The effect of training on maximal isometric back-lift strength and mean peak voltage of the erector spinae
Berger (1962) tested the static strength of the lower back muscles before and after 12 wks. of training. The isometric group improved their static strength mean by 11.13 lbs, whereas the static increase for the isotonic group was 7.3 lbs. The author concluded that static (isometric) strength was improved more by static training. Rasch and Morehouse (1957) had reported similar results on elbow flexion and isometric arm pressing. Although all subjects gained in maximal isometric back-pull strength after submaximal isometric training at 10, 20, and 30 percent of maximal pulls twice daily for 4 days and maximal training twice daily for 1 wk, Chapman and Troup (1969) noted no change in the relationship between the integrated electromyograms and external forces produced as a result of strength gains (mean gain being 14.5 kg). Thus, no change in the “efficiency,” as defined by DeVries (1968), could be shown for the lumbar musculature. Similar results were obtained by Chapman and Troup (1970) over a period of 33 days. No changes in the integrated electromyogram pattern accompanied mean isometric strength increases of 13.3 kg. It might be inferred that the increase in strength was due solely to increases in motor unit activity and that no hypertrophy occurred. Corresponding results for concentric and eccentric back-lift strength training and their effect on lifting strength and electromyograms are lacking.
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