Search PubMed⌕ Search

Biomedical subjects

R D'Ambrosia

Publications and source records attributed to R D'Ambrosia.

At least 19 recordsLinked to original sources
PubMed2000

Characterization of load-length-velocity relationships of nine different skeletal muscles.

A three-dimensional characterization of muscle load, length and velocity was obtained from nine muscles in the cat's hind limb through contractions where the muscles shortened against inertial-gravitational loads. A model based on the load-length characteristic and second-order dynamics describes shortening velocity related to load and length under these conditions. We conclude that this model describes well contraction velocity as function of length and load under inertial-gravitational load conditions, with correlation coefficients higher than 0.9 in most of the tested muscles.

Animals↗
PubMed1999

Practice expense.

Explore the source record for details and available documents.

Fees and Charges↗
PubMed1998

Mechanoreceptors in the human elbow ligaments.

The medial, annular, and lateral elbow ligaments from 6 fresh human cadavers were dissected from origin to insertion, stained, and examined with a light microscope to determine the existence of mechanoreceptors. It was shown that the anterior, posterior, and transverse medial ligaments as well as the annular and radial collateral ligaments were endowed with mechanoreceptors. The mechanoreceptors consisted of Golgi organs, Ruffini terminals, Pacinian corpuscles, and free nerve endings. The mechanoreceptors were distributed evenly throughout the annular and transverse medial ligament, but with increased density toward the origin and distal insertions in the radial, posterior, and anterior medial ligaments. It was concluded that the elbow ligaments may provide significant sensory function to the elbow joint, in addition to being its major mechanical restraints.

Collateral Ligaments↗
PubMed1997

Ligamentomuscular protective reflex in the elbow.

A reflex are from the medial elbow ligaments to the forearm pronator muscles was shown to exist in the feline model. A single articular branch emerging from the median nerve and converging on the medial collateral ligament was identified and stimulated with supramaximal pulses of 100 microseconds duration at a rate of 10 pulses/s. Stimulation of the articular nerve elicited myoelectric activity in the flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, flexor carpi ulnaris, and pronator teres. Transection of the articular nerve between the electrodes and the median nerve resulted in the disappearance of any myoelectric activity in the muscles, thus confirming the afferent nature of the articular nerve. The mean time delay from the application of the stimulus to the corresponding myoelectric discharge ranged from 3.2 to 5.8 ms for the 5 muscles. The existence of a fast-acting reflex arc from the medial elbow ligaments to the forearm muscles both confirms the concept of ligamentomuscular protective synergy (shown to exist in the knee, shoulder, and ankle joints) and extends it to the elbow. This reflex arc has significant implications for both the planning of elbow surgery while preserving the neural supply of the ligaments and for the planning of postsurgical or conservative therapeutic rehabilitation modalities.

Afferent Pathways↗
PubMed1997

Force, velocity and energy dynamics of nine load-moving muscles.

Nine architecturally different muscles of the cat's hindlimb were investigated with respect to the kinetic energy, the potential energy, and the force variations associated with shortening contractions against gravitational loads. Insight about the energy dynamics of contractile muscle can provide a unifying concept for models of muscle performance capability. In this study, it was found that as contractions shortened from passive equilibrium against a constant mass load, acceleration and deceleration phases appeared. These phase were associated with muscular force variations of up to 25% of the mass weight in fast twitch muscles at low loads. In contrast, slow twitch muscles were associated with less than 10% force variations when shortening against a gravitational load. It also was found that optimal loads exist which maximize each muscle's ability to impart kinetic and potential energy, these optimal loads tend to be in the mid-force range for highly pennate muscle and in the low-force range for justform muscles. It was concluded that the kinetic energy provided by each muscle is a small percentage of that calculated from its length-force relationship, especially at low loads. This study confirms that the efficiency of kinetic energy conversion is very low at low loads (gradually improving as the loads increase) and thereby substantiates early experiments with heat and metabolic energy.

Animals↗
PubMed1997

Reciprocating gait orthosis powered with electrical muscle stimulation (RGO II). Part I: Performance evaluation of 70 paraplegic patients.

Seventy paraplegics were fitted with an improved Reciprocating Gait Orthosis powered with or without (low-level injury) electrical stimulation of the thigh muscles (RGO II) as a secondary rehabilitation phase after the acute period. The patients comprised a broad cross-section of the paraplegic population applying for medical services and varied in age from 16 to 55 years, time since injury ranging from less than 1 to 15 years, injury levels ranging from C-6/7 to T-11/12, and varying levels of spasticity, contractures, scoliosis and other related medical and physiologic problems. The success/failure ratio was dependent on the injury level, which was 1:1 for paraplegics with injury level at C-6/7; 1.67:1 for those with injury of T-1/3; and about 4:1 for paraplegics with injury level from T-3 to T-12. Lack of motivation and medical problems unrelated to the RGO II treatment were the primary reasons for failure. The duration of treatment (outpatient service three times per week) ranged from 2 to 48 weeks (mean: 16). Forty-one patients who completed the RGO II rehabilitation and were sent home with the orthosis for independent use (for at least 6 months and up to 3 years) were surveyed by a staff member for analysis of the meaning and impact of the RGO II on the patient's life and health, and potential problems. It was shown that 80.5% of the 41 patients were regular users and 19.5% were non-users. Thirty-eight of the 41 patients declined an offer to return the RGO II equipment for a full refund, while three patients were willing to return the orthosis. It was concluded that the RGO II is viable orthosis for restoring standing and limited walking in paraplegics while providing sufficient function, safety, and reliability. The most appropriate patients for the use of such an orthosis consist primarily of those with T-3 to T-12 injury level and good motivation, although highly selected patients with higher injury levels also can benefit from its use. Regular use of the RGO II, even for exercise only, had a general positive impact on the patients' health and outlook.

Adolescent↗