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  • 1. Alkner, Björn
    et al.
    Jonsson, Lena
    Karolinska Institutet.
    Atling, Åsa
    Tesch, Per
    Resistance exercise maintains quadriceps muscle strength and size during 90 d bed rest.2003In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 35, no 5, p. 262-Article in journal (Refereed)
  • 2. Berg, H. E.
    et al.
    Eiken, Ola
    Swedish Defence Research Agency.
    Muscle control in elite alpine skiing1999In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 31, no 7, p. 1065-1067Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose of this study was to determine whether muscle control may be influenced by accelerative forces brought about by the downhill displacement of body mass in combination with the sharp turns during alpine skiing.

    METHODS: Sixteen elite skiers performed either super G (SG), giant slalom (GS), slalom (SL), or freestyle mogul (FM) skiing. Knee and hip joint angles and electromyographic (EMG) activity of the knee extensors were recorded.

    RESULTS: During the course of a turn, the minimum (deepest stance position) knee angle of the outside (main load-bearing) leg ranged from 60 degrees to 100 degrees, where the smallest angle was obtained in the FM event. Among the traditional alpine disciplines, smaller knee angles were obtained in the high-speed events (i.e., knee angle: SG<GS<SL). Knee angular velocity of the outside leg ranged from 15 degrees to 300 degrees x s(-1), with the slower movements in the high-speed disciplines (i.e., knee angular velocity: SG<GS<SL<FM). In all disciplines, EMG activity reached near-maximal levels during the course of a turn. In SG, GS, and SL, but not in FM skiing, a marked predominance of eccentric over concentric muscle actions was observed. The dominance of slow eccentric muscle actions has not been observed in other athletic activities.

    CONCLUSIONS: We believe these results have important implications for the design of specific training models.

  • 3. Berg, H E
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Tesch, P A
    Involvement of eccentric muscle actions in giant slalom racing.1995In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 27, no 12, p. 1666-70Article in journal (Refereed)
    Abstract [en]

    Joint angular movements and muscle activation (EMG), were determined in male elite racers while performing the giant slalom. Movement cycles averaged 3.5 +/- 0.6 s (left plus right turn), and knee angle ranged 66-114 degrees (180 degrees = straight leg). Knee extensor muscle use was dominated (rectified EMG; P < 0.05) by the leg controlling the outside (downhill) ski during the turn. Time spent while decreasing knee angle (eccentric muscle action) of outside leg averaged 1.0 +/- 0.2 s. This phase was longer (P < 0.05) than the average push-off (concentric muscle action) phase of 0.5 +/- 0.1 s. Moreover, EMG activity of the outside leg during eccentric muscle actions exceeded (P < 0.05) that of concentric actions and was similar to that attained during maximum isometric knee extension in laboratory tests. Knee and hip angular movement ranged 20-50 degrees. Average joint velocities equalled 20-40 degrees.s(-1) during the turning phase. Thus, competitive giant slalom skiing is dominated by slow eccentric muscle actions performed at near maximum voluntary force. Because of their greater ability to generate force, eccentric muscle actions may be warranted or even required to resist the G-forces induced during the turn phase.

  • 4. Debevec, T.
    et al.
    Pialoux, V.
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mury, P.
    Millet, G.P.
    Moderate exercise blunts oxidative stress induced by normobaric hypoxic confinement2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 1, p. 33-41Article in journal (Refereed)
    Abstract [en]

    PURPOSE: Both acute hypoxia and physical exercise are known to increase oxidative stress. This randomized prospective trial investigated whether the addition of moderate exercise can alter oxidative stress induced by continuous hypoxic exposure. METHODS: Fourteen male participants were confined to 10-d continuous normobaric hypoxia (FIO2 = 0.139 ± 0.003, PIO2 = 88.2 ± 0.6 mm Hg, ∼4000-m simulated altitude) either with (HCE, n = 8, two training sessions per day at 50% of hypoxic maximal aerobic power) or without exercise (HCS, n = 6). Plasma levels of oxidative stress markers (advanced oxidation protein products [AOPP], nitrotyrosine, and malondialdehyde), antioxidant markers (ferric-reducing antioxidant power, superoxide dismutase, glutathione peroxidase, and catalase), nitric oxide end-products, and erythropoietin were measured before the exposure (Pre), after the first 24 h of exposure (D1), after the exposure (Post) and after the 24-h reoxygenation (Post + 1). In addition, graded exercise test in hypoxia was performed before and after the protocol. RESULTS: Maximal aerobic power increased after the protocol in HCE only (+6.8%, P < 0.05). Compared with baseline, AOPP was higher at Post + 1 (+28%, P < 0.05) and nitrotyrosine at Post (+81%, P < 0.05) in HCS only. Superoxide dismutase (+30%, P < 0.05) and catalase (+53%, P < 0.05) increased at Post in HCE only. Higher levels of ferric-reducing antioxidant power (+41%, P < 0.05) at Post and lower levels of AOPP (-47%, P < 0.01) at Post + 1 were measured in HCE versus HCS. Glutathione peroxidase (+31%, P < 0.01) increased in both groups at Post + 1. Similar erythropoietin kinetics was noted in both groups with an increase at D1 (+143%, P < 0.01), a return to baseline at Post, and a decrease at Post + 1 (-56%, P < 0.05). CONCLUSIONS: These data provide evidence that 2 h of moderate daily exercise training can attenuate the oxidative stress induced by continuous hypoxic exposure.

  • 5. Fondell, Elinor
    et al.
    Lagerros, Ylva Trolle
    Sundberg, Carl Johan
    Lekander, Mats
    Bälter, Olle
    KTH, School of Computer Science and Communication (CSC), Human - Computer Interaction, MDI.
    Rothman, Kenneth J.
    Balter, Katarina
    Physical Activity, Stress, and Self-Reported Upper Respiratory Tract Infection2011In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 43, no 2, p. 272-279Article in journal (Refereed)
    Abstract [en]

    Purpose: Upper respiratory tract infection (URTI) is the most common reason for seeking primary care in many countries. Still, little is known about potential strategies to reduce susceptibility. We investigated the relationships between physical activity level, perceived stress, and incidence of self-reported URTI. Methods: We conducted a population-based prospective cohort study of 1509 Swedish men and women aged 20-60 yr with a follow-up period of 4 months. We used a Web-based questionnaire to assess disease status and lifestyle factors at the start of the study. We assessed physical activity and inactivity as total MET-hours (MET task) per day and perceived stress by the 14-item Perceived Stress Scale. Participants were contacted every 3 wk via e-mail to assess incidence of URTI. They reported a total of 1181 occurrences of URTI. We used Poisson regression models to control for age, sex, and other potential confounding factors. Results: We found that high levels of physical activity (>= 55 MET.h.d(-1)) were associated with an 18% reduced risk (incidence rate ratio (IRR) = 0.82, 95% confidence interval (CI) = 0.69-0.98) of self-reporting URTI compared with low levels of physical activity (< 45 MET.h.d(-1)). This association was stronger among those reporting high levels of stress (IRR = 0.58, 95% CI = 0.43-0.78), especially among men (IRR = 0.37, 95% CI = 0.24-0.59), but absent in the group with low levels of stress. Conclusions: We found that high physical activity was associated with a lower risk of contracting URTI for both men and women. In addition, we found that highly stressed people, particularly men, appear to benefit more from physical activity than those with lower stress levels.

  • 6. Mekjavic, I.B.
    et al.
    Exner, J.A.
    Tesch, P.A.
    Eiken, Ola
    Swedish Defence Research Agency.
    Hyperbaric oxygen therapy does not affect recovery from delayed onset muscle soreness2000In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 32, no 3, p. 558-563Article in journal (Refereed)
    Abstract [en]

    PURPOSE: This study investigated whether hyperbaric oxygen therapy (HBOT) improves recovery after exercise-induced muscle injury.

    METHODS: Healthy male subjects (N = 24) were randomly assigned to either a placebo group or a HBOT group. Subjects were tested for maximal isometric strength (preexercise) of their right elbow flexors. Each subject then completed a high-force eccentric workout of the elbow flexor muscle group to induce delayed onset muscle soreness (DOMS). On the seven successive days after this workout, the subjects were exposed to a hyperbaric environment of 2.5 ATA for 60 min, inspiring either a normoxic mixture (P(I)O2 = 0.2 ATA; placebo group) or a hyperoxic gas mixture (P(I)O2 = 2.5 ATA; HBOT group). Before the eccentric workout and daily for the next 10 d, measurements were obtained regarding: maximal isometric muscle strength of the elbow flexor muscles, right upper arm circumferences, and rating of the perceived muscle soreness.

    RESULTS: Isometric strength decreased significantly from preexercise levels of 25.1 +/- 3.8 kp to postexercise levels of 12.0 +/- 4.6 kp, for the HBOT group, and from 24.6 +/- 3.4 kp to 12.5 +/- 3.7 kp, respectively, for the placebo group. Over the 10-d recovery period, there was no difference in the rate of recovery of muscle strength between the two groups. Perceived soreness peaked at about 48 h after exercise with no difference between groups. Also, the exercise-induced increases in arm circumference were similar in the two groups.

    CONCLUSIONS: These results indicate that HBOT is not an effective therapy for the treatment of DOMS.

  • 7. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Domenis, Rossana
    Mavelli, Irene
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, Igor B.
    Grassi, Bruno
    Combined Effects of Bed Rest and Hypoxia on Skeletal Muscle Oxidative Function2012In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 44, p. 111-111Article in journal (Other academic)
  • 8. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Domenis, Rossana
    Mavelli, Irene
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Grassi, Bruno
    Effects of Hypoxia and Microgravity on Mitochondrial Respiration and Skeletal Muscle Oxidative Function2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 5, p. 297-298Article in journal (Other academic)
  • 9.
    Siebenmann, Christoph
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Hemoglobin Mass Expansion during 13 d of Altitude Training: Altitude or Training?2016In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 48, no 7, p. 1425-1425Article in journal (Refereed)
  • 10. Yamazaki, Junya
    et al.
    Gilgien, Matthias
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    McIntosh, Andrew S.
    Nachbauer, Werner
    Müller, Erich
    Bere, Tone
    Bahr, Roald
    Krosshaug, Tron
    Analysis of a Severe Head Injury in World Cup Alpine Skiing: A Case Report.2015In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 47, no 6, p. 1113-1118Article in journal (Refereed)
    Abstract [en]

    Traumatic brain injury (TBI) is the leading cause of death in alpine skiing. It has been found that helmet use can reduce the incidence of head injuries between 15% and 60%. However, knowledge on optimal helmet performance criteria in World Cup alpine skiing is currently limited owing to the lack of biomechanical data from real crash situations. Purpose: This study aimed to estimate impact velocities in a severe TBI case in World Cup alpine skiing. Methods: Video sequences from a TBI case in World Cup alpine skiing were analyzed using a model-based image matching technique. Video sequences from four camera views were obtained in full high-definition (1080p) format. A three-dimensional model of the course was built based on accurate measurements of piste landmarks and matched to the background video footage using the animation software Poser 4. A trunk-neck-head model was used for tracking the skier's trajectory. Results: Immediately before head impact, the downward velocity component was estimated to be 8 m.s(-1). After impact, the upward velocity was 3 m.s(-1), whereas the velocity parallel to the slope surface was reduced from 33 m.s(-1) to 22 m.s(-1). The frontal plane angular velocity of the head changed from 80 radIsj1 left tilt immediately before impact to 20 rad.s(-1) right tilt immediately after impact. Conclusions: A unique combination of high-definition video footage and accurate measurements of landmarks in the slope made possible a high-quality analysis of head impact velocity in a severe TBI case. The estimates can provide crucial information on how to prevent TBI through helmet performance criteria and design.

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