocol was repeated after 3 weeks. Statistical analysis was performed using repeated measures ANOVA, using factor Session and Day.
No significant Session X Day interaction occurred in all parameters. Single factor Session and Day were significant except in [CK]. Post hoc analysis revealed, compare to baseline and after first trainng, [CK] and soreness increments respectively up to 3 and 4 days, while strength loss and jump height were affected only post training. The second bout revealed significant markers decrements compared to the first one in CK (-50% and -43% after 2 and 3 days), muscle soreness (-2,8; -2,6; -3,4; -2,6 A.U. respectively after 1, 2 ,3 and 4 days) and strength ( 12%; 9%; 15%; 15%; 14% respectively immediately after training, after 1, 2, 3 and 4 days).
Inertial flywheel squat induce classical symptoms of muscle injury, even if strength loss and performance could be positively influenced by neural patterns. CK blood activity is relatively lower compared to single joint exercise because of load is divided among more muscles. However, eccentric overload does protect muscle at least up to 3 weeks. Trainers and conditioners should take in account the recovery time course after eccentric inertial squat.
Clarkson PM et al., Exercise Induced Muscle Damage in Humans. American journal of physical medicine & rehabilitation, 2002, 81(11)S: S52-69
Nosaka K et al., How long does the protective effect on eccentric exercise induced muscle damage last?. Medicine & Science in Sports & Exercise, 2001, 33(9): 1490-95
Tesch P et al., A gravity-independent ergometer to be used for resistance training in space. Aviation, space, and environmental medicine, 1994, 65(8): 752-
Factors influencing session rpe in soccer: exercise intensity distribution and time delay
No full textIntroduction
Session-RPE is a valid wide spreading measure of internal training load (TL) used in soccer [1, 2]. Nevertheless some aspects can influence the measure of perceived exertion: intensity distribution and timing in the collection of RPE. The first aim of this study was to examine the effect of different position of high-intensity activities within a training session on the overall session RPE (RPE-end). The second aim was to examine the effect of different delay on session RPE.
Methods
Nineteen junior players (age 15±0.7 yrs, height 172±4.3 cm, weight 61.9±5.1 kg) of a Switzerland soccer team were involved in the study. Heart rate (HR), RPE (Borg CR100©) were collected in 4 standardized training sessions. Total quality of recovery scale (TQR) and Visual Analogical Scale (VAS) for pain of lover limbs were used to avoid presence of fatigued players. Every session was made up by 3 blocks of 20 min different intensity: high (80-100% HR max), light (50-80% HR max) and moderate intensity (60-90% HR max), randomized in the order. RPE was collected after every block (RPE5), immediately after the session (RPE-end), after 30 min (RPE30) and 4 hours (RPE4h).
Results
RPE5 of each block were different depending on the distribution sequence (significant time x condition interaction p0.05). Delay in the RPE collection did not show effect on RPE (p>0.05).
Discussion
TQR and VAS showed similar pre-training conditions and the presence of tired players was excluded. Different intensity distribution was expected by our design and showed no effect on TL. Similarly TL was not influenced by time delay. Therefore training sessions can be designed without being afraid of the influence of distribution intensity on TL. Coaches can confide in the ability of their players to give the same perception even at the end of the session or later without affecting T
Longitudinal validity of Yo-Yo Intermittent Recovery Test in soccer players
No full textINTRODUCTION
Longitudinal validity (or external responsiveness) indicates the ability of a test to reflect changes in the reference criterion. The Yo-Yo Intermittent Recovery Test Level 1 (YO1) is the most valid soccer endurance test; its validity has been showed by its correlations with high-intensity running (HIR) during the match, also it discriminates between competitive levels and playing positions(1). To our knowledge the longitudinal validity of YO1 has been assessed only in referees. A sub-maximal version of YO1 (YO1sub), ending at the 6thmin., has been proposed for some “special” population such as injured players during rehabilitation. The aim of this study was to examine the longitudinal validity of YO1 and YO1sub in soccer players.
METHODS
Eleven players (age 24.8±6.3yrs; height 176±6.1cm; weight 73.6±7.2kg) participated in the study. A friendly match, the YO1 and YO1sub were completed in preseason (PRE) and after 15-17 weeks of training (POST). HIR was measured as the distance covered higher to 15 km/h, using a GPS system (SPIProX, 15Hz). Distance covered and percentage of heart rate max at 6th min (HR6) were considered as outcomes in YO1 and YO1sub, respectively. External responsiveness was measured with correlations between changes scores in YO1 and YO1sub with HIR.
RESULTS
Distance in YO1 (1694±243m PRE to 2385±411m POST, p<0.0001) and HIR (1202±388m PRE to 1631±466m POST, p=0.002) increased after training. HR6 showed no changes (86.2±3.9% PRE and 85.4±3.8% POST, p=0.27). Correlations between YO1 and HIR in PRE and POST were r=0.68 (CI90% 0.12 to 0.86) and r=0.59 (CI90% 0.10 to 0.85), respectively. Correlations between YO1sub and HIR in PRE and POST were r=0.32 (CI90% -0.19 to 0.69) and r=0.34 (CI90% -0.16 to 0.71). PRE-POST changes were 40% (CI90% 31 to 50), -0.9% (CI90% -2.3 to 0.5) and 37.2% (CI90% 19 to 57) in YO1, YO1sub and HIR, respectively. Correlations between changes in HIR vs.YO1 and vs. YO1sub were r=0.69 (CI90% 0.27 to 0.89) and r=-0.31(CI90%-0.72 to 0.26), respectively.
DISCUSSION
Similar to previous studies, significant and large correlations between YO1 and HIR were found in both PRE and POST tests. The correlation between changes scores in YO1 and HIR showed that an increase in the test reflected improvements in the HIR during matches, confirming its longitudinal validity. On the other hand, our data did not support the usefulness of YO1sub in detecting changes in the HI
Corrigendum for Impellizzeri FM, McCall A, Ward P, Bornn L, Coutts AJ. Training load and its role in injury prevention, part 2: conceptual and methodologic pitfalls. Journal of Athletic Training. 2020;55(9):893-901.
No full textInformation contained in our article published in the Journal of Athletic Training was intended to be complementary to, and to address the integration of, concepts introduced in our clinical commentary published in the Journal of Orthopaedic & Sports Physical Therapy. The contents of the Journal of Athletic Training article were substantively built upon some concepts initially presented in the Journal of Orthopaedic & Sports Physical Therapy clinical commentary that, regrettably, could not be explained in detail in the original publication because of word-count limitations. As the review process of the 2 manuscripts overlapped, the authors missed the opportunity to cite the first clinical commentary but acknowledge that we could have done this during the final stage of the Journal of Athletic Training review process. We acknowledge that the clinical commentary first accepted in the Journal of Orthopaedic & Sports Physical Therapy could have been cited in the Journal of Athletic Training article
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
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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