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  • Küçük Resim
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    Brief skin cooling modulates the refexes generated by whole‑body vibration
    (SPRINGER, ONE NEW YORK PLAZA, SUITE 4600 , NEW YORK, NY 10004, UNITED STATES, 2025) Kalaoğlu, Eser; Alayoğlu, Orhun; Sezikli, Selim; Atasoy, Mücahit; Türker, Kemal Sıtkı; Karacan, İlhan
    Background Whole-body vibration (WBV) is a popular exercise method known for its neuromuscular benefts, though the underlying mechanisms remain unclear. WBV activates distinct refexes based on vibration amplitude and voluntary muscle activity: low-amplitude vibration or voluntary contraction typically triggers the tonic vibration refex (TVR), whereas highamplitude vibration or quiet standing activates the bone myoregulation refex (BMR). Muscle spindles, which are sensitive to sympathetic input, may exhibit increased responsiveness to vibration during brief skin cooling. Objectives This study investigated the refex mechanisms activated by WBV during quiet standing and their modulation by skin cooling. Methods Thirty healthy young adults participated. The latency of the soleus TVR, induced by Achilles tendon vibration, and the latency of the soleus BMR, induced by WBV, were measured. These assessments were repeated during the cold pressor test (CPT), involving left-hand immersion in cold water. Results The soleus TVR latency was 36.2 ±5.1 ms, while the soleus BMR latency was 40.4 ±5.0 ms. During CPT, Achilles tendon vibration latency remained unchanged (36.2 ±5.7 ms, p= 0.319). However, the WBV-induced refex latency with CPT (36.0 ±6.1 ms, p< 0.0001) was signifcantly shorter than the soleus BMR latency and aligned with the TVR latency (p= 0.711). Conclusion WBV activates BMR in a quiet standing position, but with skin cooling, the TVR predominates, likely due to heightened spindle sensitivity. These fndings ofer valuable insights into developing targeted WBV programs.
  • Küçük Resim
    Öğe
    Enhancing motor performance through brief skin cooling: exploring the role of enhanced sympathetic tone and muscle spindle sensitivity
    (SPRINGER, ONE NEW YORK PLAZA, SUITE 4600 , NEW YORK, NY 10004, UNITED STATES, 2025) Çetin, Mert; Kökçe, Mustafa; Karaoğlu, Ayşe; Kalaoğlu, Eser; Kibar, Halime; Sezikli, Selim; Özkan, Mehmet; Türker, Kemal Sıtkı; Karacan, İlhan
    Background Although brief skin cooling (BSC) is widely used in sports medicine and rehabilitation for its positive efects on motor performance, the mechanism underlying this motor facilitation efect remains unclear. Objectives To explore the hypothesis that BSC enhances muscle force generation, with cold-induced sympathetic activation leading to heightened muscle spindle sensitivity, thereby contributing to this efect. Methods The study involved two experiments. Experiment 1 included 14 healthy volunteers. Participants submerged their hand in ice water for 3 min. Sympathetic activity was measured via heart rate (HR), muscle force generation was assessed through plantar fexor strength during maximum voluntary contraction (MVC), and cortical contribution to force generation via the volitional wave (V-wave) with and without the cold pressor test (CPT). Experiment-2 involved 11 healthy volunteers and focused on muscle spindle sensitivity and Ia synapse efcacy, assessed using soleus T-refex and H-refex recordings before, during, and after CPT. Results Experiment 1 showed signifcant increases in HR (7.8%), MVC force (14.1%), and V-wave amplitude (93.4%) during CPT compared to pre-CPT values (p=0.001, p=0.03, and p=0.001, respectively). In Experiment-2, hand skin temperature signifcantly decreased during CPT and remained lower than pre-CPT after 15 min (p<0.001). While H-refex and background EMG amplitudes remained unchanged, T-refex amplitude (113.7%) increased signifcantly during CPT and returned to pre-CPT values immediately afterward (p<0.001). A strong correlation was also observed between HR and T-refex amplitude (r=0.916, p=0.001). Conclusion BSC enhances muscle spindle sensitivity via the sympathetic nervous system, promoting more signifcant muscle force generation. The method used in this study can be safely applied in clinical practice.