Effect of Different Reduced Training Frequencies after 12 Weeks of Concurrent Resistance and Aerobic Training on Muscle Strength and Morphology.

The aim of the study was to investigate the effect of two long-term reduced concurrent training modalities, in which participants performed one training session every either 7 or 14 days, after 12 weeks of systematic concurrent resistance and aerobic training, on lower extremities' muscle strength, power, and morphology in young females. After the 12-week training period, participants were assigned into three groups and performed either one training session every 7 days (G7) or once every 14 days (G14), or detraining (GD), for 12 weeks, followed by 12 additional weeks of detraining. The following were measured before, after the systematic training period, after the end of the reduced training frequency period, and after the end of complete detraining: body composition, leg press 1-RM, countermovement jump, quadriceps cross-sectional area (CSA), vastus lateralis muscle architecture, and maximum aerobic power. Performance and muscle mass increased after the initial 12-week training period. Thereafter, leg press 1-RM, quadriceps CSA, and aerobic power remained unchanged in the G7 group, but decreased in G14 (-4.4 ± 3.5%; -5.9 ± 1.8%; -9.0 ± 7.8%, respectively, p < 0.05), maintaining 95.6 ± 3.5%, 94.1 ± 1.8%, and 91.0 ± 7.8% of the initial training adaptations, respectively. In conclusion, performing one training session every 2 weeks for 3 months may preserve 90 to 95% of the muscle mass/strength and aerobic power adaptations achieved with systematic concurrent training.

Acute effects of dryland muscular endurance and maximum strength training on sprint swimming performance in young swimmers.

The study examined acute effects of dryland muscular endurance (ME) and maximum strength (MS) sessions on performance, physiological, and biomechanical variables during a subsequent sprint swimming session. Twenty-seven swimmers (16.5 ± 2.6 yrs) completed three experimental conditions including: i) ME, 55% of 1-repetition maximum, ii) MS, 90% of 1-repetition maximum, and iii) control (CON, no dry-land). Twenty minutes following ME, MS and CON sessions swimmers performed a 10-s tethered swimming sprint, four by 50-m (4 × 50-m), and a 100-m front crawl sprints. Performance time, blood lactate, heart rate (HR), stroke rate (SR), stroke length (SL), stroke index (SI), and stroke efficiency (ηF) were measured during 4 × 50-m and 100-m. Hand grip strength (HG), and shoulder muscles isometric strength (ISO) were measured after each session. Mean 4 × 50-m time increased in ME compared to CON by 1.7 ± 2.7% (p = 0.01), while 100-m time was similar among conditions (p > 0.05). ISO was lower after dry-land training in all conditions (p = 0.01). Tethered force, HG, HR, SR, SL, SI, and ηF were no different between conditions (p > 0.05). Dryland ME session decrease swimming performance; however, ME and MS sessions did not affect technical ability during a subsequent maximum intensity swimming.

SCS 6th Annual Meeting-EEVFA-11th International Congress of Biochemistry and Physiology of Exercise, Athens, Greece, 2023.

On behalf of the Strength and Conditioning Society (SCS) and the Hellenic Society of Biochemistry and Exercise Physiology (EEVFA), we are pleased to present the abstracts of the SCS 6th Annual Meeting and EEVFA-11th International Congress of Biochemistry and Physiology of Exercise. The event was held at the Hellenic Olympic Committee headquarters in Athens, Greece, on 19-22 October 2023, and comprised several invited sessions from international and national speakers on a variety of topics related to biochemistry and exercise physiology, strength and conditioning practices and their application to health, injury prevention and sports performance. These included strength training in high-performance sports, sport science and training-competition load management in elite environments, biochemistry and exercise physiology and prescription, nutrition and biomechanics, among others. The conference also included different practical workshops conducted by renowned academics and practitioners on eccentric training, change of direction ability and strength and power training in professional team-sports, and ergospirometry and exercise prescription in specific populations. Finally, the event disseminated up-to-date strength and conditioning research by providing practitioners and researchers with the opportunity to present their most recent findings. In this regard, all abstracts of the communications presented at the SCS 6th Annual Meeting-EEVFA-11th International Congress of Biochemistry and Physiology of Exercise can be found in this Conference Report.

Fatigue and Metabolic Responses during Repeated Sets of Bench Press Exercise to Exhaustion at Different Ranges of Motion.

This study compared the acute effects of different ranges of motion (ROM) on fatigue and metabolic responses during repeated sets of bench press exercise. Ten resistance trained men performed three sets to momentary failure with two-min rest intervals at three different ROM: full ROM (FULL), and partial ROM in which the barbell was moved either at the bottom half (BOTTOM) or the top half (TOP) of the full barbell vertical displacement. In TOP, a higher load was lifted, and a higher total number of repetitions was performed compared to FULL and BOTTOM (130 ± 17.6 vs. 102.5 ± 15.9 vs. 98.8 ± 17.5 kg; 55.2 ± 9.8, 32.2 ± 6.5 vs. 49.1 ± 16.5 kg, respectively p < 0.01). Work per repetition was higher in FULL than TOP and BOTTOM (283 ± 43 vs. 205 ± 32 vs. 164 ± 31 J/repetition, p < 0.01). Mean barbell velocity at the start of set 1 was 21.7% and 12.8% higher in FULL compared to TOP and BOTTOM, respectively. The rate of decline in mean barbell velocity was doubled from set 1 to set 3 (p < 0.01) and was higher in FULL than both TOP and BOTTOM (p < 0.001). Also, the rate of mean barbell velocity decline was higher in BOTTOM compared to TOP (p = 0.045). Blood lactate concentration was similarly increased in all ROM (p < 0.001). Training at TOP ROM allowed not only to lift a higher load, but also to perform more repetitions with a lower rate of decline in mean barbell velocity. Despite the lower absolute load and work per repetition, fatigue was higher in BOTTOM than TOP and this may be attributed to differences in muscle length.

The Impact of Range of Motion on Applied Force Characteristics and Electromyographic Activity during Repeated Sets of Bench Press Exercise.

This study examined the effects of range of motion (ROM) on applied force, power output and surface electromyographic (sEMG) responses during repeated sets of bench press exercise executed as fast as possible. Ten resistance trained men performed three sets to momentary failure with two-min rest intervals under three different ROM conditions: (a) full ROM (FULL), (b) TOP, at the top half of ROM, and (c) BOTTOM, at the bottom half of ROM. Mean and peak force were higher in TOP compared to FULL and BOTTOM (mean force: 817 ± 80 vs. 657 ± 98 vs. 623 ± 122 N, respectively, p < 0.001) with no differences between FULL and BOTTOM. During repeated sets, large decreases were found in peak (by 29.4 to 45.3%) and mean power (by 55.5 to 64.7%) from the first to the last repetitions. However, the decrease in mean force was only 2% (p < 0.01) and decreases in peak force ranged from 6.7 and 8.8% to zero, indicating the velocity loss was the main contributor to fatigue in power output. Although force and power output in set 3 were unchanged in BOTTOM, mean power output decreased significantly, suggesting that lower performance and fatigue may be related to the longer muscle length. Fatigue was accompanied by an increase in sEMG activity and a decrease in median frequency in all muscles, with triceps brachialis sEMG reflecting more the force and power differences among ROMs. In conclusion, fatigue depends on velocity rather than force loss during bench press exercise at different ROMs.

Physiological Responses and Performance during an Integrated High-Intensity Interval Aerobic and Power Training Protocol.

This study compared the acute physiological responses and performance changes during an integrated high-intensity interval aerobic and power protocol. Sixteen moderately trained athletes (age: 20.1 ± 2.2 years, body height: 180.0 ± 6.5 cm, body mass: 75.7 ± 6.4 kg, VO2max: 55.8 ± 4.3 mL/kg/min) performed a 2 × 6 min interval training protocol with 2 min passive recovery between sets on two different occasions in random and counterbalanced order. Each 6 min set included repeated periods of 15 s exercise interspersed with 15 s passive rest. On one occasion (RUN), all exercise periods included running at 100% of maximal aerobic speed, while on the other occasion an integrated protocol was used (INT) in which each of the two 6 min sets included 4 × 1.5 min periods of running exercise at 100% of maximal aerobic speed in combination with jumping (i.e., 2 × 15 running with 15 s rest and 1 × 15 s drop jumping with 15 s rest). Time spent above 85% HRmax was two-fold higher in INT compared to RUN (8.5 ± 3.6 vs. 4.3 ± 3.9 min, respectively, p = 0.0014). Interestingly, heart rate increased above 95% HRmax only in INT and almost no time was spent above 95% HRmax in RUN (1.4 ± 1.9 vs. 0.1 ± 0.2 min, respectively, p = 0.008). Blood lactate concentration at the end of the second set of INT was higher than RUN (7.3 ± 3.2 vs. 4.6 ± 2.7 mmol/L, p = 0.002). Countermovement jump was higher in INT after the end of second set by 6.4% (p = 0.04), 6.7% (p = 0.04), 7.8% (p < 0.01) and 7.3% (p < 0.001), at 2, 6 and 8 min after set 2. In conclusion, the comparison between INT and RUN shows that INT not only elicits higher physiological and metabolic responses, but also acutely enhances neuromuscular performance for at least 8 min after the end of exercise. The integrated running/jumping high-intensity interval exercise approach could be a very useful and time efficient method for strength and conditioning coaches, especially in team sports, in which the time available for the improvement of physical parameters is limited.

Dietary Intake of Soccer Players before, during and after an Official Game: Influence of Competition Level and Playing Position.

Physical demands in soccer differ according to league level and playing position and may influence nutritional requirements. This study examined the effect of competition level and playing position on dietary intake in male soccer players (SP). Diet was weighed and recorded by 123 SP for 3 days; before, on the day, and the day after an official match. SP in the Super League (SL, n = 33) division reported higher (p < 0.05) average three-day energy (195 ± 36 kJ/kg), carbohydrate (6.0 ± 1.1 g/kg), and protein (2.2 ± 0.5 g/kg) intakes compared to the intakes reported by SP in the 2nd (n = 30) (energy: 159 ± 31 kJ/kg; carbohydrate: 4.6 ± 1.2 g/kg; protein: 1.9 ± 0.4 g/kg), 3rd (n = 30) (energy: 153 ± 34 kJ/kg; carbohydrate: 4.5 ± 1.2 g/kg; protein: 1.7 ± 0.4 g/kg), and 4th (n = 30) (energy: 152 ± 36 kJ/kg; carbohydrate: 4.2 ± 1.2 g/kg; protein: 1.7 ± 0.5 g/kg) national leagues (mean ± SD). Furthermore, when data were analyzed by playing position (pooled data), wide midfielders reported higher (p < 0.05) energy (183 ± 33 kJ/kg), carbohydrate (5.4 ± 1.2 g/kg), and fat (1.5 ± 0.4 g/kg) intakes compared to central defenders (energy: 147 ± 37 kJ/kg; carbohydrate: 4.1 ± 1.1 g/kg; fat: 1.2 ± 0.4 g/kg). The dietary intake of SP may differ according to the playing position and competition level, possibly due to different metabolic demands in training and competition.

Physiological Responses and Swimming-Performance Changes Induced by Altering the Sequence of Training Sets.

PURPOSE: Interval-training sets may be applied in a different sequence within a swimming training session. The aim of this study was to investigate the effect of different set sequences on performance and physiological responses in a training session. METHODS: Twelve highly trained male swimmers performed 4 sessions in randomized order. Each session included a different combination of 2 training sets: set A-set C, set C-set A, set B-set C, or set C-set B. Set A consisted of 8 × 200 m at speed corresponding to lactate threshold (30-s recovery), set B included 8 × 100 m at maximum aerobic speed (30-s recovery), and set C included 4 × 50-m all-out swimming (2-min recovery). Performance and physiological responses (lactate concentration, pH, base excess, bicarbonate, heart rate, and heart-rate variability) were measured. RESULTS: Performance in each set was similar between sessions irrespective of set sequence. Blood lactate, heart rate, and acid-base responses during set C were similar in all sessions, but blood lactate was higher in sets A and B during C-A and C-B sessions (P = .01). The overall blood lactate and acid-base response was higher in C-A and C-B sessions compared with A-C and B-C sessions, respectively (P = .01). Heart-rate variability in each set, separately as well as the overall session effect, did not differ and was thus independent to the set sequence applied. CONCLUSIONS: Training sessions including all-out swimming as a first set increase the magnitude of metabolic responses to the subsequent aerobic-dominated training set.

High-Intensity Conditioning Activity Causes Localized Postactivation Performance Enhancement and Nonlocalized Performance Reduction.

ABSTRACT: Kolinger D, Stastny P, Pisz A, Krzysztofik M, Wilk M, Tsoukos A, and Bogdanis GC. High-intensity conditioning activity causes localized postactivation performance enhancement and nonlocalized performance reduction. J Strength Cond Res 38(1): e1-e7, 2024-This study aimed to examine whether a conditioning activity (CA) performed by the legs (barbell back squat) may cause postactivation performance enhancement (PAPE) on muscle groups other than leg extensors in isokinetic (eccentric [ECC] and concentric [CON]) and dynamic movement. Twelve male basketball players (age: 21.3 ± 3.2, body mass: 89.6 ± 14.1 kg, height: 187.4 ± 4.6 cm, and 1 repetition maximum (1RM) barbell back squat: 113 ± 21 kg) with previous resistance-training experience of at least 2 years, performed 3 sets of 3-4 repetitions of back-squats with submaximal load (60, 90, and 90% 1RM) as CA. Before and after the CA, they performed pretest and post-test in the form of countermovement jumps (CMJs) (localized) or explosive push-ups (EPUs) (nonlocalized) along with isokinetic flexion and extension at the knee (localized) or at the elbow (nonlocalized). The localized and nonlocalized protocols were divided into 2 days in a randomized order. The back squat as CA significantly increased peak torque (PT) (p < 0.05) in all CON and ECC muscle actions and average power per repetition (APPR) (p < 0.05) (all muscle actions except ECC flexion) of the localized isokinetic tests with large (>0.8) and medium (0.4-0.79) effect sizes and significantly decreased (p < 0.01) the PT and APPR (p < 0.01) of the nonlocalized isokinetic test in the ECC flexion. The CMJ and EPU tests showed no significant differences (p > 0.05) between premeasures and postmeasures of take-off height. The effect of PAPE seems to be specific to the muscles most involved in the CA, and the CA inhibits PT of subsequent muscle ECC contractions in muscles not involved in the CA.

Effects of Training Sets Sequence on Swimming Performance, Training Load and Physiological Responses.

The study examined the effect of set sequence on performance and physiological responses in a training session and in each set separately. Twelve male swimmers performed four sessions in a randomized order, including a combination of two training sets: (i) set A-set C, (ii) set C-set A, (iii) set B-set C, (iv) set C-set B. Set A consisted of 8 × 200 m at a speed corresponding to lactate threshold (30 s recovery), set B included 8 × 100 m at the maximal aerobic speed (30 s recovery), set C included 8 × 50 m sprints at 95% of the maximum 50 m speed (30 s recovery). Speed, blood lactate, pH, base excess, bicarbonate and heart rate variability (HRV) were measured. Speed in each set was similar between sessions irrespective of set sequence (p > 0.05). Physiological responses during sets A and C were similar in all sessions (p > 0.05). In set B, when applied after set C, the metabolic response increased, and HRV decreased (p < 0.05). Overall, session biochemical disturbance was higher when set C was applied before sets A and B (p < 0.05). The magnitude of metabolic and HRV responses in a set conducted at maximal aerobic speed, but not at lactate threshold intensity, is increased when applied after sprint intervals.

Dietary Supplements and Musculoskeletal Health and Function.

This Special Issue of Nutrients 'Dietary Supplements and Musculoskeletal Health and Function' provides new insights into the use of a wide range of dietary supplements, such as zinc, creatine, Vitamin D, HMB, BCAA, betaine, glucoraphanin, citrulline and collagen, to improve bone and muscle structure and function [...].

Effects of blood flow restriction on mechanical properties of the rectus femoris muscle at rest.

Introduction: This study examined the effects of blood flow restriction (BFR) and reperfusion on the mechanical properties of the rectus femoris muscle at rest (frequency and stiffness). Methods: Fourteen trained men (body weight = 81.0 ± 10.3 kg; BMI = 25 ± 3.0 m/kg2; height = 181 ± 4 cm; training experience = 6.0 ± 2.2 years) participated in an experimental session involving their dominant (BFR) and non-dominant leg (control). Muscle mechanical properties were measured using Myoton's accelerometer at the midpoint of the rectus femoris muscle at five time points. In the BFR leg, an 80% arterial occlusion pressure was applied by a cuff for 5 min. No cuff was applied in the control leg. Femoral Myoton measurements were taken from both legs 2 and 4 min after the start of BRF as well as 30 s and 2 min after the end of the occlusion period. Results: The two-way ANOVA revealed a statistically significant interaction effect for stiffness and frequency (p < 0.001; η2 > 0.67). The post hoc analysis showed that both stiffness and frequency increased during BFR compared with rest and then dropped to the resting levels post BFR period. Also, stiffness and frequency were higher than control only during the BFR period, and similar during rest and post BFR. Conclusion: These results indicate that the application of BFR at rest leads to significant changes in mechanical properties of the rectus femoris muscle.

Lower Fatigue in the Eccentric than the Concentric Phase of a Bench Press Set Executed with Maximum Velocity to Failure Against Both Heavy and Light Loads.

We examined changes in barbell velocity and surface electromyographic activity (sEMG) during the concentric (CON) and eccentric (ECC) phases of a bench press set. Ten men executed a set to instant exhaustion as fast as possible, against a low (40% 1-RM) and a heavy load (80% 1-RM), one week apart. The reduction in mean barbell velocity was lower in the ECC compared with the CON phase for both loads (40%1-RM: ECC: -36 ± 21% vs. CON: -63 ± 14%, p < 0.001; 80%1-RM: ECC: -26 ± 15% vs. CON: -59 ± 9%, p < 0.001). Under both loading conditions, sEMG activity of the pectoralis major increased in the last compared to the first repetitions only in the CON phase (by 48.6% and 24.8%, p < 0.01, in the 40% and 80%1-RM, respectively). Similarly, triceps brachii sEMG increased by 15.7% (p = 0.02) and by 21.0% (p < 0.001) during the CON phase in the 40% and 80%1-RM conditions, respectively. However, during the ECC phase, sEMG remained unchanged in the last part of the set for both muscles and loads except for 80%1-RM in the pectoralis major muscle. It was concluded that fatigue measured by velocity loss was lower during the ECC than the CON phase of the bench press movement, when the exercise was performed with maximum velocity to failure, irrespective of the load. sEMG was lower in the ECC than the CON phase for all loads, and increased at the end of the set only during the CON phase, while it remained relatively unchanged in the ECC phase, with the exception of the pectoralis muscle when the load was heavier.

The Effects of Zinc and Selenium Co-Supplementation on Resting Metabolic Rate, Thyroid Function, Physical Fitness, and Functional Capacity in Overweight and Obese People under a Hypocaloric Diet: A Randomized, Double-Blind, and Placebo-Controlled Trial.

Evidence of the effectiveness of zinc (Zn) and selenium (Se) on resting metabolic rate (RMR) and physical function parameters in people with overweight and obesity is scarce, while the effects of zinc and selenium on thyroid function and body composition are still a topic of debate and controversy. The aim of this randomized, double-blind, and placebo-controlled trial was to examine the effects of a hypocaloric diet and Se-Zn co-supplementation on RMR, thyroid function, body composition, physical fitness, and functional capacity in overweight or obese individuals. Twenty-eight overweight-obese participants (mean BMI: 29.4 ± 4.7) were randomly allocated (1:1) to the supplementation group (n = 14, 31.1 ± 5.5 yrs, 9 females) and the placebo group (n = 14, 32.1 ± 4.8 yrs, 6 females). The participants received Zn (25 mg of zinc gluconate/day) and Se (200 mcg of L-selenomethionine/day) or placebo tablets containing starch for eight weeks. The participants of both groups followed a hypocaloric diet during the intervention. RMR, thyroid function, body composition, cardiorespiratory fitness (VO2max), and functional capacity (sit-to-stand tests, timed up-and-go test, and handgrip strength) were assessed before and after the intervention. A significant interaction was found between supplementation and time on RMR (p = 0.045), with the intervention group's RMR increasing from 1923 ± 440 to 2364 ± 410 kcal/day. On the other hand, no interaction between supplementation and time on the thyroid function was found (p > 0.05). Regarding the effects of Zn/Se co-administration on Se levels, a significant interaction between supplementation and time on Se levels was detected (p = 0.004). Specifically, the intervention group's Se serum levels were increased from 83.04 ± 13.59 to 119.40 ± 23.93 µg/L. However, Zn serum levels did not change over time (90.61 ± 23.23 to 89.58 ± 10.61 umol/L). Even though all body composition outcomes improved in the intervention group more than placebo at the second measurement, no supplement × time interaction was detected on body composition (p > 0.05). Cardiorespiratory fitness did not change over the intervention. Yet, a main effect of time was found for some functional capacity tests, with both groups improving similarly over the eight-week intervention period (p < 0.05). In contrast, a supplement x group interaction was found in the performance of the timed up-and-go test (TUG) (p = 0.010), with the supplementation group improving more. In conclusion, an eight-week intervention with Zn/Se co-supplementation combined with a hypocaloric diet increased the RMR, TUG performance, and Se levels in overweight and obese people. However, thyroid function, Zn levels, body composition, and the remaining outcomes of exercise performance remained unchanged.

Muscle Architecture Adaptations to Static Stretching Training: A Systematic Review with Meta-Analysis.

BACKGROUND: Long-term stretching of human skeletal muscles increases joint range of motion through altered stretch perception and decreased resistance to stretch. There is also some evidence that stretching induces changes in muscle morphology. However, research is limited and inconclusive. OBJECTIVE: To examine the effect of static stretching training on muscle architecture (i.e., fascicle length and fascicle angle, muscle thickness and cross-sectional area) in healthy participants. DESIGN: Systematic review and meta-analysis. METHODS: PubMed Central, Web of Science, Scopus, and SPORTDiscus were searched. Randomized controlled trials and controlled trials without randomization were included. No restrictions on language or date of publication were applied. Risk of bias was assessed using Cochrane RoB2 and ROBINS-I tools. Subgroup analyses and random-effects meta-regressions were also performed using total stretching volume and intensity as covariates. Quality of evidence was determined by GRADE analysis. RESULTS: From the 2946 records retrieved, 19 studies were included in the systematic review and meta-analysis (n = 467 participants). Risk of bias was low in 83.9% of all criteria. Confidence in cumulative evidence was high. Stretching training induces trivial increases in fascicle length at rest (SMD = 0.17; 95% CI 0.01-0.33; p = 0.042) and small increases in fascicle length during stretching (SMD = 0.39; 95% CI 0.05 to 0.74; p = 0.026). No increases were observed in fascicle angle or muscle thickness (p = 0.30 and p = 0.18, respectively). Subgroup analyses showed that fascicle length increased when high stretching volumes were used (p < 0.004), while no changes were found for low stretching volumes (p = 0.60; subgroup difference: p = 0.025). High stretching intensities induced fascicle length increases (p < 0.006), while low stretching intensities did not have an effect (p = 0.72; subgroup difference: p = 0.042). Also, high intensity stretching resulted in increased muscle thickness (p = 0.021). Meta-regression analyses showed that longitudinal fascicle growth was positively associated with stretching volume (p < 0.02) and intensity (p < 0.04). CONCLUSIONS: Static stretching training increases fascicle length at rest and during stretching in healthy participants. High, but not low, stretching volumes and intensities induce longitudinal fascicle growth, while high stretching intensities result in increased muscle thickness. REGISTRATION: PROSPERO, registration number: CRD42021289884.

Physiological Responses and Fatigue during a Repeated Shuttle-Sprint Running Test in Adolescent Schoolchildren: A Comparison between Sexes and Fatigue Calculation Methods.

We examined physiological responses and fatigue in adolescent boys and girls during a repeated shuttle-sprint running test in a school setting. We also compared three calculation methods to assess fatigue during repeated sprints: the fatigue index (FI), the percent sprint decrement (Sdec), and the slope of performance decrement (SlopeD). Twenty-six adolescent students (10 girls and 16 boys, age: 15.3 ± 0.5 y) performed six 30 m sprints with a 180° change of direction at 15 m, interspersed with 10 s of recovery. Blood lactate (BL), heart rate (HR) and countermovement jump performance (CMJ) were measured before and after the sprint test. Boys achieved significantly faster sprint times (11.7% to 14.8% faster than girls in all sprints, p < 0.01), and had higher post-test BL compared with girls (14.0 ± 2.9 vs. 11.3 ± 3.2 mmol/L; p = 0.02; d = 0.93). However, all fatigue indices (FI, Sdec and SlopeD) were similar in boys and girls (FI = 11.5 ± 5.0 vs. 11.5 ± 5.0; SlopeD = 10.6 ± 4.8 vs. 14.5 ± 5.1; Sdec = 5.6 ± 2.2 vs. 7.3 ± 2.2, in boys and girls, respectively, p > 0.05 for all) and were highly correlated with each other (r = 0.86 to 0.97, p < 0.01). CMJ was higher in boys (p < 0.05), but CMJ performance dropped similarly from pre- to post-test in boys and girls (13.7 ± 7.0%, p < 0.01). In conclusion, neuromuscular fatigue during and after repeated shuttle-sprint running is similar in boys and girls, despite the faster sprint times, higher CMJ and higher BL in boys. SlopeD may be used as an alternative index to quantify fatigue during repeated shuttle-sprinting, as it takes into account performance in all sprints and may provide an average sprint-by-sprint performance drop.

Effects of Concurrent High-Intensity and Strength Training on Muscle Power and Aerobic Performance in Young Soccer Players during the Pre-Season.

The aim of the present study was to evaluate two different intervention programs applied during a 4-week pre-season period. Twenty-nine players participated in this study and were divided into two groups. One group (BallTrain, n = 12, age: 17.8 ± 0.4 years, body mass: 73.9 ± 7.6 kg, height: 178 ± 0.1 cm, body fat: 9.6 ± 5.3%) performed a higher percentage of aerobic training with ball and strength training using plyometrics and exercises with body weight. The other group (HIITTrain, n = 17, age: 17.8 ± 0.7 years, body mass: 73.3 ± 5.0 kg, height: 179 ± 0.1 cm, body fat: 8.0 ± 2.3%) trained with high-intensity interval training (HIIT) without the ball and performed resistance training with weights in the same session. Both groups trained for strength (two times/week) and performed aerobic-anaerobic fitness without the ball, passing games, and tactical and small-sided games. Lower limb power (CMJ) and aerobic fitness (Yo-Yo intermittent recovery test level 1-IR1) were evaluated before and after the four-week training program. Yo-Yo IR1 performance was improved in both groups, but the improvement was greater for the HIITTrain than BallTrain group (468 ± 180 vs. 183 ± 177 m, p = 0.07). CMJ showed a non-significant improvement in the BallTrain group (5.8 ± 8.8%, p = 0.16), but it decreased by 8.1 ± 9% (p = 0.001), in the HIITTrain group. In conclusion, we have shown that a short pre-season period of training results in improvements in aerobic fitness in both groups, with high-intensity interval training showing superior adaptations than training with the ball. However, CMJ performance was reduced in this group, possibly suggesting higher fatigue levels and overload, and/or showing the effects of concurrent HIITTrain and strength training in soccer.

Acute Effects of Varied Back Squat Activation Protocols on Muscle-Tendon Stiffness and Jumping Performance.

ABSTRACT: Krzysztofik, M, Wilk, M, Pisz, A, Kolinger, D, Tsoukos, A, Zajac, A, Stastny, P, and Bogdanis, GC. Acute effects of varied back squat activation protocols on muscle-tendon stiffness and jumping performance. J Strength Cond Res 37(7): 1419-1427, 2023-Intensity, movement velocity, and volume are the principal factors to successfully use postactivation performance enhancement. Therefore, 15 resistance-trained volleyball players completed 3 different back squat configurations as a conditioning activity (CA) in randomized order: (a) 3 sets of 3 repetitions at 85% 1RM (HL); (b) a single set of back squats at 60% 1RM until 10% mean velocity loss (VB); (c) and 2 sets of back squats at 60% 1RM until 10% mean velocity loss (2VB) on subsequent countermovement jump performance, Achilles tendon, and vastus lateralis stiffness with concomitant front thigh skin surface temperature assessment. The measurements were performed 5 minutes before the CA and at 2, 4, 6, 8, and 10 minutes. The jump height was significantly increased in the second minute and at peak, post-CA compared with baseline for all conditions ( p = 0.049; ES = 0.23 and p < 0.001; ES = 0.37). Skin surface temperature was significantly increased for all post-CA time points compared with baseline in the 2VB condition ( p from <0.001-0.023; ES = 0.39-1.04) and in the fourth minute and at peak post-CA in HL condition ( p = 0.023; ES = 0.69 and p = 0.04; ES = 0.46), whereas for the VB condition, a significant decrease in peak post-CA was found ( p = 0.004; ES = -0.54). Achilles tendon stiffness was significantly decreased for second, fourth, eighth, 10th, and peak post-CA in comparison to baseline for all conditions ( p from p = 0.004-0.038; ES = -0.47 to -0.69). Vastus lateralis stiffness was significantly decreased for peak post-CA compared with baseline for all conditions ( p = 0.017; ES = -0.42). We recommend using a single set of barbell squats with a 10% velocity loss as a mechanism of fatigue control to acutely improve jump height performance and avoid unnecessary increases in training volume.

The Effect of Aerobic Fitness on Psychological, Attentional and Physiological Responses during a Tabata High-Intensity Interval Training Session in Healthy Young Women.

The current study examines the effects of a Tabata high-intensity interval training (HIIT) session on affective, cognitive and physiological indicators in women of different fitness levels. A total of 28 adult women (aged 24.2 ± 1.5 years) completed a 20 m shuttle run test and were then assigned to higher fitness and lower fitness groups (HF and LF, n = 14 each) according to their predicted aerobic power. On a separate occasion, participants completed a 30 min Tabata workout (six 4 min rounds separated by 1 min passive rest). Each round included eight exercises (20 s exercise and 10 s rest). Affective, physiological and cognitive responses were assessed prior to, during and after the protocol. Heart rate and blood lactate concentration increased similarly in both groups over time throughout the workout (p < 0.001). Total Mood Disturbance was higher for LF (111.4 ± 15.7) vs. HF (102.9 ± 11.7) (p = 0.48), vigor showed a level by time interaction of p = 0.006 and Activation−Deactivation Adjective Check List factors deteriorated over time (p < 0.001). The Concentration Grid Test was better overall for HF (10.5 ± 3.6) vs. LF (8.6 ± 3.6) (p = 0.05). The Feeling Scale and Rating of Perceived Exertion worsened similarly in both groups over time (p = 0.002 and p < 0.001, respectively). Positive and negative affect and arousal did not differ between groups or change over time (p > 0.05). These results show that, despite the different levels of aerobic fitness, physiological, metabolic, perceptual and affective responses were similar in the two groups of women during a 30 min Tabata session. This may imply that affective responses during this type of HIIT are independent of aerobic fitness.

Endocrine responses of the stress system to different types of exercise.

Physical activity is an important part of human lifestyle although a large percentage of the population remains sedentary. Exercise represents a stress paradigm in which many regulatory endocrine systems are involved to achieve homeostasis. These endocrine adaptive responses may be either beneficial or harmful in case they exceed a certain threshold. The aim of this review is to examine the adaptive endocrine responses of hypothalamic-pituitary-adrenal axis (HPA), catecholamines, cytokines, growth hormone (GH) and prolactin (PRL) to a single bout or regular exercise of three distinct types of exercise, namely endurance, high-intensity interval (HIIE) and resistance exercise. In summary, a single bout of endurance exercise induces cortisol increase, while regular endurance exercise-induced activation of the HPA axis results to relatively increased basal cortisolemia; single bout or regular exercise induce similar GH peak responses; regular HIIE training lowers basal cortisol concentrations, while catecholamine response is reduced in regular HIIE compared with a single bout of HIIE. HPA axis response to resistance exercise depends on the intensity and volume of the exercise. A single bout of resistance exercise is characterized by mild HPA axis stimulation while regular resistance training in elderly results in attenuated inflammatory response and decreased resting cytokine concentrations. In conclusion, it is important to consider which type of exercise and what threshold is suitable for different target groups of exercising people. This approach intends to suggest types of exercise appropriate for different target groups in health and disease and subsequently to introduce them as medical prescription models.