Kazunori Nosaka

Publications (90)209.39 Total impact

• Source

  Available from: Dale W Chapman

  Article: Eccentric torque-velocity relationship of the elbow flexors

  Dale Chapman, Michael Newton, Kazunori Nosaka
  ECU Publications. 04/2013;
• Source

  Available from: Dale W Chapman

  Article: Effect of Lengthening Contraction Velocity on Muscle Damage of the Elbow Flexors

  Dale Chapman, Michael Newton, Michael Mcguigan, Kazunori Nosaka
  ECU Publications. 04/2013;
• Article: Effects of weighted sled towing with heavy versus light load on sprint acceleration ability.

  Naoki Kawamori, Robert U Newton, Naruhiro Hori, Kazunori Nosaka
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  ABSTRACT: Weighted sled towing is used by athletes to improve sprint acceleration ability. The typical coaching recommendation is to use relatively light loads, as excessively heavy loads are hypothesized to disrupt running mechanics and be detrimental to sprint performance. However, this coaching recommendation has not been empirically tested. This study compared the effects of weighted sled towing with two different external loads on sprint acceleration ability. Twenty-one physically active men were randomly allocated to heavy- (n = 10) or light-load weighted sled towing (n = 11) groups. All subjects participated in two training sessions per week for 8 weeks. The subjects in the heavy and light groups performed weighted sled towing using external loads that reduced sprint velocity by ∼30% and ∼10%, respectively. Before and after the training, the subjects performed a 10-m sprint test, in which split time was measured at 5 and 10 m from the start. The heavy group significantly improved both the 5- and 10-m sprint time by 5.7 ± 5.7% and 5.0 ± 3.5%, respectively (P < 0.05), whereas only 10-m sprint time was improved significantly by 3.0 ± 3.5% (P < 0.05) in the light group. No significant differences were found between the groups in the changes in 5-m and 10-m sprint time from pre- to post-training. These results question the notion that training loads that induce greater than 10% reduction in sprint velocity would negatively affect sprint performance, and point out the potential benefit of using a heavier load for weighted sled towing.
  The Journal of Strength and Conditioning Research 03/2013; · 1.83 Impact Factor
• Article: Effect of two maximal isometric contractions on eccentric exercise-induced muscle damage of the elbow flexors.

  Trevor C Chen, Hsin-Lian Chen, Ming-Ju Lin, Che-Hsiu Chen, Alan J Pearce, Kazunori Nosaka
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  ABSTRACT: This study investigated the time wise protective effect conferred by two maximal voluntary isometric contractions (2MVCs) at 20° elbow flexion on muscle damage induced by 30 maximal isokinetic (60° s(-1)) eccentric contractions of the elbow flexors (MaxECC). Sixty-five young untrained men were randomly assigned to a control group that did not perform 2MVCs, or one of four experimental groups (n = 13 per group) who performed 2MVCs either immediately (0d), 2 (2d), 4 (4d) or 7 days (7d) before MaxECC. Changes in maximal isokinetic (60° s(-1)) concentric torque (MVC-CON), optimum angle (OA), range of motion, upper arm circumference, muscle soreness, plasma creatine kinase activity and myoglobin concentration, and ultrasound echo-intensity following MaxECC were compared among the groups by a two-way repeated measures ANOVA. No significant changes in any variables were evident following 2MVCs. The 2d and 4d groups showed 16-62 % smaller (P < 0.05) changes in all variables following MaxECC than the control, 0d and 7d groups. The 2d group showed 14-34 % smaller (P < 0.05) changes in all variables except for OA compared with the 4d group. The changes in the variables were similar among the control, 0d and 7d groups. These results show that 2MVCs that were performed between 2 and 4 days before MaxECC attenuated the magnitude of muscle damage, but no such effect was evident if the 2MVCs were performed immediately or 7 days before MaxECC. It is concluded that the protective effect conferred by 2MVCs is relatively short-lived, and there is a window for the effect to be conferred.
  Arbeitsphysiologie 01/2013; · 2.15 Impact Factor
• Article: Low-intensity eccentric contractions attenuate muscle damage induced by subsequent maximal eccentric exercise of the knee extensors in the elderly.

  Trevor C Chen, Wei-Chin Tseng, Guan-Ling Huang, Hsin-Lian Chen, Kou-Wei Tseng, Kazunori Nosaka
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  ABSTRACT: This study investigated whether low-intensity eccentric contractions of the knee extensors would attenuate the magnitude of muscle damage induced by maximal eccentric exercise of the same muscle performed 7 days later using elderly individuals. Healthy older men (66.4 ± 4.6 years) were assigned to control or experimental (Exp) group (n = 13 per group). The control group performed six sets of ten maximal eccentric contractions (MaxECC) of the knee extensors of non-dominant leg. The Exp group performed six sets of ten low-intensity eccentric contractions of the knee extensors on a leg extension machine by lowering a weight of 10 % maximal voluntary isometric knee extension strength (10 %ECC) 7 days prior to MaxECC. Changes in maximal voluntary isokinetic concentric torque (MVC-CON), angle at peak torque, range of motion (ROM), upper thigh circumference, muscle soreness, plasma creatine kinase activity and myoglobin (Mb) concentration and B-mode ultrasound echo-intensity before and for 5 days after MaxECC were compared between groups by a mixed factor ANOVA. No significant changes in any variables were observed following 10 %ECC. Following MaxECC, all variables changed significantly, and changes in all variables except for angle at peak torque were significantly different between groups. MVC-CON and ROM decreased smaller and recovered faster (P < 0.05) for Exp than control group, and changes in other variables were smaller (P < 0.05) for Exp group compared with control group. These results suggest that preconditioning knee extensor muscles with low-intensity eccentric contractions was effective for attenuating muscle damage induced by subsequent MaxECC of the knee extensors for elderly individuals.
  Arbeitsphysiologie 10/2012; · 2.15 Impact Factor
• Article: Do dominant and non-dominant arms respond similarly to maximal eccentric exercise of the elbow flexors?

  Michael J Newton, Paul Sacco, Dale Chapman, Kazunori Nosaka
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  ABSTRACT: OBJECTIVES: Two common models to investigate the effect of interventions on muscle damage include using two groups in which one group receives an intervention while the other acts as control, and using contralateral limbs of one group. The latter model is based on the assumption that changes in markers of muscle damage are similar between limbs, but this has not been examined systematically. DESIGN: This study compared changes in muscle damage markers between dominant and non-dominant arms following maximal eccentric exercise of the elbow flexors. METHODS: Eighteen men performed 60 maximal eccentric elbow flexions of each arm separated by 4 weeks with the order of testing between arms randomised. Maximal voluntary isometric torque, range of motion, upper arm circumference, plasma creatine kinase (CK) activity and muscle soreness before and for 7 days following exercise were compared between arms using two-way repeated measures ANOVA. RESULTS: No significant differences between arms were evident for any of the markers, but significant (P<0.05) differences between first and second bouts were evident for changes in strength, circumference and CK with smaller changes following the second bout. A poor correlation was found for the magnitude of changes in the markers between dominant and non-dominant arms, suggesting that responses to eccentric exercise were not necessarily the same between arms. CONCLUSIONS: These results show that the order affected the responses of dominant and non-dominant arms to the eccentric exercise; however, the contralateral limb design appears to be usable if bout order is counterbalanced and randomised among participants.
  Journal of science and medicine in sport / Sports Medicine Australia. 07/2012;
• Article: Attenuation of eccentric exercise-induced muscle damage by preconditioning exercises.

  Trevor Chung-Ching Chen, Hsin-Lian Chen, Alan J Pearce, Kazunori Nosaka
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  ABSTRACT: This study compared the effect of an initial exercise consisting of either low-intensity eccentric or maximal isometric contractions (ISOs) on protective effect against maximal eccentric contraction (MaxECC)-induced muscle damage. Untrained young men were placed into one of five groups (n = 13 per group): MaxECC, 10% ECC, 20% ECC, 90° ISO, and 20° ISO. The MaxECC, 10% ECC, and 20% ECC groups performed 30 ECCs of the elbow flexors using a dumbbell equivalent to 100%, 10%, and 20% of maximal voluntary isometric contraction strength, respectively. The 90° ISO and 20° ISO groups performed 30 ISOs at 90° and 20° of elbow flexion, respectively. Three weeks later, all subjects performed 30 MaxECCs with the arm used for the first bout. Changes in maximal voluntary isometric and concentric contraction strength, range of motion, upper arm circumference, plasma creatine kinase and myoglobin concentration, and muscle soreness before and for 5 d after the first and second exercise bouts were compared among groups by a two-way repeated-measure ANOVA. Changes in all measures after the first bout were smaller (P < 0.05) for 10% ECC, 20% ECC, 90° ISO, and 20° ISO groups compared with MaxECC group, and the changes were smaller (P < 0.05) for 10% ECC and 90° ISO than 20° ISO and 20% ECC groups. When compared with the first bout of MaxECC group, changes in the measures after the second bout were smaller for 20% ECC and 20° ISO groups with greater protective effect evident for 20° ISO group, but the protective effect conferred by these was smaller (P < 0.05) compared with MaxECCs. These results suggest that there is threshold intensity for ECCs to confer protective effect, and ISOs at a long muscle length provide preconditioning effect.
  Medicine and science in sports and exercise 06/2012; 44(11):2090-8. · 3.71 Impact Factor
• Article: Two maximal isometric contractions attenuate the magnitude of eccentric exercise-induced muscle damage.

  Hsin-Lian Chen, Kazunori Nosaka, Alan J Pearce, Trevor C Chen
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  ABSTRACT: This study investigated whether maximal voluntary isometric contractions (MVC-ISO) would attenuate the magnitude of eccentric exercise-induced muscle damage. Young untrained men were placed into one of the two experimental groups or one control group (n = 13 per group). Subjects in the experimental groups performed either two or 10 MVC-ISO of the elbow flexors at a long muscle length (20° flexion) 2 days prior to 30 maximal isokinetic eccentric contractions of the elbow flexors. Subjects in the control group performed the eccentric contractions without MVC-ISO. No significant changes in maximal voluntary concentric contraction peak torque, peak torque angle, range of motion, upper arm circumference, plasma creatine kinase (CK) activity and myoglobin concentration, muscle soreness, and ultrasound echo intensity were evident after MVC-ISO. Changes in the variables following eccentric contractions were smaller (P < 0.05) for the 2 MVC-ISO group (e.g., peak torque loss at 5 days after exercise, 23% ± 3%; peak CK activity, 1964 ± 452 IU·L(-1); peak muscle soreness, 46 ± 4 mm) or the 10 MVC-ISO group (13% ± 3%, 877 ± 198 IU·L(-1), 30 ± 4 mm) compared with the control (34% ± 4%, 6192 ± 1747 IU·L(-1), 66 ± 5 mm). The 10 MVC-ISO group showed smaller (P < 0.05) changes in all variables following eccentric contractions compared with the 2 MVC-ISO group. Therefore, two MVC-ISO conferred potent protective effects against muscle damage, whereas greater protective effect was induced by 10 MVC-ISO, which can be used as a strategy to minimize muscle damage.
  Applied Physiology Nutrition and Metabolism 05/2012; 37(4):680-9. · 2.13 Impact Factor
• Article: Relationships between ground reaction impulse and sprint acceleration performance in team-sport athletes.

  Naoki Kawamori, Kazunori Nosaka, Robert U Newton
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  ABSTRACT: Large horizontal acceleration in short-sprints is a critical performance parameter for many team-sport athletes. It is often stated that producing large horizontal impulse at each ground contact is essential for high short sprint performance, but the optimal pattern of horizontal and vertical impulses is not well understood, especially when the sprints are initiated from a standing start. This study was an investigation of the relationships between ground reaction impulses and sprint acceleration performance from a standing start in team-sport athletes. Thirty physically active young men with team-sport background performed 10-m sprint from a standing start, while sprint time and ground reaction forces were recorded during the first ground contact and at 8 m from the start. Associations between sprint time and ground reaction impulses (normalized to body mass) were determined by a Pearson's correlation coefficient (r) analysis. The 10-m sprint time was significantly (P < 0.01) correlated with net horizontal impulse (r = -0.52) and propulsive impulse (r = -0.66) measured at 8 m from the start. No significant correlations were found between sprint time and impulses recorded during the first ground contact after the start. These results suggest that applying ground reaction impulse in a more horizontal direction is important for sprint acceleration from a standing start. This is consistent with the hypothesis of training to increase net horizontal impulse production using sled towing or using elastic resistance devices, which needs to be validated by future longitudinal training studies.
  The Journal of Strength and Conditioning Research 04/2012; · 1.83 Impact Factor
• Article: Severe hypoxia affects exercise performance independently of afferent feedback and peripheral fatigue.

  Guillaume Y Millet, Makii Muthalib, Marc Jubeau, Paul B Laursen, Kazunori Nosaka
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  ABSTRACT: To test the hypothesis that hypoxia centrally affects performance independently of afferent feedback and peripheral fatigue, we conducted two experiments under complete vascular occlusion of the exercising muscle under different systemic O(2) environmental conditions. In experiment 1, 12 subjects performed repeated submaximal isometric contractions of the elbow flexor to exhaustion (RCTE) with inspired O(2) fraction fixed at 9% (severe hypoxia, SevHyp), 14% (moderate hypoxia, ModHyp), 21% (normoxia, Norm), or 30% (hyperoxia, Hyper). The number of contractions (performance), muscle (biceps brachii), and prefrontal near-infrared spectroscopy (NIRS) parameters and high-frequency paired-pulse (PS100) evoked responses to electrical muscle stimulation were monitored. In experiment 2, 10 subjects performed another RCTE in SevHyp and Norm conditions in which the number of contractions, biceps brachii electromyography responses to electrical nerve stimulation (M wave), and transcranial magnetic stimulation responses (motor-evoked potentials, MEP, and cortical silent period, CSP) were recorded. Performance during RCTE was significantly reduced by 10-15% in SevHyp (arterial O(2) saturation, SpO(2) = ∼75%) compared with ModHyp (SpO(2) = ∼90%) or Norm/Hyper (SpO(2) > 97%). Performance reduction in SevHyp occurred despite similar 1) metabolic (muscle NIRS parameters) and functional (changes in PS100 and M wave) muscle states and 2) MEP and CSP responses, suggesting comparable corticospinal excitability and spinal and cortical inhibition between SevHyp and Norm. It is concluded that, in SevHyp, performance and central drive can be altered independently of afferent feedback and peripheral fatigue. It is concluded that submaximal performance in SevHyp is partly reduced by a mechanism related directly to brain oxygenation.
  Journal of Applied Physiology 02/2012; 112(8):1335-44. · 3.75 Impact Factor
• Article: Frontal cortex activation during electrical muscle stimulation as revealed by functional near-infrared spectroscopy.

  Makii Muthalib, Marco Ferrari, Valentina Quaresima, Kazunori Nosaka
  Advances in experimental medicine and biology 01/2012; 737:45-9. · 1.09 Impact Factor
• Article: Pre-cooling with ice slurry ingestion leads to similar run times to exhaustion in the heat as cold water immersion.

  Rodney Siegel, Joseph Maté, Greig Watson, Kazunori Nosaka, Paul B Laursen
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  ABSTRACT: The purpose of this study was to compare the effects of pre-exercise ice slurry ingestion and cold water immersion on submaximal running time in the heat. On three separate occasions, eight males ran to exhaustion at their first ventilatory threshold in the heat (34.0 ± 0.1 ° C, 52 ± 3% relative humidity) following one of three 30 min pre-exercise manoeuvres: (1) ice slurry ingestion; (2) cold water immersion; or (3) warm fluid ingestion (control). Running time was longer following cold water immersion (56.8 ± 5.6 min; P = 0.008) and ice slurry ingestion (52.7 ± 8.4 min; P = 0.005) compared with control (46.7 ± 7.2 min), but not significantly different between cold water immersion and ice slurry ingestion (P = 0.335). During exercise, rectal temperature was lower with cold water immersion from 15 and 20 min into exercise compared with control and ice slurry ingestion, respectively, and remained lower until 40 min (P = 0.001). At exhaustion rectal temperature was significantly higher following ice slurry ingestion (39.76 ± 0.36 ° C) compared with control (39.48 ± 0.36 ° C; P = 0.042) and tended to be higher than cold water immersion (39.48 ± 0.34 ° C; P = 0.065). As run times were similar between conditions, ice slurry ingestion may be a comparable form of pre-cooling to cold water immersion.
  Journal of Sports Sciences 12/2011; 30(2):155-65. · 1.93 Impact Factor
• Article: Muscle damage induced by electrical stimulation.

  Kazunori Nosaka, Abdulaziz Aldayel, Marc Jubeau, Trevor C Chen
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  ABSTRACT: Electrical stimulation (ES) induces muscle damage that is characterised by histological alterations of muscle fibres and connective tissue, increases in circulating creatine kinase (CK) activity, decreases in muscle strength and development of delayed onset muscle soreness (DOMS). Muscle damage is induced not only by eccentric contractions with ES but also by isometric contractions evoked by ES. Muscle damage profile following 40 isometric contractions of the knee extensors is similar between pulsed current (75 Hz, 400 μs) and alternating current (2.5 kHz delivered at 75 Hz, 400 μs) ES for similar force output. When comparing maximal voluntary and ES-evoked (75 Hz, 200 μs) 50 isometric contractions of the elbow flexors, ES results in greater decreases in maximal voluntary contraction strength, increases in plasma CK activity and DOMS. It appears that the magnitude of muscle damage induced by ES-evoked isometric contractions is comparable to that induced by maximal voluntary eccentric contractions, although the volume of affected muscles in ES is not as large as that of eccentric exercise-induced muscle damage. It seems likely that the muscle damage in ES is associated with high mechanical stress on the activated muscle fibres due to the specificity of motor unit recruitment (i.e., non-selective, synchronous and spatially fixed manner). The magnitude of muscle damage induced by ES is significantly reduced when the second ES bout is performed 2-4 weeks later. It is possible to attenuate the magnitude of muscle damage by "pre-conditioning" muscles, so that muscle damage should not limit the use of ES in training and rehabilitation.
  Arbeitsphysiologie 08/2011; 111(10):2427-37. · 2.15 Impact Factor
• Article: Muscle damage protection by low-intensity eccentric contractions remains for 2 weeks but not 3 weeks.

  Hsin-Lian Chen, Kazunori Nosaka, Trevor C Chen
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  ABSTRACT: This study investigated the hypothesis that the protective effect conferred by a low-intensity eccentric exercise against maximal eccentric exercise would not last more than a week. Untrained men (21.3 ± 1.6 years) were allocated into either a control or one of four repeated bout groups (n = 13 per group). The repeated bout groups performed 30 low-intensity eccentric contractions (ECC) of the elbow flexors with a dumbbell set at 10% of maximal isometric strength (10%-ECC) either 2 days, 7 days (1 week), 14 days (2 weeks) or 21 days (3 weeks) before 30 maximal eccentric contractions (Max-ECC). The control group performed Max-ECC only. Changes in maximal voluntary contraction strength, optimum angle, range of motion, upper arm circumference, muscle soreness, plasma creatine kinase activity and myoglobin concentration, and ultrasound echo-intensity following 10%-ECC were analysed by a one-way repeated measures ANOVA. Changes in the variables following Max-ECC were compared among the groups by a two-way repeated measures ANOVA. The 10%-ECC did not change any variables, showing no indication of muscle damage. The changes in all variables following Max-ECC were smaller (P < 0.05) for 2-day, 1- and 2-week groups than control group, without significant differences between 2-day and 1-week groups. The 2-week group showed greater (P < 0.05) changes in all variables compared with 2-day and 1-week groups. Changes in the variables were similar between 3-week and control groups, except for muscle soreness showing smaller (P < 0.05) changes for 3-week group. These results suggest that non-damaging eccentric exercise confers a protective effect against Max-Ecc, but the effect is attenuated between 1 and 2 weeks.
  Arbeitsphysiologie 05/2011; 112(2):555-65. · 2.15 Impact Factor
• Article: Comparison in muscle damage between maximal voluntary and electrically evoked isometric contractions of the elbow flexors.

  Marc Jubeau, Makii Muthalib, Guillaume Y Millet, Nicola A Maffiuletti, Kazunori Nosaka
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  ABSTRACT: This study compared between maximal voluntary (VOL) and electrically stimulated (ES) isometric contractions of the elbow flexors for changes in indirect markers of muscle damage to investigate whether ES would induce greater muscle damage than VOL. Twelve non-resistance-trained men (23-39 years) performed VOL with one arm and ES with the contralateral arm separated by 2 weeks in a randomised, counterbalanced order. Both VOL and ES (frequency 75 Hz, pulse duration 250 μs, maximally tolerated intensity) exercises consisted of 50 maximal isometric contractions (4-s on, 15-s off) of the elbow flexors at a long muscle length (160°). Changes in maximal voluntary isometric contraction torque (MVC), range of motion, muscle soreness, pressure pain threshold and serum creatine kinase (CK) activity were measured before, immediately after and 1, 24, 48, 72 and 96 h following exercise. The average peak torque over the 50 isometric contractions was greater (P < 0.05) for VOL (32.9 ± 9.8 N m) than ES (16.9 ± 6.3 N m). MVC decreased greater and recovered slower (P < 0.05) after ES (15% lower than baseline at 96 h) than VOL (full recovery). Serum CK activity increased (P < 0.05) only after ES, and the muscles became more sore and tender after ES than VOL (P < 0.05). These results showed that ES induced greater muscle damage than VOL despite the lower torque output during ES. It seems likely that higher mechanical stress imposed on the activated muscle fibres, due to the specificity of motor unit recruitment in ES, resulted in greater muscle damage.
  Arbeitsphysiologie 05/2011; 112(2):429-38. · 2.15 Impact Factor
• Article: The effect of three different start thresholds on the kinematics and kinetics of a countermovement jump.

  César M P Meylan, Kazunori Nosaka, Jonathan Green, John B Cronin
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  ABSTRACT: Force plates are used to quantify kinematic and kinetic variables of countermovement jump (CMJ). The jump is initiated by an unloading phase resulting in the force-time curve to drop below body weight (BW). However, there is no consensus in the literature to determine the start of the analysis of the jump (i.e., start threshold). To determine the effects and reliability of 3 different start thresholds on the kinematics and kinetics of a CMJ, 10 soccer players performed 3 CMJs for maximal jump height 30 seconds apart. Initiation of the jump movement was defined as the point where the force-time curve dropped below a threshold of 2.5, 5, or 10% BW. Significant differences were found in all variables except eccentric and concentric peak force and force at zero velocity between 2.5 and 10%, and 5 and 10% thresholds. Similar results were found for the 2.5 and 5% threshold variables except that no significant difference was found in the concentric ground contact time. The different thresholds did not appear to influence the variability of the measurement and only concentric time to peak power was found to have high variability. These data suggest that the use of any of the start thresholds can be used to determine the starting point of a CMJ considering their reliability. However, the 2.5% BW threshold is preferable because most of the force-time signal can be considered for analysis, and significant differences in eccentric and concentric kinematic and kinetic variables were found when a higher threshold was used.
  The Journal of Strength and Conditioning Research 04/2011; 25(4):1164-7. · 1.83 Impact Factor
• Article: The influence of ice slurry ingestion on maximal voluntary contraction following exercise-induced hyperthermia.

  Rodney Siegel, Joseph Maté, Greig Watson, Kazunori Nosaka, Paul B Laursen
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  ABSTRACT: The purpose of this study was to determine whether ingestion of a small bolus of ice slurry (1.25 g kg(-1)) could attenuate the reduction in maximal voluntary isometric contraction (MVC) torque output during a 2-min sustained task following exercise-induced hyperthermia. On two separate occasions, 10 males (age: 24 ± 3 years, .VO(2peak): 49.8 ± 4.7 ml kg(-1) min(-1)) ran to exhaustion at their first ventilatory threshold in a hot environment (34.1 ± 0.1°C, 49.5 ± 3.6% RH). Prior to and after exercise, subjects performed a 2-min sustained MVC of the right elbow flexors in a thermoneutral environment (24.6 ± 0.8°C, 37.2 ± 4.5% RH). The post exercise MVC was performed immediately following the ingestion of either 1.25 g kg(-1) of ice slurry (-1°C; ICE) or warm fluid (40°C; CON), in a counterbalanced and randomised order. Run time to exhaustion (42.4 ± 9.5 vs. 41.7 ± 8.7 min; p = 0.530), and rectal (39.08 ± 0.30 vs. 39.08 ± 0.30°C; p = 0.934) and skin temperatures (35.26 ± 0.65 vs. 35.28 ± 0.67°C; p = 0.922) and heart rate (189 ± 5 vs. 189 ± 6 beats min(-1); p = 0.830) at the end of the run were similar between trials. Torque output during the post-exercise 2-min sustained MVC was significantly higher (p = 0.001) following ICE (30.75 ± 16.40 Nm) compared with CON (28.69 ± 14.88 Nm). These results suggest that ice slurry ingestion attenuated the effects of exercise-induced hyperthermia on MVC, possibly via internal thermoreceptive and/or temperature-related sensory mechanisms.
  Arbeitsphysiologie 03/2011; 111(10):2517-24. · 2.15 Impact Factor
• Article: Effects of flexibility training on eccentric exercise-induced muscle damage.

  Che-Hsiu Chen, Kazunori Nosaka, Hsin-Lian Chen, Ming-Ju Lin, Kuo-Wei Tseng, Trevor C Chen
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  ABSTRACT: This study investigated whether flexibility training would attenuate muscle damage induced by maximal eccentric exercise. Thirty untrained young men were allocated to static stretching (SS), proprioceptive neuromuscular facilitation (PNF), or control group (n = 10 per group). The SS consisted of 30 sets of a 30-s standard SS with a 30-s rest between sets, and the PNF included 5 sets of the 30-s standard SS followed by 3 sets of three "contract-relax-agonist-contract" procedures. These were performed three times a week for 8 wk, and all subjects performed six sets of 10 maximal isokinetic (30°·s) lengthening contractions of the knee flexors after the 8-wk training or 8 wk after the baseline measures (control). Changes in indirect markers of muscle damage before and for 5 d after the eccentric exercise were compared among the groups. The range of motion (ROM) of the hip joint increased by 25°, and the optimum angle of the knee flexors shifted (P < 0.05) to a longer muscle length by 10° after training, without significant differences between SS and PNF. No significant changes in these variables were evident for the control group. Compared with the control group, the SS and PNF groups showed significantly (P < 0.05) smaller decreases and faster recovery of knee flexor muscle strength and smaller changes in optimum angle, ROM, muscle soreness, and plasma creatine kinase activity and myoglobin concentration without significant differences between the groups. The preeccentric exercise ROM or optimum angle was significantly (P < 0.05) correlated with the changes in the muscle damage markers. These results suggest that both SS and PNF training are effective in attenuating eccentric exercise-induced muscle damage and that flexible muscles are less susceptible to the damage.
  Medicine and science in sports and exercise 03/2011; 43(3):491-500. · 3.71 Impact Factor
• Article: The repeated-bout effect: influence on biceps brachii oxygenation and myoelectrical activity.

  Makii Muthalib, Hoseong Lee, Guillaume Y Millet, Marco Ferrari, Kazunori Nosaka
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  ABSTRACT: This study investigated biceps brachii oxygenation and myoelectrical activity during and following maximal eccentric exercise to better understand the repeated-bout effect. Ten men performed two bouts of eccentric exercise (ECC1, ECC2), consisting of 10 sets of 6 maximal lengthening contractions of the elbow flexors separated by 4 wk. Tissue oxygenation index minimum amplitude (TOI(min)), mean and maximum total hemoglobin volume by near-infrared spectroscopy, torque, and surface electromyography root mean square (EMG(RMS)) during exercise were compared between ECC1 and ECC2. Changes in maximal voluntary isometric contraction (MVC) torque, range of motion, plasma creatine kinase activity, muscle soreness, TOI(min), and EMG(RMS) during sustained (10-s) and 30-repeated isometric contraction tasks at 30% (same absolute force) and 100% MVC (same relative force) for 4 days postexercise were compared between ECC1 and ECC2. No significant differences between ECC1 and ECC2 were evident for changes in torque, TOI(min), mean total hemoglobin volume, maximum total hemoglobin volume, and EMG(RMS) during exercise. Smaller (P < 0.05) changes and faster recovery of muscle damage markers were evident following ECC2 than ECC1. During 30% MVC tasks, TOI(min) did not change, but EMG(RMS) increased 1-4 days following ECC1 and ECC2. During 100% MVC tasks, EMG(RMS) did not change, but torque and TOI(min) decreased 1-4 days following ECC1 and ECC2. TOI(min) during 100% MVC tasks and EMG(RMS) during 30% MVC tasks recovered faster (P < 0.05) following ECC2 than ECC1. We conclude that the repeated-bout effect cannot be explained by altered muscle activation or metabolic/hemodynamic changes, and the faster recovery in muscle oxygenation and activation was mainly due to faster recovery of force.
  Journal of Applied Physiology 02/2011; 110(5):1390-9. · 3.75 Impact Factor
• Article: Comparison in eccentric exercise-induced muscle damage among four limb muscles.

  Trevor C Chen, Kun-Yi Lin, Hsin-Lian Chen, Ming-Ju Lin, Kazunori Nosaka
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  ABSTRACT: This study tested the hypothesis that changes in indirect markers of muscle damage following maximal eccentric exercise would be smaller for the knee extensors (KE) and flexors (KF) compared with the elbow flexors (EF) and extensors (EE). A total of 17 sedentary men performed five sets of six maximal isokinetic (90° s(-1)) eccentric contractions of EF (range of motion, ROM: 90°-0°, 0 = full extension), EE (55°-145°), KF (90°-0°), and KE (30°-120°) using a different limb with a 4-5-week interval in a counterbalanced order. Changes in maximal isometric and concentric isokinetic strength, optimum angle, limb circumference, ROM, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo-intensity of B-mode ultrasound images before and for 5 days following exercise were compared amongst the four exercises using two-way repeated-measures ANOVA. All variables changed significantly following EF, EE, and KF exercises, but KE exercise did not change the optimum angle, limb circumference, and echo-intensity. Compared with KF and KE, EF and EE showed significantly greater changes in all variables, without significant differences between EF and EE. Changes in all variables were significantly greater for KF than KE. For the same subjects, the magnitude of change in the dependent variables following exercise varied among the exercises. These results suggest that the two arm muscles are equally more susceptible to muscle damage than leg muscles, but KF is more susceptible to muscle damage than KE. The difference in the susceptibility to muscle damage seems to be associated with the use of muscles in daily activities.
  Arbeitsphysiologie 02/2011; 111(2):211-23. · 2.15 Impact Factor