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EVOLUTION OF FRESHWATER CRABS IN LAKE MALAWI AND THE LAKE MALAWI BASIN IN THE EAST AFRICAN RIFT VALLEY
Get PDFLake Malawi is the southernmost lake in the East African Rift Valley and is home to a single species of freshwater crab, the Malawi Blue Crab. Little is known about species diversity and the phylogenetic relationships of the freshwater crabs of Lake Malawi, in contrast to the lake’s highly-diverse cichlid fish species flocks. The Malawi Blue Crab is presently assigned to Potamonautes lirrangensis (Rathbun, 1904) sensu lato, which was originally described from a single female specimen from the D. R. Congo. While the distribution of P. lirrangensis s. l. ranges from the Congo River basin to other Rift Valley lakes, its current taxonomic status remains controversial. Detailed comparative morphological analysis coupled with preliminary DNA sequence data were used to determine the taxonomic status of the Malawi Blue Crab, and to determine the phylogenetic relationships between the Malawi Blue Crab and the freshwater crab fauna of the Lake Malawi basin, particularly the common and widespread species, P. montivagus. The morphological and molecular data presented here indicate that: (1) P. lirrangensis should be restricted to those specimens from the Middle Congo River in the D. R. Congo (referred to here as P. lirrangensis sensu stricto); (2) that the specimens from Lake Kivu formerly assigned to P. lirrangensis s. l. be recognized as a new species (Potamonautes sp. 1); and (3) that the Malawi Blue Crab should be properly referred to as P. orbitospinus (Cunnington, 1907). In addition, it is likely that the specimens from two crater lakes in southwest Tanzania initially identified as P. montivagus belong to a new species (Potamonautes sp. 2)
A COMPARISON OF THE NATIONAL FOOTBALL LEAGUE COACHES STRENGTH AND CONDITIONING PRACTICES 1997-1998 TO 2018
Get PDFThis study describes the results of a survey of the strength and conditioning practices of the National Football League’s strength and conditioning coaches. The survey response rate was 28.1% (9 of 32 NFL teams) agreeing to participate. Subjects test 6.83 ± 3.06 fitness variables using 9.00 ± 3.74 tests; compared to 7.0 fitness variables using 10.0 tests in ‘97-98. Subjects prescribe resistance training 2.33 ± .81 days per week when in-season; compared to 2.8 ± 0.8 days per week in ’97-98. The average in-season training session duration was 37.50 ± 12.54 mins; compared to 48.5 ±13.2 mins in ’97-98. Findings indicate that there were statistically significant results for NFL coaching tenure (p= .005) and off-season resistance training frequency (p= .007). This study serves as a review as well as a source of applied information regarding training program design
CHANGES IN INTER-LIMB MUSCLE COORDINATION INDUCED BY MUSCLE FATIGUE DURING PEDALING
Get PDFThe purpose of this study was to investigate the changes in inter-limb muscle coordination brought about by muscle fatigue during pedaling. Four healthy male road cyclists pedaled for 15 min under a 150 W exercise load and a 90 rpm cadence. First, the surface electromyography (sEMG) of the muscles of both lower limbs was measured along with crank angle. Second, the slope of median frequency of a short-time Fourier transform was used to estimate muscle fatigue. Next, non-negative matrix factorization was applied to the time-frequency components of the sEMG to investigate the inter-limb muscle coordination. The result showed that asymmetrical inter-limb muscle coordination was seen in all subjects regardless of muscle fatigue. Failure to counteract muscle fatigue could be explained by the redistribution patterns of the asymmetrical inter-limb muscle coordination, which is considered a muscle fatigue compensation strategy
LOWER EXTREMITY BIOMECHANICS OF FEMALE COLLEGE SOCCER AND BASKETBALL PLAYERS DURING SIDESTEP CUTTING
Get PDFThe purpose of this study was to investigate the biomechanics of lower extremity between female college soccer and basketball players during a sidestep cutting. Twenty college players participated in this study. Ten Vicon cameras and a Kistler force plate and Visual3D were used to collect side-step cutting and analyze the biomechanical variables. The results indicated soccer players had greater ankle plantar flexion and hip abduction angle at the foot contact. The soccer players also had greater peak knee flexion and internal rotation angle, hip adductor moment, while basketball players had greater peak braking GRF and the peak vertical GRF during cutting. It is concluded that basketball and soccer players demonstrate differences in neuromuscular control patterns during sidestep cutting tasks
Terminal and Exterior Ballisitic Evaluation of Active Shooter Countermeasures of Convenience in a Biomechanics Classroom or Laboratory
Get PDFThis study assessed the terminal and exterior ballistics of numerous school shooter countermeasures of convenience (COC) that may be present in a classroom or applied biomechanics laboratory. In this case study, the subject threw eight COC with maximum effort at a wall mounted force plate, with concomitant assessment with Doppler radar. Peak reaction forces and velocity of the projected objects were analyzed. Large, compared to smaller mass COC generally produced more force, but were slower to the target. Some COC produce highly variable flight characteristics likely due to forces such as surface drag, yaw, and oscillation. These forces can reduce and make variable the velocity and impact forces. Therefore, small, high density, uniform surface area, and symmetrical countermeasures may display superior ballistics and should be evaluated
CONCURRENT VALIDITY OF VIDEO-BASED MTHOD TO OBTAIN STEP LENGTH DURING SPRINT ACCELERATION
Get PDFThis study aimed to examine validity of the video-based method for obtaining step length during sprint acceleration when compared with the center of pressure (COP) position. Four well-trained male sprinters performed 50-m sprint for eight times each. The foot location and step length were obtained using video image for 24 steps. The Intra-class correlation coefficients between COP position and video-based method showed high validity (\u3e0.847) for foot location and step length. Although there was a significant magnitude-error correlation (r = −0.972) for the foot location, corresponding correlation was not significant for step length (r = 0.081). Accordingly, the results suggest that video-based method has enough validity for obtaining step length during sprint acceleration when compared with COP position
DESIGN OF STRENGTH EXERCISES FOR THE ABDUCTOR MUSCLES USING MUSCULOSKELETAL MODELING
Get PDFStrength training exercises, require a specific joint range of motion and muscle-specific loading to avoid injury and allow adaptation of tissue. The purpose of this study was to design suitable strength training exercises for the hip abductor muscles based on predicted joint loading and motion. Using Opensim modeling, hip abduction/adduction movement was combined with internal/external rotation of the hip and an external force that was applied to the foot. The direction of the force was systematically rotated to mimic a change of the position towards the cable pulley system. M. gluteus mediuswas divided into an anterior and a posterior part. It was not possible to find a single exercise that allowed the training of the anterior and the posterior part simultaneously with a muscle activation \u3e50%. Herein, it has been shown that modeling can be used to design strength-training exercises