overload is the act of exercising a muscle to fatigue

Muscle force is transferred posteriorly to the axial skeleton and caudal fin by connective tissue and skeletal elements.

Đang xem: Overload is the act of exercising a muscle to fatigue

From: Encyclopedia of Fish Physiology, 2011

Related terms:

Skeletal Muscle Endurance Aerobic Exercise Resistance Training Muscle Contraction

Kari Bø, … Arve Aschehoug, in Evidence-Based Physical Therapy for the Pelvic Floor (Second Edition) , 2015


Muscular strength and endurance are developed by the progressive overload principle (e.g. by increasing more than normal the resistance to movement or frequency and duration of activity; American College of Sports Medicine, 2009 ). Muscular strength is best developed by using heavier weights/resistance (that require maximum or near maximum tension development) with few repetitions, and muscular endurance is best developed by using lighter weights with a great number of repetitions (American College of Sports Medicine, 2009 ). There are several ways to overload a muscle or muscle group:

add weight or resistance;

sustain the contraction;

shorten resting periods between contractions;

increase speed of the contraction;

increase number of repetitions;

increase frequency and duration of workouts;

decrease recovery time between workouts;

alternate form of exercise;

alternate range to which a muscle is being worked.

The PT can manipulate all the above-listed factors when training the PFM. However, certain important factors are difficult to apply for PFMT (e.g. to add weight and resistance). Plevnik (1985) invented vaginal-weighted cones to make a progression of overload to the PFM (Fig. 6.12 ). Vaginal cones come in different shapes and weights and are placed above the levator muscle. The patient is asked to start with a weight that she can hold for 1 minute in standing position. The actual training is to try to stay in an upright position with the cone in place for 20 minutes. When the woman is able to walk around with a weight in place for 20 minutes, a heavier weight should replace the one used to make progression in workload. Although correct from a theoretical exercise science point of view this method can be questioned from a practical point of view. In addition, holding a contraction for a long time may decrease blood supply, cause pain and reduce oxygen consumption (Bø, 1995 ). Many women report that they are unable to hold the cones in place and adherence may be low (Cammu and Van Nylen, 1998; Bø et al., 1999 ).

Any magnitude of overload will result in strength development, but heavier resistance loads to maximal or near maximal will elicit a significantly greater training effect (American College of Sports Medicine, 2009 ). Heavy resistance training may cause an acute increase in systolic and diastolic blood pressure, especially when a Valsalva manoeuvre is evoked (American College of Sports Medicine, 2011 ). This is of importance for PFMT because many women tend to erroneously perform a Valsalva manoeuvre when attempting to perform a PFM contraction. Ferreira et al. (2013) assessed heart rate during PFMT sessions and blood pressure before and after each training session in pregnant women. Heart rate significantly increased during training, but only for a limited time. Increase in blood pressure and heart rate during the training period was within normal ranges. Anecdotally, some women report slight headache, dizziness and discomfort during their first PFMT sessions, and this may be due to an increase in blood pressure or inadequate breathing. Normal breathing during attempts to perform maximum contractions is almost impossible. Therefore, an emphasis on normal breathing between each contraction is important.

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Eccentric (lengthening) exercises are effective in increasing muscle strength ( Fleck and Kraemer, 2004 ). However, the potential for skeletal muscle soreness and muscle injury is increased when compared to concentric (shortening) or isometric contractions, particularly in untrained individuals (Fleck and Kraemer, 2004; American College of Sports Medicine, 2009 ). Eccentric contractions are also more difficult to perform (require more motor skill and muscle awareness) than concentric or isometric contractions, and are therefore not recommended at the beginning of a PFMT programme.

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Physical Activity and Exercise in the Maintenance of the Adult Skeleton and the Prevention of Osteoporotic Fractures

Dennis R. Taaffe, … Kate A. Bolam, in Osteoporosis (Fourth Edition) , 2013

Power Training – High-Velocity Resistance Training

Muscle power training (or high-velocity resistance training) has been advocated as a potentially superior form of resistance-based training to enhance physical performance, muscle power, and reduce the risk of falls in older adults <173,174> . Muscle power, which represents the product of force and velocity, is characterized by rapid concentric movements performed at moderate-to-high loads. In a meta-analysis designed to compare different types and intensities of PRT on muscle and functional outcomes in older adults, Steib et al. reported that power training was more effective for improving muscle power and physical performance (chair rising time and stair climbing ability) than traditional PRT <175> . It is hypothesized that this form of training may also provide an enhanced osteogenic effect due to the higher strain rates compared to traditional PRT. In the only study conducted to date, Stengel et al.

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compared the skeletal response in 53 postmenopausal osteopenic women who participated in either a twice weekly power training or traditional PRT program for 2 years <176, 177> . The training programs were identical except that those women undertaking traditional PRT took 4 seconds for the concentric phase of the movement whereas the power-trained group performed this phase in a rapid explosive fashion. In addition, all women performed gymnastics and home training. Following 12 months of training, total hip and lumbar spine BMD was maintained in the power training group, but decreased in the PRT group <177> . After 2 years, the beneficial effects of power training persisted at the lumbar spine, with a trend for maintenance at the hip <176> . It is important to note that the women in this study had previously participated in a 3-year exercise trial, and thus the response to the exercise training may have been attenuated based on the principle of diminished returns. Nevertheless, these findings provide preliminary evidence that power training might be an effective modality to enhance both bone health and muscle function in older adults.

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