Low-frequency resistance training enhances 2D strain-derived carotid strain and strain rate: a novel longitudinal application of strain imaging in healthy middle-aged females

Purpose
Exercise delays arterial decline in middle‑aged females, yet participation declines with age. We assessed whether 12-weeks of low‑frequency resistance training alters carotid and brachial arterial function in inactive middle‑aged females.

Methods
Sixteen inactive middle-aged females (57 ± 3 years; V̇O2peak: 25.3 ± 5.3 ml.kg.min−1) performed once-weekly resistance exercise for 12-weeks. At pre- and post-intervention, ultrasound measured common carotid artery function via conventional (β1 stiffness index and Peterson’s elastic modulus), and two-dimensional strain (peak circumferential strain and systolic strain rate). The common carotid artery was measured at rest, during, and after a three-minute isometric handgrip exercise, and brachial artery flow-mediated dilation was assessed at rest. Data were analysed using a paired sample t-test (intervention only at rest), and two-way repeated-measures ANOVA (intervention and handgrip response).

Results
Resting peak circumferential strain (%; P = 0.64) and systolic strain rate (s−1; P = 0.67) did not change pre-post intervention. However, peak circumferential strain across isometric handgrip conditions increased post intervention (rest: 4.67 ± 0.87 vs 4.87 ± 1.42; during 3.62 ± 1.40 vs 4.48 ± 1.17; and after handgrip: 3.78 ± 1.29 vs 4.87 ± 1.24; P = 0.012). Systolic strain rate across conditions also increased post intervention (rest: 0.365 ± 0.078 vs 0.394 ± 0.101; during 0.280 ± 0.107 vs 0.329 ± 0.089; and after handgrip: 0.294 ± 0.109 vs 0.371 ± 0.095; P = 0.009). β1 stiffness index (P = 0.64), Peterson’s elastic modulus (P = 0.08), and brachial flow-mediated dilation (P = 0.82) did not change pre-post intervention when measured at rest and during conditions.

Conclusion
Once-weekly resistance training improves carotid strain and strain rate in healthy middle-aged females, with effects evident under physiological stimulation. We support claims that two-dimensional strain detects arterial function changes that conventional measures may overlook.