Nuclear magnetic resonance evidence of different muscular adaptations after resistance training

Effects of Eccentric Single-Leg Decline Squat Exercise on the Morphological and Structural Properties of the Vastus Lateralis and Patellar Tendon

The purpose was to examine the effect of 6-week eccentric single-leg decline squat (SLDSe) training with two technical execution times (3 s or 6 s) on changes related to the structural properties of the vastus lateralis (VL) and patellar tendon (PT). Thirty-six physical active volunteers were randomly divided into three groups: control group (CG, n = 13, age = 20.8 ± 1.9 years, no intervention program), experimental group 1 (EG1, n = 11, age = 21.6 ± 2.5 years, execution time = 6 s) and experimental group 2 (EG2, n = 12, 21.1 ± 1.2 years, execution time = 3 s). Participants completed a 6-week SLDSe training program (80% of 1-RM) three days a week. The structural characteristics of the VL and the PT were measured with ultrasonography before and after 6-week SLDSe training and after 6 weeks of de-training. Our results indicate that EG1 increased ≈21.8% the thickness of the PT and EG2 increased ≈15.7% the thickness of the VL after the 6-week intervention program. EG1 and EG2 showed greater values (p < 0.05) of lean mass and lower values (p < 0.05) of fat percentage on the thigh after the intervention program. In conclusion, the SLDSe training carried out with the execution time of 6 s had greater effects on the structural and elastic properties of the PT, and the exercise with the execution time of 3 s caused greater structural adaptations in the VL musculature.

Resistance Training Reduces Skeletal Muscle Work Efficiency in Weight-Reduced and Non-Weight-Reduced Subjects

OBJECTIVE

The objective of this study is to determine whether resistance training is similarly effective in reducing skeletal muscle efficiency and increasing strength in weight-reduced and maximal weight subjects.

METHODS

This study examined the effects of supervised resistance exercise on skeletal muscle in 14 individuals with overweight and obesity sustaining a 10% or greater weight loss for over 6 months and a phenotypically similar group of 15 subjects who had not reduced weight and were weight stable at their maximal lifetime body weight. We assessed skeletal muscle work efficiency and fuel utilization (bicycle ergometry), strength (dynamometry), body composition (dual energy x-ray absorptiometry), and resting energy expenditure (indirect calorimetry) before and after 12 weeks of thrice-weekly resistance training.

RESULTS

Non-weight-reduced subjects were significantly (10%-20%) stronger before and after the intervention than reduced-weight subjects and gained significantly more fat-free mass with a greater decline in percentage of body fat than weight-reduced subjects. Resistance training resulted in similar significant decreases (~10%) in skeletal muscle work efficiency at low-level exercise and ~10% to 20% increases in leg strength in both weight-reduced and non-weight-reduced subjects.

CONCLUSIONS

Resistance training similarly increases muscle strength and decreases efficiency regardless of weight loss history. Increased resistance training could be an effective adjunct to reduced-weight maintenance therapy.

Effect of biological factors on successful measurements with skeletal-muscle (1)H-MRS

Background

Our purpose in this study was to clarify whether differences in subject group attributes could affect data acquisition in proton magnetic resonance spectroscopy (¹H-MRS).

Methods

Subjects without diabetes mellitus (DM) were divided into two groups (group A, in their 20s; group B, 30–60 years old). Subjects with DM formed group C (30–60 years old). The numbers of subjects were 19, 27, and 22 for group A, B, and C respectively. For all subjects, ¹H-MRS measurements were taken of the soleus muscle (SOL) and the anterior tibial muscle (AT). We defined the success of the measurements by the detection of intramyocellular lipids. Moreover, we also measured the full width at half maximum of the water peaks for all subjects.

Results

The success rate was significantly higher for the AT (100%) than for the SOL (81.6%) (P<0.01). For the SOL, the success rate was 100% in group A, 85.2% in group B, and 77.3% in group C. There was a significant difference (P<0.05) between groups A and B, as well as between groups A and C. In all subjects, there was a significant difference (P<0.01) in the full width at half maximum (Hz) of the water peak between the AT and SOL measurements.

Conclusion

We conclude that differences in the age and DM history of subjects could affect the probability of successful ¹H-MRS data acquisition.

Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training

Eccentric exercise is characterized by initial unfavorable effects such as subcellular muscle damage, pain, reduced fiber excitability, and initial muscle weakness. However, stretch combined with overload, as in eccentric contractions, is an effective stimulus for inducing physiological and neural adaptations to training. Eccentric exercise-induced adaptations include muscle hypertrophy, increased cortical activity, and changes in motor unit behavior, all of which contribute to improved muscle function. In this brief review, neuromuscular adaptations to different forms of exercise are reviewed, the positive training effects of eccentric exercise are presented, and the implications for training are considered.

Eccentric training in chronic heart failure: feasibility and functional effects. Results of a comparative study

OBJECTIVES

To evaluate, in chronic heart failure (CHF) patients, feasibility, safety, compliance and functional improvements of an eccentric (ECC) cycle training protocol personalized by the rate of perceived exertion (RPE; 9-11 Borg Scale), compared to concentric (CON) training at workload corresponding to the first ventilatory threshold.

METHODS

Thirty patients were randomly allocated to ECC or CON training (20 sessions). Compliance was evaluated with RPE, visual analog scale for muscle soreness and monitoring of heart rate (HR). Functional parameters were measured by the distance walked and the VO(2) uptake during the 6-minute walk test (6MWT) before and after training.

RESULTS

Two patients were excluded due to adverse effects in each group. RPE was 9-11 in ECC training while it reached 12-14 in CON training. HR remained stable in ECC group during exercise whereas it increased during CON exercise. 6MWT distance improved in both group (ECC: +53 m; CON: +33 m). 6MWT VO(2) uptake remained stable in ECC group whereas it increased in CON group.

CONCLUSION

ECC training tailored by RPE appears to be an efficient and safe alternative for CHF patients. Indeed, it induces functional improvement similar to conventional CON training with lower demand on the cardiovascular system during exercise.

Is it possible to individualize intensity of eccentric cycling exercise from perceived exertion on concentric test?

OBJECTIVE

To assess the safety and acute effects of a procedure using perceived exertion during a prior submaximal concentric (CON) test to individualize eccentric (ECC) cycling exercise intensity.

DESIGN

Prospective, monocentric open study.

SETTING

Technological investigation platform at a physical medicine and rehabilitation department in a university hospital.

PARTICIPANTS

Healthy subjects (N=18; 15 men, 3 women) aged between 22 and 37 years.

INTERVENTIONS

The subjects performed 3 cycling exercises: (1) incremental CON test to determine the comfortable pedaling power (CPP) corresponding to a Borg scale rating of 12 (rate of perceived exertion); (2) steady-state CON exercise at the CPP workload to determine the corresponding plantar pressure; and (3) steady-state ECC exercise with an imposed resistance corresponding to the CPP plantar pressure.

MAIN OUTCOME MEASURES

Rate of perceived exertion on Borg scale, oxygen uptake (V˙o2), heart rate, cardiac output, and stroke volume using inert gas rebreathing techniques were measured during steady-state CON and ECC exercises. Muscle soreness was rated on a visual analog scale immediately, 24, and 48 hours after the tests.

RESULTS

No adverse effects were reported. V˙o2 was about 5 times the resting value during CON exercise, while it was twice that during ECC exercise. Cardiac output was lower during ECC exercise (P<.05). This moderate increase of cardiac output was exclusively linked to a greater increase in stroke volume during ECC exercise than during CON exercise (P<.05).

CONCLUSIONS

Moderate-intensity ECC cycling exercise tailored according to perceived exertion during a prior CON test is well tolerated. It corresponds to a limited muscular use of oxygen and to an isolated increase in stroke volume. It appears to be a feasible procedure for preconditioning before ECC training.

Relationship between serum creatine kinase activity following exercise-induced muscle damage and muscle fibre composition

In this study, we examined the relationship between serum creatine kinase activity following exercise-induced muscle damage and muscle fibre composition. Seventeen untrained males volunteered and underwent a .[Vdot]O2max test, Wingate test, and an exercise-induced muscle damage protocol. Muscle soreness and blood samples were recorded before, immediately after, and 24, 48, 72, and 96 h after exercise. Biopsy samples from the vastus lateralis were collected one week after exercise-induced muscle damage and were assessed for muscle fibre composition. There was no significant relationship (P > 0.05) between muscle fibre composition and creatine kinase activity. A significant positive correlation (P < 0.05) was observed between soreness 48 h after exercise and type II and IIb fibres, and a significant negative correlation (P < 0.05) was observed between soreness 48 h after exercise and type I muscle fibres. Significant positive correlations were observed between soreness 48 h after exercise and the fatigue index, relative average power, and relative anaerobic capacity. Our results suggest that creatine kinase activity following exercise-induced muscle damage may not be related to muscle fibre proportions, and higher post-exercise muscular pain may be related to a predominance of type II muscle fibres and higher anaerobic capabilities.

Eccentric exercise in patients with chronic health conditions: a systematic review

PURPOSE

The capacity of eccentric actions to produce muscle hypertrophy, strength gains, and neural adaptations without stressing the cardiopulmonary system has led to the prescription of eccentric training programmes in patients with low tolerance to exercise, such as elders or those with chronic health conditions. The purpose of this systematic review was to analyze the evidence regarding the effectiveness and suitability of eccentric training to restore musculoskeletal function in patients with chronic diseases.

SUMMARY OF KEY POINTS

Relevant articles were identified from nine databases and from the reference lists of key articles. Articles were assessed to determine level of evidence and scientific rigour. Nine studies met the inclusion criteria. According to Sackett's levels of evidence, 7 studies were graded at level IIb, 1 study at level IV, and the remaining study at level V. Articles were also graded for scientific rigour according to the PEDro scale. One study was rated as high quality, 4 studies were rated as moderate, and 2 studies were graded as poor quality.

CONCLUSIONS

Eccentric training may be safely used to restore musculoskeletal function in patients with some specific chronic conditions. However, the heterogeneity of diseases makes it very difficult to extrapolate results and to standardize clinical recommendations for adequate implementation of this type of exercise. More studies are needed to establish the potential advantages of eccentric training in chronic conditions.

Comparative MRI analysis of T2 changes associated with single and repeated bouts of downhill running leading to eccentric-induced muscle damage

Although the exact mechanisms are still unclear, it is commonly acknowledged that acute eccentric exercise alters muscle performance, whereas the repetition of successive bouts leads to the disappearance of the deleterious signs. To clarify this issue, we measured blood creatine kinase and lactate dehydrogenase activities and proton transverse relaxation time (T2) in various leg muscles 72 h after single and repeated bouts of exhausting downhill running sessions (-15 degrees , 1.5 km/h) with either 4 or 7 days elapsed between bouts. After a single exercise bout, T2 and enzyme activities initially increased and recovered rapidly. When exercise bouts were repeated over a short time period (4 days), initial changes did not recover and endurance time throughout additional exercise sessions was significantly reduced. On the contrary, with a longer resting time between exercises (7 days), the endurance time of additional running sessions was significantly longer and muscle changes (T2 increase, muscle edema, and enzyme activity changes) slowly and completely reversed. Significant correlations were found between T2 changes and enzyme activities. T2 changes in the soleus and gastrocnemius muscle heads were differently affected by lengthening contractions, suggesting a muscle specificity and indicating that muscle alterations might be linked to different anatomical properties, such as fiber pennation angles, typology, and/or the exhausting nature of the downhill running sessions. We documented a "less muscle injury" effect due to the repetition of exercise bouts at a low frequency (i.e., 1 session per week) in accordance with the delayed muscle inflammation. This effect was not observed when the between-exercise resting time was shorter.

Exercise training for patients with cardiovascular disease

This review surveys effort training, a validated and recommended therapy, in patients with atheromatous cardiovascular disease. This true therapy reduces mortality by 25-35%, reduces clinical manifestations and complications (rhythm problems, thrombosis) and improves physical capacity, reintegration and quality of life. The effects are essentially linked to improved metabolic performance of muscles and reduced endothelial dysfunction, insulin resistance and neurohormonal abnormalities. Training also has an impact on the evolution of major risk factors, especially diabetes and arterial hypertension. The risks are limited as long as the contraindications are respected and the programmes supervised. The indications (stable angina, chronic heart failure, peripheral arterial disease) should be described more precisely by taking into account functional criteria: physical deconditioning, exclusion, compliance, mood swings, and seriousness of risk factors. The training programme should be tailor made and based on evaluation of the patient's adaptation to effort, in terms of frequency, intensity and duration of the exercises. Various types of exercise include overall or segmental physical training; concentric, eccentric, even isokinetic muscle contraction exercises; and proprioceptive rehabilitation. However, knowledge is lacking about the molecular mechanisms of the effects of training, the most effective intensity of effort, and strategies to develop physical activity in this ever-growing population for both primary and secondary prevention.

Supplementation of general endurance exercise with stabilisation training versus general exercise only. Physiological and functional outcomes of a randomised controlled trial of patients with recurrent low back pain

BACKGROUND

Determination of the mode of action of new exercise techniques in different back pain populations is lacking. The effectiveness of supplementing an exercise programme with stabilisation exercises concerning physiological and functional parameters in non-specific back pain patients is unknown.

METHODS

Randomised controlled trial, comparing a general trunk muscle endurance exercise approach enhanced with specific muscle stabilisation exercises (S&G group) with a general exercise approach only (G group). 55 patients with recurrent back pain were randomised in S&G group (n=29) and G group (n=26). Both groups received an 8-week exercise intervention and written advice. Paraspinal muscle strength and electromyographic fatigue of the erector spinae and multifidus were measured. Additionally, 3 functional speed tests were assessed. Outcomes were collected pre- and post-intervention.

FINDINGS

No differences were detected for any of the paraspinal fatigue characteristics either within or between groups, apart from a significant decrease in normalised median frequency slope of the erector spinae for the G group. Paraspinal muscle strength and all functional tests have demonstrated significant within-group improvements for both groups, without any between-group differences.

INTERPRETATION

An 8-week stabilisation exercise-enhanced approach presented equal benefits to a general endurance-based exercise programme for patients with recurrent non-specific back pain. A slightly steeper slope for the erector spinae in the G group was the only electromyographic fatigue alteration noted. Concomitant strength improvement probably reflects neural input changes rather than histochemical muscle changes. Physical exercise alone and not the exercise type was the key determinant for improvement in this patient group.

Effects of three different training modalities on the cross sectional area of the lumbar multifidus muscle in patients with chronic low back pain

OBJECTIVES

To determine the effect of different training schedules on the cross sectional area (CSA) of the lumbar multifidus muscle in patients with chronic low back pain.

METHODS

Each of 59 nine patients was randomly assigned to one of three programmes: 10 weeks of stabilisation training (group 1; n = 19); 10 weeks of stabilisation training combined with dynamic resistance training (group 2; n = 20); 10 weeks of stabilisation training combined with dynamic-static resistance training (group 3; n = 20). Before and after 10 weeks of training, multifidus CSAs were measured from standard computed tomography images at three different levels (upper end plate of L3 and L4, and lower end plate of L4).

RESULTS

The CSA of the multifidus muscle was significantly increased at all levels after training in group 3. In contrast, no significant differences were found in groups 1 and 2.

CONCLUSIONS

General stabilisation exercises and dynamic intensive lumbar resistance training have no significant effect on the CSA of the lumbar multifidus muscle in patients with chronic low back pain. The static holding component between the concentric and eccentric phase was found to be critical in inducing muscle hypertrophy during the first 10 weeks. Treatment consisting of stabilisation training combined with an intensive lumbar dynamic-static strengthening programme seems to be the most appropriate method of restoring the size of the multifidus muscle.

Effect of resistance training on muscle fatigue and recovery in intact rats

PURPOSE

To examine the effect of resistance training on muscle fatigue from intermittent contractions and subsequent recovery in intact rats.

METHODS

By using electrical stimulation, plantar flexor muscles were trained with eccentric and concentric contractions (5 x 10 repetitions, 5 d x wk(-1) for 6 wk) during ankle rotations. By using nerve stimulation, concentric contractions (40) imposed on isometric contractions (stimulation time, 1.9 s; rest period, 13.6 s; intermittent contractions) induced fatigue. During recovery, equivalent contractions were used every 5 min for 30 min.

RESULTS

Training increased isometric forces (19% and 23% at ankle positions of 1.57 and 0.70 rad), but muscle weights were not changed. After training, smaller declines in isometric (control, 68.9+/-1.4%; trained, 58.8+/-2.9%) and average concentric force (control, 71.6+/-0.7%; trained, 65.5+/-2.8%) occurred from fatigue. Recovery for 5 min returned isometric and average concentric force to 61.7+/-2.2% and 65.1+/-2.5% of initial values for controls and 76.9+/-2.2% and 77.1+/-2.2% after training. After recovery for 30 min, these forces were 87.6+/-0.7% and 89.2+/-1.1% of initial values for controls and recovered almost completely (94.2+/-1.3% and 94.6+/-1.6%) in trained muscles. During fatigue, the decline in force during successive concentric contractions was larger after training (from 19.7+/-1.1% to 50.1+/-2.0%; controls, from 19.9+/-2.0% to 41.7+/-1.4%). Recovery of this decline in force was training-independent and complete within 5 min.

CONCLUSIONS

Rat plantar flexor muscles adapt to 6 wk of 5 d x wk(-1) resistance training with: 1) increased isometric force, 2) smaller losses in isometric and average concentric force during fatigue, 3) larger force decline during concentric contractions during fatigue, and 4) improved recovery following fatigue. Different mechanisms might account for the recovery of the average concentric force and the decline in force during concentric contractions.