Klavs Madsen

Professor Department of Physical Performance

Email: klavsm@nih.no
Phone: +47 23 26 23 05
Mobile phone: +47 23 26 23 05

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Background and experience

Head of Department and Professor in Exercise Physiology, Department of Physical Performance at the Norwegian School of Sport Sciences (NIH), Olso, Norway.

Research is focused in cell biology, physiology and biochemistry of skeletal muscle. The research investigates the underlying mechanisms of skeletal muscle adaptations to training and inactivity with specific attention to carbohydrate and fat metabolism, muscle growth and muscle waste using mainly a whole-body approach.

The research concentrates on human endurance capacity, both in a performance and health perspective.

Overview of publications in Researchgate

Areas of responsibility

Head of Department, Professor in Exercise Physiology

Teaching

Lecturer in metabolism.

Main responsibility for Master in Sport Sciences, field of study Sport and Physical Performance.

Academic responsibility for "Fordypningsoppgave" (MA413) and "Project plan" (MET415).

Research

Skeletal muscle adaptations to training and inactivit, endurance training and the effect on metabolism, muscle hypertrophy and the role of testosterone, carbohydrate and protein supplementation for optimizing endurance performance.

Projects

No ongoing projects

Publications

Scientific articles and book chapters

Øistuen, Gina Flugstad; Osborne, John Owen; Sundgot-Borgen, Jorunn; Noordhof, Dionne; Taylor, Madison Y. & Heikura, Ida [Show all 16 contributors for this article] (2026). Menstrual status and bone health in athletes from different sports – a retrospective analysis. BMC sports science, medicine and rehabilitation. doi: 10.1186/s13102-026-01781-y. Full text in Research Archive Show summary
Abstract Background Relative energy deficiency in sport (REDs) is linked to low energy availability, menstrual disturbances (MD) and low bone mineral density (BMD; Z-score < -1.0). The prevalence of these symptoms across sports and their interrelationships requires further investigation. This study aimed to 1) investigate the prevalence of severe MD and low BMD among athletes from different sports, 2) compare BMD Z-scores at lumbar spine, total hip and whole-body between regularly menstruating (RM), severe MD and hormonal contraceptive (HC) users, and 3) examine factors related to BMD among endurance athletes, including menstrual status, athletic caliber and sport-specific loading characteristics. Methods Retrospective analysis of cross-sectional data from seven projects included 411 women from 34 sports (endurance: n = 257; non-endurance: n = 154). BMD was assessed using dual-energy X-ray absorptiometry. Menstrual status was defined by the three-step method, cycle tracking or questionnaire, and categorized as RM, severe MD or HC. Endurance sports were further grouped by loading characteristics (very low, low and medium). Results Among non-HC users (51%), the prevalence of severe MD was 37% in endurance, 34% in ball sport and 36% in power- and technical- sports. BMD was not different between menstrual status groups at either lumbar spine ( P = 0.334), total hip ( P = 0.079) or whole-body ( P = 0.164). Endurance athletes had lower lumbar spine BMD Z-scores than non-endurance athletes (-0.0 ± 1.0 vs 1.2 ± 1.2, P < 0.0001), with a higher prevalence of low BMD (17% vs 2%, P = 0.015). Total hip BMD Z-scores were lower in endurance than non-endurance athletes (0.6 ± 0.9 vs 1.4 ± 1.2, P < 0.05 for age < 27). Among endurance athletes, neither loading characteristics nor athletic caliber were associated with BMD. However, endurance athletes with severe MD had lower total hip BMD Z-scores compared to RM athletes ( P = 0.008) and HC users ( P = 0.021). Conclusions The prevalence of severe MD did not differ between sport types. Overall, BMD Z-scores did not differ across menstrual status categories. However, endurance athletes had lower BMD, with total hip BMD being lower in those with severe MD. Heterogenous menstrual assessment methods across the projects included in this study may have impacted the results. Future research should integrate comprehensive REDs assessments including detailed data on menstrual status, training history, bone-loading impact and injuries in female athletes from different sports.
Kristiansson, Emilia; Holmäng, Agneta; Wallenius, Kristina; Chung, H. Sophia; Hess, Sonja & Pettersson, Stefan [Show all 8 contributors for this article] (2026). Circulating protein biomarkers of physical fitness associated with cardiometabolic risk in women after gestational diabetes: a PONCH study. Cardiovascular Diabetology. 25(1). doi: 10.1186/s12933-026-03120-4. Full text in Research Archive
Taylor, Madison; Docter, Heleen; Madsen, Klavs; Tjernes, Vilde Sophie Sogn; Welde, Boye & Morseth, Bente [Show all 10 contributors for this article] (2025). The Influence of Menstrual Cycle Phase on the Physiological and Perceptual Responses to Low‐Intensity Continuous and High‐Intensity Interval Sessions in Endurance Trained Women: The FENDURA Project. European Journal of Sport Science (EJSS). ISSN 1746-1391. 26(1). doi: 10.1002/ejsc.70078. Full text in Research Archive Show summary
ABSTRACT The influence of the menstrual cycle (MC) on the acute responses to endurance training remains unclear. This study aimed to investigate the effect of the MC on the physiological and perceptual responses to standardized low‐intenstiy continuous (LIT) and high‐intensity interval sessions (HIT). Naturally menstruating endurance‐trained women performed a standardized LIT ( n = 23) and/or HIT ( n = 23) session during the early‐follicular (EFP), ovulatory (OP), and mid‐luteal (MLP) phases of 2 MCs. Physiological (i.e., oxygen uptake (O 2 ), heart rate (HR), and blood lactate concentration (BLa)) and perceptual variables (i.e., rating of perceived exertion (RPE) and mood state) were measured. MC phases were determined using urinary ovulation kits and verified with serum hormone analysis. Non‐eumenorrheic MCs were excluded from analysis. During LIT and HIT, ventilation (VE) was higher in MLP than OP ( p < 0.001) and BLa was slightly higher in EFP than OP (LIT, p = 0.004, HIT, p = 0.001). During HIT, O 2 ( p = 0.025) and HR ( p = 0.036) were slightly higher during MLP than OP. RPE was slightly higher in EFP than OP in the LIT ( p = 0.036) and HIT ( p < 0.001). Vigor ( p < 0.001) and tension ( p = 0.036) were highest in EFP. No phase by time interactions were observed for any of the outcome variables throughout either session type ( p > 0.05). MC phase had a modest effect on several physiological and perceptual measures during LIT and HIT. However, the between‐phase differences were small and no clear trends emerged across variables to indicate that the overall demands of a LIT or HIT session would be substantially altered in any one particular MC phase.
Lundervold, Anders; Ellison, Matthew; Madsen, Klavs; Werkhausen, Amelie & Rice, Hannah (2024). Altered trunk-pelvis kinematics during load carriage with a compliant versus a rigid system. Ergonomics. ISSN 0014-0139. doi: 10.1080/00140139.2024.2390125. Full text in Research Archive Show summary
Load carriage is a key component of hiking and military activity. The design of the load carriage system (LCS) could influence performance and injury risk. This study aimed to compare a traditional and a compliant LCS during walking and a step-up task to quantify differences in oxygen consumption and trunk-pelvis kinematics. Fourteen participants completed the tasks whilst carrying 16 kg in a rigid and a compliant LCS. There were no differences in oxygen consumption between conditions during either task (p > 0.05). There was significantly greater trunk-pelvis axial rotation (p = 0.041) and lateral flexion (p = 0.001) range of motion when carrying the compliant LCS during walking, and significantly greater trunk-pelvis lateral flexion range of motion during the step-up task (p = 0.003). Carrying 16 kg in a compliant load carriage system results in greater lateral flexion range of motion than a traditional, rigid system, without influencing oxygen uptake.
Lassen, Tue AH; Lindstrøm, Lars; Lønbro, Simon & Madsen, Klavs (2021). Increased Performance in Elite Runners Following Individualized Timing of Sodium Bicarbonate Supplementation. International Journal of Sport Nutrition & Exercise Metabolism. ISSN 1526-484X. 31(6), p. 453–459. doi: 10.1123/ijsnem.2020-0352. Full text in Research Archive Show summary
The present study investigated individualized sodium bicarbonate (NaHCO3−) supplementation in elite orienteers and its effects on alkalosis and performance in a simulated sprint orienteering competition. Twenty-one Danish male and female elite orienteers (age = 25.2 ± 3.6 years, height = 176.4 ± 10.9 cm, body mass = 66.6 ± 7.9 kg) were tested twice in order to identify individual time to peak blood bicarbonate (HCO3− peak) following supplementation of 0.3 g/kg body mass NaHCO3 with and without warm-up. The athletes also performed two 3.5 km time-trial runs (TT-runs) following individualized timing of NaHCO3 supplementation (SBS) or placebo (PLA) on separate days in a randomized, double-blind, cross-over design. The occurrence of individual peak HCO3− and pH ranged from 60 to 180 min. Mean HCO3− and pH in SBS were significantly higher compared with PLA 10 min before and following the TT-run (p < .01). SBS improved overall performance in the 3.5 km TT-run by 6 s compared with PLA (775.5 ± 16.2 s vs. 781.4 ± 16.1 s, respectively; p < .05). SBS improved performance in the last half of the TT-run compared with PLA (p < .01). In conclusion, supplementation with NaHCO3 followed by warm-up resulted in individualized alkalosis peaks ranging from 60 to 180 min. Individualized timing of SBS in elite orienteers induced significant alkalosis before and after a 3.5 km TT and improved overall performance time by 6 s, which occurred in the last half of the time trial. The present data show that the anaerobic buffer system is important for performance in these types of endurance events lasting 12–15 min.
Pettersson, Stefan; Edin, Fredrik; Hjelte, Carl; Scheinost, David; Wagner, Sandro & Ekblom, Björn [Show all 9 contributors for this article] (2021). Six Weeks of Aerobic Exercise in Untrained Men With Overweight/Obesity Improved Training Adaptations, Performance and Body Composition Independent of Oat/Potato or Milk Based Protein-Carbohydrate Drink Supplementation. Frontiers in Nutrition. 8. doi: 10.3389/fnut.2021.617344. Full text in Research Archive Show summary
Background: Protein availability around aerobic exercise might benefit aerobic capacity and body composition in normal weight adults. However, it is unknown if individuals with overweight/obesity elicit similar adaptations or improve other cardiometabolic/health-related markers in response to different types of protein. Thus, our aim was to study the effect of supplementation of two different protein drinks in conjunction with exercise on aerobic capacity, body composition and blood health markers in untrained subjects with overweight or obesity. Methods: The present study measured training adaptation and health parameters over a 6 week period in untrained men with overweight/obesity (n = 28; BMI 30.4 ± 2.2 kg/m2) ingesting either plant- (Oat/Potato; n = 8) or animal-based (Milk; n = 10) protein-carbohydrate drinks (10 g of protein/serving), or a control carbohydrate drink (n = 10) acutely before and after each training session (average three sessions/week @ 70% HRmax). Pre-post intervention V˙O2peak, muscle biopsies and blood samples were collected, body composition measured (DXA) and two different exercise tests performed. Body weight was controlled with participants remaining weight stable throughout the intervention. Results: For the groups combined, the training intervention significantly increased V˙O2peak (8%; P < 0.001), performance in a time-to-exhaustion trial (~ 100%; P < 0.001), mitochondrial protein content and enzyme activity (~20–200%). Lean body mass increased (1%; P < 0.01) and fat mass decreased (3%; P < 0.01). No significant effects on fasting blood glucose, insulin, lipids or markers of immune function were observed. There were no significant interactions between drink conditions for training adaptation or blood measurements. For body composition, the Oat/Potato and carbohydrate group decreased leg fat mass significantly more than the Milk group (interaction P < 0.05). Conclusions: Aerobic capacity and body composition were improved and a number of mitochondrial, glycolytic and oxidative skeletal muscle proteins and enzyme activities were upregulated by a 6 week training intervention. However, none of the parameters for endurance training adaptation were influenced by protein supplementation before and after each training session.
Hansen, Mette; Oxfeldt, Mikkel; Larsen, Anne E.; Thomsen, Lise S.; Rokkedal-Lausch, Torben & Christensen, Britt [Show all 11 contributors for this article] (2020). Supplement with whey protein hydrolysate in contrast to carbohydrate supports mitochondrial adaptations in trained runners. Journal of the International Society of Sports Nutrition (JISSN). 17. doi: 10.1186/s12970-020-00376-3. Full text in Research Archive Show summary
Background: Protein supplementation has been suggested to augment endurance training adaptations by increasing mixed muscle and myofibrillar protein synthesis and lean body mass. However, a potential beneficial effect on mitochondrial adaptations is yet to be clarified. The aim of the present study was to investigate the effect of consuming whey protein hydrolysate before and whey protein hydrolysate plus carbohydrate (PRO-CHO) after each exercise session during a six-week training period compared to similarly timed intake of isocaloric CHO supplements on biomarkers of mitochondrial biogenesis, VO2max and performance in trained runners. Methods: Twenty-four trained runners (VO2max 60.7 ± 3.7 ml O2 kg− 1 min1) completed a six-week block randomized controlled intervention period, consisting of progressive running training. Subjects were randomly assigned to either PRO-CHO or CHO and matched in pairs for gender, age, VO2max, training and performance status. The PRO-CHO group ingested a protein beverage (0.3 g kg− 1) before and protein-carbohydrate beverage (0.3 g protein kg− 1 and 1 g carbohydrate kg− 1) after each exercise session. The CHO group ingested an energy matched carbohydrate beverage. Resting muscle biopsies obtained pre and post intervention were analyzed for mitochondrial specific enzyme activity and mitochondrial protein content. Subjects completed a 6 K time trial (6 K TT) and a VO2max test pre, midway (only 6 K TT) and post intervention. Results: Following six weeks of endurance training Cytochrome C (Cyt C) protein content was significantly higher in the PRO-CHO group compared to the CHO group (p < 0.05), with several other mitochondrial proteins (Succinate dehydrogenase (SDHA), Cytochrome C oxidase (COX-IV), Voltage-dependent anion channel (VDAC), Heat shock protein 60 (HSP60), and Prohibitin (PHB1)) following a similar, but non-significant pattern (p = 0.07–0.14). β-hydroxyacyl-CoA dehydrogenase (HAD) activity was significantly lower after training in the CHO group (p < 0.01), but not in the PRO-CHO group (p = 0.24). VO2max and 6 K TT was significantly improved after training with no significant difference between groups. Conclusion: Intake of whey PRO hydrolysate before and whey PRO hydrolysate plus CHO after each exercise session during a six-week endurance training period may augment training effects on specific mitochondrial proteins compared to intake of iso-caloric CHO but does not alter VO2max or 6 K TT performance.
Riis, Simon; Møller, Andreas Buch; Dollerup, Ole; Høffner, Line; Jessen, Niels & Madsen, Klavs (2019). Acute and sustained effects of a periodized carbohydrate intake using the sleep‐low model in endurance‐trained males. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 29(12), p. 1866–1880. doi: 10.1111/sms.13541. Full text in Research Archive Show summary
Repeated periodization of carbohydrate (CHO) intake using a diet‐exercise strat-egy called the sleep‐low model can potentially induce mitochondrial biogenesis and improve endurance performance in endurance‐trained individuals. However, more studies are needed to confirm the performance‐related effects and to investigate the sustained effects on maximal fat oxidation (MFO) rate and proteins involved in in-tramuscular lipid metabolism. Thirteen endurance‐trained males (age 23‐44 years; ̇VO2‐max, 63.9 ± 4.6 mL·kg−1·min−1) were randomized into two groups: sleep‐low (LOW‐CHO) or high CHO availability (HIGH‐CHO) in three weekly training blocks over 4 weeks. The acute metabolic response was investigated during 60 min-utes of exercise within the last 3 weeks of the intervention. Pre‐ and post‐interven-tion, 30‐minute time‐trial performance was investigated after a 90‐minute pre‐load, which as a novel approach included nine intense intervals (and estimation of MFO). Additionally, muscle biopsies (v. lateralis) were obtained to investigate expres-sion of proteins involved in intramuscular lipid metabolism using Western blotting. During acute exercise, average fat oxidation rate was ~36% higher in LOW‐CHO compared to HIGH‐CHO (P = .03). This did not translate into sustained effects on MFO. Time‐trial performance increased equally in both groups (overall time effect: P = .005). We observed no effect on intramuscular proteins involved in lipolysis (ATGL, G0S2, CGI‐58, HSL) or fatty acid transport and β‐oxidation (CD‐36 and HAD, respectively). In conclusion, the sleep‐low model did not induce sustained effects on MFO, endurance performance, or proteins involved in intramuscular lipid metabolism when compared to HIGH‐CHO. Our study therefore questions the trans-ferability of acute effects of the sleep‐low model to superior sustained adaptations.
Sollie, Ove; Jeppesen, Per Bendix; Tangen, Daniel S.; Jernerén, Fredrik; Nellemann, Birgitte & Valsdottir, Thorhildur [Show all 12 contributors for this article] (2018). Protein intake in the early recovery period after exhaustive exercise improves performance the following day. Journal of applied physiology. ISSN 8750-7587. 125(6), p. 1731–1742. doi: 10.1152/japplphysiol.01132.2017. Full text in Research Archive Show summary
The aim of the present study was to investigate the effect of protein and carbohydrate ingestion during early recovery from exhaustive exercise on performance after 18-h recovery. Eight elite cyclists (V̇o2max: 74.0 ± 1.6 ml·kg−1·min−1) completed two exercise and diet interventions in a double-blinded, randomized, crossover design. Participants cycled first at 73% of V̇o2max (W73%) followed by 1-min intervals at 90% of V̇o2max until exhaustion. During the first 2 h of recovery, participants ingested either 1.2 g carbohydrate·kg−1·h−1 (CHO) or 0.8 g carbohydrate + 0.4 g protein·kg−1·h−1 (CHO + PROT). The diet during the remaining recovery period was similar for both interventions and adjusted to body weight. After an 18-h recovery, cycling performance was assessed with a 10-s sprint test, 30 min of cycling at W73%, and a cycling time trial (TT). The TT was 8.5% faster (41:53 ± 1:51 vs. 45:26 ± 1:32 min; P < 0.03) after CHO + PROT compared with CHO. Mean power output during the sprints was 3.7% higher in CHO + PROT compared with CHO (1,063 ± 54 vs. 1,026 ± 53 W; P = 0.01). Nitrogen balance in the recovery period was negative in CHO and neutral in CHO + PROT (−82.4 ± 11.5 vs. 7.0 ± 15.4 mg/kg; P < 0.01). In conclusion, TT and sprint performances were improved 18 h after exhaustive cycling by CHO + PROT supplementation during the first 2 h of recovery compared with isoenergetic CHO supplementation. Our results indicate that intake of carbohydrate plus protein after exhaustive endurance exercise more rapidly converts the body from a catabolic to an anabolic state than carbohydrate alone, thus speeding recovery and improving subsequent cycling performance.

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Published Oct. 17, 2023 1:11 PM - Last modified Dec. 13, 2023 2:34 PM