Tiril Tøien

• Tøien, Tiril; Lindberg Nielsen, Jakob; Berg, Ole Kristian Brones; Brobakken, Mathias Forsberg; Nyberg, Stian Kwak & Espedal, Lars [Vis alle 10 forfattere av denne artikkelen] (2023). The impact of life-long strength versus endurance training on muscle fiber morphology and phenotype composition in older men. Journal of applied physiology. ISSN 8750-7587. 135(6), s. 1360–1371. doi: 10.1152/japplphysiol.00208.2023.
• Pedrinolla, Anna; Berg, Ole Kristian; Tøien, Tiril & Wang, Eivind (2023). Aging increases metabolic capacity and reduces work efficiency during handgrip exercise in males. Journal of applied physiology. ISSN 8750-7587. 134(5), s. 1154–1164. doi: 10.1152/japplphysiol.00411.2022. Vis sammendrag

  Maximal oxygen uptake and exercise performance typically decline with age. However, there are indications of preserved vascular function and blood flow regulation during arm exercise. Yet, it is unknown if this potential physiological preservation with age is mirrored in peripheral metabolic capacity and V̇O2/watt ratio. Thus, to investigate the effects of aging in the arms, we measured metabolic and vascular responses to 6-minute bouts of dynamic handgrip exercise at 40% and 80% of maximal work rate (WRmax) in eleven young (26±2yr) and twelve old (80±6yr) males, applying Doppler-ultrasound combined with blood samples from a deep forearm vein. At baseline, old had a larger arterial diameter compared to young (p<0.001). During exercise, the two groups reached the same WRmax. V̇O2, blood flow, and oxygen supply were higher (40%WRmax; 80%WRmax, all p<0.01), and arterio-venous oxygen-difference lower (80%WRmax, p<0.02), in old compared to young. Old also had a higher oxygen-excess at 80%WRmax (p<0.01) than young, while no difference in muscle diffusion or oxygen-extraction was detected. Only young exhibited an increase in intensity-induced arterial dilation (p<0.05), and they had a lower mean arterial pressure than old at 80%WRmax (p<0.001). V̇O2/watt (40%WRmax; 80%WRmax) was reduced in old compared to young (both p<0.05). In conclusion, in old and young males with a similar handgrip WRmax, old had a higher V̇O2 during 80%WRmax intensity, achieved by an increased blood flow. This may be a result of the available cardiac output reserve, compensating for reduced work efficiency and attenuated vascular response observed in old.

• Tøien, Tiril; Unhjem, Runar Jakobsen; Berg, Ole Kristian; Aagaard, Per & Wang, Eivind (2022). Strength versus endurance trained master athletes : contrasting neurophysiological adaptations. Experimental Gerontology. ISSN 0531-5565. 171(January), s. 1–12. doi: 10.1016/j.exger.2022.112038. Vis sammendrag

  Neural factors play a critical role in the age-related decline in maximal strength and rate of force development (RFD). However, it is uncertain how the age-related attenuation in neuromuscular function may be mitigated in strength or endurance trained master athletes. In this study we applied evoked spinal motoneuron recordings to examine descending motor drive, i.e., efferent drive from supraspinal and spinal centres during maximal voluntary contraction (MVC; V-wave) and H-reflex excitability measured at 10 % MVC in older (>65 yrs) and younger (<35 yrs) strength athletes (n = 21), endurance athletes (n = 17) and untrained control participants (n = 30). Both strength (b = 0.09 [0.01–0.18], p = 0.038) and endurance training (b = 0.14 [0.04–0.23], p = 0.006) were associated with a high V-wave amplitude. This was likely explained by an elevated H-reflex excitability (b = 0.23 [0.11–0.35], p < 0.001) in endurance trained participants, which failed to be seen in strength trained participants. These contrasting neurophysiological properties were accompanied by different physiological traits; strength training was associated with high maximal strength (b = 107.5 [84.6 to 130.4] kg, p < 0.001) and RFD (b = 3171 [2248 to 4094] N‧s−1, p < 0.001), whereas endurance training was associated with elevated maximal oxygen uptake (V̇O2max; b = 13.6 [8.0–19.2] ml‧kg−1‧min−1, p < 0.001). This pattern was apparent irrespective of age, although all traits were negatively associated with advanced age (p < 0.05). In conclusion, strength trained individuals demonstrate higher descending motor drive (elevated V-wave responses), compared to age-matched untrained individuals. Endurance trained individuals also showed elevated V-wave responses, uniquely accompanied by enhanced α-motoneuron excitability and/or reduced pre/postsynaptic inhibition (elevated H-reflex responses). Since a high descending motor drive is a key component of strong muscle contractions, strength training should be emphasized to sustain the ability to carry out force-dependent tasks at older age. Keywords: lifelong strength training, descending motor drive, spinal motoneuron excitability, maximal muscle strength, rate of force development

• Tøien, Tiril; Malmo, Thomas; Espedal, Lars & Wang, Eivind (2022). Maximal intended velocity enhances strength training-induced neuromuscular stimulation in older adults. European Journal of Applied Physiology. ISSN 1439-6319. 122(12), s. 2627–2636. doi: 10.1007/s00421-022-05045-8. Vis sammendrag

  The age-related attenuation in neuromuscular function can be mitigated with strength training. Current recommendations for untrained and elderly recommend performing the strength training with a controlled movement velocity (CON). However, applying maximal intended velocity (MIV) in the concentric phase of movement may augment neuromuscular stimulation and potentially enhance training adaptations. Thus, applying rate of electromyography (EMG) rise (RER) recordings, we examined the acute early phase neuromuscular response to these two contraction types in quadriceps femoris during leg extension, along with actual movement velocity, in 12 older (76 ± 6 years) and 12 young men (23 ± 2 years). Results revealed that older adults had a lower one repetition maximum (1RM) than young (33 ± 9 kg vs. 50 ± 9 kg; p = 0.001) and lower actual velocity across relative intensities of ~ 10%, 30%, 50%, 70% and 90% of 1RM for CON and MIV (all p < 0.05). Older adults also had consistently reduced RER compared to young during both conditions (old: 1043–1810 μV; young: 1844–3015 μV; all p < 0.05). However, RER was higher in contractions with MIV compared to CON for both age groups, and across all intensities (98–674%, all p < 0.05). In conclusion, despite decreased maximal strength and attenuated neuromuscular response with advancing age, our results document an augmented neuromuscular activation when repetitions are performed with MIV in the concentric phase of movement.

• Tøien, Tiril; Haglo, Håvard Pedersen; Nyberg, Stian Kwak; Rao, Shalini Vasudev; Stunes, Astrid Kamilla & Mosti, Mats Peder [Vis alle 7 forfattere av denne artikkelen] (2021). Maximal strength training-induced increase in efferent neural drive is not reflected in relative protein expression of SERCA. European Journal of Applied Physiology. ISSN 1439-6319. 121(12), s. 3421–3430. doi: 10.1007/s00421-021-04807-0. Fulltekst i vitenarkiv Vis sammendrag

  Introduction Maximal strength training (MST), performed with heavy loads (~ 90% of one repetition maximum; 1RM) and few repetitions, yields large improvements in efferent neural drive, skeletal muscle force production, and skeletal muscle efficiency. However, it is elusive whether neural adaptations following such high intensity strength training may be accompanied by alterations in energy-demanding muscular factors. Methods Sixteen healthy young males (24 ± 4 years) were randomized to MST 3 times per week for 8 weeks (n = 8), or a control group (CG; n = 8). Measurements included 1RM and rate of force development (RFD), and evoked potentials recordings (V-wave and H-reflex normalized to M-wave (M) in the soleus muscle) applied to assess efferent neural drive to maximally contracting skeletal muscle. Biopsies were obtained from vastus lateralis and analyzed by western blots and real-time PCR to investigate the relative protein expression and mRNA expression of Sarcoplasmic Reticulum Ca2+ ATPase (SERCA) 1 and SERCA2. Results Significant improvements in 1RM (17 ± 9%; p < 0.001) and early (0–100 ms), late (0–200 ms) and maximal RFD (31–53%; p < 0.01) were observed after MST, accompanied by increased maximal Vmax/Msup-ratio (9 ± 14%; p = 0.046), with no change in H-reflex to M-wave ratio. No changes were observed in the CG. No pre- to post-training differences were found in mRNA or protein expressions of SERCA1 and SERCA2 in either group. Conclusion MST increased efferent neural drive to maximally contracting skeletal muscle, causing improved force production. No change was observed in SERCA expression, indicating that responses to high intensity strength training may predominantly be governed by neural adaptations.

• 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. Fulltekst i vitenarkiv
• 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.

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• Tøien, Tiril (2021). Transpersoner i OL. [TV]. NRK P2 Dagsnytt atten.
• Tøien, Tiril (2021). Når inkludering blir urettferdig. nrk.no/ytring. Vis sammendrag

  Når transkvinnen Laurel Hubbard får konkurrere i kvinneklassen, svekker vi idrettens prinsipp om rettferdig konkurranse.

• Tøien, Tiril (2023). Neuromuscular performance in the ageing human : the impact of strength training. Høgskulen i Volda; Høgskolen i Molde - Vitenskapelig høgskole i logistikk. ISSN 978-82-7962-348-9.

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