Respiratory Responses to Short Term Sustained Isometric Muscle Contraction among Undergraduates

Aim: This study sets out to investigate whether a short-term isometric abdominal exercise can benefit adults with improvement in ventilatory functions. Materials And Methods: The present study was performed in 20 adults from the student population of I-BDS students with no history of smoking and respiratory illness. The participants did a daily 20-minute static abdominal exercise over a period of three days. The lung function test was assessed using spirometry and the values of FVC, FEV1, FEV1/FVC, PEFR, FEF 25-75. Paired dependent t test was done to evaluate the anthropometric variables and changes in lung functions pre-exercise on day 1 and post-isometric exercise on day 3. Results: The study demonstrated a significant increase in the mean values of forced vital capacity and forced expiratory volume in one second. The FEV1/FVC ratio, PEFR, FEF 25-75% did not reveal significant changes. Conclusion: The study concluded an innovative finding that ventilatory functions improved after short term isometric training.

Effects of vigorous isometric muscle contraction on titin stiffness-related contractile properties in rat fast-twitch muscles

This study was conducted to examine the effects of an acute bout of vigorous isometric contractions on titin stiffness-related contractile properties in rat fast-twitch skeletal muscles. Intact gastrocnemius muscles were electrically stimulated in situ until the force was reduced to ~50% of the initial force. Immediately after cessation of the stimulation, the superficial regions of the muscles were dissected and subjected to biochemical and skinned fiber analyses. The stimulation resulted in a decrease in the titin-based passive force. The amounts of fragmented titin were unchanged by the stimulation. Protein kinase Cα-treatment increased the passive force in stimulated fibers to resting levels. The stimulation had no effect on the maximum Ca2+-activated force (max Ca2+ force) at a sarcomere length (SL) of 2.4 μm and decreased myofibrillar (my)-Ca2+ sensitivity at 2.6-μm SL. Stretching the SL to 3.0 μm led to the augmentation of the max Ca2+ force and my-Ca2+ sensitivity in both rested and stimulated fibers. For the max Ca2+ force, the extent of the increase was smaller in stimulated than in rested fibers, whereas for my-Ca2+ sensitivity, it was higher in stimulated than in rested fibers. These results suggest that vigorous isometric contractions decrease the titin-based passive force, possibly because of a reduction in phosphorylation by protein kinase Cα, and that the decreased titin stiffness may contribute, at least in part, to muscle fatigue.

The Injured Shoulder in High-Level Male Gymnasts, Part 1: Epidemiology and Pathoanatomy of Surgically Treated Lesions

Background: Weightbearing and traction-suspension movements with the upper limbs put considerable demands upon the shoulder region of high-level gymnasts. The diagnosis of instability in these gymnasts may be difficult because voluntary inferior shoulder subluxation is part of their training and is needed to perform some acrobatic figures. Purpose: To (1) assess the epidemiology of shoulder lesions requiring surgery, (2) describe the types of injuries and assess which maneuvers and equipment put the gymnast most at risk, and (3) present a pathoanatomic classification of the injured shoulder in high-level male gymnasts. Study Design: Case series; Level of evidence, 4. Methods: Over a 20-year period (1994-2014), 26 high-level male gymnasts (30 shoulders; mean age, 22 years; range, 16-33 years) were referred to our surgical center for shoulder pain or instability. Four gymnasts underwent surgery on both shoulders. All shoulders were evaluated clinically, radiologically, and arthroscopically. An independent observer evaluated the circumstances in which these lesions occurred, including the apparatus used and the maneuvers performed. Results: The mean duration of symptoms before surgery was 8 months (range, 6-24 months). Eighteen injured shoulders (60%) had chronic overuse injuries. In 27 shoulders (90%), the mechanism of injury was traction of the arm in forced flexion-rotation while using suspension equipment with locked hands on the bars or the rings. In the remaining 3 shoulders, the traumatic position was one of an isometric muscle contraction against gravity, sustained while performing strength-and-hold positions on the rings. Based on the main presenting symptoms (pain and/or instability) and main anatomic lesions found during arthroscopy, the injured gymnasts’ shoulders were classified into 2 categories: painful shoulders (n = 13) with no clinical, radiological, or arthroscopic findings of instability (mainly superior cuff and biceps anchor lesions) and unstable shoulders (n = 17) with isolated inferior capsule labral tears or mixed lesions (tendinous and capsulolabral). Some gymnasts with inferior labral tears had no recall of having suffered a dislocation or subluxation. Conclusion: The majority of injuries requiring surgery in this population occurred during traction in forced flexion-rotation using suspension equipment. Injured shoulders were classified as either painful or unstable shoulders.

Safety, Tolerability, and Effect of Nusinersen Treatment in Ambulatory Adults With 5q-SMA

Objective: To determine the safety and tolerability of nusinersen treatment in ambulatory adults with spinal muscular atrophy (SMA) and investigate the treatment effect on muscle strength, physical function, and motor unit physiology.Methods: Individuals aged 18 years or older with genetically confirmed 5q SMA, three or more copies of the SMN2 gene, and the ability to ambulate 30 feet were enrolled. Safety outcomes included the number of adverse events and serious adverse events, clinically significant vital sign or laboratory parameter abnormalities. Outcome assessments occurred at baseline (prior to the first dose of nusinersen) and then 2, 6, 10, and 14 months post-treatment.Results: Six women, seven men (mean age: 37 ± 11, range: 18–59 years) were included for analyses. The most common side effects were headache and back pain, but overall procedures and treatments were well-tolerated. No serious adverse events were reported. Maximal Voluntary Isometric Muscle Contraction Testing (MVICT) and 6-min walk test (6MWT) both showed overall stability with significant increases at 2, 6, and 10 months for the 6MWT. More consistent significant treatment effects were noted on the Hammersmith Functional Motor Scale Expanded, SMA-Functional Rating Scale, and forced vital capacity. Treatment resulted in progressively increased ulnar compound muscle action potential and average single motor unit potential amplitudes, but motor unit number estimation remained stable.Conclusions: Nusinersen treatment is safe and well-tolerated in ambulatory adults with SMA. Treatment resulted in improved motor function and electrophysiological findings suggest that this improvement may be occurring via improved motor unit reinnervation capacity.

Shortening-induced residual force depression in humans

When an isometric muscle contraction is immediately preceded by an active shortening contraction, a reduction in steady-state isometric force is observed relative to an isometric reference contraction at the same muscle length and level of activation. This shortening-induced reduction in isometric force, termed “residual force depression” (rFD), has been under investigation for over a half century. Various experimental models have revealed the positive relationship between rFD and the force and displacement performed during shortening, with rFD values ranging from 5 to 39% across various muscle groups, which appears to be due to a stress-induced inhibition of cross-bridge attachments. The current review will discuss the findings of rFD in humans during maximal and submaximal contractions.

Physiology of Distinct Modes of Muscular Contraction

Physiological changes in musculature allow widespread movements in human body. Correspondingly, varying in muscle prototypes characterise direct different training paradigms in therapeutics practice or can governs athletic performances. Mode of muscle contraction type are isometric, concentric or eccentric. Great examples of concentric exercise are walking- up-hill, stair ascent and lifting a dumbbell in bicep curl or pushing a bar up. Examples of eccentric muscle actions are walking - down-hill, satire decent and, isokinetic arm and leg extensions. During isometric muscle contraction the length of muscle does not change while muscle exert force .This type of movement can be seen while a person performs a maximal voluntary contractions (MVCs).Eccentric exercises increasing the concentric and isometric contraction as well. Performing the eccentric muscle contraction in daily life enhance quality of life and lifespan due to increasing muscle strength with low cost of energy consuming and thus it can apply in variety of domains. A simple walking task such as downhill - walking (i.e. 30 min) can provide the aforementioned conditions.

Impact of Extra Curricular Training (Basketball and Athletics) on Muscle Strength in Boys 11–14 Years of Age

Research background and hypothesis. Human growth and maturation is determined by interaction of endogenous and exogenous factors. The most sensitive to the external influences is the age period between 11 and 14 years. The investigations of this age period in boys engaged in sports may reveal the complex interaction of the endogenous and exogenous factors. Hypothesis: Improvement of the muscle capacity indices in early adolescence depends on the nature of physical load.Research aim was to examine long-term extra curricular training in basketball games and athletics (sprint) effects on muscle strength of boys in early adolescence.Research methods. 105 boys – non-athletes (n = 35), athletes – sprint runners (n = 35) and basketball players (n = 35) – participated in the study. The boys were engaged in the chosen sports for no less than 2 years. The same cohorts were followed for four years at the age of 11, 12, 13 and 14 years. The strength of the arm levators, femoral flexors, calf extensors, calf flexors, forearm extensors and forearm flexors was measured using the dynamometer “Nicholas”. The maximum force required for the isometric muscle contraction mode was obtained when the resistance, caused by the investigator, occurred.Research results. Dynamometry assessments between the groups showed that the muscle strength of the athletes – sprint runners was greater than that of non-athletes and basketball players. Statistically significant differences between boys were identified in all age groups in assessment of both right and left sides.Discussion and conclusions. Improvement of the muscle capacity indices in early adolescence depends on the nature of physical load: the muscle strength indices increased more in the athletes – sprint runners than in the basketball players.Keywords: adolescence, dynamometry, sport.

Resistance Exercise Training in McArdle Disease: Myth or Reality?

McArdle disease is a metabolic myopathy mainly characterised by symptom onset during physical activities or isometric muscle contraction. Resistance (also termed strength) training is a type of physical exercise focusing on the use of resistance (e.g., lifting weights) to induce muscular contraction, which builds muscle mass and strength. Historically people with McArdle disease were advised to avoid resistance exercises and any other form of physical activity involving high mechanical loads such as prolonged isometric contraction. Paradoxically, a clinical trial exploring the benefits of strength training in this patient population was published. The theory supporting strength training relied on the use of the ATP molecule and the creatine phosphate (ATP-phosphocreatine system) as energy sources for skeletal muscles. Here, we report two patients with McArdle disease who performed weight training at local gyms. A single set of repetitions lasted for maximum 10 seconds with minimum of 30 seconds of rest period in between sets of exercises. Benefits of this type of training included improvement in quality of life and amelioration of McArdle disease symptoms. We provide further safety evidence of this type of exercise in people with McArdle disease. We emphasise the importance of using a specific protocol developed for people affected by this condition.