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ABSTRACT: AIM: Short-term exercise training may induce metabolic and performance adaptations before any changes in mitochondrial enzyme potential. However, there has not been a study that has directly assessed changes in mitochondrial oxidative capacity or metabolic control as a consequence of such training in vivo. Therefore, we used (31) P-magnetic resonance spectroscopy ((31) P-MRS) to examine the effect of short-term plantar flexion exercise training on phosphocreatine (PCr) recovery kinetics and the control of respiration rate. METHOD: To this aim, we investigated 12 healthy men, experienced with this exercise modality (TRA), and 7 time-control subjects (TC). RESULTS: After 5 days of training, maximum work rate during incremental plantar flexion exercise was significantly improved (P < 0.01). During the recovery period, the maximal rate of oxidative ATP synthesis (PRE: 28 ± 13 mM.min(-1) ; POST: 26 ± 15 mM.min(-1) ) and the PCr recovery time constant (PRE: 31 ± 19 s; POST: 29 ± 16) were not significantly altered. In contrast, the Hill coefficient (nH ) describing the cooperativity between respiration rate and ADP was significantly increased in TRA (PRE:nH =2.7 ± 1.4; POST: nH =3.4 ± 1.9, P < 0.05). Meanwhile, there were no systematic variations in any of these variables in TC. CONCLUSION: This study reveals that 5 days of training induces rapid adaptation in the allosteric control of respiration rate by ADP before any substantial improvement in muscle oxidative capacity occurs. This article is protected by copyright. All rights reserved.
Acta Physiologica 04/2013; · 3.09 Impact Factor
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ABSTRACT: Strength training enhances muscular strength and neural drive but the underlying neuronal mechanisms remain unclear. This study used magnetic resonance imaging (MRI) to identify possible changes in corticospinal tract (CST) microstructure, cortical activation and subcortical structure volumes following unilateral strength training of the plantar flexors. Mechanisms underlying cross education of strength in the untrained leg were also investigated. Young, healthy adult volunteers were assigned to training (n=12) or control (n=9) groups. The 4 weeks of training consisted of 16 sessions of 36 unilateral isometric plantar flexions. Maximum voluntary isometric contraction torque (MVC) was tested pre and post training. MRI investigation included a T1-weighted scan, diffusion tensor imaging (DTI) and functional MRI (fMRI). Probabilistic fiber tracking of the CST was performed on the DTI images using a two-ROI approach. Fractional anisotropy and mean diffusivity (MD) were calculated for the left and right CST in each individual before and after training. Standard fMRI analyses and volumetric analyses of subcortical structures were also performed. MVC significantly increased in both the trained and untrained legs of the training group, but not the control group. A significant decrease in MD was found in the left CST following strength training of the right leg. No significant changes were detected in the right CST. No significant changes in cortical activation were observed following training. A significant reduction in left putamen volume was found after training. This study provides the first evidence for strength training-related changes in white matter and putamen in the healthy adult brain.
Journal of Applied Physiology 03/2013; · 3.75 Impact Factor
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ABSTRACT: This study compared maximal strength training (MST) with equal training volume (kg × sets × repetitions) of conventional strength training (CON) primarily with regard to work economy, and second one repetition maximum (1RM) and rate of force development (RFD) of single leg knee extension. In an intra-individual design, one leg was randomized to knee-extension MST (4 or 5RM) and the other leg to CON (3 × 10RM) three times per week for 8 weeks. MST was performed with maximal concentric mobilization of force while CON was performed with moderate velocity. Eight untrained or moderately trained men (26 ± 1 years) completed the study. The improvement in gross work economy was -0.10 ± 0.08 L min(-1) larger after MST (P = 0.011, between groups). From pre- to post-test the MST and CON improved net work economy with 31 % (P < 0.001) and 18 % (P = 0.01), respectively. Compared with CON, the improvement in 1RM and dynamic RFD was 13.7 ± 8.4 kg (P = 0.002) and 587 ± 679 N s(-1) (P = 0.044) larger after MST, whereas isometric RFD was of borderline significance 3,028 ± 3,674 N s(-1) (P = 0.053). From pre- to post-test, MST improved 1RM and isometric RFD with 50 % (P < 0.001) and 155 % (P < 0.001), respectively whereas CON improved 1RM and isometric RFD with 35 % (P < 0.001) and 83 % (P = 0.028), respectively. Anthropometric measures of quadriceps femoris muscle mass and peak oxygen uptake did not change. In conclusion, 8 weeks of MST was more effective than CON for improving work economy, 1RM and RFD in untrained and moderately trained men. The advantageous effect of MST to improve work economy could be due to larger improvements in 1RM and RFD.
Arbeitsphysiologie 01/2013; · 2.15 Impact Factor
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ABSTRACT: Objective: To compare peak oxygen uptake (VO2peak) between: (i) functional electrical stimulation lower extremity pulsed isometric muscle contractions combined with arm cycling (FES iso hybrid), (ii) functional electrical stimulation cycling combined with arm cycling (FES hybrid cycling), and (iii) arm cycling exercise (ACE) in individuals with spinal cord injury with level of injury above and below T6. Design: Cross-over repeated measures design. Methods/participants: Individuals with spinal cord injury (n = 15) with level of injury between C4 and T12, were divided into groups; above (spinal cord injury - high, n = 8) and below (spinal cord injury - low, n = 7) T6 level. On separate days, VO2peak was compared between: (i) ACE, (ii) FES iso hybrid, and (iii) FES hybrid cycling. Results: In the SCI-high group, FES iso hybrid increased VO2peak (17.6 (standard deviation (SD) 5.0) to 23.6 (SD 3.6) ml/kg/min; p = 0.001) and ventilation (50.4 (SD 20.8) to 58.2 (SD 20.7) l/min; p = 0.034) more than ACE. Furthermore, FES hybrid cycling resulted in a 6.8 ml/kg/min higher VO2peak (p = 0.001) and an 11.0 litres/minute (p = 0.001) higher ventilation. ACE peak workload was 10.5 W (p = 0.001) higher during FES hybrid cycling compared with ACE. In the spinal cord injury - low group, no significant differences were found between the modalities. Conclusion: VO2peak increased when ACE was combined with FES iso hybrid or FES hybrid cycling in persons with spinal cord injury above the T6 level. Portable FES may serve as a less resource-demanding alternative to stationary FES cycling, and may have important implications for exercise prescription for spinal cord injury.
Journal of rehabilitation medicine: official journal of the UEMS European Board of Physical and Rehabilitation Medicine 01/2013; · 1.88 Impact Factor
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ABSTRACT: BACKGROUND: Patients with schizophrenia frequently have disabling gait deficits. The net mechanical efficiency of walking (epsilonnet) is an accurate measure often used to evaluate walking performance. Patients with gait deficits have a reduced epsilonnet with excessive energy expenditure during sub-maximal walking. Maximal strength training (MST) improves epsilonnet in healthy individuals and is associated with reduced risk of mortality. The aim of this study was to investigate whether MST improves epsilonnet in patients with schizophrenia. METHODS: Patients (ICD-10 schizophrenia, schizotypal or delusional disorders (F20-F29)) were included in a non-randomized trial. Patients were assigned to one of two groups: 1) MST consisting of 4x4 repetitions at 85-90% one repetition maximum (1RM) performed in a leg press apparatus or 2) playing computer games (CG). Both groups carried out their activity three days per week for eight weeks. 1RM, epsilonnet at 60 watt walking, peak oxygen uptake (VO2peak), the Positive and Negative Syndrome Scale (PANSS) and the 36-items short form (SF-36) were measured pre and post intervention. RESULTS: The baseline epsilonnet was 17.3 +/- 1.2% and 19.4 +/- 3.0% in the MST (n = 6) and CG groups (n = 7), respectively, which is categorized as mechanical inefficiency. The MST group improved 1RM by 79 kg (p = 0.006) and epsilonnet by 3.4% (p = 0.046) more than the CG group. The MST group improved 1RM and epsilonnet, by a mean of 83 kg (p = 0.028) and 3.4% (p = 0.028), respectively. VO2peak at baseline was 34.2 +/- 10.2 and 38.3 +/- 9.8 ml * kg-1 * min-1 in the MST and CG groups, respectively, and did not change (p > 0.05). No change was observed in PANSS or SF-36 (p > 0.05). CONCLUSIONS: MST improves 1RM and epsilonnet in patients with schizophrenia. MST could be used as a therapeutic intervention for patients with schizophrenia to normalize their reduced epsilonnet.
BMC Research Notes 07/2012; 5(1):344.
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ABSTRACT: This study aimed to demonstrate that maximal strength training improves muscle strength and to assess the effect of training on function, aerobic status, and quality-of-life among chronic stroke survivors.
Ten patients acted as their own controls for 4 wks, before an 8-week training intervention. Patients trained 3 days/wk, with four sets of four repetitions at 85%-95% one repetition maximum in unilateral leg press and plantarflexion with an emphasis on maximal mobilization of force in the concentric phase.
After training, leg press strength improved by 30.6 kg (75%) and 17.8 kg (86%); plantarflexion strength improved by 35.5 kg (89%) and 28.5 kg (223%) for the unaffected and affected limbs, respectively, significantly different from the control period (all P < 0.01). The 6-min walk test improved by 13.9 m (within training period; P = 0.01), and the Timed Up and Go test time improved by 0.6 secs (within training period; P < 0.05). There were no significant changes in walking economy, peak aerobic capacity, Four-Square Step Test, or health-related quality-of-life after training.
Maximal strength training improved muscle strength in the most affected as well as in the nonaffected leg and improved Timed-Up-And-Go time and 6-min walk distance but did not alter Four-Step Square Test time, aerobic status, or quality-of-life among chronic stroke survivors.
American journal of physical medicine & rehabilitation / Association of Academic Physiatrists 02/2012; 91(5):393-400. · 1.56 Impact Factor
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ABSTRACT: Peak oxygen uptake (VO(2peak)) is a strong predictor of cardiovascular disease (CVD) and all-cause mortality, but is inadequately described in patients with schizophrenia. The aim of this study was to evaluate treadmill VO(2peak), CVD risk factors and quality of life (QOL) in patients with schizophrenia (ICD-10, F20-29).
33 patients, 22 men (33.7 ± 10.4 years) and 11 women (35.9 ± 11.5 years), were included. Patients VO(2peak) were compared with normative VO(2peak) in healthy individuals from the Nord-Trøndelag Health Study (HUNT). Risk factors were compared above and below the VO(2peak) thresholds; 44.2 and 35.1 ml·kg⁻¹·min⁻¹ in men and women, respectively.
VO(2peak) was 37.1 ± 9.2 ml·kg⁻¹·min⁻¹ in men with schizophrenia; 74 ± 19% of normative healthy men (p < 0.001). VO(2peak) was 35.6 ± 10.7 ml·kg⁻¹·min⁻¹ in women with schizophrenia; 89 ± 25% of normative healthy women (n.s.). Based on odds ratio patients were 28.3 (95% CI = 1.6-505.6) times more likely to have one or more CVD risk factors if they were below the VO(2peak) thresholds. VO(2peak) correlated with the SF-36 physical functioning (r = 0.58), general health (r = 0.53), vitality (r = 0.47), social function (r = 0.41) and physical component score (r = 0.51).
Men with schizophrenia have lower VO(2peak) than the general population. Patients with the lowest VO(2peak) have higher odds of having one or more risk factors for cardiovascular disease. VO(2peak) should be regarded as least as important as the conventional risk factors for CVD and evaluation of VO(2peak) should be incorporated in clinical practice.
BMC Psychiatry 12/2011; 11:188. · 2.55 Impact Factor
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ABSTRACT: The objective of this study was to compare the neuromuscular function of the paretic and non-paretic plantar flexors (i.e. soleus, gastrocnemius medialis, lateralis) in chronic stroke patients. It was hypothesized that the contractile rate of force development (RFD) and neural activation, assessed by electromyogram (EMG) and V-waves normalized to the M-wave, and voluntary activation (twitch interpolation) would be reduced during plantar flexor maximum voluntary isometric contraction and that the evoked muscle twitch properties would be reduced in the paretic limb. Ten chronic stroke survivors completed the study. The main findings were that the paretic side showed deteriorated function compared to the non-paretic leg in terms of (1) RFD in all analyzed time windows from force onset to 250 ms, although relative RFD (i.e. normalized to maximum voluntary force) was similar; (2) fast neural activation (for most analyzed time windows), assessed by EMG activity in time windows from EMG onset to 250 ms; (3) V-wave responses (except for gastrocnemius medialis); (4) voluntary activation; (5) the evoked peak twitch force, although there was no evidence of intrinsic muscle slowing; (6) EMG activity obtained at maximal voluntary force. In conclusion, this study demonstrates considerable neuromuscular asymmetry of the plantar flexors in chronic stroke survivors. Effective rehabilitation regimes should be investigated.
Arbeitsphysiologie 04/2011; 111(12):3041-9. · 2.15 Impact Factor
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ABSTRACT: The aim of this study was to determine the effect of high-intensity interval training during combined arm cycling exercise (ACE) and functional electrical stimulation leg cycling (hybrid exercise), on peak stroke volume and peak oxygen consumption in individuals with spinal cord injury (SCI).
A baseline control trial at an outpatient SCI clinic (St. Olav's University Hospital, Norway) was conducted. Participants included six men with SCI in stable neurologic recovery (ASIA Impairment Scale grade A). The study intervention included aerobic high-intensity hybrid exercise training three times a week for 8 wks preceded by a 7-wk control period of regular daily activity. Main outcome measures were peak stroke volume during hybrid cycling and peak oxygen consumption during hybrid cycling, ACE, and functional electrical stimulation leg cycling. The tests were conducted at three time points: 1, baseline; 2, control; and 3, post-training.
Data are presented as mean (SD). From control to post-training tests, a significant increase in peak stroke volume by 33% (P = 0.004), from 77.7 (9.9) to 103.4 (17.1) ml/beat, was found. Furthermore, between control and post-training tests, hybrid peak oxygen consumption increased by 24.4%, from 24.6 (3.9) to 30.6 (5.2) ml kg (-1) min (-1) (P = 0.003), and peak oxygen consumption during isolated ACE and functional electrical stimulation cycling increased by 25.9% (P = 0.001) and 23.5% (P = 0.007), respectively.
Training aerobic high-intensity hybrid intervals at 85%-95% of peak Watt was feasible for this group of SCI men and significantly increased peak stroke volume and peak oxygen uptake. Because aerobic capacity is directly linked to mortality and morbidity, the present study may be useful for designing training programs sufficient to reverse the risk of cardiovascular disease in SCI.
American journal of physical medicine & rehabilitation / Association of Academic Physiatrists 03/2011; 90(5):407-14. · 1.56 Impact Factor
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ABSTRACT: This study was designed to assess the reliability of the first volitional (V) wave, which can be used as a measure of efferent neural drive, while also reflecting reflex excitability. Ten subjects volunteered for one familiarization session followed by an experimental test session and an identical retest session spaced 3 to 8 days apart. V-waves were evoked in the tibial nerve during plantar flexion maximal voluntary isometric contractions (MVCs). Test-retest reliability was assessed using the intraclass correlation coefficient (ICC), along with standard error of measurement and 95% confidence intervals for the following variables: MVC force, surface electromyogram activity (EMG), and the peak-to-peak V-wave amplitude in soleus (SOL) and gastrocnemius medialis (GM). The superimposed M-wave (MSUP) accompanying V-wave stimulation was also obtained for normalization purposes. Substantial reliability was documented for V/MSUP in both SOL (ICC = 0.86) and GM (0.90), as well as for the non-normalized V-wave in SOL (0.92). Moderate reliability was displayed for the non-normalized V-wave response in GM (0.78). Substantial reliability was also established for EMG/MSUP (>0.82) and MVC force (0.98). This study provides novel evidence that V-wave responses can be consistently measured in the SOL and GM, thus advocating its continued use in future research.
Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society 03/2011; 28(2):217-21. · 1.47 Impact Factor
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ABSTRACT: Impaired metabolism in peripheral skeletal muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine the energy cost and skeletal muscle energetics in six patients with COPD during dynamic plantar flexion exercise compared with six well-matched healthy control subjects. Patients with COPD displayed a higher energy cost of muscle contraction compared with the controls (control: 6.1 ± 3.1% of rest·min(-1)·W(-1), COPD: 13.6 ± 8.3% of rest·min(-1)·W(-1), P = 0.01). Although, the initial phosphocreatine resynthesis rate was also significantly attenuated in patients with COPD compared with controls (control: 74 ± 17% of rest/min, COPD: 52 ± 13% of rest/min, P = 0.04), when scaled to power output, oxidative ATP synthesis was similar between groups (6.5 ± 2.3% of rest·min(-1)·W(-1) in control and 7.8 ± 3.9% of rest·min(-1)·W(-1) in COPD, P = 0.52). Therefore, our results reveal, for the first time that in a small subset of patients with COPD a higher ATP cost of muscle contraction may substantially contribute to the lower mechanical efficiency previously reported in this population. In addition, it appears that some patients with COPD have preserved mitochondrial function and normal energy supply in lower limb skeletal muscle.
AJP Regulatory Integrative and Comparative Physiology 02/2011; 300(5):R1142-7. · 3.34 Impact Factor
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ABSTRACT: Patients with schizophrenia have a high risk of cardiovascular disease (CVD). High aerobic intensity training (HIT) improve peak oxygen uptake (VO(2peak)), net mechanical efficiency of walking and risk factors for CVD but has not been investigated in patients with schizophrenia.
To investigate effects from HIT on VO(2peak), net mechanical efficiency of walking and risk factors for CVD in patients with schizophrenia.
25 inpatients (F20-29, ICD-10) were allocated to either HIT or playing computer games (CG), 3 days per week for 8 weeks. HIT consisted of 4 × 4-min intervals with 3-min break periods, at 85-95% and 70% of peak heart rate, respectively. Results: 12 and seven patients completed HIT and CG, respectively. The baseline VO(2peak) in both groups combined (n = 19) was 36.8 ± 8.2 ml/kg/min and 3.12 ± 0.55 l/min. The HIT group improved VO(2peak) by 12% from 3.17 ± 0.59 to 3.56 ± 0.68 l/min (P < 0.001), more than the CG group (P = 0.014). Net mechanical efficiency of walking improved by 12% in the HIT group from 19.8 ± 3.0% to 22.2 ± 4.5% (P = 0.005), more than the CG group (P = 0.031). The psychiatric symptoms, expressed as the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS), did not improve in either group.
VO(2peak) and net mechanical efficiency of walking improved significantly by 8 weeks of HIT. HIT should be included in rehabilitation in order to improve physical capacity and contribute risk reduction of CVD.
Nordic journal of psychiatry 02/2011; 65(4):269-75. · 0.99 Impact Factor
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ABSTRACT: Maximal strength training with a focus on maximal mobilization of force in the concentric phase improves endurance performance that employs a large muscle mass. However, this has not been studied during work with a small muscle mass, which does not challenge convective oxygen supply. We therefore randomized 23 adult females with no arm-training history to either one-arm maximal strength training or a control group. The training group performed five sets of five repetitions of dynamic arm curls against a near-maximal load, 3 days a week for 8 weeks. This training increased maximal strength by 75% and improved rate of force development during both strength and endurance exercise, suggesting that each arm curl became more efficient. This coincided with a 17-18% reduction in oxygen cost at standardized submaximal workloads (work economy), and a 21% higher peak oxygen uptake and 30% higher peak load during maximal arm endurance exercise. Blood flow assessed by Doppler ultrasound in the axillary artery supplying the working biceps brachii and brachialis muscles could not explain the training-induced adaptations. These data suggest that maximal strength training improved work economy and endurance performance in the skeletal muscle, and that these effects are independent of convective oxygen supply.
Journal of Sports Sciences 01/2011; 29(2):161-70. · 1.93 Impact Factor
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ABSTRACT: The present study investigated the relationship between running economy (RE) at 15 km/h(-1) , 3.000-m race time, maximal strength, and a number of physiological, anthropometrical, and mechanical variables. The variables measured included RE, maximal oxygen consumption, heart rate, step length and frequency, contact time, and the peak horizontal and vertical forces of each step. Maximal strength was measured as the 1 repetition maximum (1RM) half-squat using a leg press machine. Eleven male elite endurance athletes with a V(O2)max of 75.8 ± 6.2 mL/kg(-1)/min(-1) participated in this study. After the anthropometric data were collected, they were tested for RE, running characteristics, and force measures on a level treadmill at 15 km/h(-1). The athletes wore contact soles, and the treadmill was placed on a force platform. Maximal oxygen consumption and 1RM were tested after the RE measurements. The sum of horizontal and vertical peak forces revealed a significant inverse correlation (p < 0.05) both with 3,000-m performance (R = 0.71) and RE (R = 0.66). Inverse correlations were also found (p < 0.05) between RE and body height (R = 0.61) and between RE and body fat percentage (R = 0.62). In conclusion, the sum of horizontal and vertical peak forces was found to be negatively correlated to running economy and 3,000-m running performance, indicating that avoiding vertical movements and high horizontal braking force is crucial for a positive development of RE.
The Journal of Strength and Conditioning Research 01/2011; 25(1):117-23. · 1.83 Impact Factor
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ABSTRACT: Multiple sclerosis (MS) patients suffer from impaired muscle activation and lower limb strength. Strength training enhances muscle activation and muscle strength, but neural adaptations to strength training remain unexplored in MS patients. The hypothesis was that maximal strength training (MST) using high loads and few repetitions would improve central neural drive and thus strength capacity of MS patients. 14 MS patients staying at a national MS rehabilitation center were randomly assigned to a MST group or a control group (CG). Both groups received "today's treatment". In addition, the MST group trained 4 x 4 repetitions of unilateral dynamic leg press and plantar flexion 5 days a week for 3 weeks. Neural adaptations of the soleus muscle were assessed by surface electromyography (EMG) activity, and by superimposed H-reflexes and V-waves obtained during maximum voluntary isometric plantar flexor contractions (MVCs). H-reflexes and V-waves were normalized by the M-wave (H(SUP)/M(SUP), V/M(SUP), respectively). In the MST group, MVC increased by 20 +/- 9% (P < 0.05). Soleus EMG activity and V/M(SUP) ratio increased by 40 and 55%, respectively, in the MST group compared to the CG (P <or= 0.05). The H(SUP)/M(SUP) ratio remained unchanged. No change was apparent in the CG. MST group subjects were able to complete all training sessions. No adverse effects were reported. This randomized study provides evidence that MST is effective of augmenting the magnitude of efferent motor output of spinal motor neurons in MS patients, alleviating some neuromuscular symptoms linked to the disease.
Arbeitsphysiologie 09/2010; 110(2):435-43. · 2.15 Impact Factor
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ABSTRACT: To assess physical outcome of early maximal strength training after total hip arthroplasty.
Six- and 12-mo follow-up of 24 (22) total hip arthroplasty patients randomly assigned to 4 wks of maximal strength training and conventional rehabilitation and to conventional rehabilitation only was conducted. After the intervention period, all patients attended conventional rehabilitation. Outcome measures were hip abduction and leg press strength, gait patterns, work efficiency, maximal oxygen consumption, and health-related quality of life.
Work efficiency was significantly higher in the strength training and conventional rehabilitation group compared with the conventional rehabilitation-only group after 6 and 12 mos by 29% and 30%, respectively. Leg press for the healthy leg and rate of force development for the operated leg were significantly higher in the strength training and conventional rehabilitation group compared with the conventional rehabilitation-only group 12 mos postoperatively by 36% and 74%, respectively.
This study demonstrates higher work efficiency after 6 and 12 mos and improved rate of force development after 12 mos in total hip arthroplasty patients who performed early maximal strength training combined with conventional rehabilitation after total hip arthroplasty surgery compared with total hip arthroplasty patients receiving conventional rehabilitation only. However, the study indicates that a prolonged maximal strength training program and aerobic endurance training are required to fully recover total hip arthroplasty patients.
American journal of physical medicine & rehabilitation / Association of Academic Physiatrists 04/2010; 89(4):304-14. · 1.56 Impact Factor
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ABSTRACT: The present study investigated whether there are differences in running economy at different velocities for well-trained distance runners, and to what extent a commonly used incremental protocol for measuring oxygen uptake (VO(2)) at different velocities affects the reliability of these measurements. Fifteen well-trained distance runners (9 male and 6 female) participated in this study. Gross oxygen cost of running (C (R)), heart rate (HR) and [La(-)](b) during 5-min runs at velocities ranging from 8.0 to 17 km h(-1), representing intensities ranging from 60 to 90% of maximal oxygen consumption (VO(2max)) was measured on two different days in random order. The athletes were also tested for lactate threshold, VO(2max) and time to exhaustion at MAS ((t)MAS). No significant differences in C (R) between the different relative velocities or the different set velocities were found up to 90% of VO(2max). The incremental protocol for measuring VO(2) at different velocities was found not to affect the reliability of these measurements. All athletes reached their VO(2max) whilst running to exhaustion at MAS. The females showed significantly lower VO(2max), but significantly better C (R) than the males. At velocities representing intensities between 60 and 90% of VO(2max), no differences in C (R) were found. The commonly used incremental protocol for measuring oxygen uptake (VO(2)) at different velocities was found not to affect the reliability of these measurements. This means that C (R) measured at sub-maximal velocities are representative for C (R) at race velocity for distances above 10,000 m for most runners.
Arbeitsphysiologie 12/2009; 108(6):1099-105. · 2.15 Impact Factor
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ABSTRACT: Husby VS, Helgerud J, Bjørgen S, Husby OS, Benum P, Hoff J. Early maximal strength training is an efficient treatment for patients operated with total hip arthroplasty.
To compare muscle strength, work efficiency, gait patterns, and quality of life in patients undergoing total hip arthroplasty (THA) randomly assigned to either maximal strength training or a conventional rehabilitation program.
A randomized controlled study.
Research laboratory, rehabilitation center, and physical therapy clinic.
Patients (N=24) with osteoarthritis as the main reason for THA were randomly assigned to perform maximal strength training (n=12) or conventional rehabilitation (n=12).
The maximal strength training group (STG) performed maximal strength training in leg press and abduction with the operated leg only 5 times a week for 4 weeks in addition to the conventional rehabilitation program. The conventional rehabilitation group (CRG) received supervised physical therapy 3 to 5 times a week for 4 weeks.
1-repetition maximum (1RM) leg press strength, 1RM abduction strength, rate of force development (RFD), work efficiency, gait patterns, and quality of life.
1RM increased in the bilateral leg press (P<.002) and in the operated leg separately (P<.002) in the STG compared with the CRG. 1RM abduction strength in the operated leg (P<.002) and the healthy leg (P<.002) increased in the STG compared with the CRG. RFD increased in the STG compared with the CRG (P(g)=.030), followed by a trend towards increased peak force in the STG (P(g)=.053) (P(g) = probability for differences between groups). Work efficiency tended to improve in the STG compared with the CRG (P=.065). No differences in gait patterns were revealed between the groups after the training intervention.
Early maximal strength training 1 week postoperatively is feasible and an efficient treatment to regain muscular strength for patients who have undergone THA, demonstrated by a significantly larger increase in muscular strength and a trend towards a better work efficiency in the STG compared with the CRG.
Archives of physical medicine and rehabilitation 10/2009; 90(10):1658-67. · 2.18 Impact Factor
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ABSTRACT: The purpose of the present study was to investigate the effect of maximal strength training on cycling economy (CE) at 70% of maximal oxygen consumption (Vo2max), work efficiency in cycling at 70% Vo2max, and time to exhaustion at maximal aerobic power. Responses in 1 repetition maximum (1RM) and rate of force development (RFD) in half-squats, Vo2max, CE, work efficiency, and time to exhaustion at maximal aerobic power were examined. Sixteen competitive road cyclists (12 men and 4 women) were randomly assigned into either an intervention or a control group. Thirteen (10 men and 3 women) cyclists completed the study. The intervention group (7 men and 1 woman) performed half-squats, 4 sets of 4 repetitions maximum, 3 times per week for 8 weeks, as a supplement to their normal endurance training. The control group continued their normal endurance training during the same period. The intervention manifested significant (p < 0.05) improvements in 1RM (14.2%), RFD (16.7%), CE (4.8%), work efficiency (4.7%), and time to exhaustion at pre-intervention maximal aerobic power (17.2%). No changes were found in Vo2max or body weight. The control group exhibited an improvement in work efficiency (1.4%), but this improvement was significantly (p < 0.05) smaller than that in the intervention group. No changes from pre- to postvalues in any of the other parameters were apparent in the control group. In conclusion, maximal strength training for 8 weeks improved CE and efficiency and increased time to exhaustion at maximal aerobic power among competitive road cyclists, without change in maximal oxygen uptake, cadence, or body weight. Based on the results from the present study, we advise cyclists to include maximal strength training in their training programs.
The Journal of Strength and Conditioning Research 10/2009; 24(8):2157-65. · 1.83 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the effects of 4-week (16 sessions) unilateral, maximal isometric strength training on contralateral neural adaptations. Subjects were randomised to a strength training group (TG, n = 15) or to a control group (CG, n = 11). Both legs of both groups were tested for plantar flexion maximum voluntary isometric contractions (MVCs), surface electromyogram (EMG), H-reflexes and V-waves in the soleus (SOL) and gastrocnemius medialis (GM) superimposed during MVC and normalised by the M-wave (EMG/M(SUP), H(SUP)/M(SUP), V/M(SUP), respectively), before and after the training period. For the untrained leg, the TG increased compared to the CG for MVC torque (33%, P < 0.01), SOL EMG/M(SUP) (32%, P < 0.05) and SOL V/M(SUP) (24%, P < 0.05). For the trained leg, the TG increased compared to the CG for MVC torque (40%, P < 0.01), EMG/M(SUP) (SOL: 38%, P < 0.05; GM: 60%, P < 0.05) and SOL V/M(SUP) (72%, P < 0.01). H(SUP)/M(SUP) remained unchanged for both limbs. No changes occurred in the CG. These results reinforce the concept that enhanced neural drive to the contralateral agonist muscles contributes to cross-education of strength.
Arbeitsphysiologie 09/2009; 107(6):723-30. · 2.15 Impact Factor
