Tiril Tøien

• Unhjem, Runar Jakobsen; Tøien, Tiril; Kvellestad, Ann Charlotte; Øren, Thomas Storehaug & Wang, Eivind (2020). External resistance is imperative for training-induced efferent neural drive enhancement in older adults. The journals of gerontology. Series A, Biological sciences and medical sciences.  ISSN 1079-5006.  76(2), s 224- 232 . doi: 10.1093/gerona/glaa160 Vis sammendrag

  Strength training performed with heavy loads and maximal intended velocity is documented to enhance efferent neural drive to maximally contracting musculature in older adults. However, it remains unclear whether the neural plasticity following training result from motor skill learning or if external resistance is a prerequisite. To investigate this, we assessed electrically evoked potentials (H-reflex and V-waves normalized to maximal M-wave) and voluntary activation (VA) in 36 older adults (73 ± 4 years) randomized to 3 weeks of plantar flexion strength training, with (maximal strength training [MST]) or without (unloaded ballistic training [UBT]) heavy external loading (90% of one repetition maximum), or a control group. Both training groups aimed to execute the concentric phase of movement as fast and forcefully as possible. The MST group improved maximal voluntary contraction (MVC) and rate of force development (RFD) by 18% ± 13% (p = .001; Hedges g = 0.66) and 35% ± 17% (p < .001; g = 0.94), respectively, and this was different (MVC: p = .013; RFD: p = .001) from the UBT group which exhibited a 7% ± 8% (p = .033; g = 0.32) increase in MVC and a tendency to increase RFD (p = .119; g = 0.22). Concomitant improvements in efferent neural drive (Vmax/Msup ratio: 0.14 ± 0.08 to 0.24 ± 0.20; p = .010) and a tendency towards increased VA (79% ± 9% to 84% ± 5%; p = .098), were only apparent after MST. No changes were observed in Hmax/Mmax ratio for the groups. In conclusion, external loading during exercise training appears to be a prerequisite for efferent neural drive enhancement in older adults. Thus, strength training with heavy loads should be recommended to counteract the typically observed age-related decline in motoneuron firing frequency and recruitment. Keywords: Ballistic training, Firing frequency, Motor unit recruitment, Strength training.

• Tøien, Tiril; Haglo, Håvard Pedersen; Unhjem, Runar Jakobsen; Hoff, Jan & Wang, Eivind (2018). Maximal strength training : the impact of eccentric overload. Journal of Neurophysiology.  ISSN 0022-3077.  120(6), s 2868- 2876 . doi: 10.1152/jn.00609.2018
• Øvretveit, Karsten & Tøien, Tiril (2018). Maximal strength training improves strength performance in grapplers. Journal of Strength and Conditioning Research.  ISSN 1064-8011.  32(12), s 3326- 3332 . doi: 10.1519/JSC.0000000000002863 Fulltekst i vitenarkiv.
• Tøien, Tiril; Unhjem, Runar Jakobsen; Øren, Thomas Storehaug; Kvellestad, Ann Charlotte; Hoff, Jan & Wang, Eivind (2017). Neural plasticity with age: Unilateral maximal strength training augments efferent neural drive to the contralateral limb in older adults. The journals of gerontology. Series A, Biological sciences and medical sciences.  ISSN 1079-5006.  73(5), s 596- 602 . doi: 10.1093/gerona/glx218 Vis sammendrag

  Efferent neural drive during strong muscle contractions is attenuated with age, even after life-long strength training. However, it is unknown if this deterioration may impede contralateral neural plasticity, and limit the clinical value of unilateral strength training. We assessed muscle force-generating capacity, evoked potentials recordings (V-wave and H-reflex normalized to M-wave; V/M-ratio and H/M-ratio) and voluntary activation (VA) in the plantar flexors of the contralateral limb following unilateral maximal strength training (MST) with the dominant limb for 3 weeks (nine sessions). Twenty-three 73 ± 4(SD) year old males were randomized to a MST group (N = 11), exercising with an intensity of ~90% of maximal strength, or a control group (CG, N = 12). MST improved contralateral maximal strength (107.6 ± 27.0 to 119.1 ± 34.8 Nm; 10%) and rate of force development (197.3 ± 54.1 to 232.8 ± 77.7 Nm s−1; 18%) (both p < .05). These strength gains were associated with (r = 0.465–0.608) an enhanced soleus V/M-ratio (0.12 ± 0.09 to 0.21 ± 0.17) and VA (79.5 ± 5.1 to 83.3 ± 5.2%) (all p < .05). H/M-ratio (10% maximal strength) remained unaltered after MST, and no changes were apparent in the CG. In conclusion, cross-limb effects in older adults are regulated by efferent neural drive enhancement, and advocate the clinical relevance of MST to improve neuromuscular function in individuals with conditions that results in unilateral strength reductions.

Se alle arbeider i Cristin