Surgical Mobilization of Skeletal Muscles Changes Functional Properties-Implications for Tendon Transfers.

Purpose: Tendon transfer surgery restores function by rerouting working muscle-tendon units to replace the function of injured or paralyzed muscles. This procedure requires mobilizing a donor muscle relative to its surrounding myofascial connections, which improves the muscle's new line of action and increases excursion. However, the biomechanical effect of mobilization on a donor muscle's force-generating function has not been previously studied under in vivo conditions.

Non-linear Scaling of Passive Mechanical Properties in Fibers, Bundles, Fascicles and Whole Rabbit Muscles.

Defining variations in skeletal muscle passive mechanical properties at different size scales ranging from single muscle fibers to whole muscles is required in order to understand passive muscle function. It is also of interest from a muscle structural point-of-view to identify the source(s) of passive tension that function at each scale. Thus, we measured passive mechanical properties of single fibers, fiber bundles, fascicles, and whole muscles in three architecturally diverse muscles from New Zealand White rabbits ( = 6) subjected to linear deformation.

Moment arms of the human digital flexors.

For the extrinsic hand flexors (flexor digitorum profundus, FDP; flexor digitorum superficialis, FDS; flexor pollicis longus, FPL), moment arm corresponds to the tendon's distance from the center of the metacarpalphalangeal (MP), proximal interphalangeal (PIP), or distal interphalangeal (DIP) joint. The clinical value of establishing accurate moment arms has been highlighted for biomechanical modeling, the development of robotic hands, designing rehabilitation protocols, and repairing flexor tendon pulleys (Brand et al., 1975; An et al.

Whole muscle length-tension relationships are accurately modeled as scaled sarcomeres in rabbit hindlimb muscles.

An a priori model of the whole active muscle length-tension relationship was constructed utilizing only myofilament length and serial sarcomere number for rabbit tibialis anterior (TA), extensor digitorum longus (EDL), and extensor digitorum II (EDII) muscles. Passive tension was modeled with a two-element Hill-type model. Experimental length-tension relations were then measured for each of these muscles and compared to predictions.

The architectural design of the gluteal muscle group: implications for movement and rehabilitation.

The organization of fibers within a muscle (architecture) defines the performance capacity of that muscle. In the current commentary, basic architectural terms are reviewed in the context of the major hip muscles and then specific illustrative examples relevant to lower extremity rehabilitation are presented. These data demonstrate the architectural and functional specialization of the hip muscles, and highlight the importance of muscle physiology and joint mechanics when evaluating and treating musculoskeletal disorders.

Correlation between isometric force and intramuscular pressure in rabbit tibialis anterior muscle with an intact anterior compartment.

To determine the degree to which intramuscular pressure (IMP) and muscle force are correlated in an intact compartment, a custom pressure transducer was inserted into the rabbit tibialis anterior (TA) while activating the muscle via the peroneal nerve and measuring TA muscle force distal to the ankle retinaculum. In general, IMP was more variable compared with muscle force throughout the entire isometric length-tension relationship. In contrast to results obtained on isolated TA muscles, IMP-force relations with the compartment intact were not significantly different between the ascending and descending limbs of the length-tension curve.

A novel muscle biopsy clamp yields accurate in vivo sarcomere length values.

The measurement of in vivo muscle sarcomere length facilitates the definition of in vivo muscle functional properties and comparison of muscle designs amongst functional muscle groups. In vivo sarcomere lengths are available for just a handful of human muscles, largely due to the technical challenges associated with their measurement. The purpose of this report was to develop and test a muscle biopsy clamp that can quickly and accurately measure in vivo muscle sarcomere length.