THE INFLUENCE OF LENGTH CHANGE SPEED AND DIRECTION ON DYNAMIC FUNCTION POTENTIATION IN FAST MOUSE MUSCLE

The purpose of this study was to test the hypothesis that the potentiation of dynamic function was dependent upon both length change speed and direction. Mouse EDL was cycled in vitro (25º C) about optimal length (Lo) with constant peak strain (± 2.5% Lo) at 1.5, 3.3 and 6.9 Hz before and after a conditioning stimulus. A single pulse was applied during shortening or lengthening and peak dynamic (concentric or eccentric) forces were assessed at Lo. Stimulation increased peak concentric force at all frequencies (range: 19 ± 1 to 30 ± 2%) but this increase was proportional to shortening speed, as were the related changes to concentric work/power (range: -15 ± 1 to 39 ± 1 %). In contrast, stimulation did not increase eccentric force, work or power at any frequency. Thus, results reveal a unique hysteresis like effect for the potentiation of dynamic output wherein concentric and eccentric forces increase and decrease, respectively, with work cycle frequency.

THE INFLUENCE OF LENGTH CHANGE SPEED AND DIRECTION ON DYNAMIC FUNCTION POTENTIATION IN FAST MOUSE MUSCLE

The purpose of this study was to test the hypothesis that the potentiation of dynamic function was dependent upon both length change speed and direction. Mouse EDL was cycled in vitro (250 C) about optimal length (Lo) with constant peak strain (± 2.5% Lo) at 1.5,3.3 and 6.9 Hz before and after a conditioning stimulus. A single pulse was applied during shortening or lengthening and peak dynamic (concentric or eccentric) forces were assessed at Lo. Stimulation increased peak concentric force at all frequencies (range: 19±1 to 30 ± 2%) but this increase was proportional to shortening speed, as were the related changes to concentric work/power (range: -15 ± 1 to 39 ± 1 %). In contrast, stimulation did not increase eccentric force, work or power at any frequency. Thus, results reveal a unique hysteresis like effect for the potentiation of dynamic output wherein concentric and eccentric forces increase and decrease, respectively, with work cycle frequency.

Photograph - Margaret Julia Woodruff Band (Full Length Photograph)

Black and white photograph, 24 cm x 16 cm, of Margaret Julia Woodruff Band. This is a full length photograph in which she is wearing a lace dress. The photo was taken by Dudley Hoyt of New York.

Chart of station 2, crop sections of the old back ditch on the south side of the feeder, station 45, station 118 and the total length from the culvert to lot no. 5

Chart of station 2, crop sections of the old back ditch on the south side of the feeder, station 45, station 118 and the total length from the culvert to lot no. 5. This is signed by Fred Holmes, April 13, 1857.

County of Welland estimate of work done on section no.1 of the tap drain at Marshville by Edward Henderson

County of Welland estimate of work done on section no.1 of the tap drain at Marshville by Edward Henderson, signed by S.D. Woodruff. Estimate no.1, June, 1856.

County of Welland estimate of work done on constructing a bridge across the tap drain at Marshville by Alexander Lattimer

County of Welland estimate of work done on constructing a bridge across the tap drain at Marshville by Alexander Lattimer, signed by S.D. Woodruff. Estimate no.1, June, 1856.

County of Welland estimate (copy) of work done on sections 2 and 3 of the tap drain at Marshville by George Stanford

County of Welland estimate (copy) of work done on sections 2 and 3 of the tap drain at Marshville by George Stanford, signed by S.D. Woodruff. Estimate no.1, July, 1856.

County of Welland estimate (copy) of work done on section no. 5 of the tap drain at Marshville by Andrew Mains

County of Welland estimate (copy) of work done on section no. 5 of the tap drain at Marshville by Andrew Mains, signed by S.D. Woodruff. Estimate no.1, Sept., 1856.

County of Welland estimate (copy) of work done on section no. 4 of the tap drain at Marshville by Brown and Hershall

County of Welland estimate (copy) of work done on section no. 4 of the tap drain at Marshville by Brown and Hershall, signed by S.D. Woodruff. Estimate no.1, Sept., 1856.

County of Welland estimate (copy) of work done on sections 2 and 3 of the tap drain at Marshville by George Stanford

County of Welland estimate (copy) of work done on sections 2 and 3 of the tap drain at Marshville by George Stanford, signed by S.D. Woodruff. Estimate no.2, Oct., 1856.

County of Welland estimate (copy) of work done on section no. 4 of the tap drain at Marshville by Brown and Hershall,

County of Welland estimate (copy) of work done on section no. 4 of the tap drain at Marshville by Brown and Hershall, signed by S.D. Woodruff. Estimate no.2, Oct., 1856.

County of Welland estimate of work done on section no.1 and cleaning below the culvert of the tap drain at Marshville by Edward Henderson

County of Welland estimate of work done on section no.1 and cleaning below the culvert of the tap drain at Marshville by Edward Henderson, signed by S.D. Woodruff. Estimate no.2, Oct., 1856.

Abstracts given to Andrew Mains for ditching done in the tap drain of the marsh lands

Abstracts given to Andrew Mains for ditching done in the tap drain of the marsh lands, Oct. 1856.