Muscle Physiology - Types of Contractions
The Force Velocity relationship can be seen in the figure below. A higher speed during a concentric contraction, results in a lower force. In concentric contractions, the force generated by the muscle is always velocity shortening contractions, a force-velocity relationship can be. In shortening (concentric) muscle actions, where contraction velocity is high, muscle force In lengthening (eccentric) muscle actions, the force velocity relationship is the .. and concentric training at different velocities on muscle hypertrophy.
The authors compared two groups performing the same exercise with the same total work, but one of the groups had previously followed a familiarization process aimed to avoid any muscle damage during the "real" training.
No differences between groups were found for muscle size or strength gains. Furthermore, the significant increases in mean cross-sectional area and strength were similar in both groups. Therefore, this study concluded that muscle hypertrophy can take place independently of any discernible sing of muscle damage.
They described higher muscle activity during ECC actions with flywheel training ECC overload compared to standard weight lifting in healthy men. These results are supported by Tesch et al. Taking into account data from these two studies [ 3637 ], it seems that mechanical stress plays a critical role in muscle hypertrophy processes.
Mechanical loading is a critical stimulus to increase strength and size of skeletal muscle [ 3 ]. Furthermore, acute resistance exercise comprising only ECC or CON actions, elicited similar rate of protein synthesis despite the markedly less relative mechanical load employed in the ECC mode [ 39 ].
They found greater hypertrophy, in a shorter period, with ECC training, although they argued that their results could be related to a larger amount of work done during ECC muscle actions. Smith and Rutherford [ 42 ] suggested that metabolic cost and not high forces, may be the stimuli for muscle hypertrophy and strength gains following high-resistance training.
However, this hypothesis still needs to be confirmed. Another study [ 43 ] compared ECC and traditional rehabilitation training during the first fifteen weeks following anterior cruciate ligament reconstruction. They found greater short-term increases in muscle mass and strength in the ECC training group. They suggested that the improved oxidative mechanical power output could be due mainly to a greater muscle CSA.
However, a study with rats failed to find an association between the total amount of force generated during each contraction ISO, CON and ECC and hypertrophy response [ 45 ]. Since voluntary resistance training in humans is complicated by factors such as the potential for motor learning, the authors claimed that discrepancies between human and animal data may be explained by factors such as neural adaptation.
Nevertheless, it is necessary to take into account that results may differ depending on the methods used to assess muscle mass muscle girth, dual x-ray absorptiometry DEXAultrasound, magnetic resonance image MRI or computerized tomography CT. However, there are examples of conflicting results even when the same methodology to track muscle mass changes was used. Since variables like studied population and type of intervention were comparable among those studies, the reasons for these discrepancies remain unclear.
Besides the mode of muscle action ISO, CON or ECCthe magnitude of the training induced increase in CSA depends on several factors, including the initial strength of the individual, the durations of the training program, and the training technique used [ 49 ]. Similarly, 60 days of isokinetic training at 2. In contrast, twentyfour weeks of dynamic training by experienced body builders failed to elicit an increase in the CSA of muscle fibers in Biceps brachii [ 54 ].
Force Velocity Relationship | Fitness Science
Given all the variables that can influence the hypertrophy response of a strength training program, and the controversial results found in ECC training studies, research comparing these variables in the hypertrophy response to ECC training seems mandatory. Conclusion Increased muscle cross-sectional area following resistance training occurs when the rate of protein synthesis is greater than protein degradation [ 32 ].
Considering the different qualities that eccentric muscle actions present compare to isometric or concentric muscle actions, it is theoretically possible that the benefits eccentric actions present may improve resistance training programs increasing several performance factors. The characteristics of eccentric actions include greater gains of muscle size and strength, decreased muscle soreness, and improvement of neural factors.
Furthermore, eccentric exercise requires a lower metabolic cost than concentric or isometric exercise.
Eccentric Resistance Training and Muscle Hypertrophy
Thus, the special characteristics of eccentric actions are becoming an important field of research trying to increase the positive outcomes of strength training while, at the same time, reduce the time of work [ 55 ].
On the other hand, negative aspects such damage and soreness, reduced neural reflexes, altered resting state and acute strength losses should be considered, and minimized, in an eccentric training programs.
Specificity of power improvements through slow and fast isokinetic training. Journal of Applied Physiology, 51 6 Force—velocity relationship of leg extensors obtained from loaded and unloaded vertical jumps. European Journal of Applied Physiology, 8 Force-velocity relationship on a cycle ergometer and knee-extensor strength indices.
Canadian Journal of Applied Physiology, 27 3 Effects of velocity of isokinetic training on strength, power, and quadriceps muscle fibre characteristics. The effects of eccentric and concentric training at different velocities on muscle hypertrophy.
European Journal of Applied Physiology, 89 6 Muscular force at different speeds of shortening. The Journal of Physiology, 85 3 A comparison of the kinematics, kinetics and muscle activity between pneumatic and free weight resistance.
European Journal of Applied Physiology, 6 Journal of Applied Biomechanics. Interdependence of torque, joint angle, angular velocity and muscle action during human multi-joint leg extension. Muscle fascicle shortening behaviour of vastus lateralis during a maximal force—velocity test. European Journal of Applied Physiology, The heat of shortening and the dynamic constants of muscle.
Proceedings of the Royal Society of London B: Biological Sciences, Role of concentric force in limiting improvement in muscular strength. Journal of Applied Physiology, 68 2 Effects of load and contraction velocity during three-week biceps curls training on isometric and isokinetic performance. Eccentric contractions allow the dissipation of mechanical energy during body deceleration Konow and Roberts, ; e. Such energy is then regained during limb support, resulting in less muscle work and energy required in locomotion.
Eccentric and concentric contractions fundamentally differ one from the other from a mechanical, metabolic and neural control point of view. Moreover, recent evidence obtained in our laboratory shows that distinct differences in terms of muscle morphological adaptations to resistive training exist between eccentric and concentric contractions. Eccentric contractions can produce greater force than concentric contractions through different mechanisms of force generation The two contraction types involve different mechanisms of force generation at the contractile protein level; this constitutes one of the main reasons for the greater force production during active lengthening compared to shortening.
Muscle force development is the result of the interaction between the contractile filaments.
- Force velocity relationship
Maximum force is produced when the overlap of the myosin and actin filaments enables the formation of the maximum number of cross-bridges, which occurs at the optimum sarcomere length Gordon et al. The force developed by a muscle not only depends on sarcomere length and cross-bridges formation, but also on the velocity of shortening Hill, or lengthening Katz,