A Cadaveric Study of Palmaris Longus Muscle

Background: Aim: To assess the palmaris longus muscle.Methods:40 formalin fixed cadavers of both genders were included. Routine dissection of the upper limb was carried following the Cunnigham’s Manual of Practical Anatomy. During the dissection of the anterior compartment of forearm, the Palmaris longus muscle was identified & carefully dissected.Results:Out of 40 cadavers, 22 were of males and 18 were of females. Morphology of Palmaris longus found to be normal in 18, agenesis in 6, fusiform in 4, hybrid in 6, bifurcated tendon in 5 and fleshy in 1 case. A significant difference was observed (P< 0.05).Conclusions:Surgeon must be aware of the variations of palmaris longus muscle. Morphology of Palmaris longus found to be normal, agenesis, fusiform, hybrid, bifurcated tendon and fleshy.

Effect of Peroneus Longus Muscle Release on Abductor Hallucis Muscle Activity and Medial Longitudinal Arch before Toe-Tap Exercise in Participants with Flexible Pes Planus

Pes planus is a medical condition of the foot wherein there is a flattening or lowering of the medial longitudinal arch. The abductor hallucis muscle starts at the heel bone and attaches to the medial side of the first toe. Whenever it contracts, it plays a key role in elevating the medial longitudinal arch. Hence, the abductor hallucis muscle should be strong enough to control the depression on the medial longitudinal arch. The peroneus longus muscle plantarflexes the ankle and everts the ankle and subtalar joint. If this muscle contracts more than the abductor hallucis muscle does, the medial longitudinal arch of the foot is depressed. This study aimed to investigate the effect of myofascial release of the peroneus longus before performing the toe-tap exercise for strengthening the abductor hallucis muscle in participants with flexible pes planus. This cross-over study included 16 volunteers with flexible pes planus. The participants performed a toe-tap exercise before and after the myofascial release of the peroneus longus. During the toe-tap exercise, the muscle activity of the abductor hallucis and peroneus longus were measured using a Delsys Trigno Wireless Electromyography System. The angle of the medial longitudinal arch was measured using Image J software. Photos in the sagittal plane were used. The peroneus longus activity and medial longitudinal arch angles were significantly decreased. On the other hand, the activity of the abductor hallucis significantly increased after the myofascial release of the peroneus longus before performing the toe-tap exercise (p < 0.05). Individuals with flexible pes planus should be encouraged to perform myofascial release of the peroneus longus before the toe-tap exercise to improve the abductor hallucis activity and to elevate the medial longitudinal arch.

Prevalence of agenesis of palmaris longus in male and female genders on clinical examination – a review

Palmaris longus is a muscle that is located in the anterior compartment of the forearm. Among the muscles belonging to the flexor compartment of forearm, palmaris longus is located at the most superficial position and that is why it is easy to access. It exhibits high variability and its prevalence ranges between 1.5% and 63.9%. The knowledge of prevalence of agenesis of palmaris longus is essential both in terms of updating anatomical information and also for physicians, radiologists, physiotherapists and surgeons. The surgeons must know about the variability as it may be beneficial while they plan surgeries involving the palmaris muscle as a graft. The current narrative review was planned to highlight the variability pattern of palmaris longus muscle in terms of prevalence, gender and laterality. Palmaris longus agenesis is more common in females and on the left side. Besides, unilateral agenesis is more common compared to bilateral agenesis.

Tuned muscle and spring properties increase elastic energy storage

Elastic recoil drives some of the fastest and most powerful biological movements. For effective use of elastic recoil, the tuning of muscle and spring force capacity is essential. While studies of invertebrate organisms that use elastic recoil show evidence of increased force capacity in their energy loading muscle, changes in the fundamental properties of such muscles have yet to be documented in vertebrates. Here we used three species of frogs (Cuban tree frogs, bullfrogs, and cane toads) that differ in jumping power to investigate functional shifts in muscle-spring tuning in systems using latch-mediated spring actuation (LaMSA). We hypothesized that variation in jumping performance would result from increased force capacity in muscles and relatively stiffer elastic structures resulting in greater energy storage. To test this, we characterized the force-length property of the plantaris longus muscle-tendon unit (MTU), and quantified the maximal amount of energy stored in elastic structures for each species. We found that the plantaris longus MTU of Cuban tree frogs produced higher mass-specific energy and mass-specific forces than the other two species. Moreover, we found that the plantaris longus MTU of Cuban tree frogs had higher pennation angles than the other species suggesting that muscle architecture was modified to increase force capacity through packing of more muscle fibers. Finally, we found that the elastic structures were relatively stiffer in Cuban tree frogs. These results provide a mechanistic link between the tuned properties of LaMSA components, energy storage capacity and whole system performance.

Measurement of Lateral Transmission of Force in the Extensor Digitorum Longus Muscle of Young and Old Mice

The main function of skeletal muscles is to generate force. The force developed by myofiber contraction is transmitted to the tendon. There are two pathways of force transmission from myofibers to tendons: longitudinal transmission that depends on tension elicited via the myotendinous junction and lateral transmission that depends on shear elicited via the interface between the myofiber surface and surrounding connective tissue. Experiments using animal muscle and mathematical models indicated that lateral transmission is the dominant pathway in muscle force transmission. Studies using rat muscle showed that the efficiency of lateral force transmission declines with age. Here, the lateral transmission of force was measured using the extensor digitorum longus muscle from young and old mice. Dependence on longitudinal transmission increased in the old muscle, and there was a trend for lower efficiency of lateral force transmission in the old muscle compared to the young muscle. There was a noticeable increase in the connective tissue volume in the old muscle; however, there was no significant change in the expression of dystrophin, a critical molecule for the link between the myofiber cytoskeleton and extracellular matrix. This study demonstrates the measurement of lateral force transmission in mouse muscles and that alteration in force transmission property may underlie age-related muscle weakness.