Regional Differences in Skeletal Muscle O2 Dynamics During Body-Weight Resistance Exercise with Slow Movement and Tonic Force Generation.

The aim of this study was to investigate the effects of body weight resistance training with slow movement and tonic force generation on muscle deoxygenation during arterial occlusion at rest. Eleven untrained healthy young male subjects performed Bulgarian split squat training for 3days per week for 8weeks. Each training session consisted of 4 sets of 10 repetitions (or until volitional failure). Before and after training, with the subject at rest in supine position, a pneumatic cuff was placed at the proximal site of the thigh and inflated to 250mmHg to induce the occlusion of arterial blood flow. During arterial occlusion, in the thigh distal to the cuff, muscle O2 saturation (SmO2) was continuously monitored at the vastus lateralis (VL) and rectus femoris (RF) muscles using spatially resolved near-infrared spectroscopy. During occlusion, the slope of desaturation and area above the curve (AAC) from baseline values were evaluated. At VL, a significantly shallower desaturation slope was found after training, compared to before. As a result, AAC from baseline was significantly lower after training. In contrast, no significant changes in the desaturation slope or AAC were observed at RF. Body weight resistance training for 8weeks may cause a shallow desaturation slope during arterial occlusion at rest, though the effects of resistance training on desaturation response during arterial occlusion may be regional in quadriceps muscles.

Push-up is considered as an excellent exercise for both assessment and training in athletes. However, the influence of its mode of application on activation of shoulder girdle musculature has been scantily studied by previous research in young overhead athletes. To investigate the activity of pectoralis major (PM) and triceps brachii (TB) muscle during push-up exercise performed on the push-up bar and perfect push-up using shoulder width (SW), narrow shoulder width (NSW) and wide shoulder width (WSW) hand positions in young overhead athletes. 24 young overhead athletes were recruited for the present study. Surface electromyography (EMG) was recorded for the PM and the TB muscles during the performance of push-up exercise on the push-up bar and perfect push-up using different hand positions (SW, NSW, and WSW). Root mean square (RMS) of the EMG signal was analyzed during each variation of push-up exercise for both muscles. Muscle activity was calculated as percentage maximum voluntary isometric contraction (% MVIC). EMG activity of PM muscle was significantly greater in WSW hand position as compared to SW (p < 0.01) and NSW (p < 0.01) hand position; whereas, the activity of TB was significantly greater in NSW hand position as compared to SW (p < 0.01) and WSW (p < 0.01) hand position. There were no significant differences in the EMG activity of PM (p = 0.54) and TB (p = 0.68) muscles between the push-up bar versus the perfect push-up. WSW hand position may be used during a push-up when the goal is to strengthen PM; whereas, an NSW hand position may be utilized for the selective strengthening of TB muscle. Both perfect push-up and push-up bar may be utilized by overhead athletes for performing push-ups based on the availability of equipment.

The purpose of this study was to investigate the difference in muscle oxygenation between the individual muscles involved in an exhaustive knee-extension exercise. Eight active women performed exercise by extending the knee joint from 90 degrees to 30 degrees (60 extensions min-1) at 20%, 30%, and 40% maximum voluntary contraction (MVC). Changes in oxy-(delta HbO2), deoxy-(delta Hb), and total (delta HbT) hemoglobin concentrations, and oxygen saturation (delta SO2NIRS = HbO2/HbT) in the vastus lateralis (VL) and rectus femoris (RF) muscles were measured with a spatially resolved near-infrared spectrometer (NIRS). The delta SO2NIRS in the VL and RF decreased rapidly from the pre-exercise control value (VL: 75.6 +/- 0.9%; RF: 81.6 +/- 1.6%) at the onset of exercise at three different intensities, although no significant difference in delta SO2NIRS was found between the two muscles at this time. However, the delta SO2NIRS decreased more rapidly thereafter and reached a lower value at exhaustion in the VL than in the RF. The difference in delta SO2NIRS between the VL (-10.3 +/- 1.7%) and RF (-4.0 +/- 1.0%) was significant (p < 0.05) when exercise intensity was 30% MVC. When the decreases in delta HbO2 and delta HbT (p < 0.05) were compared at different exercise intensities, the values at 30% and 40% MVC were significantly lower (delta HbO2: p < 0.01; delta HbT: p < 0.05) than those at 20% MVC in the VL, but there was no significant difference in any of the parameters in the RF, or in delta Hb in the VL. These results suggest that the muscle oxidative response to exhaustive knee-extension exercise differed between the VL and RF muscles. At exhaustion, oxygen saturation decreased to a lower level in the VL than in the RF, and an intensity-dependent difference in muscle oxygenation parameters was observed at 30% MVC in the VL but not in the RF muscles.

Objective:The purpose of this study was to measure muscle activation during ascending and descending phases of the push-up exercise on both stable and unstable support surfaces.Participants:Fourteen asymptomatic male amateur badminton players. During push-up exercises on stable and unstable bases, muscle activation measurements were collected with phase divisions (ascending and descending phase).Methods:Electromyography (EMG) was utilized to measure activation of the upper trapezius (UT) and lower trapezius (LT), middle serratus anterior (MSA) and lower serratus anterior (LSA), pectoralis major (PM), and triceps brachii (TB) muscles.Results:An unstable support surface produced significantly greater activation of the UT, LT, LSA, and PM muscles than a stable support surface (p &lt; 0.05). The MSA, LSA, TB, and PM muscles demonstrated greater activation during the ascending phase than the descending phase of the push-up exercise (p &lt; 0.05).Conclusions:The unstable support surface appeared to produce relatively greater activation of the LSA than that of the MSA. The descending phase of the push-up did not demonstrate a higher level of activation for any of the muscles tested.

The purpose of this study was to compare the EMG activity of blood flow restricted (limb) and nonrestricted (trunk) muscles during multi-joint exercise with and without KAATSU. Twelve (6 women and 6 men) healthy college students [means (SD) age: 24.1 (3.5) yrs] performed 4 sets (30, 15, 15, and 15 reps) of flat bench press exercise (30% of a predetermined one repetition maximum, 1-RM) during two different conditions [with KAATSU and without KAATSU (Control)]. In the KAATSU condition, a specially designed elastic cuff belt (30 mm wide) was placed at the most proximal position of the upper arm and inflated to a pressure of 100% of individual's resting systolic blood pressure. Surface EMG was recorded from the muscle belly of the triceps brachii (TB) and pectoralis major (PM) muscles, and mean integrated EMG (iEMG) was analyzed. During 4 sets of the exercise, gradual increases in iEMG were observed in both TB and PM muscles for the KAATSU condition. The magnitude of the increases in iEMG in the TB and PM muscles were higher (P<0.05) with KAATSU compared to the Control condition. In the first set, the mean exercise intensity from normalized iEMG was approximately 40% of 1-RM in both Control and KAATSU conditions. However, the mean exercise intensity of both muscles were 60-70% of 1-RM for the KAATSU condition and only about 50% of 1-RM for the Control condition, respectively, during the fourth set. We concluded that increases in iEMG in the trunk muscle during KAATSU might be an important factor for KAATSU training-induced trunk muscle hypertrophy.

Background: Although numerous exercises are prescribed for quadriceps femoris (QF) injury prevention and rehabilitation, few studies have compared QF muscle activation across commonly used bodyweight strength tasks. This study compared EMG activity of the rectus femoris proximal (RFP), rectus femoris medial (RFM), vastus lateralis (VL), and vastus medialis (VM) during seven bodyweight exercises with different stance positions. Methods: Twenty healthy male amateur football players performed three staggered-stance exercises (Split Squat, Bulgarian Split Squat, Backward Lunge), three parallel-stance exercises (Half-Squat, Russian Belt, Reverse Nordic), and one single-leg stance exercise (Lateral Step-Down). Surface EMG signals were recorded, and mean peak EMG values for each exercise were averaged and normalized to maximal isometric voluntary contraction (MVIC). Results: The highest VM and VL activation occurred during the Bulgarian Split Squat (VM: 85.4%; VL: 67.6% MVIC) and Backward Lunge (VM: 74.5%; VL: 59.9% MVIC). RFP and RFM showed the greatest activation during the Russian Belt (RFP: 49.8%; RFM: 39.6% MVIC) and Backward Lunge (RFP: 40.4%; RFM: 31.4% MVIC). VM and VL activation were significantly higher than RFP and RFM activation for all exercises except for Russian Belt and Reverse Nordic (p &lt; 0.005). Conclusions: Exercises imposing greater knee stability demands preferentially activated VM and VL, whereas exercises with longer knee extensor lever arms maximized rectus femoris activation.

Reliability of knee extensor neuromuscular structure and function and functional tests’ performance

This study assessed muscle activity (root mean square, RMS, and median frequency, MDF) to evaluate the acute response to blood flow restriction (BFR) resistance exercise (RE) and conventional moderate intensity (MI) RE. We also performed exploratory analyses of differences based on sex and exercise-induced hypoalgesia (EIH). Fourteen asymptomatic individuals performed four sets of unilateral leg press with their dominant leg to volitional fatigue under two exercise conditions: BFR RE and MI RE. Dominant side rectus femoris (RF) and vastus lateralis (VL) muscle activity were measured using surface electromyography (sEMG) through exercise. RMS and MDF were calculated and compared between conditions and timepoints using a linear mixed model. Pressure pain thresholds (PPT) were tested before and immediately after exercise and used to quantify EIH. Participants were then divided into EIH responders and nonresponders, and the differences on RMS and MDF were compared between the two groups using Hedges' g. RMS significantly increased over time (RF: p = 0.0039; VL: p = 0.001) but not between conditions (RF: p = 0.4; VL: p = 0.67). MDF decreased over time (RF: p = 0.042; VL: p < 0.001) but not between conditions (RF: p = 0.74; VL: p = 0.77). Consistently lower muscle activation was found in females compared with males (BRF, RF: g = 0.63; VL, g = 0.5. MI, RF: g = 0.72; VL: g = 1.56), with more heterogeneous findings in MDF changes. For BFR, EIH responders showed greater RMS changes (Δ RMS) (RF: g = 0.90; VL: g = 1.21) but similar MDF changes (Δ MDF) (RF: g = 0.45; VL: g = 0.28) compared to nonresponders. For MI, EIH responders demonstrated greater increase on Δ RMS (g = 0.61) and decrease on Δ MDF (g = 0.68) in RF but similar changes in VL (Δ RMS: g = 0.40; Δ MDF: g = 0.39). These results indicate that when exercising to fatigue, no statistically significant difference was observed between BFR RE and conventional MI RE in Δ RMS and Δ MDF. Lower muscle activity was noticed in females. While exercising to volitional fatigue, muscle activity may contribute to EIH.

Dynamics of thermographic skin temperature response during squat exercise at two different speeds

The squat is a movement that keeps the knee angle at 90° while keeping the weight of the one's shoulder to the shoulder width and maintaining equal weight load on the left and right legs. However, sufficient muscle activation of the lower limb is necessary to maintain a knee angle of 90 degrees. Thus, this study has been conducted to confirm the possibility that a modified squat exercise compared to traditional squat exercise can be recommended for elderly or patients. Two healthy adult males participated in this study. They performed a traditional squat exercise and a modified squat exercise. The modified squat exercise was performed in a general squat exercise posture while keeping the knee at 90 degrees and extending the hip joint with leaning the ball behind the back (supine position). The muscle activity of rectus femoris, vastus medialis, vastus lateralis, and gastrocnemius during exercises was measured by surface electromyography. As a result of this study, it was found that muscle activities were less in the right and left rectus femoris, vastus lateralis, vastus medialis during the modified squat exercise compared to the traditional squat exercise. The results showed that the muscle strength of the lower limb was activated to less than 50% compared with the traditional squat exercise during the modified squat exercise. These results may be used as an effective rehabilitation method for patients with weak muscles in the lower limb.

Pullover and straight arm pulldown exercises are commonly used in resistance exercise programs to improve sports performance or in physical activity health programs. This study aimed to evaluate the individual electromyographic (EMG) activity of the pectoralis major (clavicular, sternal, and costal portions), latissimus dorsi, anterior deltoid, triceps brachii, and rectus abdominis muscles in a barbell pullover exercise at a 100% biacromial width and a straight arm pulldown exercise at a 100% and 150% biacromial width and to compare the EMG activity in these selected muscles and exercises. Twenty healthy and physically active adults performed a set of eight repetitions of each exercise against 30% of their body mass. The barbell pullover exercise presented a higher EMG activity (p ≤ 0.01) than the straight arm pulldown exercise in both biacromial widths in all evaluated muscles except for the latissimus dorsi and the triceps brachii. These muscles showed the highest EMG activity in the straight arm pulldown exercise at both biacromial widths. In all of the exercises and muscles evaluated, the concentric phase showed a greater EMG activity than the eccentric phase. In conclusion, the barbell pullover exercise can highlight muscle activity in the pectoralis major (mainly in the sternal and lower portions), triceps brachii, and rectus abdominis muscles. However, the straight arm pulldown exercise at 100% and 150% biacromial widths could be a better exercise to stimulate the latissimus dorsi and triceps brachii muscles. Moreover, all exercises showed significantly greater EMG activity (p &lt; 0.001) in the concentric phase than in the eccentric phase for all the evaluated muscles.

BackgroundThe extremely low loads (e.g., <30% of one-repetition maximum) involved in performing resistance exercise are effective in preventing musculoskeletal injury and enhancing exercise adherence in various populations, especially older individuals and patients with chronic diseases. Nevertheless, long-term intervention using this type of protocol is known to have little effects on muscle size and strength adaptations. Despite this knowledge, very low-intensity resistance exercise (VLRE) with slow movement and tonic force generation (ST) significantly increases muscle size and strength. To further explore efficacy of ST-VLRE in the clinical setting, this study examined the effect of ST-VLRE on post-exercise inhibitory control (IC). MethodsTwenty healthy, young males (age: 21 ± 0 years, body height: 173.4 ± 1.2 cm, body weight: 67.4 ± 2.2 kg) performed both ST-VLRE and normal VLRE in a crossover design. The load for both protocols was set at 30% of one-repetition maximum. Both protocols were programmed with bilateral knee extension for six sets with ten repetitions per set. The ST-VLRE and VLRE were performed with slow (3-sec concentric, 3-sec eccentric, and 1-sec isometric actions with no rest between each repetition) and normal contractile speeds (1-sec concentric and 1-sec eccentric actions and 1-sec rests between each repetition), respectively. IC was assessed using the color-word Stroop task at six time points: baseline, pre-exercise, immediate post-exercise, and every 10 min during the 30-min post-exercise recovery period. ResultsThe reverse-Stroop interference score, a parameter of IC, significantly decreased immediately after both ST-VLRE and VLRE compared to that before each exercise (decreasing rate >32 and 25%, respectively, vs. baseline and/or pre-exercise for both protocols; all Ps < 0.05). The improved IC following ST-VLRE, but not following VLRE, remained significant until the 20-min post-exercise recovery period (decreasing rate >48% vs. baseline and pre-exercise; both Ps < 0.001). The degree of post-exercise IC improvements was significantly higher for ST-VLRE than for VLRE (P = 0.010 for condition × time interaction effect). ConclusionsThese findings suggest that ST-VLRE can improve post-exercise IC effectively. Therefore, ST-VLRE may be an effective resistance exercise protocol for improving cognitive function.

Resistance exercise improves daily glycemic control. Low-intensity resistance exercise with slow movements and tonic force generation (LST) is a resistance exercise protocol that can increase skeletal muscle mass and strength without considerable physical burden; however, its effect on glycemic variability is unknown. The aim of this study was to investigate the effect of LST on short-term glycemic variability, expressed as the M-value, in healthy individuals. We recruited 20 healthy subjects (mean age: 27.9 ± 3.9 years) with normal glucose tolerance, and subjects were randomly assigned to the control (n = 10) or LST (n = 10) groups. Subjects in the LST group performed the resistance exercise with 40–50% of the one-repetition maximum for 40 min. All subjects wore a subcutaneous continuous glucose monitoring system and a triaxial accelerometer, and their daily glycemic variability and physical activity were measured. One hour after the intervention, in the LST group, the variability of blood glucose levels was significantly decreased compared to the control group (M-values in the LST group: pre 3.5 ± 6.2, post 2.7 ± 2.7, p = 0.575; M-values in the control group: pre 0.4 ± 0.7, post 2.7 ± 2.0, p = 0.017). However, there were no differences in total physical activity and daily glycemic control between groups. The findings of this study suggest that LST improves short-term glycemic variability in healthy subjects.

Background/Objectives: The purpose of this experiment is to find out the degree of improvement by clarifying the effects of squats after attaching them to EMS through the functions of the body, such as muscle strength, jumping, and muscle endurance. Methods: The participants were divided into EMS squat group (ESG), squat group (SG), and control group (CoN) without squat exercise, and measured all subjects. Squat exercise was performed at 90° knee flexion with broad legs and straightened waist. Using ultrasonography, we measured the thickness of vastus intermedius (IM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), rectus abdominis (RA), external abdominal oblique (EO), internal abdominal oblique (IO), and transverse abdominis (TrA). And we measured jump, height, endurance, and agility. Findings: Squat movement applied with EMS improved jump, endurance, and agility, and increased the thickness of quadriceps muscle except VL, VM, and abdominal muscle, except TrA. However, we found that in endurance, there is not much difference from squat exercise. Improvements: There was a time constraint because the study was conducted for a short period, and the study was limited due to the occurrence of the elimination due to the strength of exercise.

Background: Life in modern society has become convenient, but the lack of exercise due to a sedentary lifestyle has led to muscle weakness. The quadriceps femoris is essential for walking, standing, and using stairs in daily life. Muscle weakness can lead directly to impaired function. Squatting is the most representative exercise for effective muscle development and increasing the knee extensor strength. This study examined the effects of ankle angle during wall squats on the muscle activity of the vastus medialis oblique (VMO), vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), rectus abdominis (RA), and erector spinae (ES) to determine which ankle angle can better strengthen the vastus medialis oblique as a method of rehabilitation training after a knee joint injury. Methods: All subjects (n = 20) performed the following three types of wall squats randomly: (1) GWS (General Wall Squat), (2) WSD 10° (Wall Squat with dorsiflexion 10°), and (3) WSP 10° (Wall Squat with plantarflexion 10°). Each subject completed all three kinds of wall squatting exercises three different times, and the muscle activity data of the VMO, VL, RF, BL, RA, and ES were recorded. Results: Compared to GWS exercise, the VMO and RF muscle activity increased significantly under WSP 10° exercise (p &lt; 0.05), whereas the VL, BF, RA, and ES activity did not increase significantly (p &gt; 0.05). No significant change between WSD 10° and WSP 10° was observed (p &gt; 0.05). Conclusions: WSP 10° can help increase the quadriceps muscle activity. Wall squat exercise with different ankle angles can be used for quadriceps muscle strengthening training for normal people and for recovery training for patellofemoral pain syndrome (PFPS) patients in the rehabilitation stage.