Isometric Leg Press Research Articles

Physical Fitness Determinants of a Military Casualty Evacuation Test.

Casualty evacuation has been identified as a typical and essential single military task which every soldier should be able to perform rapidly during combat. Previous studies suggest that casualty evacuation is typically conducted by dragging and demands e.g., lean body mass and anaerobic performance. Association of physical fitness with casualty evacuation by dragging has been studied widely but previous studies lack comprehensive assessment of all physical fitness determinants. The purpose of the present study was to examine comprehensively how casualty emergency evacuation (CEE) performance associates with physical fitness and body composition. A total of 25 conscripts (20 men, 5 women) volunteered for measurements of height, weight, waist circumference, body composition, 1-min sit-ups and push-ups, grip strength, isometric bench and leg press, standing long jump, 30-s cycle ergometer test, and 12-min run test. Subjects performed a CEE test in which evacuation time (ET), heart rate, blood lactate concentration, and rate of perceived exertion were measured. In the CEE test, subjects wore combat gear (11.7 ± 1.6 kg) and dragged a doll wearing combat gear (80.2 kg) 28 m while crawling (go round two cones, Z-pattern) and 20 m upright (straightforward). Correlations and backward regression analysis were used for statistical analyses. The level of significance was set to P ≤ .05. Evacuation time lasted on average 87 ± 32 s with a peak heart rate of 184 ± 6 bpm, lactate concentration of 9.4 ± 2.7 mmol/l, and RPE of 17 ± 1. Evacuation time correlated inversely and strongly with anaerobic capacity and power (r = -0.72-0.78, P ≤ .001), but not with aerobic fitness. Inverse and strong correlations were observed between ET and maximal strength variables (r = -0.58-0.69, P ≤ .01), whereas muscular endurance and ET revealed non-significant correlations. Evacuation time correlated moderate to strongly with body fat percentage (r = 0.48, P ≤ .05) and inversely with lean body mass (r = -0.74, P ≤ .001) and body height (r = -0.53, P ≤ .01). The backward regression analysis showed that anaerobic capacity (standardized β = -0.52, P ≤ .001), fat percentage (standardized β = 0.40, P ≤ .001), and isometric leg press (standardized β = -0.25, P ≤ .1) together explained the variance of ET significantly (adjusted R2 = 0.84, P ≤ .001). This study examined thoroughly how different physical fitness dimensions and body composition relate to a CEE test performed by a combination of dragging while crawling and in upright position. Casualty emergency evacuation was discovered as a high-intensity military task, which demands most importantly high anaerobic performance, lean body mass, and maximal strength capabilities. Improving these dimensions of physical fitness should be considered highly important as CEE is essential and possibly one of the most demanding military tasks which every soldier should be able to conduct in combat. From operational perspective, it is relevant that soldiers are able to perform CEE during operations; therefore, further research is needed on how acute operational stress changes the nature of CEE and its physical determinants.

Exploring the Association between Health-Related Physical Fitness and Quality of Life in Patients with Cancer: A Cross-Sectional Study.

Whereas an exercise intervention effectively improves patients' quality of life, little information is available about the contribution of each physical fitness component. This study aims to explore the association between physical fitness components and the quality-of-life domain in patients with cancer. Between September 2021 and August 2023, 160 patients with mixed cancer types visiting the Oncology Unit were selected on a consecutive basis according to selection criteria. They underwent a comprehensive baseline assessment including the six-minute walking test, the handgrip strength test, the isometric leg press test, the back scratch, sit and reach tests, their waist-hip ratio, and their body mass index. The European Organization for Research and Treatment of Cancer Quality of Life and Core Questionnaire was used to measure the quality of life. The sample size was based on the use of regression models to study associations between clinical characteristics and fitness outcomes. All of the analyses were performed using the SPSS v.25 statistical package. Patients had a mean age of 58 years, 68% were female, 42% were affected by breast cancer, and all were receiving anticancer treatments. Higher functional capacity was associated with better global health status (p < 0.0001) and physical (p < 0.0001), role (p < 0.0001), emotional (p = 0.026), and social function (p = 0.016) and inversely linked with fatigue (p = 0.001). Lower-limb flexibility was significantly associated with all of the domains except for role and social functions. The waist-hip ratio was inversely associated with physical function (p < 0.0001) and positively related to fatigue (p = 0.037). Exercise programs aiming to improve the quality of life in cancer should be addressed to optimize these fitness components.

Effects of Different Recovery Periods Following a Very Intense Interval Training Session on Strength and Explosive Performance in Elite Female Ice Hockey Players.

Petré, H, Tinmark, F, Rosdahl, H, and Psilander, N. Effects of different recovery periods following a very intense interval training session on strength and explosive performance in elite female ice hockey players. J Strength Cond Res 38(7): e383-e390, 2024-This study investigates how different recovery periods after high-intensity interval training (HIIT) affects strength and explosive performance during a power training (PT) session. Fifteen female elite ice hockey players (22.5 ± 5.2 years) performed PT, including 6 sets of 2 repetitions (reps) of isometric leg press (ILP) and 6 sets of 3 reps of countermovement jump (CMJ), following a rested state and 10 minutes, 6 hours, or 24 hours after HIIT (3 sets of 8 × 20 seconds at 115% of power output at maximal oxygen consumption on a cycle ergometer). Peak force (PF) and peak rate of force development (pRFD) were measured during the ILP. Peak jump height (PJH), concentric phase duration (ConDur), eccentric phase duration, total duration, peak power (PP), velocity at peak power (V@PP), and force at peak power were measured during CMJ. The following variables were significantly reduced when only a 10-minute recovery period was allowed between HIIT and PT: PF was reduced by 7% ( p < 0.001), pRFD by 17% ( p < 0.001), PJH by 4% ( p < 0.001), ConDur by 4% ( p = 0.018), PP by 2% ( p = 0.016), and V@PP by 2% ( p = 0.007). None of the measured variables were reduced when PT was performed 6 and 24 hours after HIIT. We conclude that strength and explosive performance of elite female ice hockey players is reduced 10 minutes after HIIT but not negatively affected if a rest period of at least 6 hours is provided between HIIT and PT.

Association of multi-phase rates of force development during an isometric leg press with vertical jump performances.

This study aimed to elucidate characteristics of explosive force-production capabilities represented by multi-phase rate of force developments (IRFDs) during isometric single-leg press (ISLP) through investigating relationships with countermovement (CMJ) and rebound continuous jump (RJ) performances. Two-hundred-and-thirty male athletes performed ISLP, CMJ with an arm swing (CMJAS), and RJ with an arm swing (RJAS). IRFDs were measured during ISLP using a custom-built dynamometer, while CMJAS and RJAS were measured on force platforms. The IRFDs were obtained as rates of increase in force across 50 ms in the interval from the onset to 250 ms. Jump height (JH) was obtained from CMJAS, while RJAS provided JH, contact time (CT), and reactive strength index (RSI) values. All IRFDs were correlated with CMJAS-JH (ρ = 0.20-0.45, p ≤ 0.003), RJAS-JH (ρ = 0.22-0.46, p ≤ 0.001), RJAS-RSI (ρ = 0.29-0.48, p < 0.001) and RJAS-CT (ρ = -0.29 to -0.25, p ≤ 0.025). When an influence of peak force was considered using partial rank correlation analysis, IRFDs during onset to 150 ms were correlated with CMJAS-JH (ρxy/z = 0.19-0.36, p ≤ 0.004), IRFDs during onset to 100 ms were correlated with RJAS-JH and RJAS-RSI (ρxy/z = 0.33-0.36, p < 0.001), and IRFD during onset to 50 ms was only correlated with RJAS-CT (ρxy/z = -0.23, p < 0.001). The early phase (onset to 150 ms) IRFDs measured using ISLP enabled the assessment of multiple aspects of leg-extension strength characteristics that differ from maximal strength; these insights might be useful in the assessment of the athletes' leg-extension strength capabilities.

Two-week step-reduction has limited negative effects on physical function and metabolic health in older adults

PurposeThis study determined the effects of a 2-week step-reduction period followed by 4-week exercise rehabilitation on physical function, body composition, and metabolic health in 70–80-year-olds asymptomatic for injury/illness.MethodsA parallel-group randomized controlled trial (ENDURE-study, NCT04997447) was used, where 66 older adults (79% female) were randomized to either intervention or control group. The intervention group reduced daily steps to < 2000, monitored by accelerometer, for two weeks (Period I) and then step-reduction requirement was removed with an additional exercise rehabilitation 4 times per week for 4 weeks (Period II). The control group continued their habitual physical activity throughout with no additional exercise intervention. Laboratory tests were performed at baseline, after Period I and Period II. The primary outcome measure was leg lean mass (LLM). Secondary outcomes included total lean and fat mass, blood glucose and insulin concentration, LDL cholesterol and HDL cholesterol concentration, maximal isometric leg press force (MVC), and chair rise and stair climb performance.ResultsLLM remained unchanged in both groups and no changes occurred in physical function nor body composition in the intervention group in Period I. HDL cholesterol concentration reduced after Period I (from 1.62 ± 0.37 to 1.55 ± 0.36 mmol·L−1, P = 0.017) and returned to baseline after Period II (1.66 ± 0.38 mmol·L−1) in the intervention group (Time × Group interaction: P = 0.065). MVC improved after Period II only (Time × Group interaction: P = 0.009, Δ% = 15%, P < 0.001).ConclusionShort-term step-reduction in healthy older adults may not be as detrimental to health or physical function as currently thought.

A Feasibility Study Investigating an Exercise Program in Metastatic Cancer Based on the Patient-Preferred Delivery Mode.

Feasibility of exercise in patients with metastatic cancer is still a challenge. This study aimed to determine the feasibility and preliminary efficacy of an exercise intervention based on a patient-preferred delivery mode in patients affected by metastatic cancer. Forty-four patients with a confirmed diagnosis of metastatic cancer were recruited in a 3-month exercise program. Whereas the exercise program consisted of aerobic and resistance activities performed twice a week, the participants may choose the mode of delivery: home based, personal training, or group based. The primary endpoint was the feasibility, defined by recruitment rate, attendance, adherence, dropout rate, tolerability (comparing the session RPE with the target RPE), and safety (using the Common Terminology Criteria for Adverse Events, version 5.0). Secondary endpoints included cardiorespiratory fitness (six minutes walking test), muscle strength (handgrip strength test and isometric leg press test), flexibility (the back scratch and chair sit and reach tests), anthropometric parameters (body mass index and waist-hip ratio), quality of life (EORTC QLQ C-30 questionnaire), and amount of physical exercise (Godin's Shepard Leisure Time Exercise Questionnaire). Descriptive statistics, Student t test, and Wilcoxon signed rank test were used to analyze data. The study recruitment rate was 81%. Out of 44 recruited patients, 28 chose the personal training program, 16 chose the home-based program, and none chose the group-based program. Nine dropouts occurred (20%), 6 in the personal training program, and 3 in the home-based intervention. The median attendance rate was 92%, adherence was 88%, tolerability was 100%, and 9 nonsevere adverse events were registered during the exercise sessions. An increase in cardiorespiratory fitness (P < .001) and flexibility (P = .011 for chair sit and reach; P = .040 for back scratch) was observed at the end of the intervention, while no changes in anthropometric values and muscle strength were detected. Different quality-of-life domains were improved following the intervention, including physical (P = .002), emotional (P < .001), and role functioning (P = .018), fatigue (P = .030), and appetite loss (P = .005). A 3-month exercise program based on a patient-preferred delivery mode is feasible in patients with metastatic cancer and may improve physical function and quality of life. NCT04226508.

Physical Determinants of Sprint and Long Jump Performance in Male Youth Track-and-Field Athletes With Differing Maturity Statuses.

This study examined the physical determinants of 60-m sprint and long jump (LJ) performance and differences between maturity groups in physical characteristics in young male track-and-field athletes. Competition results, countermovement jump, isometric leg press, 10-5 repeated jump test, and 50-m sprint were collected over 3 seasons for 54 male athletes (age 13 [1]y; stature 160.0 [8.9]cm; body mass, 48.0 [9.8]kg; percentage predicted adult height 92.2% [5.5%]) grouped by maturity status: approaching- (n = 16), circa- (n = 19), and post-peak height velocity (PHV) (n = 19). There were significant between-group differences in 60m, LJ, and all physical testing variables (P < .001, g = 0.88-5.44) when comparing the approaching- and circa-PHV groups with the post-PHV group. Significant differences were identified between the approaching- and circa-PHV groups in 40-m (P = .033, g = 0.89), 50-m (P = .024, g = 1.64), and 60-m (P < .001, g = 0.89) sprint times. Countermovement jump and 50-m sprint variables were consistently important for projection of 60m and LJ performance across the valid multivariate models. Large differences in performance across maturity groups highlight the importance of understanding athletes' maturity status to accurately interpret performance. Several physical performance variables were important for projecting competition 60m and LJ performance.

An exploration of the mechanistic link between the enhanced paper grip test and the risk of falling

The enhanced paper grip test (EPGT) offers an easy-to-use measure of hallux plantar-flexion strength that does not need expensive specialised equipment. Literature suggests that it could be a useful screening tool to assess the risk of falling in older people. However, research on a specific mechanistic link to the risk of falling is lacking. It is hypothesised here that muscle weakening (assessed by the EPGT) is indicative of impaired ability to recover balance after a slip or a trip. To get an initial assessment of validity of the above hypothesis, the EPGT is compared against an established lab-based measure of lower-limb strength that is capable of assessing a person’s ability to recover balance after a slip or a trip: maximum isometric leg press push-off force (leg press force). A gender-balanced sample of twenty people (median age=34 y) was recruited. Two different but equaly valid techniques of administering the EPGT were included regarding whether the participants’ ankle was supported by the examiner or not. Results for the two EPGT techniques differed susbtantialy but they were both significantly associated with leg press force and therefore linked to better ability to maintain balance after a slip or a trip. The “ankle not held” EPGT technique was more strongly correlated to leg press force (r(18) = 0.652, p = 0.002) than the “ankle held” (r(18) = 0.623, p = 0.003) and appears to be the more favourable technique to administer the EPGT. These findings offer new insight on a potential mechanistic link between the EPGT and the risk of falling and support its optimal use in future research involving older people.

SPECIFIC FORCE-TIME CHARACTERISTICS OF LEG EXTENSORS IN ELITE VOLLEYBALL PLAYERS BOTH GENDER IN SERBIA

Adequate preparation of the leg extensors is highly important especially in sports which involve several jumping techniques. Information on force-time characteristics of the certain muscle group is the basic information on athlete ability which are gathered with intention to control the athlete`s physical preparation. The aim of this paper was to determine descriptive and sexual dimorphism of different specific isometric characteristics of force-time model related to leg extensors in elite volleyball Serbian players. Nineteen male (height=199.21±4.94 cm, mass=91.05±6.95 kg, age=22.58±2.97 years) and twenty female (height=184.65±7.00 cm, mass=70.65±6.15 kg, age=22.92±3.73 years) elite volleyball players performed a standardized “isometric leg press” test in order to assess the characteristics of isometric force from their leg extensors. The measurement range was defined by 8 variables according to 4 different dimensions – 1) the level of achieved force, 2) rate of force development, 3) the time necessary for reaching the certain level of force, 4) different index parameters; covering the space of basic, specific and special characteristics of leg extensors muscle force. MANOVA established that there is a significant difference of p 0.05 in all contractile characteristics among observed sub-samples at the level of Wilks´ Lambda 0.098, F = 25.814, p = 0.000. The present findings demonstrated that the male volleyball players produce higher values than the female players in all contractile characteristics of covering the space of specific and special characteristics of leg extensors muscle force. It is highly likely that these differences cannot be explained only on the basis of sexual differences, but on the basis of overall intensity and volume and/or type of power and strength training during the training process as well, factors which deserves attention in work with athletes. The obtained data can be used as a reverse information on characteristics of a certain leg extensors contractile ability in elite volleyball players in order to follow fitness profile of athletes, to control and optimize training process.

Long Jump Performance Is Not Related to Inter-Limb Asymmetry in Force Application in Isometric and Vertical Jump Tests

The aim of the study was to examine the inter-limb asymmetry in force application in a 1-s maximum isometric leg press test (ISOM) and vertical jump tests without an arm swing (VJ)of male long jumpers. Nine experienced jumpers (age: 18–30 y, LJ personal best: 6.50–8.05 m) were examined. Participants performed: (a) bilateral VJs from the squatting position (SQJ) and with a countermovement (CMJ), (b) unilateral CMJ from the take-off (TOL) and swing (SWL) leg used in the LJ take-off, and c) bilateral 1-s ISOM tests. Data were collected for each lower limb with separate force dynamometers (sampling frequency: VJs = 1 kHz, ISOM = 500 Hz). The inter-limb asymmetry of the peak applied force was evaluated using the symmetry angle. The paired samples T-test revealed non-significant (p &gt; 0.05) inter-limb differences for the force output in the bilateral jump tests, in the unilateral jump tests, and in the ISOM. In conclusion, despite the fact that a powerful unilateral take-off is required for the optimization of long jump performance, no asymmetry was found in the examined tests, suggesting that the dominant/take-off leg was not stronger than the contra-lateral leg. This is possibly due to the intensive execution of other bilateral tasks involved, like the approach run.

Contribution of different strength determinants on distinct phases of Olympic rowing performance in adolescent athletes

ABSTRACT Aerobic metabolism dominates Olympic rowing, but research on the relative contribution of strength and power demands is limited. This study aimed to identify the contribution of different strength determinants for distinct phases of rowing ergometer performance. The cross-sectional analysis comprised of 14 rowing athletes (4 female, 10 male, age: 18.8 ± 3.0y, 16.9 ± 2.2y). Measurements included anthropometrics, maximal strength of leg press, trunk extension and flexion, mid-thigh pull (MTP) and handgrip strength, VO2max, and a 2000 m time trial, where peak forces at the start, middle and end phase were assessed. Additionally, rate of force development (RFD) was assessed during the isometric leg press and MTP with intervals of 150, 350 ms and 150, 300 ms, respectively. Stepwise regression models for ergometer performance showed that the start phase was mainly explained by maximal trunk extension and RFD 300 ms of MTP (R2 = 0.91, p < 0.001) and the middle section by VO2max, maximal leg press strength and sitting height (R2 = 0.84, p < 0.001). For the end phase, a best fit was observed for trunk flexion, RFD 350 ms of leg press, body height and sex (R2 = 0.97 p < 0.001), whereas absolute VO2max, trunk flexion and sex explained variance over the entire 2000 m time trial (R2 = 0.98, p < 0.001). It appears that for the high acceleration in the start phase, force transmission through maximum strength for trunk extension is essential, while fast power production along the kinetic chain is also relevant. Additionally, the results support that maximal force complements the reliance on VO2max. Further intervention studies are needed to refine training recommendations.

Influence of muscle strength, power, and rapid force capacity on maximal club head speed in male national level golfers

ABSTRACT This study investigated the relationships between maximal club head speed (CHS) and physiological and anthropometric parameters in 21 national-level male golfers (age: 21.9 ± 3.9 years; handicap: +1.1 ± 1.7). Maximal isometric strength (MVC) was measured during isometric mid-thigh pull and bench press, while MVC and rate of force development (RFD) were measured during isometric leg press. Power, lower limb stiffness, positive impulse, jump height and RFDdyn were measured during countermovement jump (CMJ). Moreover, rotational trunk power, active range of motion (AROM) and anthropometrics were determined. Comparisons were made between participants with high (FTG) and low (STG) CHS, respectively. FTG demonstrated greater isometric mid-thigh pull and isometric bench press MVC, leg press RFD, rotational trunk power, and CMJ parameters (except RFDdyn) as well as reduced hip AROM compared to STG (P < 0.01). CHS was positively correlated to isometric mid-thigh pull and isometric bench press MVC, leg press RFD, rotational trunk power and CMJ parameters (P < 0.01). In conclusion, strong positive correlations were observed between maximal CHS and maximal strength and power parameters. Consequently, improving maximal neuromuscular strength and power may be considered of importance for golfers, as greater CHS and accompanying driving distance may lead to competitive advantages.

Between-Session Reliability of Strength- and Power-Related Variables Obtained during Isometric Leg Press and Countermovement Jump in Elite Female Ice Hockey Players

Isometric leg press (ILP) and countermovement jump (CMJ) are commonly used to obtain strength- and power-related variables with important implications for health maintenance and sports performance. To enable the identification of true changes in performance with these measurements, the reliability must be known. This study evaluates the between-session reliability of strength- and power-related measures obtained from ILP and CMJ. Thirteen female elite ice hockey players (21.5 ± 5.1 years; 66.3 ± 8.0 kg) performed three maximal ILPs and CMJs on two different occasions. Variables from the ILP (peak force and peak rate of force development) and CMJ (peak power, peak force, peak velocity, and peak jump height) were obtained. The results were reported using the best trial, an average of the two best trials, or an average of three trials. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were high (ICC &gt; 0.97; CV &lt; 5.2%) for all outcomes. The CV for the CMJ (1.5–3.2%) was lower than that for the ILP (3.4–5.2%). There were no differences between reporting the best trial, an average of the two best trials, or an average of the three trials for the outcomes. ILP and CMJ are highly reliable when examining strength- and power-related variables in elite female ice hockey players.

Differential effects of strength determinants on different phases of olympic rowing performance in adolescent athletes

Background&#x0D; Olympic rowing relies heavily on aerobic metabolism, but the demands on strength and power have not yet been thoroughly investigated (Lawton et al., 2011). As the characteristic pacing strategy compounds an initial start sprint, a sustained middle section and end spurt, the neuromuscular and physiological requirements of the particular phases need to be considered more closely (Garland, 2005; Mikulic, 2011). Therefore, the purpose of this study was to identify strength qualities for distinct phases in rowing performance in adolescent athletes.&#x0D; Methods&#x0D; The cross-sectional analysis of fourteen national competitive rowing athletes (4 female; 10 male) included anthropometrics, isometric and isokinetic leg press, back extension and flexion, isometric mid-thigh pull (MTP) and handgrip strength, VO2max, and a 2000 m time trial, in which peak forces were measured in the start, middle and end phase. The rate of force developments (RFD) were obtained for isometric leg press (150 and 350 ms) and MTP (150 ms and 300 ms). Stepwise regression models were created for ergometer performance in the start, middle and end phases.&#x0D; Results&#x0D; The best fit model for the start phase included isometric back extension and RFD 300 ms of MTP (R2 = 0.912, p &lt; 0.001), while for the middle section it were VO2max, isometric leg press and sitting height (R2 = 0.844, p &lt; 0.001). For the end phase a best fit was observed for isometric back flexion, RFD 350 ms of leg press, body height and sex (R2 = 0.965 p &lt; 0.001), whereas absolute VO2max, isokinetic back flexion and sex explained variance over the entire 2000 m time trial (R2 = 0.975, p &lt; 0.001).&#x0D; Conclusion&#x0D; For the high acceleration at the start, force transmission through maximum back strength seems to be essential, while fast power production along the kinetic chain is also relevant (Baudouin &amp; Hawkins, 2002). In addition to VO2max, produced maximum strength in the leg press explains the importance for the force production of the sustained middle section (Cosgrove et al., 1999). These results indicate that maximal force complements the reliance on VO2max, as well as neuromuscular parameters and maximal force transmission seems to be important for the start phase. Further research through intervention studies is needed to refine training recommendations.&#x0D; References&#x0D; Baudouin, A., &amp; Hawkins, D. (2002). A biomechanical review of factors affecting rowing performance. British Journal of Sports Medicine, 36(6), 396-402. http://dx.doi.org/10.1136/bjsm.36.6.396&#x0D; Cosgrove, M. J., Wilson, J., Watt, D., Grant, S. F. (1999). The relationship between selected physiological variables of rowers and rowing performance as determined by a 2000 m ergometer test. Journal of Sports Sciences, 17(11), 845-852. https://doi.org/10.1080/026404199365407&#x0D; Garland, S. (2005). An analysis of the pacing strategy adopted by elite competitors in 2000 m rowing. British Journal of Sports Medicine, 39(1), 39-42. https://doi.org/10.1136/bjsm.2003.010801&#x0D; Lawton, T. W., Cronin, J. B., &amp; McGuigan, M. R. (2011). Strength testing and training of rowers: A review. Sports Medicine, 41(5), 413-432. https://doi.org/10.2165/11588540-000000000-00000&#x0D; Mikulic, P. (2011). Maturation to elite status: A six-year physiological case study of a world champion rowing crew. European Journal of Applied Physiology, 111(9), 2363-2368. https://doi.org/10.1007/s00421-011-1870-y

A post-exercise infrared sauna session improves recovery of neuromuscular performance and muscle soreness after resistance exercise training.

The aim of this study was to investigate effects of a single infrared sauna (IRS) session on post-exercise recovery of neuromuscular performance, autonomic nervous system function, subjective sleep quality, and muscle soreness. Male basketball players (n = 16) performed two trials consisting of a complex resistance exercise protocol (maximal strength with plyometrics), followed by either 20 min passive recovery (PAS) or IRS (temperature 43 ± 5°C), in a randomized crossover design, with trials separated by one week. Recovery of neuromuscular performance was assessed using 20 m maximal sprint, maximal countermovement-jump (CMJ), and isometric leg press tests, performed 14 hours after exercise. Heart rate (HR), heart rate variability (HRV), sleep diary, muscle soreness, and indirect muscle damage markers were measured pre and post exercise. The decrease in CMJ performance from pre- to post-exercise was attenuated after IRS compared to PAS (p < 0.01). The IRS session resulted in higher HR and lower root mean square of successive differences between normal heartbeats (RMSSD), and high and low frequency power, compared to PAS (p < 0.002). Post-exercise night-time HR and HRV did not differ following IRS vs. PAS. Muscle soreness was less severe, and perceived recovery was higher after IRS compared to PAS (p < 0.01). Post-exercise IRS attenuated the drop in explosive performance and decreased subjective muscle soreness after resistance training, which may enhance mood, readiness, and physical performance of an athlete. A single IRS session had no detrimental effects on recovery of the autonomic nervous system.

Acute neuromuscular and hormonal responses to 20 versus 40% velocity loss in males and females before and after 8 weeks of velocity‐loss resistance training

New Findings What is the central question of this study? Do males and females differ in fatiguability during dynamic loadings, and what are the acute neuromuscular and hormonal responses to 20 versus 40% velocity‐loss resistance loadings? How does an 8‐week velocity‐loss resistance training period modify acute neuromuscular and hormonal responses in males and females? What is the main finding and its importance? Using resistance training methods that regulated the within‐set fatigue limit, males appeared to be more susceptible to fatigue than females before the training period. This between‐sex difference was diminished after training. The predominant mechanisms of fatigue from 20 and 40% velocity‐based resistance training appear to be within the musculature. Scientific examination of velocity‐based resistance training (VBRT) has increased recently, but how males and females respond to different VBRT protocols or how these acute responses are modified after a period of training is unknown. Habitually resistance‐trained males and females followed either a 20 or 40% velocity‐loss programme for 8 weeks. Acute squat loading tests (five sets, 70% one‐repetition maximum load, 3 min rest) were performed before and after the training period. Tests of maximum neuromuscular performance and blood sampling were conducted before, within 10 min of completion (POST) and 24 h after each acute loading test. Testing included countermovement jump, resting femoral nerve electrical stimulation and bilateral isometric leg press. Blood samples were analysed for whole‐blood lactate, serum testosterone, cortisol, growth hormone and creatine kinase concentrations. Countermovement jump height, maximum isometric bilateral leg‐press force and the force from a 10 Hz doublet decreased in all groups at POST after 20 and 40% velocity loss. Only males showed reduced force from the 100 Hz doublet and voluntary force over 100 ms at POST before training. The 40% velocity loss led to increased blood lactate and growth hormone responses before training in both males and females. After training, more systematic and equivalent responses in force over 100 ms, force from a 100 Hz doublet and blood lactate were observed regardless of sex/VBRT protocol. Overall, acute responses were greater from 40% VBRT, and males were more susceptible to acute loss in force production capacity before the training period. These VBRT protocol‐ and sex‐related differences were diminished after training.

Vitamin D supplementation and increased dairy protein intake do not affect muscle strength or physical function in healthy 6-8-year-old children: the D-pro randomized trial.

PurposeTo investigate separate and combined effects of vitamin D supplementation during the extended winter and increased dairy protein intake on muscle strength and physical function in children, and furthermore to explore potential sex differences.MethodsIn a 2 × 2-factorial, randomized winter trial, 183 healthy, 6–8-year-old children received blinded tablets with 20 µg/day vitamin D3 or placebo, and substituted 260 g/day dairy with yogurts with high (HP, 10 g protein/100 g) or normal protein content (NP, 3.5 g protein/100 g) for 24 weeks during winter at 55° N. We measured maximal isometric handgrip and leg press strength, and physical function by jump tests and a 30 s sit-to-stand test. Physical activity was measured by 7-day accelerometry.ResultsBaseline (mean ± SD) serum 25-hydroxyvitamin D was 80.8 ± 17.2 nmol/L, which increased to 88.7 ± 17.6 nmol/L with vitamin D supplementation and decreased to 48.4 ± 19.2 nmol/L with placebo. Baseline protein intake was 15.5 ± 2.4 E%, which increased to 18.4 ± 3.4 E% with HP and was unchanged with NP. We found no separate or combined effects of vitamin D supplementation and/or increased dairy protein intake on muscle strength or physical function (all P > 0.20). There was an interaction on the sit-to-stand test (Pvitamin×yogurt = 0.02), which however disappeared after adjusting for physical activity (P = 0.16). Further, vitamin D supplementation increased leg press strength relatively more in girls compared to boys (mean [95% CI] 158 [17, 299] N; Pvitamin×sex = 0.047).ConclusionOverall, vitamin D and dairy protein supplementation during the extended winter did not affect muscle strength or physical function in healthy children. Potential sex differences of vitamin D supplementation should be investigated further.Registered at clinicaltrials.govNCT0395673.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00394-022-02912-0.

Aerobic Capacity Determines Habitual Walking Acceleration, Not Electromyography-Indicated Relative Effort

Objective: Habitual walking is important for health and can be measured with accelerometry, but accelerometry does not measure physiological effort relative to capacity. We compared accelerometer-measured absolute intensity and electromyography (EMG)-measured relative muscle activity between people with low versus excellent aerobic fitness levels during their habitual walking. Methods: Forty volunteers (19 women; age 49.3 ± 17.1 years, body mass index 24.0 ± 2.6 kg/m2; peak oxygen uptake 40.3 ± 12.5 ml/kg/min) wore EMG-shorts and a hip-worn accelerometer simultaneously for 11.6 ± 2.2 hr on 1.7 ± 1.1 days. Continuous gait bouts of at least 5-min duration were identified based on acceleration mean amplitude deviation (MAD, in milli gravitational acceleration, mg) and mean EMG amplitude, with EMG normalized to maximal isometric knee extension and flexion (EMG, in percentage of maximal voluntary contraction EMG). Peak oxygen uptake was measured on a treadmill and maximal strength in isometric leg press (leg press max). MAD and EMG were compared between age- and sex-specific fitness groups (low-average, good, and excellent) and in linear models. Results: During habitual walking bouts (4.1 ± 4.1 bouts/day, 0.9 ± 1.0 min/bout), the low-average fit participants had an approximately 28% lower MAD (245 ± 64.3 mg) compared with both good fit and excellent fit participants (313 ± 68.1 mg, p &lt; .05), but EMG was the same (13.1% ± 8.42% maximal voluntary contraction EMG, p = .10). Absolute, relative to body mass, and relative to skeletal muscle mass peak oxygen uptake (but not leg press max) was positively associated with MAD independent of age and sex (p &lt; .01), but there were no associations with EMG. Conclusions: People with low-average aerobic capacity habitually walk with a lower accelerometer-measured absolute intensity, but the physiological stimulus for lower-extremity muscles is similar to those with excellent aerobic capacity. This should be considered when measuring and prescribing walking for health.

Evaluation of the Isometric and Dynamic Rates of Force Development in Multi-Joint Muscle Actions

The rate of force development (RFD) in the isometric leg press (ILP), the countermovement jump (CMJ) and the squat jump (SJ) were examined in twenty-three (9 females) team sport athletes aged 21-24 years. Peak force (Fpeak), peak rate of force development (RFDpeak) and RFD at different time epochs (0-50, 50-100, 100-150, 150-200) were calculated from the force-time curve, as well as CMJ and SJ height and the center of mass displacement. RFDpeak, RFD at 0-50, 50-100 and 100-150 ms and Fpeak were similar between the CMJ and the SJ (p = 0.26 to 0.99). Furthermore, RFD0-50 ms was similar between the ILP, the CMJ, and the SJ (p = 0.99 to 0.57). Higher values were observed in the ILP compared with the CMJ and the SJ in RFD50-100 ms and RFD100-150 ms (p < 0.001) and these differences were maintained even when RFD was scaled to body mass. The higher RFD normalized to Fpeak was attained at the 50-100 ms time interval with no differences between the ILP, CMJ and SJ and between males and females. These results suggest that the ability to exert rapid force is similar between the CMJ and the SJ, irrespective of the type of muscle action. Furthermore, RFD normalized to Fpeak is a muscle-force independent index of explosive force production, facilitating comparisons between individuals with different levels of muscle strength. The similarities between the CMJ and the SJ in RFDpeak, Fpeak, and RFD at different time epochs may imply that these types of jumps could be used interchangeably to assess explosive lower limb performance.

Reference data on anthropometrics, aerobic fitness and muscle strength in young Norwegian men and women

PurposeAnthropometrics, aerobic fitness and muscle strength are measured in one-third of all 18-year-old Norwegian men and women during yearly selection for compulsory military service. The large sample size and geographical representativity make these data valuable for reference. The main purpose of this study was to present reference data for anthropometrics and physical fitness in young Norwegian men and women.MethodsAll 154,659 subjects (66% men and 34% women, 17–21 years old) who completed physical examinations at conscript selection from 2011 to 2019 were included in the study. Body mass index (BMI) was calculated from height and weight measurements. Peak oxygen uptake (VO2peak) was estimated from performance on a maximal treadmill test. Muscle strength was measured by isometric chest and leg press, or seated medicine ball throw, standing long jump and pull-ups.ResultsMean BMI (SD) was 23.1 (3.4) and 22.9 (3.3) kg·m−2 in men and women, respectively (P < 0.001), and 24% of men and 21% of women had a BMI ≥ 25 kg·m−2. Estimated VO2peak was 52.9 (4.6) and 42.7 (3.9) mL·kg−1·min−1 in men and women, respectively (P < 0.001). Men performed significantly better than women on all muscle strength tests, with corresponding effect sizes varying from 1.14 for isometric leg press to 2.96 for seated medicine ball throw.ConclusionThe presented reference data on physical fitness in young Norwegian men and women can be used to evaluate population health, serve as reference material for future studies and describes sex differences in several physical fitness parameters.