A morphometrical comparison of right and left whole human vastus lateralis muscle: how to reduce sampling errors in biopsy techniques

Summary. In studies of the effects of different training programmes, one muscle—most commonly the vastus lateralis—is used for the experiment while the contralateral muscle serves as a control, at the same time as muscle biopsies are taken from both sides. In order to increase the reliability of such studies, the sources and the magnitude of the sampling errors in the biopsy techniques need to be assessed in detail. In this study, cross-sections of whole right and left vastus lateralis muscle from six young sedentary right-handed men were prepared, and the total number and size of fibres and the proportion of the different fibre types were caluclated. A significant difference (P < 0·05-P < 0·001) between the right and the left muscle was found for at least one of the three variables in each of the six men, but there was no systematic difference and, therefore, no significant right-left difference for the whole group. The maximum difference between the right and the left side for the mean fibre size was 25% and for the fibre type proportion 5%; these differences are much smaller than the known variation within individual muscles. In conclusion, any study involving biopsies from both the right and the left vastus lateralis may use either muscle for the experiment while the contralateral muscle serves as a control without leading to systematic sampling error, whereas the errors involved in taking small samples from each muscle are much more important to control and to reduce.     

Effects of strength and endurance training on muscle fibrecharacteristics in elderly women

The effects of 18weeks’ intensive strength and endurance training on fibre characteristics of the vastuslateralis muscle were studied in 76- to 78-year-old women. Type I and type IIa fibresconstituted over 90% of the cell population and were almost equally represented. Nochanges were observed in the proportions of the different fibre types. When comparing thebaseline and the 18-week measurements within the groups, the strength group showed a meanincrease of 34% (P=0·028) in mean type I fibre area. Thefrequency histograms showed an increased proportion of larger type I fibres after strengthtraining and a decreased proportion of smaller type IIa fibres after endurance training. In thecontrol subjects, the proportion of smaller type I and type IIa fibres increased during theexperimental period. The results indicate that intensive strength training induces type I fibrehypertrophy, whereas the effects of endurance training are less evident. The considerablevariation found in the change in muscle fibre cross-sectional areas is also noteworthy.     

High blood pressure and muscle morphology/metabolism – causal relationship or only associated factors?

As muscle tissue constitutes a main target organ for glucose metabolism and is responsible for the development of insulin resistance, it seems plausible to elucidate the relationship between blood pressure and muscle morphology and metabolism. The association between blood pressure and capillarization/morphology of the vastus lateralis muscle and metabolic variables was evaluated in 24 perimenopausal obese women [body mass index (BMI) 34·9 ± 1·1; waist–hip ratio (WHR) 0·90 ± 0·02]. The muscle enzyme activity of lipoprotein lipase (LPL), citrate synthase and glycogen synthase was determined. There was a significant negative correlation between the percentage of type I fibres and relative fibre area of type I on the one hand and systolic and diastolic blood pressure on the other. There was a negative correlation between the capillary density (i.e. number of capillaries/muscle fibre) and a positive correlation between the diffusion distance (fibre area supplied by one capillary) and diastolic blood pressure. The activities of LPL and citrate synthase were positively correlated with the percentage of type I and negatively correlated with the percentage of type II muscle fibres. The activity of LPL was also negatively correlated with plasma glucose and the insulin/C-peptide ratio. The insulin/C-peptide ratio was positively correlated with the percentage of type II muscle fibres. In stepwise multiple regression analyses, 20–30% of the variation in systolic and diastolic blood pressure could be explained by the variables of muscle fibre distribution. Excluding muscle morphological variables from the regression model, the insulin/C-peptide ratio accounted for 13% of the variation in systolic and diastolic blood pressure. The results of the study show the close association between muscle morphology and blood pressure. It remains to be elucidated whether this association indicates a causal relationship.     

The effect of stretching exercises on the fibre angle of the vastus lateralis and vastus medialis oblique: an ultrasound study

[Purpose] To investigate the effects of a seven-week quadriceps stretching program on the muscle fibre orientation of the vastus medialis oblique and vastus lateralis in the lower limbs by ultrasound imaging. [Participants and Methods] Twenty-seven healthy, physically fit, asymptomatic females and males (age 21.5 ± 1.3, Tegner activity level score ≥4) were recruited. Their initial vastus medialis oblique and vastus lateralis fibre angles were determined using ultrasound. They then undertook a seven-week quadriceps stretching program, 3 sets of stretches to be performed on both lower limbs, 3 times a week on 3 separate days. One volunteer was assigned as an intra-rater control and did not take part in the stretching program. The vastus lateralis and vastus medialis oblique fibre angles were measured again on completion of the exercise regime. [Results] A statistically significant decrease in muscle fibre angle was observed in both the right and left vastus medialis oblique, and the right and left vastus lateralis. [Conclusion] A 7-week stretching program can result in a significant decrease in muscle fibre angle in both the vastus medialis oblique and the vastus lateralis. This can help in understanding the effects of prescribed stretching exercises on athletic patients with PFP.     

The influence of functional electrical stimulation on the properties of vastus lateralis fibres following total knee arthroplasty.

The influence of functional electrical muscle stimulation (FES) on selected properties of vastus lateralis muscle fibres was studied in patients recovering from total knee arthroplasty for osteoarthritis. Prior to surgery, on the average, muscle biopsies from the vastus lateralis could be characterized as having a predominance of Type I fibres which were significantly larger in cross-sectional area than the Type II fibres in the same sample. Following surgery, muscle biopsies from a group of patients (n = 7) which received continuous passive motion and no FES, exhibited a marked increase in the proportion of Type II fibres along with a general atrophy of both the Type I and Type II fibres. Patients receiving passive motion and FES (n = 9) also showed an increase in the relative percentage of Type II fibres. Post-operatively, however, there was no significant reduction in fibre area in the stimulated muscles. These data suggest that FES was effective in attenuating the muscle atrophy associated with total knee arthroplasty but had no influence on those metabolic properties which were related to muscle fibre type classification criteria.     

Muscle morphology and enzymes in proximal and distal muscle groups of lower limb from patients with corticosteroid treated rheumatoid arthritis: the relationship to maximal isokinetic muscle strength

Abnormal morphological and enzymatic patterns in the lateral vastus muscle have been found in women with corticosteroid treated rheumatoid arthritis. By means of biopsies from the lateral heads of right gastrocnemius muscles, the histology and enzyme activities were compared with those found in right vastus lateralis biopsies. The findings were correlated with isometric and isokinetic strength of the plantar flexors. The relative occurrence of type I fibres in the gastrocnemius muscle was 46.4 +/- 18.7 (SD) %, which is significantly higher than found in the vastus lateralis [35.7 +/- 13.3 (SD) %] (P less than 0.03). The relatively lower percentage of type II fibres in the gastrocnemius muscle was due to a relatively low percentage of type II A fibres [mean 27.9 +/- 16.4 (SD) %] (P less than 0.05). The area of type I fibres in the gastrocnemius muscle was 26.1 X 10(2) +/- 10.0 (SD) micron 2, which is 74% of the mean area for type I fibres found in the vastus lateralis (P less than 0.01). The area of type II fibres in the gastrocnemius was 14.9 X 10(2) +/- 7.1 (SD) micron 2, which is 77% of the mean area for type II fibres found in the vastus lateralis. The isokinetic muscle strength of the plantar flexors in corticosteroid treated patients with rheumatoid arthritis was reduced to less than 50% at all angular velocities when compared with healthy women. The same difference was found in the knee extensors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Histochemical demonstration of skeletal muscle fibre types and capillaries on the same transverse section

Summary. Serial transverse sections of m. vastus lateralis biopsies from six healthy men were reacted:

• 1 for myofibrillar adenosine triphosphatase (mATPase) to identify fibre types;
• 2 with α-amylase, periodic acid-Schiff (αPAS) to visualize capillaries. Sections were also processed with a new histochemical method for identification of fibre types and capillaries on the same skeletal muscle slice (mATPase/αPAS). Fibre type composition using either method was 41% type I, 37% type IIA and 22% type IIB. Types I, HA and IIB least diameter areas (mean±SE, μm²) were similar in sections processed for mATPase/αPAS or mATPase (3976±338, 5187±373 and 4389±514 vs. 4092±345, 5100±360 and 4289±474, respectively). The number of capillaries per mm² and per fibre did not differ in sections processed using the αPAS (315±29 and 1·48 ±0·12) or mATPase/αPAS (317±25 and 1·43±0·10) method. The number of capillaries was greater (P<0·05) around types I or IIA than type IIB fibres whether a section was processed for mATPase/αPAS (4·5±0·2 or 4·6±0·2 vs. 3·4±0·3) or when fibre profiles of serial sections reacted for mATPase or αPAS were ‘matched’ (4·5±0·2 or 4·4±0·2 vs. 3·4±0·3). The results indicate that histochemical and morphometric measures can be made on the same transverse section using the new method with substantial savings of time, cost and energy.

     

Associations of intramyocellular lipid in vastus lateralis and biceps femoris with blood free fatty acid and muscle strength differ between young and elderly adults

The present study aimed to determine relationships between intramyocellular lipid and biochemical profiles or muscle strength in elderly (n = 15; mean age, 71 years) and young (n = 15; mean age, 21 years) male and female adults. Levels of intramyocellular lipid in the vastus lateralis and biceps femoris muscles were determined using ¹H‐magnetic resonance spectroscopy. Fasting blood samples were collected to measure levels of glucose, insulin, haemoglobin A1c, total cholesterol, high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol, free fatty acid, triglyceride, adiponectin, and high‐sensitivity C‐reactive protein. Muscle strength was assessed as maximal voluntary contraction during isometric knee extension. Muscle cross‐sectional area in the vastus lateralis was measured using magnetic resonance imaging. Specific force (N cm^?2) indicating force generation capacity was calculated as muscle strength (N) divided by the muscle cross‐sectional area of the vastus lateralis (cm²). The intramyocellular lipid content was similar in both muscles in both groups. The intramyocellular lipid content in the biceps femoris significantly correlated with serum free fatty acid levels (r = 0·62, P<0·05), and that in the vastus lateralis significantly and inversely correlated with specific force (r = ?0·58, P<0·05) in the young, but not in the elderly adults. The relationship between the intramyocellular lipid content in the thigh muscles and biochemical profiles, or specific force differed between elderly and young adults. Age‐associated changes in morphology, function and metabolic factors apparently influence intramyocellular lipid metabolism in the thigh muscles.     

Impact of blood flow‐restricted bodyweight exercise on skeletal muscle adaptations

This study ascertains the ability of bodyweight blood flow‐restricted (BFR) exercise training to promote skeletal muscle adaptations of significance for muscle accretion and metabolism. Six healthy young individuals (three males and three females) performed six weeks of bodyweight BFR training. Each session consisted of five sets of sit‐to‐stand BFR exercise to volitional failure with 30‐second inter‐set recovery. Prior to, and at least 72 h after training, muscle biopsies were taken from m. vastus lateralis to assess changes in fibre type‐specific cross‐sectional area (CSA), satellite cell (SC) and myonuclei content and capillarization, as well as mitochondrial protein expression. Furthermore, magnetic resonance imaging was used to assess changes in whole thigh muscle CSA. Finally, isometric knee extensor muscle strength was evaluated. An increase in knee extensor whole muscle CSA was observed at middle and distal localizations after training (3·2% and 3·5%, respectively) (P<0·05), and a trend was observed towards an increase in type I fibre CSA, whereas muscle strength did not increase. Additionally, the number of SCs and myonuclei associated with type I fibres increased by 65·7% and 20%, respectively (P<0·05). No significant changes were observed in measures of muscle capillarization and mitochondrial proteins. In conclusion, six weeks of bodyweight‐based BFR exercise promoted myocellular adaptations related to muscle accretion, but not metabolic properties. Moreover, the study revealed that an appropriate total training volume needs further investigation before recommending bodyweight BFR to patient populations.     

Dynamic muscle strength alterations to detraining and retraining in elderly men

To investigate the effects of cessation and subsequent resumption of training on muscle strength in elderly men, 11 men (aged 65–77 years), just completing a 24-week randomized controlled trial of recombinant human growth hormone (rhGH) and resistance exercise (rhGH, n=6; placebo, n=5), detrained for 12 weeks and subsequently retrained for 8 weeks. During the detraining and retraining phase, subjects did not receive rhGH. The resistance programme included three sets of eight repetitions at 75% of one-repetition maximum (1-RM), three times per week, for 10 upper and lower body exercises. Dynamic muscle strength was assessed by the 1-RM method every 2 weeks for 44 weeks. Needle biopsies of vastus lateralis muscle were obtained from seven men. Muscle strength increased during initial training by 40·4±5·5% (mean±SEM), ranging from 26·0±5·0 to 83·9±15·6%, depending on muscle group. Increased strength was accompanied by hypertrophy (P<0·05) of type I (17·4±4·1%) and II (25·8±12·4%) muscle fibres. Of initial strength gains, only 29·9±5·2% was lost with detraining. However, type I and II fibre cross-sectional area reverted to pretraining values. After 8 weeks of retraining, muscle strength returned to trained values, but without a significant change in fibre morphology. The results indicate that elderly men lose some muscle strength following short-term detraining, but that only a brief period of retraining suffices to regain maximal strength. Reversal of fibre cross-sectional area with detraining, and only modest improvement with retraining, suggests that much of the retention in strength with detraining and reacquisition of lost strength with retraining reflects neural adaptation.     

Insulin treatment increases skeletal muscle fibre area in patients with diabetes mellitus type 2

The effects of insulin treatment on skeletal muscle characteristics were studied in 18 patients (62 ± 11 years) with poorly controlled diabetes mellitus type 2 (mean duration 7·5 ± 6 years). Skeletal muscle biopsy samples were taken from the lateral portion of the quadriceps muscle before and after a period of insulin treatment of 40 ± 14 days. Enzyme activities (phosphofructokinase, 3‐hydroxyacyl‐CoA dehydrogenase, citrate synthase, lactate dehydrogenase and creatine kinase) and myoglobin content were assessed. In a subgroup of 11 patients (60 ± 11 years), skeletal muscle fibre type composition (type I, IIA, IIB and IIC) and fibre type cross‐sectional area were also analysed. Following insulin treatment there were 32 and 38% increases, respectively, in the cross‐sectional areas of type IIA and IIB fast‐twitch fibres (P<0·02). The fibre type distribution did not change. The myoglobin content in muscle decreased by 20% (P<0·01). Of the enzymes tested, the 3‐hydroxyacyl‐CoA dehydrogenase activity decreased by 10% (P<0·04). Serum glucose, HbA1_C and serum triglyceride levels decreased (P<0·001) and body weight and arm muscle circumference increased (P<0·02). In conclusion, insulin treatment of patients with poorly controlled non‐insulin‐dependent diabetes mellitus increased the fast‐twitch fibre area, reduced myoglobin levels and decreased muscle enzyme activity related to fatty acid oxidation.     

Effect of hyperthyroidism on fibre-type composition,fibre area,glycogen content and enzyme activity in human skeletal muscle

Summary. Seven hyperthyroid patients were studied by repeated muscle biopsies (vastus lateralis) before and after a period of medical treatment which averaged 10 months. The biopsies were analysed with regard to fibre-type composition, fibre area, capillary density, glycogen content and enzyme activities representing the glycolytic capacity (hexokinase, 6-phosphofructokinase), oxidative capacity (oxoglutarate dehydrogenase, citrate synthase) and Ca²⁺- and Mg²⁺-stimulated ATPase in muscle. In the pretreatment biopsy (hyperthyroid state), there was a significantly lower proportion of type I fibres (30% vs. 41%), a higher capillary density (23%), lower glycogen content (33%), and higher hexokinase activity (32%) compared with the post-treatment biopsy. No significant changes in the activity of the remaining enzymes were observed. The present study indicates that hyperthyroidism induces a transformation from type I to type II fibres in human skeletal muscle. The increase in hexokinase activity probably reflects a higher glucose utilization by skeletal muscle in order to compensate partially for the reduced glycogen content.     

Local architecture of the vastus intermedius is a better predictor of knee extension force than that of the other quadriceps femoris muscle heads

The purpose of this study was to determine whether the muscle architecture of each head of the quadriceps femoris (QF) at multiple regions can be used to predict knee extension force. Muscle thickness and pennation angle were measured using sonographic images from multiple regions on each muscle of the QF with the knee flexed to 90°. The fascicle lengths of the rectus femoris (RF), vastus lateralis (VL) and vastus intermedius (VI) muscles were estimated based on sonographic images taken along the length of the thigh. The muscle architecture of the vastus intermedius was determined in two separate locations using sonographic images of the anterior (ant‐VI) and lateral portions (lat‐VI). The maximal voluntary contraction (MVC) was measured during isometric knee extension at a knee joint angle of 90°. The relationship between MVC force and muscle architecture was examined using a stepwise linear regression analysis with MVC force as the dependent variable. The muscle thickness of the ant‐VI was selected as an independent variable in the first step of the linear regression analysis (R² = 0·66, P<0·01). In the second step, pennation angle of the lat‐VI was added to the model (R² = 0·91, P<0·01). These results suggest that among the four muscles that make up the QF, the muscle architecture of the VI is the best predictor of knee extension force.     

Central and peripheral circulation in relation to muscle-fibre composition in normo- and hyper-tensive man.

1. Fibre composition in the vastus lateralis muscle, and blood pressure, were determined in age-matched normotensive (n = 22) subjects and previously untreated patients (n = 19) with essential hypertension. 2. In all subjects the muscle fibres were classified, as fast-twitch (FT) and slow-twitch (ST), and blood pressure was recorded. Eleven patients and seven of the normotensive subjects participated in an extended haemodynamic study with intra-arterial pressure measurements and determinations of leg blood flow. 3. In both normo- and hyper-tensive subjects, ambulant and intra-arterial blood pressure and leg vascular resistance were negatively correlated to the percentage of ST fibres; no significant correlation was found to total leg blood flow. 4. The findings show that muscles with a high proportion of FT fibres have a higher resistance than muscles rich in ST fibres and suggest that the type of fibre in skeletal muscle might be of importance for the development of the hypertensive disease.     

The influence of prednisone on the muscle morphology and muscle enzymes in patients with rheumatoid arthritis

Thirty-five female patients, mean age 63 years, suffering from rheumatoid arthritis participated the study. Twenty patients had been on long-term low-dose corticosteroid treatment. Fifteen patients had never received corticosteroids. A control group of 15 age- and sex-matched healthy subjects was also studied. Examination of muscle biopsies from the (right) vastus lateralis and measurements of isokinetic and isometric knee-extension muscle strength were performed in all subjects. Rheumatoid arthritis patients treated with corticosteroid showed a low percentage of type I fibres, mean 35.7 (range 17-66) % compared with patients who did not receive corticosteroid (P less than 0.005). The latter group did not differ from the controls. The muscle fibre areas also were affected in the corticosteroid treated rheumatoid patients. Type I and type II mean fibre areas were reduced by 32% and 50%, respectively, when compared with non-prednisone treated patients. The latter group did not differ from the controls in this respect. A correlation was found between the isokinetic muscle strength of the knee extensors and the mean areas of type I and type II in patients treated with prednisone (r = 0.48, P less than 0.05 and r = 0.58, P less than 0.02 respectively). No such correlation was found when using isometric measurements of the knee extensors. A positive correlation was found in both groups of rheumatoid arthritis patients between the areas of the type I and type II fibres (r = 0.66 - 0.68, P less than 0.05 - 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of resistance training on blood pressure in normotensive women

Summary. The purpose of the present study was to determine whether conventional resistance training alters 24-h ambulatory and manually determined casual blood pressure of normotensive women. Seven individuals (23 ± 2 years old) trainined 2 days week¹ for 20 weeks emphasizing the hip and knee extensor muscle groups. Three sets to exhaustion of the knee extension, squat, knee flexion and leg press exercises were performed. The load for each exercise represented approximately 8045% of the one-repetition maximum. Average values for 24-h ambulatory blood pressure were not different (P>0·05) pre- and post-training (systolic, 107 ± 4 vs. 109±1 mmHg; diastolic, 73±2 vs. 71±2 mmHg). Ambulatory values over 8-h segments of the 24 h (day, evening, night) and casual resting determinations of blood pressure were also not affected. The lack of change in blood pressure cannot be explained by an insufficient training response. Knee extensor strength during dynamic or isokinetic actions increased (?43%, P<0·05). In addition, biopsies from the vastus lateralis muscle showed an increase (P<0·05) in average muscle fibre cross-sectional area of 32%. This hypertrophic response was further substantiated by an increase (P<0·05) in lean body mass (41·2±1·3 kg to 43·4±1·5 kg). These results indicate that resistance training, which increases muscular strength, muscle fibre area and lean body mass, does not alter ambulatory or casual blood pressure. Thus, the concern that conventional resistance training may chronically elevate blood pressure does not appear warranted, at least in normotensive women.     

Acute effects of proprioceptive neuromuscular facilitation and static stretching on maximal voluntary contraction and muscle electromyographical activity in indoor soccer players

The aim was to investigate and compare the effects of proprioceptive neuromuscular facilitation (PNF) and static stretching (SS) on maximal voluntary contraction (MVC) and muscle activation in indoor soccer players. Thirty‐three young adult men were divided into two groups: (i) sedentary and (ii) trained. Each group completed three different experimental trials: SS, PNF and no stretching (NS). The MVC of knee extension was evaluated before and immediately after each condition along with electromyography from the vastus lateralis (VL) and rectus femoris (RF) muscles of the dominant leg. PNF or SS techniques induced no decrease on MVC and muscle electromyographical activity in indoor soccer players (P>0·05). The electromyography of the RF and VL was lower after SS only in the sedentary group (P≤0·05). Short‐duration PNF or SS has no effect on isometric MVC and muscle activity in indoor soccer players.     

Muscle fiber characteristics in postmenopausal women with normal or impaired glucose tolerance.

OBJECTIVE: Muscle fiber characteristics are altered in type 2 diabetes. We studied whether these alterations also exist in impaired glucose tolerance (IGT) and whether they are determinants of insulin sensitivity and glucose tolerance in postmenopausal women. RESEARCH DESIGN AND METHODS: Percutaneous muscle biopsies from the vastus lateralis muscle were obtained from 77 postmenopausal women aged 57-59 years: 50 women with normal glucose tolerance (NGT) and 27 with IGT. The IGT group had a reduced insulin sensitivity compared with the NGT group (euglycemic-hyperinsulinemic clamp) (P = 0.003). RESULTS: The groups did not differ in muscle fiber composition, as judged by the percentage of type I, IIa, or IIx fibers. In contrast, the IGT group had increased size of the IIa (mean +/-SD 3,776+/-987 vs. 3,078+/-862 microm2, P = 0.002) and IIx fibers (2,730+/-1,037 vs. 2,253+/-672 microm2, P = 0.017). There was a trend for the capillary diffusion areas (the muscle area supplied by each capillary) to be larger in the IGT group for the IIa (1,132+/-286 vs. 1,013+/-240 microm2, P = 0.061) and IIx fibers (1,020+/-246 vs. 906+/-240 microm2, P = 0.058). In the entire group, insulin sensitivity correlated with the size of the type IIa fibers (r = -0.28, P = 0.013), but not with the percentages of muscle fiber types. In a multiple regression, insulin sensitivity was determined by body fat content and HDL cholesterol level, while the size of the IIa fibers was not included in the model. Glucose tolerance was independently predicted by the number of capillaries/type I fiber, as well as by insulin sensitivity and triglyceride levels. CONCLUSIONS: We conclude that although muscle fiber composition is not altered, women with IGT have larger type IIa and IIx muscle fibers and a trend for increased capillary diffusion areas for these fibers, compared with women with NGT. In the entire group, insulin sensitivity was determined mainly by body fat content, while muscle fiber capillarization may be of importance for glucose tolerance.     

Knee joint angle and vasti muscle electromyograms during fatiguing contractions

We compared vasti muscle electromyograms for two knee joint angles during fatiguing tetanic contractions. Tetanic contraction of the knee extensors was evoked for 70 s by electrical stimulation of the femoral nerve at knee joint angles of 60° (extended, with 0° indicating full extension) and 110° (flexed) in eight healthy men. Surface electromyography was recorded from the vastus intermedius (VI), vastus lateralis (VL) and vastus medialis (VM) muscles. Knee extension force and M‐wave amplitudes and durations were calculated every 7 s, which were normalized by the initial value. Normalized knee extension force was decreased at the flexed knee joint angle compared with that of the extended knee joint angle (P<0·05). Decreased normalized M‐wave amplitude and increased normalized M‐wave duration of the VI were greater at the flexed knee joint angle than the extended knee joint angle (P<0·05), whereas those for the VL and VM were similar (P>0·05). These results suggest that peripheral fatigue profiles of the VI might be greater at the flexed than the extended knee joint angles, but that of VL and VM might be similar in the tested range of knee joint angles (i.e. 60°–110°) during continuous tetanic contraction induced by electrical stimulation. Therefore, greater reduction of knee extension force at the flexed knee joint angle than the extended knee joint angle may reflect fatigue development of the VI more than other quadriceps femoris components.     

Proprioceptive neuromuscular facilitation induces muscle irradiation to the lower limbs – A cross-sectional study with healthy individuals

IntroductionThis study aimed to evaluate the effectiveness of proprioceptive neuromuscular facilitation (PNF) in promoting muscle irradiation to the lower limbs and to relate these findings with muscle activation during the sit-to-stand task.MethodsTwenty-four healthy women were recruited via convenience sampling and submitted to four PNF patterns: upper limb pattern with flexion-abduction-external rotation (UL), lower limb pattern with flexion-adduction-external rotation with knee flexion (lower limb pattern 1 [LL1]), lower limb pattern with flexion-abduction-internal rotation with knee flexion (lower limb pattern 2 [LL2]), and lifting to the right. Electromyography was recorded from the gluteus maximus, gluteus medius, vastus medialis, vastus lateralis, and soleus during the PNF patterns and during the sit-to-stand task.ResultsThe most recruited muscles during the sit-to-stand task were the vastus lateralis, vastus medialis, and soleus (p < 0.05). Lifting to the right induced the greatest activation of the gluteus maximus (p < 0.001). Lifting to the right and LL2 were better than UL at recruiting the gluteus medius (p < 0.05). Lifting to the right and LL1 were better than UL at recruiting the vastus medialis and lateralis (p < 0.05; p < 0.05). and Lower limb pattern 1 and 2 were better than UL at recruiting the soleus muscle (p < 0.05).ConclusionPNF can be used to induce muscle irradiation to maintain or improve muscle activity to the muscles recruited during the sit-to-stand task. The best PNF pattern for inducing muscle irradiation to muscles recruited during the sit-to-stand task are lifting to the right, LL2, and LL1.