Single-joint Exercises Research Articles

Exercise selection plays an important role in inducing non-uniform acute responses on elbow flexors muscle thickness

The muscle thickness (MT) acutely increases in response to the redirection of blood flow during exercise, with this muscle swelling being a proxy to quantify the degree of muscle stimuli and involvement in an exercise. The present study aims to compare the MT acute variations between the biceps brachii (BB) and brachialis (BRA) muscles in two different unilateral exercises, the dumbbell curl (DC) and dumbbell row (DR). Sixteen well-trained young males performed a 10-repetition maximum (10RM) load test and retest for each exercise. Four sets were performed with the 10RM load for each exercise until the concentric failure. The BB and BRA muscles MT were measured pre and post-intervention with a B-mode ultrasound images. The main finding of this study was that, when DC is performed, the BB presented greater MT changes (18.67% ± 6.23) compared to BRA (12.27% ± 6.20) (p = 0.025), and compared to BB when performed in DR (12.23% ± 6.03) (p = 0.024). It was also found that BB greatest increase from BRA was not observed in DR and the BRA results were similar in both exercises. These results indicate that the structural acute responses can be muscle-specific among the elbow flexors muscles for the single-joint exercise and also exercise-specific. Therefore, either one of these two exercises can be chosen to stimulate BRA, but it would be interesting to use DC to offer greater stimuli for BB.

Effects of Blood Flow Restriction Resistance Training on Autonomic and Endothelial Function in Persons with Parkinson's Disease.

Autonomic dysfunction precedes endothelial dysfunction in Parkinson's disease (PD) and causes blood pressure and circulation abnormalities that are highly disruptive to one's quality of life. While exercise interventions have proven helpful for motor symptoms of PD, improving associated non-motor symptoms is limited. Low-intensity resistance training with blood flow restriction (LIRT-BFR) improves autonomic dysfunction in non-PD patients and high-intensity resistance training (HIRT) is recommended for motor symptom improvements for people with PD (PwPD). To determine the effects of LIRT-BFR and HIRT on homocysteine and autonomic and endothelial function in PwPD and to determine the hemodynamic loads during LIRT-BFR and HIRT in PwPD using a novel exercise protocol. Thirty-eight PwPD were assigned LIRT-BFR, HIRT or to a control (CNTRL) group. The LIRT-BFR and HIRT groups exercised three days per week for four weeks. The LIRT-BFR protocol used 60% limb occlusion pressure (LOP) and performed three sets of 20 repetitions at 20% of the one-repetition maximum (1RM). The HIRT group performed three sets of eight repetitions at 80% 1RM. The CNTRL group was asked to continue their normal daily routines. LIRT-BFR significantly improved orthostatic hypotension (p = 0.026), homocysteine levels (p < 0.001), peripheral circulation (p = 0.003), supine blood pressure (p = 0.028) and heart rate variability (p = 0.041); LIRT-BFR improved homocysteine levels (p < 0.018), peripheral circulation (p = 0.005), supine blood pressure (p = 0.007) and heart rate variability (p = 0.047) more than HIRT; and hemodynamic loads for LIRT-BFR and HIRT were similar. LIRT-BFR may be more effective than HIRT for autonomic and endothelial function improvements in PwPD and hemodynamic loads may be lessened in LIRT-BFR protocols using single-joint exercises with intermittent blood flow restriction. Further research is needed to determine if non-motor symptoms improve over time and if results are sustainable.

Resistance Exercise Sessions Comprising Multijoint vs. Single-Joint Exercises Result in Similar Metabolic and Hormonal Responses, But Distinct Levels of Muscle Damage in Trained Men.

Barbosa, PH, Bueno de Camargo, JB, Jonas de Oliveira, J, Reis Barbosa, CG, Santos da Silva, A, Dos-Santos, JW, Verlengia, R, Barreira, J, Braz, TV, and Lopes, CR. Resistance exercise sessions comprising multijoint vs. single-joint exercises result in similar metabolic and hormonal responses, but distinct levels of muscle damage in trained men. J Strength Cond Res 38(5): 842-847, 2024-Resistance-type exercise (RE) elicits distinct acute metabolic and hormonal responses, which can be modulated by the manipulation of training variables. The purpose of this study was to compare the metabolic (blood lactate and estimated lactic anaerobic system energy expenditure) and hormonal (growth hormone [GH]) responses to RE sessions composed exclusively of multijoint (MULTI) or single-joint (SINGLE) exercises. Assessments of creatine kinase (CK) levels were also performed. In a crossover design, 10 recreationally resistance-trained men (age: 26.9 ± 3.0 years, total body mass: 83.2 ± 13.8 kg; height: 176 ± 7.0 cm; training experience: 5.5 ± 2.4 years) were randomly submitted to both protocols. Blood collections were made pre, 3 minutes after, and 36 hours after each experimental session. No significant difference between MULTI vs. SINGLE was observed for the rises in blood lactate (p = 0.057) and GH (p = 0.285) levels. For CK, a significant difference between the protocols was noted, in which MULTI resulted in significant rises after 3 minutes (p = 0.017) and 36 hours (p = 0.043) compared with SINGLE. In conclusion, the findings of this study suggest that resistance-trained individuals display similar metabolic and hormonal responses when performing MULTI and SINGLE exercise protocols. Also, RE sessions comprising MULTI exercises induce a higher magnitude of muscle damage, which may require a longer recovery period compared with SINGLE.

Pedal Quadrant-Specific Strength and Conditioning Considerations for Endurance Cyclists

ABSTRACT The performance-enhancing effects of strength training on cycling are well documented with findings from research, demonstrating resistance training with heavy loads conducted 2–3 times per week for at least 8 weeks can improve power output (maximal and submaximal), extend time to exhaustion, and reduce completion time for set distances, while not adding to the total body mass. Despite the evident benefits of strength training, there remains a lack of consensus regarding the most effective exercises to enhance endurance cycling. This uncertainty is evident when considering movement-specific exercises to enhance dynamic transfer to cycling. A range of lower-limb exercises involving hip, knee, and ankle flexion and extension seems to enhance cycling performance more so than static or single-joint exercises. These improvements may be attributed to enhanced coordination and improved pedaling technique. This study presents 5 strength training exercises designed to target cycling pedaling quadrants and replicate the unilateral opposing nature of cycling (simultaneous flexion and extension of the legs) to enhance transfer from weight room-based strength training to the bike. These exercises are presented in example programs alongside established “traditional” exercises that may be used to guide the development of strength training for cyclists.

Accuracy of Predicted Intraset Repetitions in Reserve (RIR) in Single- and Multi-Joint Resistance Exercises Among Trained and Untrained Men and Women.

We assessed the accuracy of intraset repetitions in reserve (RIR) predictions on single-joint machine-based movements of trained and untrained men and women. Participants were 27 men (M age = 22, SE = 0.6 years; M weight = 90.8, SE = 4.0kg; M height = 182.3, SE = 1.4cm; M training experience = 66, SE = 9 months) and 31 women (M age = 20, SE = 0.4 years; M weight = 67.8, SE = 2.3kg; M height = 167.6, SE = 1.1cm; M training experience = 22, SE = 4 months). In one session, participants performed a five-repetition maximum (5RM) test on biceps curl, triceps pushdown, and seated row exercises; we then estimated one repetition maximum (1RM). Participants then performed four sets of each exercise, in a randomized order, to the point of momentary muscular failure at 72.5% of 1RM. During each set, participants indicated when they first perceived 5RIR and then predicted RIR on every repetition thereafter until failure. The difference between actual repetitions performed and predicted repetitions at each intraset prediction was determined to be the RIR difference (RIRDIFF). A 3-way repeated measures ANCOVA found that a 3-way interaction was not statistically significant (p = 0.435) and no covariates of sex (p = 0.917), training experience (p = 0.462) nor experience rating RIR significantly affected RIRDIFF (p = 0.462-0.917). There were significant main effects for the proximity to failure of the prediction and the set number (p < 0.01) but not for exercise (p = 0.688). Thus, intraset RIR predictions were more accurate when closer to failure and in later sets, but sex, training experience, and experience rating RIR did not significantly influence RIR prediction accuracy on machine-based single-joint exercises.

Applying an Exercise Snack-Based Health Promotion Strategy

Lack of time, lack of access to equipment, and environmental constraints are generally perceived as barriers to regular physical activity. Moreover, insufficient activity is known to promote sedentary behavior, which is a factor in many chronic diseases, negatively affects mental health, and reduces quality of life. Exercise snacks, defined as short and efficient bursts of exercise, are convenient and easy to implement, reduce sedentary time, increase physical activity, and promote the development of good exercise habits. Previous studies have found exercise snacks to be safe and feasible for the elderly, promoting physical function and reducing the incidence of falls and metabolic diseases. Exercise snacks have also been found to be effective in healthy adults as well as in patients with obesity and diabetes, helping decrease blood sugar and promoting cardiorespiratory fitness. Depending on the participant's age and tolerance, exercise snack patterns may be extended and distinguished into two forms: 10-minute bouts of gentle intermittent exercise twice a day and 60-second bouts of vigorous exercise 3 to 8 times a day. The main considerations for exercise snacks include: multi-joint exercise is better than single-joint exercise, lower body exercise is better than upper body exercise, and dynamic and rapid movement that pushes away from the ground promotes osteogenesis and helps prevent osteoporosis and fractures. Exercise snacks may be applied in healthcare practice and related research to promote health and improve quality of life for all.

RETRACTED ARTICLE: Statement of Retraction: Single joint exercises do not provide benefits in performance and anthropometric changes in recreational bodybuilders

This article refers to:RETRACTED ARTICLE: Single joint exercises do not provide benefits in performance and anthropometric changes in recreational bodybuilders

Deconstructing the Ergogenic Effects of Photobiomodulation: A Systematic Review and Meta-analysis of its Efficacy in Improving Mode-Specific Exercise Performance in Humans.

Photobiomodulation therapy (PBMT) is defined as non-thermal electromagnetic irradiation through laser or light-emitting diode sources. In recent decades, PBMT has attracted attention as a potential preconditioning method. The current meta-analysis was conducted to assess the effectiveness of PBMT in improving mode-specific exercise performance in healthy young adults. A computerized literature search was conducted, ending on 15 May 2022. The databases searched were PubMed, Cochrane Central Register of Controlled Trials, Embase, SPORTDiscus, and the Physiotherapy Evidence Database. Inclusion/exclusion criteria limited articles to crossover, double-blind, placebo-controlled studies investigating the PBMT effects as a preconditioning method. The included trials were synthesized according to exercise mode (single-joint, cycling, running, and swimming). All results were combined using the standardized mean differences (SMDs) method and the 95% confidence intervals (CIs) were described. A total of 37 individual studies, employing 78 exercise performance measurements in 586 participants, were included in the analyses. In single-joint exercises, PBMT improved muscle endurance performance (SMD 0.27, 95% CI 0.12-0.41; p < 0.01) but not muscle strength performance (p = 0.92). In cycling, PBMT improved time to exhaustion performance (SMD 0.35, 95% CI 0.10-0.59; p < 0.01) but had no effect on all-out sprint performance (p = 0.96). Similarly, PBMT had no effect on time to exhaustion (p = 0.10), time-trial (p = 0.61), or repeated-sprint (p = 0.37) performance in running and no effect on time-trial performance in swimming (p = 0.81). PBMT improves muscle endurance performance in single-joint exercises and time to exhaustion performance in cycling but is not effective for muscle strength performance in single-joint exercises, running, or swimming performance metrics.

Maximizing the efficiency of resistance training

Introduction and objective: Resistance training is the main intervention that can develop an individual’s strength and muscle mass. When executed regularly, it provides significant health benefits. The aim of this study is to analyze the current level of knowledge on maximizing the efficiency of resistance training in the context of muscle hypertrophy and increase in muscle strength.&#x0D; Materials and methods: PubMed and Google Scholar databases were searched. The criteria for qualifying the article for the review were the following keywords: hypertrophy, resistance training, muscle strength, and efficiency. 10 articles from 2017 to 2022 were analyzed.&#x0D; Description of the state of knowledge: To optimize the way of performing RT, its assumptions should be individually adapted to the exercising person. In the conventional model of muscle hypertrophy, three main factors are distinguished: muscle tension, metabolic stress, and muscle damage. Maintaining greater mechanical muscle tension during training primarily promotes an increase in its strength while increasing metabolic stress is responsible for the intensification of hypertrophy. In terms of hypertrophy, it has been observed that more series of exercises per week means greater gains in muscle mass. Multi-joint exercises involve more muscle mass than single-joint exercises.&#x0D; Summary: To control the effectiveness of training 1RM should be measured before and after the training cycle. Performing exercises with a high load (RM ≤7) may be the most effective training method for people with limited time resources. To maximize the efficiency of training, only multi-joint exercises may be used.&#x0D; Key words: hypertrophy; resistance training; muscle strength; efficiency

Hypertrophic Effects of Single- Versus Multi-Joint Exercise of the Limb Muscles: A Systematic Review and Meta-analysis

ABSTRACT We performed a systematic review and meta-analysis comparing the effects of single-joint (SJ) and multijoint (MJ) resistance exercises on muscle hypertrophy of the limb muscles. A systematic search was performed to identify randomized trials that directly compared hypertrophic changes between SJ and MJ resistance exercises, as well as combinations of the 2, in healthy adults. A total of 7 studies met inclusion criteria, comprising 10 nested comparisons. Meta-analysis indicated a trivial standardized point estimate with a relatively moderate precision for the confidence interval estimate. Subgroup analyses showed no effect on results when stratifying studies according to combined SJ + MJ versus MJ training alone, as well as under volume-equated or nonequated conditions. However, scrutiny of individual studies in conjunction with related indirect evidence collectively indicate that SJ exercise may provide the ability to preferentially hypertrophy muscular subdivisions, potentially promoting more complete muscle development. We conclude that current evidence indicates similar whole muscle hypertrophy between MJ and SJ training. There may be added benefit to combining SJ and MJ exercises for targeting individual aspects of a given muscle, although this hypothesis remains understudied. Future studies are needed to explore the effects of SJ and MJ exercises in resistance training on regional muscle hypertrophy.

Near-infrared spectroscopy-derived muscle kinetics after moderate running exercise in healthy males: reliability and associations with parameters of aerobic fitness.

What is the central question of this study? What is the reliability of near-infrared spectroscopy-derived muscle oxygen uptake ( ) kinetics following running exercise and what is the relationship between the time constant of off-kinetics and parameters of aerobic fitness? What is the main finding and its importance? The time constant of kinetics in gastrocnemius following moderate running exercise presents good to excellent reliability. In addition, it was well correlated with parameters of aerobic fitness, such as maximal speed of an incremental test, ventilatory threshold and pulmonary on-kinetics. Therefore, near-infrared spectroscopy-derived muscle oxidative capacity together with other physiological measurements may allow a concomitant local and systemic analysis of the components of the oxidative system. Near-infrared spectroscopy-derived muscle oxygen uptake ( ) kinetics following single-joint exercise has been used to assess muscle oxidative capacity. However, little evidence is available on the use of this technique following whole-body exercise. Therefore, this study aimed to assess the reliability of the NIRS-derived kinetics following running exercise and to investigate the relationship between the time constant of off-kinetics ( ) and parameters of aerobic fitness. After an incremental test to determine , first (VT1 ) and second (VT2 ) ventilatory thresholds, and maximal speed (Smax ), 13 males (age=21±4years; =55.9±3.4mlkg-1 min-1 ) performed three sets (two on the first day and one on a subsequent day) of two repetitions of 6-min running exercise at 90%VT1 . The pulmonary ( ) on-kinetics and off-kinetics in gastrocnemius were assessed. presented no systematic change and satisfactory reliability (the standard error of the measurement (SEM) and intraclass correlation coefficient of 4.21s and 0.49 for between transitions; and 2.65s and 0.74 averaging within each time set), with no difference (P>0.3) between the within- (SEM=2.92s) and between-day variability (SEM=2.78s and 2.19s between first vs. third set, and second vs. third set, respectively). (28.5±4.17s) correlated significantly (P<0.05) with Smax (r=-0.66), VT1 (r=-0.64) and time constant of the p on-kinetics (r=0.69). These findings indicate that NIRS-derived kinetics in the gastrocnemius following moderate running exercise is a useful and reliable parameter to assess muscle oxidative capacity.

Sex Differences May Exist for Performance Fatigue but Not Recovery After Single-Joint Upper-Body and Lower-Body Resistance Exercise.

Lewis, MH, Siedler, MR, Lamadrid, P, Ford, S, Smith, T, SanFilippo, G, Waddell, B, Trexler, ET, Buckner, S, and Campbell, BI. Sex differences may exist for performance fatigue but not recovery after single-joint upper-body and lower-body resistance exercise. J Strength Cond Res 36(6): 1498-1505, 2022-This study evaluated sex differences in performance recovery and fatigue during dynamic exercise. Twenty-eight resistance-trained males (n = 16) and females (n = 12) completed a repeated-measures, randomized, parallel-groups design. The protocol consisted of a baseline assessment, a recovery period (4, 24, or 48 hours), and a postrecovery assessment. The assessments were identical consisting of 4 sets of 10 repetition maximum (10RM) bicep curls and 4 sets of 10RM leg extensions to failure. Recovery was quantified as the number of total repetitions completed in the postrecovery bout. Fatigue was quantified as the number of repetitions completed set to set within the session. For analysis, we set the level of significance at p ≤ 0.05. No sex differences in performance recovery were observed across any of the investigated time periods for either exercise modality. Regarding fatigue, significant effects were observed for set (p < 0.001) and sex (p = 0.031) for bicep curls. Repetitions dropped in later sets, and females generally completed a greater number of repetitions than males (8.8 ± 0.5 vs. 7.2 ± 0.5). For leg extension, a significant sex × set interaction was observed (p = 0.003), but post hoc tests revealed these sex differences as marginal. Our results suggest that in dynamic bicep curls and leg extensions, other factors unrelated to sex may be more impactful on performance recovery. To optimize an athlete's desired adaptations, it may be more important to consider other variables unrelated to sex such as volume, perceived exertion, and training history when formulating training prescriptions for single-joint exercises.

Electromyographic and Systemic Physiological Thresholds in Single-Joint Elbow Flexion Movements.

Reported relationships between electromyographic (EMG) thresholds and systemic thresholds based on lactate, ventilation, or heart rate are contradictory. This might be related to the complexity of the investigated whole-body movements involving many muscles with different activation patterns. Therefore, the aim of the study was to investigate these relationships during an incremental single-joint exercise. Eighteen male subjects (29.7 [4.4]y) performed single-arm elbow flexions on a biceps curl machine with loads increasing every minute until exhaustion. EMG signals of the main elbow flexors (short and long head of the biceps brachii, flexor carpi radialis, and brachioradialis) as well as gas exchange variables, blood lactate concentration, and heart rate were measured, and 2 turn points based on a 3-phase model of metabolism were determined for each variable. The first and second turn points for EMG were determined at 32.0% to 33.1% and 64.4% to 66.5% of maximal achieved performance (maximum weight), respectively. Systemic turn points were determined at 33.3% to 34.4% and 65.9% to 66.7% of maximum weight and were not significantly different from EMG turn points. Furthermore, systemic and EMG turn points showed a strong or very strong relationship at the first (ρ = .54-.93, P < .05) and second turn point (ρ = .76-.93, P < .01). A close relationship between EMG and systemic turn points could be confirmed for the applied movement of a small muscle group. The determination of local single muscle thresholds using EMG provides additional muscle-specific information about performance-limiting properties of muscles involved in endurance-type incremental exercise.

Impact of resistance exercise order on postexercise hemodynamic measures in middle-aged and older women

Aim: to compare the impact of different resistance exercise orders on postexercise hemodynamic measures in resistance-trained nonhypertensive middle-aged and older women. Methods: Twenty-three women (age 50-78 yrs) were randomized into two resistance training (RT) groups: one group started training sessions performing multi-joint exercises followed by single-joint exercises (MS, n = 12; 58.92 ± 5.53 yrs), while the other group performed their sessions in the opposite order (SM, n = 11; 57.93 ± 11.89 yrs). Both groups performed their RT sessions composed of 7 exercises performed in 3 sets of 10-15 repetitions maximum. Blood pressure was measured by automated equipment during pre-training and at 10, 20, 30, 40, 50, and 60 min after the training session. Results: Repeated-measures analysis of variance (ANOVA) identified an isolated effect of time only for systolic blood pressure (p = 0.003) with statistically significant reductions in pre-session measurement at 60 min post-session in both groups (MS: 117.67 ± 15.89 mmHg vs. 111.25 ± 11.84 mmHg and SM: 118.64 ± 15.13 mmHg vs. 111.50 ± 15.62 mmHg). Regarding diastolic blood pressure and subjective perception of effort, no difference was identified between groups (p > 0.05). Conclusion: We conclude that a RT session can promote post-exercise hypotension for systolic blood pressure after 60 min of recovery in middle-aged and nonhypertensive older women regardless of the exercise order.

Influence of Adding Single-Joint Exercise to a Multijoint Resistance Training Program in Untrained Young Women: Retraction.

Journal of Strength and Conditioning Research: January 2022 - Volume 36 - Issue 1 - p e1 doi: 10.1519/JSC.0000000000004185

The time course of recovery of indirect markers of exercise-induced muscle damage induced by multi- and single-joint exercises

Strength training is performed using multi-joint (MJ) or single-joint (SJ) exercises; however, it is not clear whether different time of recovery is necessary between the two types of exercise. The aim of the present study was to compare the time course of recovery of indirect markers of exercise-induced muscle damage (EIMD) in the elbow flexors after performing MJ and SJ exercises. Twenty-four (n = 24) untrained men were randomized in to the MJ (n = 12) or SJ group (n = 12). Exercise protocol to induce muscle damage consisted of four sets of ten repetitions at 80% of one repetition maximum (1RM) in front pull-down (MJ exercise) or biceps curl (SJ exercise). Maximal voluntary isometric contraction, muscle soreness during elbow extension, ultrasound imaging (muscle thickness and echo intensity) and creatine kinase (CK) were measured before and up to 96 h after exercise. Significant effect of time (p < 0.05) at all times after exercise was observed for isometric strength, muscle soreness, muscle thickness and at 48, 72 and 96 h for echo intensity, with no time × group interaction. However, significant time × group interaction (p = 0.03) was observed only for CK activity at 96 h (MJ = 3348 ± 2911 IU/l vs. SJ = 890 ± 1426 IU/l; p < 0.05). In addition, there was a significant increase in CK after MJ at 48 h, 72 h and 96 h after exercise (p < 0.05), while SJ increased only at 48 h after exercise. Despite a dissimilar time course of CK response, MJ and SJ exercises induced a similar recovery pattern for muscle strength, thickness, echo intensity and soreness.

Performing Repetitions to Failure in Lower-Limb Single-Joint Exercise Does Not Reduce Countermovement Jump Performance in Trained Male Adults.

Performing repetitions to failure (RF) is a strategy that might acutely reduce neuromuscular performance, as well as increase the rating of perceived exertion (RPE) and the internal training load (ITL) during and after a resistance training (RT) session. Thus, this study aimed to analyze the acute effects of RF or repetitions not to failure (RNF) on countermovement jump (CMJ) performance and the ITL in trained male adults. Eleven men performed two experimental protocols in randomized order (RF vs. RNF). Under the RF condition, participants performed three sets of the leg extension exercise using 100% of the 10RM load and rest intervals of 180-s between sets. Under the RNF condition, participants were submitted to six sets of five repetitions with the same intensity and an 80-s rest interval between sets in the same exercise. The CMJ test was analyzed before and following (15-s and 30-min, respectively) each experimental session. The ITL was evaluated by multiplying the RPE and the total session time, 30-min after the protocol. No main effect or interaction time vs. condition was found for CMJ performance (p > 0.05). In contrast, the ITL showed higher values under the RF condition (p = 0.003). Therefore, even though RF-induced a greater ITL, our results suggest that adopting this strategy in one single-joint exercise for the lower limbs does not seem sufficient to reduce CMJ height.

Does Varying Repetition Tempo in a Single-Joint Lower Body Exercise Augment Muscle Size and Strength in Resistance-Trained Men?

Pearson, J, Wadhi, T, Barakat, C, Aube, D, Schoenfeld, BJ, Andersen, JC, Barroso, R, Ugrinowitsch, C, and De Souza, EO. Does varying repetition tempo in a single-joint lower body exercise augment muscle size and strength in resistance-trained men? J Strength Cond Res 36(8): 2162-2168, 2022-This study compared the effects of FAST and SLOW eccentric repetition tempo in a single exercise volume-matched intervention on muscle thickness (MT) and strength in resistance-trained men. Using a within-subject design, 13 subjects had each leg randomly assigned to SLOW (1-0-3) or FAST (1-0-1) repetition tempo. Subjects underwent an 8-week strength-training (ST) intervention performed twice weekly. Unilateral leg-extension one repetition-maximum (1RM) and anterior thigh MT at the proximal (MTP) and distal (MTD) portions were assessed via ultrasound imaging at baseline and after 8 weeks of RT. Rating of perceived exertion (RPE) assessments of the training sessions (i.e., 16 per leg) were averaged for further analysis. Both legs similarly increased MTP (estimated differences: FAST: 0.24 cm, 3.6%; SLOW: 0.20 cm, 3.1%). However, for MTD, analysis of covariance analysis showed a leg effect ( p = 0.02) in which absolute pre-to-post change was greater in FAST compared with SLOW (estimated differences: FAST 0.23 cm, 5.5%; SLOW: 0.13 cm, 2.2%). For 1RM, both legs similarly increased maximum strength (estimated differences: FAST: 9.1 kg, 17.0%; SLOW: 10.4 kg, 22.1%, p ≤ 0.0001). The SLOW group had a higher RPE than FAST (8.59 vs. 7.98, p = 0.002). Despite differences in RPE, our results indicate that both repetition tempos produced similar muscular adaptations. However, they also suggest that the FAST tempo may provide a small hypertrophic advantage at the distal quadriceps. From a practical standpoint, strength and conditioning professionals may implement a FAST tempo at least in one single-joint exercise during an 8-week training period to enhance regional hypertrophic adaptations in trained individuals.

Dissociated Time Course of Indirect Markers of Muscle Damage Recovery Between Single-Joint and Multi-joint Exercises in Resistance-Trained Men.

de Camargo, JBB, Braz, TV, Batista, DR, Germano, MD, Brigatto, FA, and Lopes, CR. Dissociated time course of indirect markers of muscle damage recovery between single-joint and multi-joint exercises in resistance-trained men. J Strength Cond Res 36(8): 2089-2093, 2022-This study compared the time course of indirect markers of muscle damage after multi-joint and single-joint exercises. Ten resistance-trained men (years: 26.9 ± 3.0; total body mass: 83.2 ± 13.8 kg; height: 176 ± 7.0 cm; resistance training [RT] experience: 5.5 ± 2.4 years; RT frequency: 5.3 ± 0.7 sessions; relative squat 1 repetition maximum: 1.4 ± 0.3) performed, in a random order, 5 sets of 8 repetition maximum of the back squat (BS) and knee extension (KE) exercises. Rectus femoris muscle thickness (MT RF ), leg circumference (LC), and muscle soreness (MS) were recorded at baseline (pre), 0, 12, 24, and 36 hours after each exercise protocol. There was a significant increase ( p < 0.05) in dependent variables at every time point after both the multi-joint and single-joint exercise sessions. However, MT RF and LC were greater at 0 and 36 hours, and MS was greater at 24 and 36 hours after BS when compared with KE (all p < 0.05). This study shows that resistance-trained individuals can experience significant higher levels of indirect markers of muscle damage when performing a multi-joint lower-limb exercise compared with a single one.

The Association of Obesity With Quadriceps Activation During Sit-to-Stand.

Obesity reduces voluntary recruitment of quadriceps during single-joint exercises, but the effects of obesity on quadriceps femoris muscle activation during dynamic daily living tasks, such as sit-to-stand (STS), are largely unknown. The purpose of this study was to determine how obesity affects quadriceps muscle recruitment during STS. In this cross-sectional study, 10 women who were lean and 17 women who were obese completed STS from a chair with arms crossed over the chest. Three-dimensional motion analysis was used to define 3 distinct phases (I-III) of the STS cycle. The electromyographic (EMG) activity of the vastus medialis, vastus lateralis, and semitendinosus was measured. STS duration was greater (3.02 [SD=0.75] seconds vs 1.67 [SD=0.28] seconds) and peak trunk flexion angle was lower (28.9 degrees [SD=10.4 degrees] vs 35.8 degrees [SD=10.1 degrees]) in the women who were obese than in the women who were lean. The mean EMG activity of the knee extensors increased from phase I to phase II in both groups; however, the mean EMG activities of both the vastus medialis (32.1% [SD=16.6%] vs 47.3% [SD=19.6%] maximal voluntary isometric contraction) and the vastus lateralis (31.8% [SD=19.4%] vs 47.5% [SD=19.6%] maximal voluntary isometric contraction) were significantly lower during phase II in the women who were obese. The mean EMG activity of the semitendinosus increased throughout STS but was not significantly different between the 2 groups. Coactivation of the semitendinosus and knee extensors tended to be greater in the women who were obese but failed to reach statistical significance. Knee extensor EMG amplitude was reduced in women who were obese during STS, despite reduced trunk flexion. Reduced knee extensor recruitment during STS in obesity may redistribute forces needed to complete this task to other joints. Functional movement training may help improve knee extensor recruitment during STS in people who are obese. People with obesity often have low quadriceps muscle strength and impaired mobility during daily activities. This study shows that women who are obese have lower voluntary recruitment of quadriceps when rising from a chair than women who are lean do, which could increase workload on hip or ankle muscles during this important daily task. Quadriceps strengthening exercises might improve the ability to rise from sitting to standing.