/her overall readiness to train and compete. 11 There is a growing body of evidence suggesting that a reduction in subjective wellness has a negative impact on the subsequent external load of training. 4 , 10 Recently, Gallo et al 4 were able to demonstrate that a reduced wellness z score corresponded to
Phillip M. Bellinger, Cameron Ferguson, Tim Newans and Clare L. Minahan
external loads to muscles. 14 However, there are external loads acting on the muscles and joints, such as acceleration, deceleration, jumping to certain heights, and the defensive actions of opponents. 12 , 15 These issues might additionally deteriorate sports movement efficiency. Thus, the
Yusuf Köklü, Utku Alemdaroğlu, Hamit Cihan and Del P. Wong
rating of perceived exertion [RPE]) and external loads (eg, total distance covered; maximum speed; quantity of low-, moderate-, and high-intensity running). While high-intensity aerobic training sessions are used for the development of endurance performance in athletes, 1 for soccer players an
Dawn Scott, Dean Norris and Ric Lovell
are theoretically able to better tolerate or even perform greater absolute match running performances (if necessary) in matches. Application of player-specific speed thresholds based upon fitness attributes is one method of individualizing the evaluation of external loads in team sports. A number of
Carlo Castagna, Stefano D’Ottavio, Stefano Cappelli and Susana Cristina Araújo Póvoas
the relevance of acceleration and deceleration, more than sustained speed in determining external load in all-out SSG. 4 , 5 In this regard, emphasis on players’ maximal or near maximal effort maintenance for a prolonged period of time (ie, 30–40 s) has been proposed as a LSA training aim. 4 The
Sonia Sahli, Haithem Rebai, Mohamed Habib Elleuch, Zouheir Tabka and Georges Poumarat
There is limited information about the effects of increasing load while squatting
To quantify tibiofemoral joint kinetics during squatting with variable loads.
20 male students.
Tibiofemoral joint kinetics and electromyographic (EMG) activity of four involved muscles were determined by recording the half squat with variable external loads.
Main Outcome Measures:
Tibiofemoral joint force and external moment components and EMG activity of four involved muscles.
Throughout the exercise, a posterior direction for the antero-posterior shear force and a net extension for the external moment were observed. They increased with knee flexion reaching peak force of 29% of the subject body weight (BW) and moment of 88Nm (without external load). All force and moment components and muscle activities increased as the external load increased.
These findings suggest that half squat may be safe to use for quadriceps strengthening with very low potential loading on the anterior cruciate ligament (ACL). Our data can help clinicians choose the appropriate external load.
Carlo Castagna, Matthew Varley, Susana C.A. Póvoas and Stefano D’Ottavio
To test the interchangeability of 2 match-analysis approaches for external-load detection considering arbitrary selected speeds and metabolic power (MP) thresholds in male top-level soccer.
Data analyses were performed considering match physical performance of 60 matches (1200 player cases) of randomly selected Spanish, German, and English first-division championship matches (2013–14 season). Match analysis was performed with a validated semiautomated multicamera system operating at 25 Hz.
During a match, players covered 10,673 ± 348 m, of which 1778 ± 208 m and 2759 ± 241 m were performed at high intensity, as measured using speed (≥16 km/h, HI) and metabolic power (≥20 W/kg, MPHI) notations. High-intensity notations were nearly perfectly associated (r = .93, P < .0001). A huge method bias (980.63 ± 87.82 m, d = 11.67) was found when considering MPHI and HI. Very large correlations were found between match total distance covered and MPHI (r = .84, P < .0001) and HI (r = .74, P < .0001). Player high-intensity decelerations (≥–2 m/s2) were very largely associated with MPHI (r = .73, P < .0001).
The speed and MP methods are highly interchangeable at relative level (magnitude rank) but not absolute level (measure magnitude). The 2 physical match-analysis methods can be independently used to track match external load in elite-level players. However, match-analyst decisions must be based on use of a single method to avoid bias in external-load determination.
Susan K. Grimston, Jack R. Engsberg, Reinhard Kloiber and David A. Hanley
Increased incidence of stress fracture has been reported for amenorrheic runners, while some studies have reported decreased spinal bone mass in amenorrheic runners. Based on results from these studies, one tends to associate decreased spinal bone mass with an increased risk of stress fracture. The present study compared regional bone mass and external loads during running between six female runners reporting a history of stress fracture (seven tibial and three femoral neck) and eight female runners with no history of stress fracture. Dual photon absorptiometry measures indicated significantly greater spinal (L2-L4) and femoral neck bone mineral density in stress fracture subjects (p<0.05) but no differences between groups for tibial bone density. Normalized forces recorded from Kistler force plates indicated significantly greater vertical propulsive, maximal medial, lateral, and posterior forces for stress fracture subjects during running (p<0.05).
’ external loads. 2 – 4 Locomotor activities such as total distance covered (TDC), high-speed running distance covered (HSR), or sprinting distance covered (SP 4 ) are common external load metrics used by practitioners. More recently, accelerometers have been utilized to monitor the external load of soccer
A two-dimensional model has been developed to predict and explain the effects of the variation of muscle moment arms during dynamic exercises involving heavy external loads. The analytical dependence of the muscle moment arm on the joint angle and on the origin and insertion position was derived for an ideal uniaxial hinge joint, modeling the muscle as a cable following an idealized minimum distance path from the origin to insertion that wraps around the bony geometry. Analytical expressions for the ratios of muscular force and the joint restraining reaction components to the external load weight were deduced, for isokinetic and static exercises, as a function of joint angle, joint angular velocity, and the other geometric parameters defining the model. Therefore, external load weight, joint angular velocity, and constraints to joint range of motion may be adjusted reciprocally in order to control in advance the peak value of the components of the joint load during isokinetic exercises. A dynamic formulation of forearm flexion/extension was solved numerically under the condition of constant biceps force in order to highlight the key role played by the variation in muscle moment arm in preventing injury during lifting of external loads against gravity. For example, our analysis indicates that the mean and peak resultant joint loads decrease by 5% and 14%, respectively, as a result of the change in muscle moment arm that occurs over the range of motion.