scholarly journals Neural adaptations to long-term resistance training: evidence for the confounding effect of muscle size on the interpretation of surface electromyography

2021 ◽  
Author(s):  
Jakob Škarabot ◽  
Thomas Grant Balshaw ◽  
Sumiaki Maeo ◽  
Garry J. Massey ◽  
Marcel Bahia Lanza ◽  
...  
Keyword(s):  
Knee Extensor ◽  
Positive Association ◽  
Compound Action Potential ◽  
Muscle Size ◽  
Discrete Measure ◽  
Cross Sectional ◽  
Electrophysiological Properties ◽  
Emg Amplitude ◽  
Muscle Groups

This study compared elbow flexor (EF; Experiment 1) and knee extensor (KE; Experiment 2) maximal compound action potential (Mmax) amplitude between long-term resistance trained (LTRT; n=15 and n=14, 6±3 and 4±1 years of training) and untrained (UT; n=14 and n=49) men; and examined the effect of normalising electromyography (EMG) during maximal voluntary torque (MVT) production to Mmax amplitude on differences between LTRT and UT. EMG was recorded from multiple sites and muscles of EF and KE, Mmax was evoked with percutaneous nerve stimulation, and muscle size was assessed with ultrasonography (thickness, EF) and magnetic resonance imaging (cross-sectional area, KE). Muscle-electrode distance (MED) was measured to account for the effect of adipose tissue on EMG and Mmax. LTRT displayed greater MVT (+66-71%, p<0.001), muscle size (+54-56%, p<0.001), and Mmax amplitudes (+29-60%, p≤0.010) even when corrected for MED (p≤0.045). Mmax was associated with the size of both muscle groups (r≥0.466, p≤0.011). Compared to UT, LTRT had higher absolute voluntary EMG amplitude for the KE (p<0.001), but not the EF (p=0.195), and these differences/similarities were maintained after correction for MED; however, Mmax normalisation resulted in no differences between LTRT and UT for any muscle and/or muscle group (p≥0.652). The positive association between Mmax and muscle size, and no differences when accounting for peripheral electrophysiological properties (EMG/Mmax), indicates the greater absolute voluntary EMG amplitude of LTRT might be confounded by muscle morphology, rather than provide a discrete measure of central neural activity. This study therefore suggests limited agonist neural adaptation after LTRT.

Muscle Strength, Size, and Composition Following 12 Months of Gender-affirming Treatment in Transgender Individuals

2019 ◽  
Vol 105 (3) ◽  
pp. e805-e813 ◽  
Author(s):  
Anna Wiik ◽  
Tommy R Lundberg ◽  
Eric Rullman ◽  
Daniel P Andersson ◽  
Mats Holmberg ◽  
...  
Keyword(s):  
Muscle Mass ◽  
Muscle Function ◽  
Treatment Initiation ◽  
Hormone Replacement ◽  
Knee Extensor ◽  
Muscle Volume ◽  
Muscle Size ◽  
Thigh Muscle ◽  
Cross Sectional ◽  
One Year

Abstract Context As many sports are divided in male/female categories, governing bodies have formed regulations on the eligibility for transgender individuals to compete in these categories. Yet, the magnitude of change in muscle mass and strength with gender-affirming treatment remains insufficiently explored. Objective This study explored the effects of gender-affirming treatment on muscle function, size, and composition during 12 months of therapy. Design, settings, participants In this single-center observational cohort study, untrained transgender women (TW, n = 11) and transgender men (TM, n = 12), approved to start gender-affirming medical interventions, underwent assessments at baseline, 4 weeks after gonadal suppression of endogenous hormones but before hormone replacement, and 4 and 12 months after treatment initiation. Main outcome measures Knee extensor and flexor strength were assessed at all examination time points, and muscle size and radiological density (using magnetic resonance imaging and computed tomography) at baseline and 12 months after treatment initiation. Results Thigh muscle volume increased (15%) in TM, which was paralleled by increased quadriceps cross-sectional area (CSA) (15%) and radiological density (6%). In TW, the corresponding parameters decreased by –5% (muscle volume) and –4% (CSA), while density remained unaltered. The TM increased strength over the assessment period, while the TW generally maintained their strength levels. Conclusions One year of gender-affirming treatment resulted in robust increases in muscle mass and strength in TM, but modest changes in TW. These findings add new knowledge on the magnitude of changes in muscle function, size, and composition with cross-hormone therapy, which could be relevant when evaluating the transgender eligibility rules for athletic competitions.

scholarly journals Quadriceps Recovery After Anterior Cruciate Ligament Reconstruction With Quadriceps Tendon Versus Patellar Tendon Autografts

2019 ◽  
Vol 7 (4) ◽  
pp. 232596711983978 ◽  
Author(s):  
Jennifer L. Hunnicutt ◽  
Chris M. Gregory ◽  
Michelle M. McLeod ◽  
Shane K. Woolf ◽  
Russell W. Chapin ◽  
...  
Keyword(s):  
Functional Outcomes ◽  
Ligament Reconstruction ◽  
Cruciate Ligament ◽  
Knee Extensor ◽  
Quadriceps Tendon ◽  
Step Length ◽  
Quadriceps Muscle ◽  
Muscle Size ◽  
Cross Sectional ◽  
Anterior Cruciate

Background: Quadriceps tendon (QT) autografts are being increasingly used for anterior cruciate ligament reconstruction (ACLR). A paucity of studies exist that compare QT autografts with alternative graft options. Additionally, concerns exist regarding quadriceps recovery after graft harvest insult to the quadriceps muscle-tendon unit. Purpose/Hypothesis: The purpose of this study was to compare quadriceps recovery and functional outcomes in patients with QT versus bone–patellar tendon–bone (BPTB) autografts. The hypothesis was that those with QT autografts would demonstrate superior outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: Active patients with a history of primary, unilateral ACLR with soft tissue QT or BPTB autografts participated. Quadriceps recovery was quantified using variables of strength, muscle size, and activation. Knee extensor isometric and isokinetic strength was measured bilaterally with an isokinetic dynamometer and normalized to body weight. Quadriceps activation was measured with the superimposed burst technique. The maximal cross-sectional area of each quadriceps muscle was measured bilaterally using magnetic resonance imaging. Assessors of muscle size were blinded to the graft type and side of ACLR. Functional tests included hop tests and step length symmetry during walking, measured via spatiotemporal gait analysis. Self-reported function was determined with the International Knee Documentation Committee (IKDC) questionnaire. Neuromuscular and functional outcomes were expressed as limb symmetry indices (LSIs: [surgical limb/nonsurgical limb]*100%). Wilcoxon rank-sum tests were used to compare the LSIs and IKDC scores between groups. Results: There were 30 study participants (19 male, 11 female; median age, 22 years [range, 14-41 years]; median time since surgery, 8 months [range, 6-23 months]), with 15 patients in each group. There were no significant between-group differences in demographic variables or outcomes. LSIs were not significantly different between the QT versus BPTB group, respectively: knee extensor isokinetic strength at 60 deg/s (median, 70 [range, 41-120] vs 68 [range, 37-83]; P = .285), activation (median, 95 [range, 85-111] vs 92 [range, 82-105]; P = .148), cross-sectional area of the vastus medialis (median, 79 [range, 62-104] vs 77 [range, 62-95]; P = .425), single-leg hop test (median, 88 [range, 35-114] vs 77 [range, 49-100]; P = .156), and step length symmetry (median, 99 [range, 93-104] vs 98 [range, 92-103]; P = .653). The median IKDC scores between the QT and BPTB groups were also not significantly different: 82 (range, 67-94) versus 83 (range, 54-94); respectively ( P = .683). Conclusion: Patients with QT autografts demonstrated similar short-term quadriceps recovery and postsurgical outcomes compared with patients with BPTB autografts.

scholarly journals Osteoarthritis and the Mediterranean Diet: A Systematic Review

Nutrients ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1030 ◽  
Author(s):  
Isabel Morales-Ivorra ◽  
Montserrat Romera-Baures ◽  
Blanca Roman-Viñas ◽  
Lluis Serra-Majem
Keyword(s):  
Systematic Review ◽  
Mediterranean Diet ◽  
Positive Association ◽  
Cartilage Degradation ◽  
Epidemiological Evidence ◽  
Cross Sectional ◽  
The Mediterranean ◽  
The Relationship

Osteoarthritis (OA) affects 240 million people globally. Few studies have examined the links between osteoarthritis and the Mediterranean diet (MD). The aim of this paper was to systematically review and analyze the epidemiological evidence in humans on the MD and its association with OA. A systematic search of EMBASE identified three studies that explored the association between MD and OA. Two of them were cross-sectional and the third one was a 16-week randomized clinical trial. Prisma declaration was followed to carry out this review. These studies described a positive association between a higher adherence to a MD and the quality of life of participants suffering OA. The prevalence of OA was lower in participants with a higher adherence to a Mediterranean diet. Biomarkers of inflammation and cartilage degradation related to OA were also analyzed and significant differences were detected only for IL1-α, which decreased in the MD group. Exploring the relationship between MD and OA is complex, moreover, the limited evidence and methodological differences in such studies makes it difficult to compare results. In conclusion, the three studies included in this systematic review demonstrated some relation between osteoarthritis and a Mediterranean diet. However, prospective and longer interventions are required to evaluate the long-term efficacy of the Mediterranean diet to improve symptomatology and preventing osteoarthritis.

scholarly journals Decreased Muscle Strength Relates to Self-Reported Stooping, Crouching, or Kneeling Difficulty in Older Adults

2010 ◽  
Vol 90 (1) ◽  
pp. 67-74 ◽  
Author(s):  
Manuel E. Hernandez ◽  
Allon Goldberg ◽  
Neil B. Alexander
Keyword(s):  
Older Adults ◽  
Muscle Strength ◽  
Fall Risk ◽  
Knee Extensor ◽  
Community Dwelling ◽  
Functional Mobility ◽  
Plantar Flexor ◽  
Cross Sectional ◽  
Muscle Groups ◽  
Flexor Strength

Background Bending down and kneeling are fundamental tasks of daily living, yet nearly a quarter of older adults report having difficulty performing or being unable to perform these movements. Older adults with stooping, crouching, or kneeling (SCK) difficulty have demonstrated an increased fall risk. Strength (force-generating capacity) measures may be useful for determining both SCK difficulty and fall risk. Objective The purposes of this study were: (1) to examine muscle strength differences in older adults with and without SCK difficulty and (2) to examine the relative contributions of trunk and leg muscle strength to SCK difficulty. Design This was a cross-sectional observational study. Methods Community-dwelling older adults (age [X̅±SD]=75.5±6.0 years) with SCK difficulty (n=27) or without SCK difficulty (n=21) were tested for leg and trunk strength and functional mobility. Isometric strength at the trunk, hip, knee, and ankle also was normalized by body weight and height. Results Compared with older adults with no SCK difficulty, those with SCK difficulty had significant decreases in normalized trunk extensor, knee extensor, and ankle dorsiflexor and plantar-flexor strength. In 2 separate multivariate analyses, raw ankle plantar-flexor strength (odds ratio [OR]=0.97, 95% confidence interval [CI]=0.95–0.99) and normalized knee extensor strength (OR=0.61, 95% CI=0.44–0.82) were significantly associated with SCK difficulty. Stooping, crouching, and kneeling difficulty also correlated with measures of functional balance and falls. Limitations Although muscle groups that were key to rising from SCK were examined, there are other muscle groups that may contribute to safe SCK performance. Conclusions Decreased muscle strength, particularly when normalized for body size, predicts SCK difficulty. These data emphasize the importance of strength measurement at multiple levels in predicting self-reported functional impairment.

Muscle size, neuromuscular activation, and rapid force characteristics in elderly men and women: effects of unilateral long-term disuse due to hip-osteoarthritis

2007 ◽  
Vol 102 (3) ◽  
pp. 942-948 ◽  
Author(s):  
C. Suetta ◽  
P. Aagaard ◽  
S. P. Magnusson ◽  
L. L. Andersen ◽  
S. Sipilä ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Muscle Mass ◽  
Muscle Activation ◽  
Hip Osteoarthritis ◽  
Muscle Size ◽  
Elderly Men ◽  
Neuromuscular Activation ◽  
Emg Amplitude ◽  
Age Related

Substantial evidence exists for the age-related decline in muscle strength and neural function, but the effect of long-term disuse in the elderly is largely unexplored. The present study examined the effect of unilateral long-term limb disuse on maximal voluntary quadriceps contraction (MVC), lean quadriceps muscle cross-sectional area (LCSA), contractile rate of force development (RFD, Δforce/Δtime), impulse (∫force d t), muscle activation deficit (interpolated twitch technique), maximal neuromuscular activity [electromyogram (EMG)], and antagonist muscle coactivation in elderly men (M: 60–86 yr; n = 19) and women (W: 60–86 yr; n = 20) with unilateral chronic hip-osteoarthritis. Both sides were examined to compare the effect of long-term decreased activity on the affected (AF) leg with the unaffected (UN) side. AF had a significant lower MVC (W: 20%; M: 20%), LCSA (W: 8%; M: 10%), contractile RFD (W: 17–26%; M: 15–24%), impulse (W: 10–19%, M: 19–20%), maximal EMG amplitude (W: 22–25%, M: 22–28%), and an increased muscle activation deficit (−18%) compared with UN. Furthermore, women were less strong (AF: 40%; UN: 39%), had less muscle mass (AF: 33%; UN: 34%), and had a lower RFD (AF: 38–50%; UN: 41–48%) compared with men. Similarly, maximum EMG amplitude was smaller for both agonists (AF: 51–63%; UN: 35–61%) and antagonist (AF: 49–64%; UN: 36–56%) muscles in women compared with men. However, when MVC and RFD were normalized to LCSA, there were no differences between genders. The present data demonstrate that disuse leads to a marked loss of muscle strength and muscle mass in elderly individuals. Furthermore, the data indicate that neuromuscular activation and contractile RFD are more affected by long-term disuse than maximal muscle strength, which may increase the future risk for falls.

CT-Based Muscle Attenuation May be Able to Account for Age- and Muscle-Specific Differences in Maximum Muscle Stress

2012 ◽  
Author(s):  
Dennis E. Anderson ◽  
Alexander G. Bruno ◽  
Brett T. Allaire ◽  
Mary L. Bouxsein
Keyword(s):  
Muscle Strength ◽  
Muscle Size ◽  
Plantar Flexors ◽  
Cross Sectional ◽  
Age Related ◽  
Musculoskeletal Models ◽  
Muscle Attenuation ◽  
Muscle Stress ◽  
Muscle Groups ◽  
Isometric Muscle

In musculoskeletal modeling, isometric muscle strength has been primarily determined based on muscle size. Specifically, the maximum force a muscle can produce may be calculated as: (1)FMAX=MMS×PCSA where FMAX is maximum isometric muscle force, MMS is maximum muscle stress, and PCSA is muscle physiological cross-sectional area. In general, modeling studies have selected a constant value of MMS, and applied it to all muscles in the model. However, the values reported in the literature for MMS vary widely [1, 2], from as little as 23 N/cm2 up to 137 N/cm2. Furthermore, MMS is likely lower in older adults than young adults, as age-related declines in muscle strength are significantly greater than declines in muscle mass [3], and the specific tension of gastrocnemius fascicles is 30% lower in elderly men than young men [4]. In addition, MMS is not constant between muscle groups. For example, the MMS of the elbow flexors is much greater than that of the elbow extensors [1], while the MMS of the ankle dorsiflexors is more than twice that of the ankle plantar flexors [5]. Thus, the use of a single constant for MMS in musculoskeletal models does not account for differences between individuals or muscle groups, and there is a need for a quantitative approach to assign different values of MMS to muscles in musculoskeletal models.

Resistance exercise-induced fluid shifts: change in active muscle size and plasma volume

1995 ◽  
Vol 269 (3) ◽  
pp. R536-R543 ◽  
Author(s):  
L. L. Ploutz-Snyder ◽  
V. A. Convertino ◽  
G. A. Dudley
Keyword(s):  
Resistance Exercise ◽  
Plasma Volume ◽  
Muscle Size ◽  
Blue Dye ◽  
Fluid Loss ◽  
Cross Sectional ◽  
Muscle Involvement ◽  
Absolute Increase ◽  
Muscle Groups ◽  
Exercise Induced

The purpose of this study was to test the hypothesis that the reduction in plasma volume (PV) induced by resistance exercise reflects fluid loss to the extravascular space and subsequently selective increase in cross-sectional area (CSA) of active but not inactive skeletal muscle. We compared changes in active and inactive muscle CSA and PV after barbell squat exercise. Magnetic resonance imaging (MRI) was used to quantify muscle involvement in exercise and to determine CSA of muscle groups or individual muscles [vasti (VS), adductor (Add), hamstring (Ham), and rectus femoris (RF)]. Muscle involvement in exercise was determined using exercise-induced contrast shift in spin-spin relaxation time (T2)-weighted MR images immediately postexercise. Alterations in muscle size were based on the mean CSA of individual slices. Hematocrit, hemoglobin, and Evans blue dye were used to estimate changes in PV. Muscle CSA and PV data were obtained preexercise and immediately postexercise and 15 and 45 min thereafter. A hierarchy of muscle involvement in exercise was found such that VS > Add > Ham > RF, with the Ham and RF showing essentially no involvement. CSA of the VS and Add muscle groups were increased 10 and 5%, respectively, immediately after exercise in each thigh with no changes in Ham and RF CSA. PV was decreased 22% immediately following exercise. The absolute loss of PV was correlated (r2 = 0.75) with absolute increase in muscle CSA immediately postexercise, supporting the notion that increased muscle size after resistance exercise reflects primarily fluid movement from the vascular space into active but not inactive muscle.

Atrophy, but not necrosis, in rabbit skeletal muscle denervated for periods up to one year

2007 ◽  
Vol 292 (1) ◽  
pp. C440-C451 ◽  
Author(s):  
Z. Ashley ◽  
H. Sutherland ◽  
H. Lanmüller ◽  
M. F. Russold ◽  
E. Unger ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Morphological Changes ◽  
Fiber Type ◽  
Common Peroneal Nerve ◽  
Cross Sectional Area ◽  
Extensive Literature ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Groups

Our understanding of the effects of long-term denervation on skeletal muscle is heavily influenced by an extensive literature based on the rat. We have studied physiological and morphological changes in an alternative model, the rabbit. In adult rabbits, tibialis anterior muscles were denervated unilaterally by selective section of motor branches of the common peroneal nerve and examined after 10, 36, or 51 wk. Denervation reduced muscle mass and cross-sectional area by 50–60% and tetanic force by 75%, with no apparent reduction in specific force (force per cross-sectional area of muscle fibers). The loss of mass was associated with atrophy of fast fibers and an increase in fibrous and adipose connective tissue; the diameter of slow fibers was preserved. Within fibers, electron microscopy revealed signs of ultrastructural disorganization of sarcomeres and tubular systems. This, rather than the observed transformation of fiber type from IIx to IIa, was probably responsible for the slow contractile speed of the muscles. The muscle groups denervated for 10, 36, or 51 wk showed no significant differences. At no stage was there any evidence of necrosis or regeneration, and the total number of fibers remained constant. These changes are in marked contrast to the necrotic degeneration and progressive decline in mass and force that have previously been found in long-term denervated rat muscles. The rabbit may be a better choice for a model of the effects of denervation in humans, at least up to 1 yr after lesion.

Aerobic exercise does not compromise muscle hypertrophy response to short-term resistance training

2013 ◽  
Vol 114 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Tommy R. Lundberg ◽  
Rodrigo Fernandez-Gonzalo ◽  
Thomas Gustafsson ◽  
Per A. Tesch
Keyword(s):  
Resistance Exercise ◽  
Muscle Hypertrophy ◽  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Muscle Size ◽  
Mrna Levels ◽  
Cross Sectional ◽  
Before And After

This study tested the hypothesis that chronic aerobic and resistance exercise (AE+RE) would elicit greater muscle hypertrophy than resistance exercise only (RE). Ten men (25 ± 4 yr) performed 5 wk unilateral knee extensor AE+RE. The opposing limb was subjected to RE. AE completed 6 hr prior to RE consisted of ∼45 min one-legged cycle ergometry. RE comprised 4 × 7 maximal concentric-eccentric knee extensions. Various indexes of in vivo knee extensor function were measured before and after training. Magnetic resonance imaging (MRI) assessed m. quadricep femoris (QF) cross-sectional area (CSA), volume, and signal intensity (SI). Biopsies obtained from m. vastus lateralis determined fiber CSA, enzyme levels, and gene expression of myostatin, atrogin-1, MuRF-1, PGC-1α, and VEGF. Increases ( P < 0.05) in isometric strength and peak power, respectively, were comparable in AE+RE (9 and 29%) and RE (11 and 24%). AE+RE showed greater increase (14%; P < 0.05) in QF volume than RE (8%). Muscle fiber CSA increased 17% after AE+RE ( P < 0.05) and 9% after RE ( P > 0.05). QF SI increased (12%; P < 0.05) after AE+RE, but not RE. Neither AE+RE nor RE showed altered mRNA levels. Citrate synthase activity increased ( P < 0.05) after AE+RE. The results suggest that the increased aerobic capacity shown with AE+RE was accompanied by a more robust increase in muscle size compared with RE. Although this response was not carried over to greater improvement in muscle function, it remains that intense AE can be executed prior to RE without compromising performance outcome.

Determinants for Stair Climbing by Elderly from Muscle Morphology

2002 ◽  
Vol 94 (3) ◽  
pp. 814-816 ◽  
Author(s):  
Kazumi Masuda ◽  
Jundong Kim ◽  
Ryuta Kinugasa ◽  
Kai Tanabe ◽  
Shin-Ya Kuno
Keyword(s):  
Elderly Women ◽  
Knee Extensor ◽  
Stair Climbing ◽  
Cross Sectional ◽  
Stair Ascent ◽  
Psoas Major Muscle ◽  
Potential Capacity ◽  
Muscle Groups ◽  
Psoas Major ◽  
Muscle Cross Sectional Area

The relationship between muscle cross-sectional area (CSA) of the hip joint and lower extremities and speed of stair ascent/descent was investigated in a sample of 127 elderly women (ages: 60–70 years old). The participants performed ascent and descent of stairs with 12 steps for which the speeds for ascent and descent separately from video film were calculated. The ascent speed significantly correlated with CSAs of knee extensor ( r = .21, p<.05) and psoas major muscle ( r = .25, p<.01), which were assessed by magnetic resonance imaging. The descent speed also correlated with CSAs of the same muscle groups (with knee extensor: r = .20, p<.05, with m. psoas major: r = .18, p<.05). The rest of the muscle groups were not related to the ascent/descent speeds of the step. These results suggested that the muscle mass of the knee extensor muscle group and also the psoas major muscle could be a factor in potential capacity in stair ascent/descent by humans.

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