Ole Kristian Hoemsnes Berg

• Berg, Ole Kristian; Kwon, Oh. Sung; Hureau, Thomas J.; Clifton, Heather L.; Thurston, Taylor; Le Fur, Yann; Jeong, Eun-Kee; Amann, Markus; Richardson, Russel S.; Trinity, Joel D.; Wang, Eivind & Layec, Gwenael (2018). Maximal strength training increases muscle force generating capacity and the anaerobic ATP synthesis flux without altering the cost of contraction in elderly. Experimental Gerontology.  ISSN 0531-5565.  111(October), s 154- 161 . doi: 10.1016/j.exger.2018.07.013 Show summary

  Aging is associated with a progressive decline in skeletal muscle function, then leading to impaired exercise tolerance. Maximal strength training (MST) appears to be a practical and effective intervention to increase both exercise capacity and efficiency. However, the underlying physiological mechanisms responsible for these functional improvements are still unclear. Accordingly, the purpose of this study was to examine the intramuscular and metabolic adaptations induced by 8 weeks of knee-extension MST in the quadriceps of 10 older individuals (75 ± 9 yrs) by employing a combination of molecular, magnetic resonance 1H-imaging and 31P-spectroscopy, muscle biopsies, motor nerve stimulation, and indirect calorimetry techniques. Dynamic and isometric muscle strength were both significantly increased by MST. The greater torque-time integral during sustained isometric maximal contraction post-MST (P = 0.002) was associated with increased rates of ATP synthesis from anaerobic glycolysis (PRE: 10 ± 7 mM·min−1; POST: 14 ± 7 mM·min−1, P = 0.02) and creatine kinase reaction (PRE: 31 ± 10 mM·min−1; POST: 41 ± 10 mM·min−1, P = 0.006) such that the ATP cost of contraction was not significantly altered. Expression of fast myosin heavy chain, quadriceps muscle volume, and submaximal cycling net efficiency were also increased with MST (P = 0.005; P = 0.03 and P = 0.03, respectively). Overall, MST induced a shift toward a more glycolytic muscle phenotype allowing for greater muscle force production during sustained maximal contraction. Consequently, some of the MST-induced improvements in exercise tolerance might stem from a greater anaerobic capacity to generate ATP, while the improvement in exercise efficiency appears to be independent from an alteration in the ATP cost of contraction.

• Berg, Ole Kristian; Nyberg, Stian Kwak; Windedal, Tobias Midtvedt & Wang, Eivind (2018). Maximal strength training-induced improvements in forearm work efficiency are associated with reduced blood flow. American Journal of Physiology. Heart and Circulatory Physiology.  ISSN 0363-6135.  314(4), s H853- H862 . doi: 10.1152/ajpheart.00435.2017 Show summary

  Maximal strength training (MST) improves work efficiency. However, since blood flow is greatly dictated by muscle contractions in arms during exercise, and vascular conductance is lower, it has been indicated that arms rely more upon adapting oxygen extraction than legs in response to the enhanced work efficiency. Thus, to investigate if metabolic and vascular responses are arm-specific, we utilized Doppler-ultrasound and a catheter placed in the subclavian vein to measure blood flow and a-vO2diff during steady state work in seven young males (24{plus minus}3(SD) years) following six-weeks of handgrip MST. As expected, MST improved maximal strength (49{plus minus}9 to 62{plus minus}10kg) and rate of force development (923{plus minus}224 to 1086{plus minus}238N·s-1), resulting in a reduced submaximal V̇O2 (30{plus minus}9 to 24{plus minus}10ml·min-1) and concomitantly increased work efficiency (9.3{plus minus}2.5 to 12.4{plus minus}3.9%) (all p<0.05). In turn, the work efficiency improvement was associated with a reduced blood flow (486{plus minus}102 to 395{plus minus}114ml·min-1), mediated by a lower blood velocity (43{plus minus}8 to 32{plus minus}6cm·s-1) (all p<0.05). Conduit artery diameter and a-vO2diff remained unaltered. The maximal work test revealed increased time to exhaustion (949{plus minus}239 to 1102{plus minus}292seconds) and maximal work rate (both p<0.05), but no change in peak oxygen uptake. In conclusion, despite prior indications of metabolic and vascular limb-specific differences, these results reveal that improved work efficiency following small muscle mass strength training in the upper extremities is accompanied by a blood flow reduction, and coheres with what has been documented for lower extremities.

• Nyberg, Stian Kwak; Berg, Ole Kristian; Helgerud, Jan & Wang, Eivind (2018). Reliability of forearm oxygen uptake during handgrip exercise : assessment by ultrasonography and venous blood gas. Physiological Reports.  ISSN 2051-817X.  6:e13696(10), s 1- 11 . doi: 10.14814/phy2.13696 Full text in Research Archive. Show summary

  Assessment of forearm oxygen uptake (O2) during handgrip exercise is a keenly investigated concept for observing small muscle mass metabolism. Although a combination of Doppler ultrasound measurements of brachial artery blood flow () and blood gas drawn from a deep forearm vein has been utilized to calculate forearm O2 for more than two decades, the applicability of this experimental design may benefit from a thorough evaluation of its reliability during graded exercise. Therefore, we evaluated the reliability of this technique during incremental handgrip exercise in ten healthy young (24 ± 3(SD) years.) males. O2 and work rate (WR) exhibited a linear relationship (1.0 W: 43.8 ± 10.1 mL·min−1; 1.5 W: 53.8 ± 14.1 mL·min−1; 2.0 W: 63.4 ± 16.3 mL·min−1; 2.5 W: 72.2 ± 17.6 mL·min−1; 3.0 W: 79.2 ± 18.6 mL·min−1; r = 0.65, P < 0.01). In turn, O2 was strongly associated with (1.0 W: 359 ± 86 mL·min−1; 1.5 W: 431 ± 112 mL·min−1; 2.0 W: 490 ± 123 mL·min−1; 2.5 W: 556 ± 112 mL·min−1; 3.0 W: 622 ± 131 mL·min−1; r = 0.96; P < 0.01), whereas arteriovenous oxygen difference (a‐vO2diff) remained constant following all WRs (123 ± 11–130 ± 10 mL·L−1). Average O2 test–retest difference was −0.4 mL·min−1 with ±2SD limits of agreement (LOA) of 8.4 and −9.2 mL·min−1, respectively, whereas coefficients of variation (CVs) ranged from 4–7%. Accordingly, test–retest difference was 11.9 mL·min−1 (LOA: 84.1 mL·min−1; −60.4 mL·min−1) with CVs between 4 and 7%. Test–retest difference for a‐vO2diff was −0.28 mL·dL−1 (LOA: 1.26mL·dL−1; −1.82 mL·dL−1) with 3–5% CVs. In conclusion, our results revealed that forearm O2 determination by Doppler ultrasound and direct venous sampling is linearly related to WR, and a reliable experimental design across a range of exercise intensities.

• Nyberg, Stian K.; Berg, Ole Kristian; Helgerud, Jan & Wang, Eivind (2017). Blood flow regulation and oxygen uptake during high-intensity forearm exercise. Journal of applied physiology.  ISSN 8750-7587.  122(4), s 907- 917 . doi: 10.1152/japplphysiol.00983.2016 Show summary

  The vascular strain is very high during heavy handgrip exercise, but the intensity and kinetics to reach peak blood flow, and peak oxygen uptake, are uncertain. We included 9 young (25 ± 2 yr) healthy males to evaluate blood flow and oxygen uptake responses during continuous dynamic handgrip exercise with increasing intensity. Blood flow was measured using Doppler-ultrasound, and venous blood was drawn from a deep forearm vein to determine arteriovenous oxygen difference (a-vO 2diff) during 6-min bouts of 60, 80, and 100% of maximal work rate (WR max), respectively. Blood flow and oxygen uptake increased ( P < 0.05) from 60%WR max [557 ± 177(SD) ml/min; 56.0 ± 21.6 ml/min] to 80%WR max (679 ± 190 ml/min; 70.6 ± 24.8 ml/min), but no change was seen from 80%WR max to 100%WR max Blood velocity (49.5 ± 11.5 to 58.1 ± 11.6 cm/s) and brachial diameter (0.49 ± 0.05 to 0.50 ± 0.06 cm) showed concomitant increases ( P < 0.05) with blood flow from 60% to 80%WR max, whereas no differences were observed in a-vO 2diff Shear rate also increased ( P < 0.05) from 60% (822 ± 196 s -1) to 80% (951 ± 234 s -1) of WR max The mean response time (MRT) was slower ( P < 0.05) for blood flow (60%WR max 50 ± 22 s; 80%WR max 51 ± 20 s; 100%WR max 51 ± 23 s) than a-vO 2diff (60%WR max 29 ± 9 s; 80%WR max 29 ± 5 s; 100%WR max 20 ± 5 s), but not different from oxygen uptake (60%WR max 44 ± 25 s; 80%WR max 43 ± 14 s; 100%WR max 41 ± 32 s). No differences were observed in MRT for blood flow or oxygen uptake with increased exercise intensity. In conclusion, when approaching maximal intensity, oxygen uptake appeared to reach a critical level at ~80% of WR max and be regulated by blood flow. This implies that high, but not maximal, exercise intensity may be an optimal stimulus for shear stress-induced small muscle mass training adaptations. NEW & NOTEWORTHY This study evaluated blood flow regulation and oxygen uptake during small muscle mass forearm exercise with high to maximal intensity. Despite utilizing only a fraction of cardiac output, blood flow reached a plateau at 80% of maximal work rate and regulated peak oxygen uptake. Furthermore, the results revealed that muscle contractions dictated bulk oxygen delivery and yielded three times higher peak blood flow in the relaxation phase compared with mean values.

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• Berg, Ole Kristian (2019). Blood flow regulation and cost of muscle contraction during small muscle mass endurance performance. Ph.d.-avhandlinger i helse- og sosialfag. 2019:1.
• Berg, Ole Kristian & Klemetzen, Kristian Havnes (2017, 22. august). Vit om nærmeste hjertestarter.  Romsdals Budstikke. Show summary

  Treningsfysiolog Ole Kristian Berg med råd til trenere og ledere innenfor idretten. Det er viktig at trenere i det minste har et bevisst forhold til dette med førstehjelp og hjertestarter. Det kan redde liv.

• Berg, Ole Kristian; Nyberg, Stian K.; Windedal, Tobias M. & Wang, Eivind (2017). Forearm blood flow regulation following maximal strength training-induced improvements in work efficiency. Medicine & Science in Sports & Exercise.  ISSN 0195-9131.  49(5S), s 60 Show summary

  Maximal strength training (MST) improves submaximal work efficiency (WE) in the arms. However, since assessment of muscle oxygen uptake (V̇ O2) during exercise is lacking, the behavior of MST-induced adaptations is unknown, and it remains elusive if metabolic and vascular responses in arms may contrast what has been observed in legs.

• Berg, Ole Kristian & Waagbø, Arild Johan (2017, 17. januar). Stipendiat forsker på trening som medisin. [Internett].  Panorama : nettavis for Høgskolen i Molde. Show summary

  HiMolde-stipendiat Ole Kristian Berg (28) skal undersøke hvordan styrketrening kan hjelpe hoftebruddspasienter. Studien er et ledd i doktorgradsutdanningen i helse- og sosialfag han tar ved HiMolde, og han har satt av 2017 til å undersøke helseeffekten av styrketreningen for 20 hoftebruddspasienter mot en kontrollgruppe på 20 som får ordinær behandling.

• Nyberg, Stian K.; Berg, Ole Kristian; Helgerud, Jan & Wang, Eivind (2017). Validity of forearm oxygen uptake during handgrip exercise : assessment by ultrasonography and venous blood gas. Medicine & Science in Sports & Exercise.  ISSN 0195-9131.  49(5S), s 65 . doi: 10.1249/01.mss.0000517004.27687.52 Show summary

  Assessment of forearm oxygen uptake (V[Combining Dot Above]O2) during handgrip exercise is a keenly investigated concept for observing small muscle mass metabolism. Although a combination of Doppler-ultrasound measurements of brachial artery blood flow and blood gas drawn from a deep forearm vein has been utilized to calculate forearm V[Combining Dot Above]O2 for more than two decades, this experimental design has, somewhat surprisingly, not been validated.

• Wang, Eivind; Nyberg, Stian K.; Berg, Ole Kristian & Helgerud, Jan (2017). Blood flow regulation and oxygen uptake during high intensity forearm exercise. Medicine & Science in Sports & Exercise.  ISSN 0195-9131.  49(5S), s 826 . doi: 10.1249/01.mss.0000519218.77124.86

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