It has been suggested that deep squats could cause an increased injury risk of the lumbar spine and the knee joints. Avoiding deep flexion has been recommended to minimize the magnitude of knee-joint ...forces. Unfortunately this suggestion has not taken the influence of the wrapping effect, functional adaptations and soft tissue contact between the back of thigh and calf into account. The aim of this literature review is to assess whether squats with less knee flexion (half/quarter squats) are safer on the musculoskeletal system than deep squats. A search of relevant scientific publications was conducted between March 2011 and January 2013 using PubMed. Over 164 articles were included in the review. There are no realistic estimations of knee-joint forces for knee-flexion angles beyond 50° in the deep squat. Based on biomechanical calculations and measurements of cadaver knee joints, the highest retropatellar compressive forces and stresses can be seen at 90°. With increasing flexion, the wrapping effect contributes to an enhanced load distribution and enhanced force transfer with lower retropatellar compressive forces. Additionally, with further flexion of the knee joint a cranial displacement of facet contact areas with continuous enlargement of the retropatellar articulating surface occurs. Both lead to lower retropatellar compressive stresses. Menisci and cartilage, ligaments and bones are susceptible to anabolic metabolic processes and functional structural adaptations in response to increased activity and mechanical influences. Concerns about degenerative changes of the tendofemoral complex and the apparent higher risk for chondromalacia, osteoarthritis, and osteochondritis in deep squats are unfounded. With the same load configuration as in the deep squat, half and quarter squat training with comparatively supra-maximal loads will favour degenerative changes in the knee joints and spinal joints in the long term. Provided that technique is learned accurately under expert supervision and with progressive training loads, the deep squat presents an effective training exercise for protection against injuries and strengthening of the lower extremity. Contrary to commonly voiced concern, deep squats do not contribute increased risk of injury to passive tissues.
Replacement supplements are required for optimal muscular hypertrophy in athletes. However, not all athletes can afford high-protein supplements due to their high expenses. The aim of this paper is ...to investigate and demonstrate the efficacy of protein-based supplements in enhancing the effects of resistance training on muscle growth. This method of study is a pseudo-experimental pre-test-posttest design. Using the entire sampling technique, 14 PPLP West Sumatra Indonesian Pencak silat athletes were used as study samples. The research procedure includes the measurement of thigh muscle circumference and thigh fat thickness of athletes (pretest), treatment of lunges 1-8 times, measurement of thigh muscle circumference and thigh fat thickness of athletes after eight treatments (midtest), and the size of thigh muscle circumference and thigh fat thickness after 9-16 lunges training sessions (posttest). Soy flour was administered depending on the athlete's average food intake, administered 30 minutes after the lunges exercise. The lunge training consisted of 16 sessions, moderate intensity (30% - 50% of maximum capacity), six repetitions, five sets, and 3 - 6 minute intervals. A tape meter was used to measure thigh muscle circumference and skinfold thickness to calculate thigh fat thickness using the formula MTMC = MTC - skinfold thickness (3.14 x TSF). The test utilized was the Kruskal-Wallis test. The examination of the data yielded a p-value of 0.03 < 0.05 and a percentage increase of 10.68%. In lunges training, high-protein soy flour can be administered as an alternative or replacement for supplements for muscular hypertrophy.
Tapering Practices of New Zealandʼs Elite Raw Powerlifters Pritchard, Hayden J; Tod, David A; Barnes, Matthew J ...
Journal of strength and conditioning research,
2016-July, 2016-Jul, 2016-07-00, 20160701, Letnik:
30, Številka:
7
Journal Article
Recenzirano
Odprti dostop
ABSTRACTPritchard, HJ, Tod, DA, Barnes, MJ, Keogh, JW, and McGuigan, MR. Tapering practices of New Zealandʼs elite raw powerlifters. J Strength Cond Res 30(7)1796–1804, 2016—The major aim of this ...study was to determine tapering strategies of elite powerlifters. Eleven New Zealand powerlifters (28.4 ± 7.0 years, best Wilks score of 431.9 ± 43.9 points) classified as elite were interviewed, using semistructured interviews, about their tapering strategies. Interviews were transcribed verbatim and content analyzed. Total training volume peaked 5.2 ± 1.7 weeks from competition while average training intensity (of 1 repetition maximum) peaked 1.9 ± 0.8 weeks from competition. During tapering, volume was reduced by 58.9 ± 8.4% while intensity was maintained (or slightly reduced) and the final weight training session was performed 3.7 ± 1.6 days out from competition. Participants generally stated that tapering was performed to achieve full recovery; that accessory work was removed around 2 weeks out from competition; and deadlifting takes longer to recover from than other lifts. Typically participants stated that trial and error, and changes based on “feel” were the sources of tapering strategies; equipment used and movements performed during tapering are the same as in competition; nutrition was manipulated during the taper (for weight cutting or performance aims); and poor tapering occurred when too long (1 week or more) was taken off training. These results suggest that athletes may benefit from continuing to strength train before important events with reduced volume and maintained intensity. Only exercises that directly assist sports performance should remain in the strength program during tapering, to assist with reductions in fatigue while maintaining/improving strength expression and performance.
Understanding the degree to which human facial expressions co-vary with specific social contexts across cultures is central to the theory that emotions enable adaptive responses to important ...challenges and opportunities
. Concrete evidence linking social context to specific facial expressions is sparse and is largely based on survey-based approaches, which are often constrained by language and small sample sizes
. Here, by applying machine-learning methods to real-world, dynamic behaviour, we ascertain whether naturalistic social contexts (for example, weddings or sporting competitions) are associated with specific facial expressions
across different cultures. In two experiments using deep neural networks, we examined the extent to which 16 types of facial expression occurred systematically in thousands of contexts in 6 million videos from 144 countries. We found that each kind of facial expression had distinct associations with a set of contexts that were 70% preserved across 12 world regions. Consistent with these associations, regions varied in how frequently different facial expressions were produced as a function of which contexts were most salient. Our results reveal fine-grained patterns in human facial expressions that are preserved across the modern world.
Pneumomediastinum in a Heavy Weightlifter Swaminathan, Neeraja; Agrawal, Akanksha; Ram, Pradhum
European journal of case reports in internal medicine,
2019, Letnik:
6, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The presence of air in the mediastinal cavity (i.e., pneumomediastinum) is an uncommon condition. It is usually precipitated by an event such as penetrating trauma, barotrauma or increased ...intrathoracic pressure caused by severe vomiting or coughing. We present the case of a 32-year-old man who developed pneumomediastinum as a result of heavy weightlifting.
Pneumomediastinum should be considered in the differential diagnosis of acute onset shortness of breath and chest pain.Pneumomediastinum can be precipitated without any obvious trauma as in cases of increased coughing/vomiting or heavy weightlifting.It is generally managed conservatively and resolves spontaneously.
Sport scholars have argued that to protect athlete health, competitive sport cultures must begin to de-emphasize the importance of leanness for athletic performance. However, there is a notable lack ...of analyses of the pressures towards leanness experienced by athletes in sports that are not considered most ‘at-risk’ for the development of disordered bodily practices, such as Olympic Weightlifting. Based on interviews with sixteen competitive American Olympic Weightlifters, this study uses Foucauldian insights about the inseparability of culture, language, and the body to examine how weightlifters come to understand—and rationalize—their weight classes, body compositions, and avoidance of body fat. We find that while weightlifters characterized a wide range of body compositions as being functional for the sport, their own weight class choices were informed by a sport-specific narrative that condemned body fat. We critically interrogate this preference for leanness-focused bodily practices in a ‘non-lean’ sport, looking to the ‘Sport Ethic’ and other dominant bodily discourses as possible sources of influence.
Although lower-body strength is correlated with sprint performance, whether increases in lower-body strength transfer positively to sprint performance remain unclear.
This meta-analysis determined ...whether increases in lower-body strength (measured with the free-weight back squat exercise) transfer positively to sprint performance, and identified the effects of various subject characteristics and resistance-training variables on the magnitude of sprint improvement.
A computerized search was conducted in ADONIS, ERIC, SPORTDiscus, EBSCOhost, Google Scholar, MEDLINE and PubMed databases, and references of original studies and reviews were searched for further relevant studies. The analysis comprised 510 subjects and 85 effect sizes (ESs), nested with 26 experimental and 11 control groups and 15 studies.
There is a transfer between increases in lower-body strength and sprint performance as indicated by a very large significant correlation (r = -0.77; p = 0.0001) between squat strength ES and sprint ES. Additionally, the magnitude of sprint improvement is affected by the level of practice (p = 0.03) and body mass (r = 0.35; p = 0.011) of the subject, the frequency of resistance-training sessions per week (r = 0.50; p = 0.001) and the rest interval between sets of resistance-training exercises (r = -0.47; p ≤ 0.001). Conversely, the magnitude of sprint improvement is not affected by the athlete's age (p = 0.86) and height (p = 0.08), the resistance-training methods used through the training intervention, (p = 0.06), average load intensity % of 1 repetition maximum (RM) used during the resistance-training sessions (p = 0.34), training program duration (p = 0.16), number of exercises per session (p = 0.16), number of sets per exercise (p = 0.06) and number of repetitions per set (p = 0.48).
Increases in lower-body strength transfer positively to sprint performance. The magnitude of sprint improvement is affected by numerous subject characteristics and resistance-training variables, but the large difference in number of ESs available should be taken into consideration. Overall, the reported improvement in sprint performance (sprint ES = -0.87, mean sprint improvement = 3.11 %) resulting from resistance training is of practical relevance for coaches and athletes in sport activities requiring high levels of speed.
This study compared the effects of six warm-up modalities on peak power output (PPO) during the high-pull exercise. Nine resistance-trained males completed six trials using different warm-ups: ...high-pull specific (HPS), cycle, whole body vibration (WBV), cycle+HPS, WBV+HPS and a control. Intramuscular temperature (T
m
) was increased by 2°C using WBV or cycling. PPO, T
m
and electromyography (EMG) were recorded during each trial. Two high-pulls were performed prior to and 3 min after participants completed the warm-up. The greatest increase in PPO occurred with HPS (232.8 ± 89.7 W, P < 0.001); however, this was not different to combined warm-ups (cycle+HPS 158.6 ± 121.1 W; WBV+HPS 177.3 ± 93.3 W, P = 1.00). These modalities increased PPO to a greater extent than those that did not involve HPS (all P < 0.05). HPS took the shortest time to complete, compared to the other conditions (P < 0.05). EMG did not differ from pre to post warm-up or between modalities in any of the muscles investigated. No change in T
m
occurred in warm-ups that did not include cycling or WBV. These results suggest that a movement-specific warm-up improves performance more than temperature-related warm-ups. Therefore, mechanisms other than increased muscle temperature and activation may be important for improving short-term PPO.
The purpose of this study was to investigate the validity of a smartphone app to measure biomechanical barbell parameters during the snatch. Ten collegiate NCAA division I athletes performed two ...repetitions each at 40, 50, 60, 70, and 80% of their 1-repetition maximum snatch. Barbell motions were simultaneously recorded with a motion capture system and the smartphone app. The motion capture system recorded the 3-D position of a reflective marker attached to the end of the barbell while the smartphone app was used to record sagittal plane video and track the shape of the weight plate from which the barbell center was derived. Peak forward (PFD) and backward (PBD) displacements and peak vertical displacement (PVD) and velocity (PVV) were calculated from both sets of data. Significant, strong to very strong Pearson's product-moment correlation coefficients between both systems were noted for all parameters (r = 0.729-0.902, all p < 0.001). Small significant biases between systems were observed for PVD (ES = 0.284, p < 0.001) and PFD (ES=0.340, p < 0.01), while trivial to small, non-significant biases were observed for PBD (ES = 0.143) and PVV (ES = -0.100). Collectively, the results suggest that the app can provide biomechanical data of barbell motions similar to a 3-D motion capture system.
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