Serial sarcomere adaptation to eccentric overload training is blunted in ovariectomized rats

FIGURE 1. Experimental timeline demonstrating the mechanical testing, training and morphological data collection. Female rats (n = 40; 20 ovary intact, 20 OVX) underwent 4 weeks of eccentric overload (n = 20) or conventional resistance training (n = 20). The ovary‐intact group represented the high estrogen condition, and the OVX group represented the low estrogen condition. Mechanical testing was done pre and post 4 weeks of training. Rats were anesthetized and placed supine on a heated platform (37°C) with a nose cone providing isoflurane. The left leg was secured with a leg clamp around the knee (150°), with the left foot secured with tape to a foot plate attached to a torque motor/transducer. Percutaneous stimulation electrodes were positioned over the plantar flexors as well as the tibial nerve to evoke contractions. The ankle is pictured at 90° with a range of motion of 70°–110°.

FIGURE 2. Differences in plantar‐flexor torque with eccentric overload and conventional training in ovary‐intact (n = 19) and OVX (n = 19) rats at a 90° and 70° ankle angle. (a) Absolute plantar flexor torque pre and post training at 90° for ovary intact and OVX. (b) Absolute plantar flexor torque pre and post training at 70° where the CONV group is shown in blue and the ECCOVERLOAD group is shown in orange. Statistical comparisons were performed using a three‐way repeated measures ANOVA (Group × Training × Hormone Status). Data are displayed as mean ± standard deviation.

FIGURE 3. Differences in passive plantar flexor torque in ovary‐intact (n = 19) and OVX (n = 19) rats with eccentric overload and conventional at a 90° and 70° ankle angle. (a) Passive plantar flexor torque at a 90° ankle angle. (b) Passive plantar flexor torque at a 70° ankle angle where the CONV group is shown in blue and the ECCOVERLOAD group is shown in orange. Statistical comparisons were performed using a three‐way repeated measures ANOVA (Group × Training × Hormone Status). Data are displayed as mean ± standard deviation.

FIGURE 4. Changes in plantar flexor peak power, velocity at peak power and torque at peak power with training in ovary‐intact (n = 19) and OVX rats (n = 19). (a) Peak power pre and post training. (b) Changes in torque at peak power with training. (c) Differences in velocity at peak power in response to training. The CONV group is shown in blue, and the ECCOVERLOAD group is shown in orange. Statistical comparisons were performed using a three‐way repeated measures ANOVA (Group × Training × Hormone Status). Data are displayed as mean ± standard deviation.

FIGURE 5. Differences in soleus (a) muscle wet weight and (b) physiological cross‐sectional area (PCSA) pre to post training in ovary‐intact (n = 19) and OVX (n = 19) rats. The CONV group is shown in blue, and the ECCOVERLOAD group is shown in orange. Statistical comparisons were performed using a three‐way repeated measures ANOVA (Group × Training × Hormone Status). Data are displayed as mean ± standard deviation.

FIGURE 6. Differences in MG (a) muscle wet weight and (b) physiological cross‐sectional area (PCSA) pre to post training in ovary‐intact (n = 19) and OVX (n = 19) rats. The CONV group is shown in blue, and the ECCOVERLOAD group is shown in orange. Statistical comparisons were performed using a three‐way repeated measures ANOVA (Group × Training × Hormone Status). Data are displayed as mean ± standard deviation.

FIGURE 7. Changes in soleus and MG serial sarcomere number with training in OVX (n = 19) and ovary‐intact (n = 19) rats. Pre represents the untrained right leg as an internal control and post represents the trained left leg. (a) Differences in soleus serial sarcomere number in the trained (left) and untrained (right) leg in OVX (n = 19) and ovary‐intact (n = 19) rats. (b) Changes in MG serial sarcomere number with training. The CONV group is shown in blue, and the ECCOVERLOAD group is shown in orange. Statistical comparisons were performed using a three‐way repeated measures ANOVA (Group × Training × Hormone Status). Data are displayed as mean ± standard deviation.