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  • 1. Alkner, B.
    et al.
    Norrbrand, Lena
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Tesch, P.
    Neuromuscular adaptations following 90 days bed rest with or without resistance exercise.2016In: Aerospace Medicine and Human Performance, ISSN 2375-6322, Vol. 87, no 7, p. 610-617Article in journal (Refereed)
  • 2. 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)
  • 3. Alkner, Björn
    et al.
    Norrbrand, Lena
    Karolinska Institutet.
    Tesch, Per
    Effects of 90 d bed rest with or without resistance exercise on knee extensor muscle fatigue2004In: 25th Annual International Gravitational Physiology Meeting, 2004Conference paper (Refereed)
  • 4. Alkner, Björn
    et al.
    Norrbrand, Lena
    Karolinska Institutet.
    Tesch, Per
    Knee extensor and plantar flexor muscle size and function in response to 90 d bed rest with or without resistance exercise2004In: 7th Scandinavian Congress on Medicine and Science in Sports, 2004Conference paper (Refereed)
  • 5. Broman, Gi
    et al.
    Jonsson, Lena
    Stockholm University College of Physical Education and Sports.
    Kaijser, Lennart
    Golf: a high intensity interval activity ofor elderly men2004In: Aging Clinical and Experimental Research, ISSN 1594-0667, E-ISSN 1720-8319, Vol. 16, no 5, p. 375-381Article in journal (Refereed)
    Abstract [en]

    Background and aims: The aim was to quantify the time spent at different exercise intensities for male golfers, in relation to age, while walking a "normal' 18-hole golf course. Methods: 19 healthy male golfers (six 27 (5) years old, seven of 50 (7) and six of 75 (4) years) performed a maximal exercise test on a treadmill (maximal oxygen uptake and maximal heart rate were measured). Within one week, they played an "average" 18-hole course starting at 7.00 a.m. During the round, their heart rate was monitored with a Polar Vantage heart rate monitor, which sampled the heart rate every 5 seconds. Body weight was measured before and after the round. Blood glucose was taken at rest before the round and after each 3rd hole. Perceived exertion and perceived pain in muscles and joints were rated using the CR 10 Borg scale just before reaching each green and after a few selected uphill parts of the course. Results: High intensity of exercise was reached during 6% of the total playing time for the young, 30% for the middle-aged and 70% for the elderly golfers, playing 18 holes (p<0.05). The golfers’ heart rate was below 50% of their individual maximal heart rate, 18% of total time for young golfers, 16% for the middle-aged, and not at all for the elderly. Perceived exertion, breathlessness and leg fatigue were rated in a similar manner for all three groups. Perceived pain in joints and muscles was rated extremely weak except in a few players who had some known joint or muscle problem. The mean blood glucose level fell by 20% for the young (p<0.05), 10% for the middle-aged and 30% for the elderly players (p<0.05) after 18 holes of play. Body weight was reduced 0.7% similarly for all three groups (p<0.05). Conclusions: Walking an 18-hole golf course corresponds to an exercise intensity which is moderate and high for the elderly, mainly low to moderate for the middle-aged, and low for young male golfers. All golfers, regardless of age, perceived their exertion similarly as weak to moderate.

  • 6. Fluckey, Jim
    et al.
    Norrbrand, Lena
    Karolinska Institutet.
    Pozzo, Marco
    Smith, L.
    Tesch, Per
    Acute insulin is not necessary for post exercise elevations of muscle protein synthesis after 5 weeks of resistance exercise training2006Conference paper (Refereed)
  • 7.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Norrbrand, Lena
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Effekt av gasdensitet på ventilation och arteriell oxygenmättnad vid normobar och hypobar hypoxi2016Conference paper (Refereed)
  • 8.
    Jönsson, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Munkhammar, Tobias
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Norrbrand, Lena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Berg, Hans E
    Karolinska Institutet.
    Foot centre of pressure and ground reaction force during quadriceps resistance exercises; a comparison between force plates and a pressure insole system.2019In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 87, p. 206-210, article id S0021-9290(19)30182-4Article in journal (Refereed)
    Abstract [en]

    The study compared the centre of pressure measurements (COP) and vertical ground reaction forces (vGRF) from a pressure insole system to that from force plates (FP) during two flywheel quadriceps resistance exercises: leg press and squat. The comparison was performed using a motion capture system and simultaneous measurements of COP and vGRF from FP and insoles. At lower insole-vGRF (<250 N/insole) COP accuracy deteriorated and those data were excluded from further analysis. The insoles systematically displaced the COP slightly posteriorly and medially compared to the FP measurements. Pearson's coefficient of correlation (r) between insole- and FP-COP showed good agreement in both the anteroposterior (squat: r = 0.96, leg press: r = 0.97) and mediolateral direction (squat: r = 0.84, leg press: r = 0.90), whereas the root-mean-square errors (RMSE) were lower in the mediolateral (squat: 3.9 mm, leg press: 4.5 mm) than the anteroposterior (squat and leg press: 11.8 mm) direction. Vertical GRF was slightly overestimated by the insoles in leg press and RMSE were greater in leg press (8% of peak force) than in squat (6%). Overall, results were within the range of previous studies performed on gait. The strong agreement between insole and FP measurements indicates that insoles may replace FPs in field applications and biomechanical computations during resistance exercise, provided that the applied force is sufficient.

  • 9.
    Keramidas, Michail E.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Siebenmann, Christoph
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Norrbrand, Lena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Gadefors, Magnus
    Mil Acad Karlberg, Stockholm, Sweden..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    A brief pre-exercise nap may alleviate physical performance impairments induced by short-term sustained operations with partial sleep deprivation - A field-based study2018In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 35, no 10, p. 1464-1470Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to evaluate the recuperative efficacy of pre-exercise napping on physical capacity after military sustained operations (SUSOPS) with partial sleep deprivation. Before and after a 2-day SUSOPS, 61 cadets completed a battery of questionnaires, and performed a 2-min lunges trial and a 3,000-m running time-trial. After the completion of SUSOPS, subjects were randomized to either a control [without pre-exercise nap (CON); n = 32] or a nap [with a 30-min pre-exercise nap (NAP); n = 29] group. SUSOPS enhanced perceived sleepiness and degraded mood in both groups. Following SUSOPS, the repetitions of lunges, in the CON group, were reduced by similar to 2.3%, albeit the difference was not statistically significant (p = 0.62). In the NAP group, however, the repetitions of lunges were increased by similar to 7.1% (p = 0.01). SUSOPS impaired the 3,000-m running performance in the CON group (similar to 2.3%; p = 0.02), but not in the NAP group (0.3%; p = 0.71). Present results indicate, therefore, that a relatively brief pre-exercise nap may mitigate physical performance impairments ensued by short-term SUSOPS.

  • 10.
    Machado-Moreira, Christiano
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Norrbrand, Lena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Thermoregulation upon transition from exercise in a warm environment to exposure to a markedly cold environment; effects of a ventilated vest2018In: Proceedings from Physiology and Pharmacology Annual Scientific Meeting, 2018, 2018Conference paper (Refereed)
  • 11.
    Norrbrand, Lena
    Mittuniversitetet, Institutionen för Hälsovetenskap.
    Acute and early chronic responses to resistance exercise using flywheel or weights2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Resistance exercise using weights typically offers constant external load during coupled shortening (concentric) and lengthening (eccentric) muscle actions in sets of consecutive repetitions until failure. However, the constant external load and the inherent capability of skeletal muscle to produce greater force in the eccentric compared with the concentric action, would infer that most actions are executed with incomplete motor unit involvement. In contrast, use of the inertia of flywheels to generate resistance allows for maximal voluntary force to be produced throughout the concentric action, and for brief episodes of greater eccentric than concentric loading, i.e. “eccentric overload”. Thus, it was hypothesized that acute flywheel resistance exercise would induce greater motor unit and muscle use, and subsequent fatigue, compared with traditional weight stack/free weight resistance exercise. Furthermore, it was hypothesized that flywheel training would induce more robust neuromuscular adaptations compared with training using weights.

    A total of 43 trained and untrained men were investigated in these studies. Knee extensor muscle activation, fatigue response and muscle use were assessed during exercises by recording electromyographic signals and by means of functional magnetic resonance imaging, respectively. Flywheel resistance exercise provoked maximal or near maximal muscle activation from the first repetition, induced robust fatigue, and prompted more substantial motor unit and muscle use than weight stack/free weight resistance exercise in both novice and resistance trained men. Both prior to and following five weeks of unilateral knee extension training, the eccentric muscle activation was greater with flywheel than weight stack training. Furthermore, weight stack training generated greater increases of dynamic strength and neural adaptations, while flywheel training generated more prominent hypertrophy of individual quadriceps muscles and greater improvement of maximal isometric strength.

    Hence, due to the preferential metabolic cost of the concentric rather than eccentric actions, the maximal activation through the entire range of the concentric action within each repetition of a set during flywheel resistance exercise probably evoked the marked fatigue, and prompted more substantial muscle use than resistance exercise using weights. Furthermore, while any cause-effect relationship remains to be determined, results of the present study suggest that brief episodes of “eccentric overload” amplify muscular adaptations following concentric-eccentric resistance training.

  • 12.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Ekberg, Annelie
    Alkner, Björn
    Tesch, Per A.
    Hamstrings muscle atrophy following 35-89 days of unloading2008In: 13th Annual Congress of the European College of Sport Science, 2008Conference paper (Refereed)
  • 13.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Fluckey, James D
    Pozzo, Marco
    Tesch, Per A
    Resistance training using eccentric overload induces early adaptations in skeletal muscle size2008In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 102, no 3, p. 271-281Article in journal (Refereed)
    Abstract [en]

    Fifteen healthy men performed a 5-week training program comprising four sets of seven unilateral, coupled concentric-eccentric knee extensions 2-3 times weekly. While eight men were assigned to training using a weight stack (WS) machine, seven men trained using a flywheel (FW) device, which inherently provides variable resistance and allows for eccentric overload. The design of these apparatuses ensured similar knee extensor muscle use and range of motion. Before and after training, maximal isometric force (MVC) was measured in tasks non-specific to the training modes. Volume of all individual quadriceps muscles was determined by magnetic resonance imaging. Performance across the 12 exercise sessions was measured using the inherent features of the devices. Whereas MVC increased (P < 0.05) at all angles measured in FW, such a change was less consistent in WS. There was a marked increase (P < 0.05) in task-specific performance (i.e., load lifted) in WS. Average work showed a non-significant 8.7% increase in FW. Quadriceps muscle volume increased (P < 0.025) in both groups after training. Although the more than twofold greater hypertrophy evident in FW (6.2%) was not statistically greater than that shown in WS (3.0%), all four individual quadriceps muscles of FW showed increased (P < 0.025) volume whereas in WS only m. rectus femoris was increased (P < 0.025). Collectively the results of this study suggest more robust muscular adaptations following flywheel than weight stack resistance exercise supporting the idea that eccentric overload offers a potent stimuli essential to optimize the benefits of resistance exercise.

  • 14.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Johannesson, Björn
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Extensive increase of metabolic demand while walking wearing night vision goggles in hilly terrain2017In: Journal of Science and Medicine in Sport, ISSN 1440-2440, E-ISSN 1878-1861, Vol. 20, article id S77Article in journal (Refereed)
    Abstract [en]

    Introduction: The motivation for the foot-borne soldiers to carry out nighttime operations may be to reduce heat strain. We have previously found elevated metabolic demand (+7 %), and hence endogenous heat production, during walking on a flat gravel road in darkness wearing Night Vision Goggles (NVG) compared with wearing a headlamp. The aim of the present study was to evaluate the effect of wearing NVG while walking in a hilly forest terrain, and compare results between skilled and unskilled NVG users.

    Methods: A group of cadets, i.e. unskilled (5 men, 6 women, age: 23±3 yrs, height: 172±10 cm, weight: 75±12 kg) and skilled NVG users (9 men, age: 26±2 yrs, height: 184±6 cm, weight: 84±5 kg) participated. At night time, subjects walked 1.1 km at a self-selected comfortable pace in a hilly forest, following a trail in the uphill part, and walking on the under bush in the downhill part. Walks were performed wearing either a headlamp (Light), monocular NVG (MNVG), binocular NVG (BNVG), or MNVG and 25 kg extra weight (backpack and body armor). Oxygen uptake, heart rate, rate of perceived exertion and walking speed were measured. To evaluate walking economy, oxygen uptake was expressed in relation to body mass and distance covered (VO2 mL·kg-1·km-1). 

    Results: In both groups, VO2 (mL·kg-1·km-1) was higher in all three conditions with limited vision (MNVG; BNVG; Backpack) than in the Light condition, both during the Uphill (MNVG/BNVG; skilled: +25/+24%, unskilled: +35/+28%) and Downhill part (MNVG/BNVG; skilled: +42/+44%, unskilled: +67/+51%). In the Backpack condition, the inter-group difference in mechanical efficiency was maintained or exaggerated: Uphill (skilled: +46%, unskilled: +80%), Downhill (skilled: +70%, unskilled: +115%). The skilled NVG users walked faster, but there was no difference in heart rate between groups. In the unskilled, heart rate was higher in the MNVG and BNVG than in the Light condition during the Downhill part. Likewise, in the unskilled, the rate of perceived exertion was higher in the MNVG and BNVG than in the Light condition. 

    Conclusions: Despite that in darkness foveal vision is markedly improved by NVG, it appears that the mechanical efficiency during walking in hilly terrain is markedly lower whilst wearing NVG than with full vision, regardless of whether the soldier is a skilled or unskilled NVG user.

  • 15.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Johannesson, Björn
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rappe, A
    Sjölin, J
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Metabolic demand during walking with night vision goggles2014Conference paper (Refereed)
  • 16.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Johannesson, Björn
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rappe, Annika
    Sjölin, Johan
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Walking with night vision goggles increases metabolic demand2014Conference paper (Refereed)
  • 17.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    No association between hand and foot temperature responses during local cold stress and rewarming.2017In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 6, p. 1141-1153Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose was to examine whether associations exist between temperature responses in the fingers vs. toes and hand vs. foot during local cold-water immersion and rewarming phases.

    METHODS: Seventy healthy subjects (58 males, 12 females) immersed their right hand or right foot, respectively, in 8 °C water for 30 min (CWI phase), followed by a 15-min spontaneous rewarming (RW) in 25 °C air temperature.

    RESULTS: Temperature was lower in the toes than the fingers during the baseline phase (27.8 ± 3.0 vs. 33.9 ± 2.5 °C, p < 0.001), parts of the CWI phase (min 20-30: 8.8 ± 0.7 vs. 9.7 ± 1.4 °C, p < 0.001), and during the RW phase (peak temperature: 22.5 ± 5.1 vs. 32.7 ± 3.6 °C, p < 0.001). Cold-induced vasodilatation (CIVD) was more common in the fingers than in the toes (p < 0.001). Within the first 10 min of CWI, 61% of the subjects exhibited a CIVD response in the fingers, while only 6% of the subjects had a CIVD response in the toes. There was a large variability of temperature responses both within and between extremities, and there was a weak correlation between finger- and toe temperature both during the CWI (r = 0.21, p = 0.08) and the RW phases (r = 0.26, p = 0.03).

    CONCLUSIONS: Results suggest that there is generally a lower temperature in the toes than the fingers after a short time of local cold exposure and that the thermal responses of the fingers/hands are not readily transferable to the toes/foot.

  • 18.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Pozzo, Marco
    Tesch, Per
    EMG activity of eccentric quadriceps muscle actions is greater during flywheel than weight stack training2009In: 14th Annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 2009Conference paper (Refereed)
  • 19.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Pozzo, Marco
    Tesch, Per A.
    Changes in quadriceps muscle volume and strength following 5 weeks of resistance training using a flywheel device vs. gravity dependent weights2005In: European Space Biomedicine Congress and Exhibition, 2005Conference paper (Refereed)
  • 20.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Pozzo, Marco
    Tesch, Per A
    Flywheel resistance training calls for greater eccentric muscle activation than weight training2010In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 110, no 5, p. 997-1005Article in journal (Refereed)
    Abstract [en]

    Changes in muscle activation and performance were studied in healthy men in response to 5 weeks of resistance training with or without "eccentric overload". Subjects, assigned to either weight stack (grp WS; n = 8) or iso-inertial "eccentric overload" flywheel (grp FW; n = 9) knee extensor resistance training, completed 12 sessions of four sets of seven concentric-eccentric actions. Pre- and post-measurements comprised maximal voluntary contraction (MVC), rate of force development (RFD) and training mode-specific force. Root mean square electromyographic (EMG(RMS)) activity of mm. vastus lateralis and medialis was assessed during MVC and used to normalize EMG(RMS) for training mode-specific concentric (EMG(CON)) and eccentric (EMG(ECC)) actions at 90°, 120° and 150° knee joint angles. Grp FW showed greater (p < 0.05) overall normalized angle-specific EMG(ECC) of vastii muscles compared with grp WS. Grp FW showed near maximal normalized EMG(CON) both pre- and post-training. EMG(CON) for Grp WS was near maximal only post-training. While RFD was unchanged following training (p > 0.05), MVC and training-specific strength increased (p < 0.05) in both groups. We believe the higher EMG(ECC) activity noted with FW exercise compared to standard weight lifting could be attributed to its unique iso-inertial loading features. Hence, the resulting greater mechanical stress may explain the robust muscle hypertrophy reported earlier in response to flywheel resistance training.

  • 21.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Pozzo, Marco
    Tesch, Per A.
    Jämförelse av träningseffekter efter 5 veckors styrketräning med två olika belastningsstrategier2005In: Svenska Läkaresällskapets Riksstämma: Stockholm, 2005Conference paper (Refereed)
  • 22.
    Norrbrand, Lena
    et al.
    Karolinska Institutet.
    Tous-Fajardo, Julio
    Tesch, Per
    The Squat: Iso-inertial resistance exercise promotes greater quadriceps muscle use than the barbell exercise2006In: 11th annual Congress of the European College of Sport Science, 2006Conference paper (Refereed)
  • 23.
    Norrbrand, Lena
    et al.
    Karolinska Institutet, Department of Physiology and Phamacology.
    Tous-Fajardo, Julio
    Vargas, Roberto
    Tesch, Per A.
    Quadriceps muscle use in the flywheel and barbell squat2011In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 82, no 1, p. 13-19Article in journal (Refereed)
    Abstract [en]

    Background: Resistance exercise has been proposed as an aid to counteract quadriceps muscle atrophy in astronauts during extended missions in Orbit. While space authorities have advocated the squat exercise should be prescribed, no exercise system suitable for in-flight use has been validated with regard to quadriceps muscle use. We compared muscle involvement in the terrestrial “gold standard” squat using free weights and a non-gravity dependent flywheel resistance exercise device aimed at use in space. Methods: Ten strength-trained men performed five sets of 10 repetitions using the Barbell Squat (BS; 10 repetition maximum) or Flywheel Squat (FS; each repetition maximal), respectively. Functional magnetic resonance imaging (MRI) and surface electromyography (EMG) techniques assessed quadriceps muscle use. Exercise-induced contrast shift of MR images was measured by means of transverse relaxation time (T2). EMG root mean square (RMS) was measured during concentric (CON) and eccentric (ECC) actions and normalized to EMG RMS determined during maximal voluntary contraction. Results: The quadriceps muscle group showed greater exercise-induced T2 increase following FS compared with BS. Among individual muscles, the rectus femoris displayed greater T2 increase with FS (+24±14%) than BS (+8±4%). Normalized quadriceps EMG showed no difference across exercise modes. Discussion: Collectively, the results of this study suggest that quadriceps muscle use in the squat is comparable, if not greater, with flywheel compared with free weight resistance exercise. Data appears to provide support for use of flywheel squat resistance exercise as a countermeasures adjunct during spaceflight.

  • 24. Pozzo, Marco
    et al.
    Alkner, Björn
    Norrbrand, Lena
    Karolinska Institutet.
    Farina, Dario
    Tesch, Per
    Muscle fiber conduction velocity during dynamic fatiguing exercise on a flywheel exercise device2005In: 26th Annual International Gravitational Physiology Meeting, 2005Conference paper (Refereed)
  • 25. Pozzo, Marco
    et al.
    Alkner, Björn
    Norrbrand, Lena
    Karolinska Institutet.
    Farina, Dario
    Tesch, Per A.
    Muscle fiber conduction and fatigue during dynamic actions on a flywheel exercise device2005In: Journal of Gravitational Physiology, ISSN 1077-9248, Vol. 12, no 1, p. 113-114Article in journal (Refereed)
    Abstract [en]

    Exposure to microgravity has adverse effects on skeletal muscle size and function. Such effects can be counteracted by training using a Flywheel Exercise Device (FWED). Multichannel EMG signals were detected in nine males from vastus medialis and laterialis muscles during 30 coupled concentric (CON) and eccentric (ECC) actions on the FWED. Muscle fiber conduction velocity (CV) was assessed for each action. CV initial values depended on muscle action type (CON/ECC) and were higher in CON than ECC actions. CV decreased (P<0.05) over time during the task. Its slope was greater for VL than VM but was not different between CON and ECC. It was concluded that direct measure of CV is feasible during dynamic exercise, and that this technique may be used for objective assessment of the effect of resistance training in counteracting microgravity-induced muscle atrophy.

  • 26. Pozzo, Marco
    et al.
    Alkner, Björn
    Norrbrand, Lena
    Karolinska Institutet.
    Farina, Dario
    Tesch, Per A
    Muscle-fiber conduction velocity during concentric and eccentric actions on a flywheel exercise device2006In: Muscle and Nerve, ISSN 0148-639X, E-ISSN 1097-4598, Vol. 34, no 2, p. 169-177Article in journal (Refereed)
    Abstract [en]

    A gravity-independent flywheel exercise device (FWED) has been proven effective as a countermeasure to loss of strength and muscle atrophy induced by simulated microgravity. This study assessed muscle-fiber conduction velocity (CV) and surface EMG instantaneous mean power spectral frequency (iMNF) during brief bouts of fatiguing concentric (CON) and eccentric (ECC) exercise on a FWED in order to identify electromyographic (EMG) variables that can be used to provide objective indications of muscle status when exercising with a FWED. Multichannel surface EMG signals were recorded from vastus lateralis and medialis muscles of nine men during: (1) isometric, 60-s action at 50% of maximum voluntary action (MVC); (2) two isometric, linearly increasing force ramps (0-100% MVC); and (3) dynamic CON/ECC coupled actions on the FWED. Muscle-fiber CV and iMNF were computed over time during the three tasks. During ramps, CV, but not iMNF, increased with force (P < 0.001). Conduction velocity and iMNF decreased with the same normalized rate of change in constant-force actions. During CON/ECC actions, the normalized rate of change over time was larger for CV than iMNF (P < 0.05). These results suggest that, during fatiguing, dynamic, variable-force tasks, changes in CV cannot be indirectly inferred by EMG spectral analysis. This underlines the importance of measuring both CV and spectral variables for muscle assessment in dynamic tasks.

  • 27. Tous-Fajardo, Julio
    et al.
    Norrbrand, Lena
    Karolinska Institutet.
    Pozzo, Marco
    Tesch, Per
    Quadriceps electromyographic activity during two different squat activities: flywheel multigym vs barbell half-squat2006Conference paper (Refereed)
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