Reinterpretation of the Tension Response of Muscle to Stretches and Releases  Gerald Offer, K.W. Ranatunga  Biophysical Journal  Volume 111, Issue 9, Pages 2000-2010 (November 2016) DOI: 10.1016/j.bpj.2016.09.031 Copyright © 2016 Biophysical Society Terms and Conditions

Figure 1 Kinetic model of the cross-bridge cycle. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 2 (a and b) Comparison of experimental tension responses to releases and stretches of the same magnitude, with length steps of (a) 3 nm/hs and (b) 1.5 nm/hs. Data from (2). The tensions have been normalized to the isometric tension. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 3 Dependence on length step size of the rates of the fast and slow phases of experimental traces. Circles, fast rate; squares, slow rate. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 4 (a–c) Comparison of the tension responses of the model to stretches and releases of the same size: (a) 3 nm/hs, (b) 1.5 nm/hs, and (c) 0.5 nm/hs. In each panel the upper transient is a stretch and the lower transient is a release. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 5 (a and b) Dependence on length step of the (a) rates and (b) amplitudes of the model for fast and slow phases of early tension recovery. Circles, fast phase; squares, slow phase. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 6 Time courses of the net rates of steps in the cross-bridge cycle in response to length steps. (a–c) Stretch of 6 nm/hs. (d–f) Release of 6 nm/hs. Shown are the net rates of the first tensing step (black line), second tensing step (gray line), and attachment of pretensing heads (dashed line), and the rate of detachment of posttensing heads (dotted line). Note the changes in the timescale and the sign and magnitude of the ordinate in the different panels. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 7 Time course of incremental total tension and tension contributions by steps in the cross-bridge cycle after length steps. (a–c) Stretches and (d–f) releases of 6, 3, and 1.5 nm/hs. Shown are the incremental total tension (black line with squares) and the incremental tension contributed by the first tensing step (black line), second tensing step (dark gray line), attachment of pretensing heads (dotted line), detachment of pretensing heads (dashed line), and detachment of posttensing heads (light gray line). All tensions have been normalized to the isometric tension. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions

Figure 8 Dependence on the length step of T1, T1′, T2, and the reciprocal half-time of early tension recovery. (a) T1 (open squares), T1′ (solid squares), and T2 (solid circles). (b) Reciprocal half-time of early tension recovery. T1′ is the value of T1 corrected for the tension recovery in the length step itself. Biophysical Journal 2016 111, 2000-2010DOI: (10.1016/j.bpj.2016.09.031) Copyright © 2016 Biophysical Society Terms and Conditions