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At least 1,045 records · Page 58Linked to original sources
PubMed1988

Ratio of hamstring to quadriceps femoris muscles' strength in the anterior cruciate ligament insufficient knee. Relationship to long-term recovery.

The purposes of this study were 1) to investigate the peak torque and total-work ratios of hamstring to quadriceps femoris muscles' (HQ) in 41 subjects (27 male, 14 female; means age = 35 years) with an anterior cruciate ligament insufficient knee (ACLIK) and 2) to determine the relationship between HQ ratios and long-term subject outcome. Quadriceps femoris and hamstring musculature strengths of both legs were measured at follow-up with an isokinetic dynamometer, and peak torque values were recorded at lower (60 degrees/sec) and higher (180 degrees/sec) speeds. Maximal isometric extension and flexion outputs were measured at a 60-degree knee-flexion angle. Three standardized knee-scoring scales were used to determine the overall outcome of the ACLIK. High intersubject variability of the HQ ratios (range = 23%-205%) was observed in all strength tests, including tests of healthy knees. The injured knee of all subjects had a higher HQ ratio (46%-95%) in every test than the healthy knee (42%-85%). The HQ ratio difference between knees was significant at the isokinetic higher speed (p less than .05) and for the total-work (p less than .05) tests because of the weak quadriceps femoris muscle of the injured knee. Outcome scores did not differ significantly between the groups with low, optimal, or high HQ ratios of the ACLIK but were significantly better in subjects whose HQ ratio of the injured knee was similar to that of their uninjured knee.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Increasing extraocular muscle strength with insulin-like growth factor II.

PURPOSE: Botulinum toxin type A and, more recently, the immunotoxin ricin-mAb35 have been effective as means of pharmacologically weakening the extraocular muscle. However, currently there are no drug treatments to strengthen an underacting extraocular muscle. In limb muscle, treatment with insulin-like growth factor causes myofiber hypertrophy. In this study, the short-term effects of insulin-like growth factor II (IGF-II) on extraocular muscle morphometry and force generation were examined. METHODS: One superior rectus muscle in normal adult rabbits received a single injection of 10 micro g IGF-II, and the contralateral muscle received an injection of saline only. One week after injection, muscle morphology and muscle force were compared between the IGF-treated and control muscles. RESULTS: In the treated muscle, there was no significant change in the mean cross-sectional area of myofibers compared with the control. However, there was an increase in the heterogeneity of myofiber cross-sectional area, with increases in both small and very large myofibers. Mean single-twitch force generation was 0.48 +/- 0.12 mN/cm(3) compared with 0.27 +/- 0.04 mN/cm(3) (P = 0.0473) in control samples. Mean tetanic force generation was increased significantly at all stimulation frequencies. Treatment had no effect on muscle fatigability. CONCLUSIONS: Extraocular muscle is very responsive to direct injection of IGF-II. Although no difference was seen in mean myofiber cross-sectional area, overall there was sufficient alteration in myofiber heterogeneity to result in increased force generation. If a sustained treatment effect can be achieved with IGF-II and, potentially, other growth factors, the pharmacological treatment of strabismus could be advanced by simultaneous injection of agonist-antagonist pairs with agents that weaken and strengthen the treated extraocular muscle.

Animals↗
PubMed2006

Increased extraocular muscle strength with direct injection of insulin-like growth factor-I.

PURPOSE: Previous work has demonstrated the effectiveness of insulin-like growth factor (IGF)-II in increasing force generation in extraocular muscle (EOM). Studies in the literature have suggested that IGF-I would be even more effective than IGF-II. This study was performed to assess the effects on muscle mass and force generation of IGF-I injection in adult rabbit superior rectus muscle. METHODS: Adult rabbits received a single injection of IGF-I at one of several doses into one superior rectus muscle. One week after treatment, the rabbits were euthanatized, and the superior rectus muscle from each orbit was removed. Force generation was measured using an in vitro apparatus, and injected muscles were compared with the contralateral control. A second group of animals were injected similarly, and the muscles were examined at 1 week for changes in cross-sectional area of individual myofibers. RESULTS: EOMs demonstrate significant numbers of cells expressing the IGF receptor. After the EOMs were injected with IGF-I, there were significant increases both in muscle force generation and cross-sectional area at all doses tested in this study. Doses of 10 and 25 microg IGF-I were most effective. CONCLUSIONS: Direct muscular injection of IGF-I effectively increases EOM force generation without the potential biomechanical hazards of surgery such as permanently altered muscle length or insertional position on the globe.

Animals↗
PubMed2001

Inspiratory muscle strength in acute asthma.

STUDY OBJECTIVES: The aim of this study was to measure inspiratory pressure-generating capacity in patients presenting with acute asthma, as it has been suggested that inspiratory muscle fatigue may contribute to breathlessness and acute respiratory failure. DESIGN: Descriptive study. SETTING: Emergency departments of two inner-city hospitals. PATIENTS: Fifty-one patients with acute asthma, and 45 patients without respiratory disease who served as control subjects. MEASUREMENTS AND RESULTS: Maximum inspiratory pressure-generating capacity was measured soon after presentation by the sniff nasal inspiratory pressure (SNIP) method. The mean (SD) SNIP was 110 cm H(2)O (23 cm H(2)O) in men with asthma (mean for control subjects, 126 cm H(2)O [25 cm H(2)O]; p < 0.05) and 80 cm H(2)O [24 cm H(2)O] in women with asthma (mean for control subjects, 105 cm H(2)O (26 cm H(2)O); p < 0.01). In a second study of simultaneous SNIP and intrathoracic pressure measurements in a group of patients with acute asthma (n = 10) and control subjects (n = 11), the effect of airways obstruction on SNIP was assessed. The measurement of sniff esophageal pressure was more negative than SNIP by approximately 16% in asthmatic patients and by 4% in control subjects. Taking account of the likely effect of airways obstruction on SNIP, the reduction in inspiratory pressure-generating capacity that was observed in these patients with moderately severe acute asthma was minor and was consistent with the modest hyperinflation observed. CONCLUSIONS: This study did not find evidence of inspiratory muscle weakness or fatigue in patients with moderately severe acute asthma presenting to the emergency department.

Adolescent↗