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At least 19 recordsLinked to original sources
PubMed2005

The impact of metabolic stress on hormonal responses and muscular adaptations.

PURPOSE: The purpose of this study was to examine the impact of exercise-induced metabolic stress on hormonal responses and chronic muscular adaptations. METHODS: We compared the acute and long-term effects of an "NR regimen" (no-rest regimen) and those of a "WR regimen" (regimen with rest period within a set). Twenty-six male subjects were assigned to either the NR (N = 9), WR (N = 9), or control (CON, N = 8) groups. The NR regimen consisted of 3-5 sets of 10 repetitions at 10-repetition maximum (RM) with an interset rest period of 1 min (lat pulldown, shoulder press, and bilateral knee extension). In the WR regimen, subjects completed the same protocol as the NR regimen, but took a 30-s rest period at the midpoint of each set of exercises in order to reduce exercise-induced metabolic stress. Acute hormonal responses to both regimens were measured followed by a 12-wk period of resistance training. RESULTS: Measurements of blood lactate and serum hormone concentrations after the NR and WR regimens showed that the NR regimen induced strong lactate, growth hormone (GH), epinephrine (E), and norepinephrine (NE) responses, whereas the WR regimen did not. Both regimens failed to cause significant changes in testosterone. After 12 wk of resistance training, the NR regimen caused greater increases in 1RM (P < 0.01), maximal isometric strength (P < 0.05), and muscular endurance (P < 0.05) with knee extension than the WR regimen. The NR group showed a marked increase (P < 0.01) in muscle cross-sectional area, whereas the WR and CON groups did not. CONCLUSION: These results suggest that exercise-induced metabolic stress is associated with acute GH, E, and NE responses and chronic muscular adaptations following resistance training.

Adult↗
PubMed1997

Muscular adaptation and strength during the early phase of eccentric training: influence of the training frequency.

We investigated the effects of different training frequencies on maximum isometric voluntary contraction (MVC) force and plasma concentrations of muscle proteins during the early phase of eccentric training. MVC and plasma concentrations of creatine kinase (CK) and slow-twitch skeletal (cardiac beta-type) myosin heavy chain (MHC) fragments were measured before and 4 and 7 d after performing the first and last training task. Training tasks, which comprised 70 high-force eccentric contractions involving the thigh muscles (single leg), were performed under supervision in three groups (A, B, C) at the beginning and at the end of the study period (7 wk). In addition, groups A (N = 10) and B (N = 10) trained during the study period starting 1 wk after the first training task. Group A performed one training task once a week for 5 wk and group B (N = 10) twice a week for 2 wk and three times a week during the subsequent 3 wk. In all three groups the first training task resulted in delayed CK and MHC peaks and decrements in MVC, which were comparable (P > 0.05). Only training regimen B resulted in a significant increase in the MVC. Compared with the first training task training regimens, A and B significantly (P < 0.01) reduced the increase in serum muscle protein and muscle function impairment. The responses to the last training task did not differ significantly between groups A and B. In group C the responses after the second training task did not differ significantly from those observed after the first task. Our results suggest that, compared with group A, additional eccentric exercise in group B is the essential basis for the increase in muscle strength during the early phase of eccentric training without further benefits for muscular adaptation. In group C we found no muscular adaptation.

Adaptation, Physiological↗
PubMed2004

Muscular adaptations to computer-guided strength training with eccentric overload.

AIMS: In order to investigate the muscular adaptations to a novel form of strength training, 18 male untrained subjects performed 4 weeks of low resistance-high repetition knee extension exercise. METHODS: Nine of them trained on a conventional weight resistance device (Leg curler, CON/ECC group), with loads equivalent to 30% of the concentric one-repetition maximum (1RM) for both the concentric and eccentric phase of movement. The other nine trained on a newly developed computer-driven device (CON/ECC-OVERLOAD group) with the concentric load equivalent to 30% of the concentric 1RM and the eccentric load equivalent to 30% of the eccentric 1RM. RESULTS: Training resulted in significantly (P < or = 0.05) increased peak torque and a tendency (P=0.092) to increased muscle cross-sectional area for the CON/ECC-OVERLOAD but not the CON/ECC group, while strength endurance capacity was significantly (P < or = 0.05) increased in the CON/ECC group only. RT-PCR revealed significantly increased myosin heavy chain (MHC) IIa and lactate dehydrogenase (LDH) A mRNAs, a tendency for increased MHC IIx mRNA (P = 0.056) and high correlations between the changes in MHC IIx and LDH A mRNAs (r=0.97, P=0.001) in the CON/ECC-OVERLOAD group. CONCLUSIONS: These results indicate a shift towards a more type II dominated gene expression pattern in the vasti laterales muscles of the CON/ECC-OVERLOAD group in response to training. We suggest that the increased eccentric load in the CON/ECC-OVERLOAD training leads to distinct adaptations towards a stronger, faster muscle.

Adaptation, Physiological↗
PubMed2006

Independent and combined effects of liquid carbohydrate/essential amino acid ingestion on hormonal and muscular adaptations following resistance training in untrained men.

This investigation examined chronic alteration of the acute hormonal response associated with liquid carbohydrate (CHO) and/or essential amino acid (EAA) ingestion on hormonal and muscular adaptations following resistance training. Thirty-two untrained young men performed 12 weeks of resistance training twice a week, consuming ~675 ml of either, a 6% CHO solution, 6 g EAA mixture, combined CHO + EAA supplement or placebo (PLA). Blood samples were obtained pre- and post-exercise (week 0, 4, 8, and 12), for determination of glucose, insulin, and cortisol. 3-Methylhistidine excretion and muscle fibre cross-sectional area (fCSA) were determined pre- and post-training. Post-exercise cortisol increased (P<0.05) during each training phase for PLA. No change was displayed by EAA; CHO and CHO + EAA demonstrated post-exercise decreases (P<0.05). All groups displayed reduced pre-exercise cortisol at week 12 compared to week 0 (P<0.05). Post-exercise insulin concentrations showed no change for PLA; increases were observed for the treatment groups (P<0.05), which remained greater for CHO and CHO + EAA (P<0.001) than PLA. EAA and CHO ingestion attenuated 3-methylhistidine excretion 48 h following the exercise bout. CHO + EAA resulted in a 26% decrease (P<0.01), while PLA displayed a 52% increase (P<0.01). fCSA increased across groups for type I, IIa, and IIb fibres (P<0.05), with CHO + EAA displaying the greatest gains in fCSA relative to PLA (P<0.05). These data indicate that CHO + EAA ingestion enhances muscle anabolism following resistance training to a greater extent than either CHO or EAA consumed independently. The synergistic effect of CHO + EAA ingestion maximises the anabolic response presumably by attenuating the post-exercise rise in protein degradation.

Adaptation, Physiological↗
PubMed1996

Muscle biopsy as a tool for assessing muscular adaptation to training in horses.

OBJECTIVE: To describe an applied method for quantitative estimation of training condition in horses. ANIMALS: 17 sedentary adult (5 to 14 years old) stallions of several breeds endurance trained for 3 months. PROCEDURE: Muscle biopsy specimens from 2 depths (20 and 60 mm) of the gluteus medius muscle were obtained before and after training and were analyzed for fiber type distribution, mean cross-sectional area, relative fiber area, and mean number of capillaries in contact with each fiber type relative to their mean area. Fiber types were designated as types 1, 2A, and 2B (high, low, and moderate myosin ATPase activities at pH 4.5, respectively). Data were subjected to discriminant and principal component analyses. RESULTS: 77% of the observations were correctly discriminated according to training condition of horses by use of discriminant analyses when histochemical and morphometric data from the 2 muscle biopsy specimens were used. Principal component analysis indicated that the most efficient variables describing muscular adaptation to training are fiber area and number of capillaries in contact with type-1 and type-2A fibers, particularly from the deepest sampling site of the muscle. CONCLUSION: It is possible to satisfactorily classify an individual horse in a given training category on the basis of a physiologic muscle index. CLINICAL RELEVANCE: These methods could become a useful aid for evaluation of the individual horse's response to training.

Acclimatization↗
PubMed2003

Muscular adaptation to gradual advancement of the mandible.

Muscular activity of the superficial masseter muscle and anterior portion of the temporal muscle before, during, and after treatment, with gradual advancement of the mandible, was evaluated by assessing the average integrated electromyogram (EMG) with the mandible in retruded position (RP) and incisal edge-to-edge (EE) position on 23 consecutive subjects with skeletal Class II malocclusion. Toward the end of active treatment and follow-up, the RP position and EE position coincided. At any given registration, the EMG activity of the masseter muscle was at least twice (P < .001) that of the anterior portion of the temporal muscle. The EMG activity in RP for the anterior portion of the temporal muscle was not affected significantly, whereas the EMG activity at EE position decreased significantly (P < .05) during the initial treatment, but, thereafter, it increased continuously. The difference in EMG activity between six months of follow-up and pretreatment level reached statistical significance (P < .05). For the masseter muscle, the EMG activity at both RP and EE position was reduced about 20% during the initial treatment but returned to the pretreatment level during active treatment and exceeded pretreatment level by approximately 30% to 50% at two and six months of follow-up, respectively. In conclusion, it seemed that gradual advancement affected the anterior portion of the temporal muscle to a minor extent, whereas the effect on the masseter muscle was significant.

Adaptation, Physiological↗
PubMedDate not supplied

Low-intensity exercise, vascular occlusion, and muscular adaptations.

The study investigated the effects of low-intensity exercise on muscular fitness when combined with vascular occlusion. Nineteen college male and female students performed two sets of a 5-min step exercise using a 12-inch bench three times per week for 5 weeks. During the step exercise, blood flow to one leg was restricted (vascular occlusion) with a blood pressure cuff, while the other leg was not occluded. Muscular strength of the occluded leg was significantly increased over the nonoccluded leg (p < 0. 05). Muscular endurance and muscle mass were improved after 5 weeks of training (p < 0.05); however, the changes between the two legs were not significantly different (p > 0.05). Exercise with vascular occlusion has the potential to be an alternative form of training to promote muscular strength.

Adaptation, Physiological↗
PubMed2002

Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones.

Thirty-two untrained men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body mass 77.8 (11.9) kg] participated in an 8-week progressive resistance-training program to investigate the "strength-endurance continuum". Subjects were divided into four groups: a low repetition group (Low Rep, n = 9) performing 3-5 repetitions maximum (RM) for four sets of each exercise with 3 min rest between sets and exercises, an intermediate repetition group (Int Rep, n = 11) performing 9-11 RM for three sets with 2 min rest, a high repetition group (High Rep, n = 7) performing 20-28 RM for two sets with 1 min rest, and a non-exercising control group (Con, n = 5). Three exercises (leg press, squat, and knee extension) were performed 2 days/week for the first 4 weeks and 3 days/week for the final 4 weeks. Maximal strength [one repetition maximum, 1RM), local muscular endurance (maximal number of repetitions performed with 60% of 1RM), and various cardiorespiratory parameters (e.g., maximum oxygen consumption, pulmonary ventilation, maximal aerobic power, time to exhaustion) were assessed at the beginning and end of the study. In addition, pre- and post-training muscle biopsy samples were analyzed for fiber-type composition, cross-sectional area, myosin heavy chain (MHC) content, and capillarization. Maximal strength improved significantly more for the Low Rep group compared to the other training groups, and the maximal number of repetitions at 60% 1RM improved the most for the High Rep group. In addition, maximal aerobic power and time to exhaustion significantly increased at the end of the study for only the High Rep group. All three major fiber types (types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant increases were demonstrated for either the High Rep or Con groups. However, the percentage of type IIB fibers decreased, with a concomitant increase in IIAB fibers for all three resistance-trained groups. These fiber-type conversions were supported by a significant decrease in MHCIIb accompanied by a significant increase in MHCIIa. No significant changes in fiber-type composition were found in the control samples. Although all three training regimens resulted in similar fiber-type transformations (IIB to IIA), the low to intermediate repetition resistance-training programs induced a greater hypertrophic effect compared to the high repetition regimen. The High Rep group, however, appeared better adapted for submaximal, prolonged contractions, with significant increases after training in aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce similar muscular adaptations, at least after short-term training in previously untrained subjects. Overall, however, these data demonstrate that both physical performance and the associated physiological adaptations are linked to the intensity and number of repetitions performed, and thus lend support to the "strength-endurance continuum".

Adaptation, Physiological↗
PubMed1999

Reflex and muscular adaptations in rat soleus muscle after hindlimb suspension.

Reflex, mechanical and histochemical adaptations of the soleus muscle following 3 weeks of hindlimb suspension (HS) were measured in the rat. HS transformed the soleus muscle fibre type composition from predominantly slow, type I, to approximately equal proportions of fast, type II and slow fibres. Consistent with this transformation was an increase in the maximum shortening velocity, V(max), and a decrease in the stiffness of the series elastic component. Disuse also produced muscle atrophy and a resultant decrease in twitch and tetanic force. Reflex responses of the ankle extensors were also obtained at 5 and 9 weeks of age for six control rats (C group) and six rats subjected to HS for 3 weeks (HS group). The soleus reflexes to a mechanical tap applied to the Achilles tendon (T reflex) and to an electrical stimulation of the sciatic nerve (H reflex) were measured. The maximal amplitude of these reflexes (T(max) and H(max)) were normalised to the maximal direct motor response (M(max)) and the T(max)/H(max) ratio was also calculated to give an index of the relative adaptations of the peripheral and central components of the reflex pathway. The HS group showed significantly higher H reflex gains than the C group, possibly due to changes in synaptic efficiency after HS. Conversely, the HS group presented strongly inhibited T reflexes and negative gains for the T(max)/H(max) ratios. This result indicated a reduced spindle solicitation after HS, which may reflect changes in the spindle sensitivity itself, but it could also be due to the decrease in stiffness of the musculo-tendinous elements in series with the muscle spindles. Such mechanical changes may play an important part in the decreased T reflex responses.

Adaptation, Physiological↗
PubMed2004

Muscular adaptations to combinations of high- and low-intensity resistance exercises.

Acute and long-term effects of resistance-training regimens with varied combinations of high- and low-intensity exercises were studied. Acute changes in the serum growth hormone (GH) concentration were initially measured after 3 types of regimens for knee extension exercise: a medium intensity (approximately 10 repetition maximum [RM]) short interset rest period (30 s) with progressively decreasing load ("hypertrophy type"); 5 sets of a high-intensity (90% of 1RM) and low-repetition exercise ("strength type"); and a single set of low-intensity and high-repetition exercise added immediately after the strength-type regimen ("combi-type"). Postexercise increases in serum GH concentration showed a significant regimen dependence: hypertrophy-type > combi-type > strength-type (p < 0.05, n = 8). Next, the long-term effects of periodized training protocols with the above regimens on muscular function were investigated. Male subjects (n = 16) were assigned to either hypertrophy/combi (HC) or hypertrophy/ strength (HS) groups and performed leg press and extension exercises twice a week for 10 weeks. During the first 6 weeks, both groups used the hypertrophy-type regimen to gain muscular size. During the subsequent 4 weeks, HC and HS groups performed combi-type and strength-type regimens, respectively. Muscular strength, endurance, and cross sectional area (CSA) were examined after 2, 6, and 10 weeks. After the initial 6 weeks, no significant difference was seen in the percentage changes of all variables between the groups. After the subsequent 4 weeks, however, 1RM of leg press, maximal isokinetic strength, and muscular endurance of leg extension showed significantly (p < 0.05) larger increases in the HC group than in the HS group. In addition, increases in CSA after this period also tended to be larger in the HC group than in the HS group (p = 0.08). The results suggest that a combination of high- and low-intensity regimens is effective for optimizing the strength adaptation of muscle in a periodized training program.

Adaptation, Physiological↗
PubMed1998

Nuclear magnetic resonance evidence of different muscular adaptations after resistance training.

OBJECTIVE: To evaluate muscle bioenergetics, muscle cross-sectional area (CSA), and soreness when the gastrocnemius was subjected to concentric and concentric/eccentric resistance training modes. DESIGN: Prospective study, before and after training. The subjects served as their own controls. SETTING: Rehabilitation center and nuclear magnetic resonance spectroscopy unit of a university hospital. PARTICIPANTS: Sixteen healthy young volunteers from the local physiotherapist school. INTERVENTION: Two distinct resistive training programs were evaluated on the gastrocnemius: a protocol consisting of concentric contractions only and a mixed concentric/eccentric program. MAIN OUTCOME MEASURES: Maximal isometric resistance was measured after each training session. Before and after training, muscle CSA was appreciated using magnetic resonance imaging, whereas changes in muscle pH, phosphorus metabolite ratios, maximal oxidative power (Pmax), and oxidative phosphorylation were studied using 31P nuclear magnetic resonance spectroscopy at rest and during an incremental exercise protocol. RESULTS: Magnetic resonance imaging revealed a significant increase (7.1%) in the gastrocnemius CSA in the concentric-eccentric group only. The PCr/Pi (8.3 +/- 0.9 vs 10.4 +/- 1.7) and PCr/ATP (3.68 +/- .36 vs 4.07 +/- .27) resting ratios increased significantly (p = .008) after concentric-eccentric resistance training. Pmax was significantly improved in the concentric-eccentric group (7.0 +/- 2.1W vs 8.4 +/- 1.8W: p < .02). This mixed protocol also reduced the incidence of muscular soreness. CONCLUSION: The data suggest that the improved oxidative mechanical power output could be due mainly to a greater muscle cross-section in the concentric-eccentric group, with circumstantial evidence suggesting a relatively higher type IIa fiber activity.

Adult↗
PubMed2001

[Increase in strength after active therapy in chronic low back pain (CLBP) patients: muscular adaptations and clinical relevance].

INTRODUCTION: Active treatments are advocated for the management of non-specific chronic low back pain (CLBP), although few studies have documented the relative efficacy of differing types of programme. A number of the available treatments comprise exercise routines on specially designed training machines, which are ostensibly better disposed to reverse the compromised trunk muscle function displayed by these patients than are 'free exercise' programmes. However, in using these muscle-training programmes, the physiological or anatomical adaptations that might account for the improved performance are rarely investigated, let alone identified. This is an important issue, because if the 'newly-acquired strength' is mostly specific to performance on the devices on which the patient has trained and been tested, and reflects the skill in executing these particular tasks, this will not necessarily assist the patient during performance of his/her everyday activities. The aims of the present study were (1) to quantify the changes in back muscle performance in chronic LBP patients following 3 months active therapy, and (2) to analyse the corresponding changes in activation and cross-sectional area of the paraspinal muscles. METHODS: 148 individuals (57% women) with CLBP (age 45.0+/-10.0 years; duration of LBP 10.9+/-9.5 years) were randomised to a treatment which they attended 2/week for 3 months: active physiotherapy, muscle reconditioning on training devices, or low-impact aerobics. Pre- and post-therapy, assessments were made of isometric trunk muscle strength in each plane of movement and of erector spinae activation (using surface electromyography) during back extension. In a sub-group of 56 patients, the cross-sectional area of the paravertebral muscles was determined using magnetic resonance imaging (MRI). In all patients, self-rated pain intensity, pain frequency and disability were assessed before and after therapy. RESULTS: 132/148 patients completed the therapy. Isometric strength in each movement plane increased significantly in all groups post-therapy. Apart from trunk extension, the changes were significantly greater in the devices group than in the other two groups (Fig 1). Activation of the paraspinal muscles during back extension also increased significantly in all groups (Fig 2) and was weakly, but significantly (r = 0.37; p = 0.0001) correlated with increased strength in back extension. Although, at baseline, highly significant correlations were observed between the size of the paraspinal muscles (at L3/4 and at L4/5) and isometric back extension strength (r=0.75; p< 0.0001), post-training increases in strength were not accompanied by corresponding changes in muscle size. None of the improvements in strength showed any relationship with the clinical changes in pain and disability, regardless of whether the latter were examined on an individual basis or in relation to 'outcome groups'. CONCLUSION: The superior trunk strength shown by the devices group post-therapy was considered to be attributable, in part, to a 'learning effect', of the type often seen when training and testing are carried out on the same machines. These gains are considered to be mostly 'task-specific'. However, part of the improvement in strength after active therapy (in all groups) also appeared to be due to an increased neural activation of the trunk muscles. These positive effects should be transferable to the performance of everyday activities for which the same muscles are employed, although the percentage improvement is probably not as high as the measured increase in strength might suggest. Possible roles for improved co-ordination and changes in motivation and/or pain tolerance after therapy cannot be excluded. No differences in the clinical outcome were observed between the three therapy groups, and the changes in physical performance after therapy did not correlate with the clinical outcome. It is therefore questionable whether strength measurements have any clinical significance in documenting the success of rehabilitation programmes, other than on a motivational basis. The results of the present study suggest that the value of supervised active therapy programmes does not reside in the reversal of specific muscular deficiencies, but rather in the provision of a source of confirmation/encouragement for the patient, that movement is not harmful, and a foundation upon which to further build. Whether the utilisation of specific training devices, or individual instruction, is necessary to elicit these particular effects is questionable.

Adaptation, Physiological↗
PubMed1993

Duration of pain and muscular adaptations in patients with dysfunction of the cervical spine.

Biopsies of the sternocleidomastoid and omohyoid muscle were taken from 24 patients who underwent arthrodesis for cervical dysfunction of different etiologies. The two muscles, which are involved differently in movements of the head and cervical spine, were investigated histochemically. Muscle fibers were classified as type I, IIA, IIB, or IIC (transitional fibers) according to the pH lability of myofibrillar ATPase and calculated relative distribution. In both muscles, fiber transformations (as evidenced by an increase in the relative amount of type-IIC fibers) were regularly observed within the first 2 years after the onset of the symptoms. The occurrence of the transformation processes was independent of the patient's age and sex and was the same for the different etiologies. Since the overall fiber composition of the muscles remained essentially unchanged, the fiber transformations must occur alternatingly in both directions (from "slow" to "fast" and the reverse). Muscles of patients with a long case history showed no greater signs of fiber transformation. Therefore, fiber transformations in response to cervical dysfunction occur in the initial stage of the disease and involve different types of muscles. The muscles then return to a "stable" condition, independent of the continuation of the dysfunction and the chronic neck pain.

Adaptation, Physiological↗
PubMed2005

Do blood cells mimic gene expression profile alterations known to occur in muscular adaptation to endurance training?

Exercise is known to upregulate mRNA synthesis for carnitine palmitoyl transferase1 (CPT1) and possibly also other mitochondrial carnitine acyltransferases in muscle tissue. The aim of this study was to test whether such an adaptation of oxidative metabolism in skeletal muscle is a systemic process and consequently, also affects other cells. Messenger RNA levels of five genes [carnitine palmitoyl transferases 1 and 2 (CPT1 and CPT2), carnitine acetyltransferase (CRAT), carnitine palmitoyltransferase 2 (CPT2), microsomal carnitine palmitoyltransferase (GRP58) and organic cation transporter (OCTN2)] were determined with quantitative real time polymerase chain reaction (PCR) in blood cells and in muscle biopsy samples from six cross country skiers before and 6 months after a high volume/low intensity exercise training, when training had elicited a significantly slower rate of lactate accumulation. Quantitative real time PCR showed that levels of mRNA in blood cells correlated significantly (CPT1B: P< 0.001) with those in muscle tissue from the same donors. After 6-months training, there was a 15-fold upregulation of CPT1B mRNA, a six to ninefold increase of CRAT mRNA, of CPT2 mRNA, GRP58 mRNA, and of OCTN2 mRNA. The observation of a concordant stimulation of CPT1, CPT2, CRAT, GRP58 and OCTN2 transcription in blood cells and muscle tissue after 6-month-endurance training leads the hypothesis of a common stimulation mechanism other than direct mechanical stress or local chemical environment, but rather humoral factors.

Adaptation, Physiological↗
PubMed1985

Muscular adaptations to exercise and training.

This article provides an overview of the characteristics of skeletal muscle, with an emphasis on equine skeletal muscle. A discussion of many of the adaptive processes that can occur in this tissue in response to altered states of physical activity is also included.

3-Hydroxyacyl CoA Dehydrogenases↗