The Influence of Unstable Load and Traditional Free-Weight Back Squat Exercise on Subsequent Countermovement Jump Performance.

The purpose of the present study was to examine the effects of a back squat exercise with unstable load (UN) and traditional free-weight resistance (FWR) on subsequent countermovement jump (CMJ) performance. After familiarisation, thirteen physically active males with experience in resistance training visited the laboratory on two occasions during either experimental (UN) or control (FWR) conditions separated by at least 72 h. In both sessions, participants completed a task-specific warm-up routine followed by three maximum CMJs (pre-intervention; baseline) and a set of three repetitions of either UN or FWR back squat exercise at 85% 1-RM. During the UN condition, the unstable load was suspended from the bar with elastic bands and accounted for 15% of the total load. Post-intervention, three maximum CMJs were performed at 30 s, 4 min, 8 min and 12 min after the last repetition of the intervention. The highest CMJ for each participant was identified for each timepoint. No significant increases (p > 0.05) in jump height, peak concentric power, or peak rate of force development (RFD) were found after the FWR or UN conditions at any timepoint. The lack of improvements following both FWR and UN conditions may be a consequence of the low percentage of unstable load and the inclusion of a comprehensive task-specific warm-up. Further research is required to explore higher UN load percentages (>15%) and the chronic effects following the implementation of a resistance training programme.

The beneficial effect of leaf removal during fruit set on physiological, biochemical, and qualitative indices and volatile organic compound profile of the Cypriot reference cultivar 'Xynisteri'.

BACKGROUND: 'Xynisteri' is the reference Cypriot white cultivar that, despite its significant societal and economic impact, is poorly characterized regarding its qualitative properties, while scarce information exists regarding its aroma profile. In the current study, the effect of leaf removal during fruit set (BBCH 71) on 6-year cordon-trained, spur-pruned grapevines was assessed and an array of physiological, biochemical, and qualitative indices were monitored during successive developmental stages (BBCH 75, BBCH 85, BBCH 87, and BBCH 89). Grapes were additionally monitored for the volatile organic compounds (VOCs) profile during the advanced on-vine developmental stages (BBCH 85-BBCH 89) with the employment of gas chromatography-mass spectrometry (GC-MS), Fourier-transform near infrared (FT-NIR) spectra and electronic nose (E-nose) techniques. RESULTS: Grape berries from the vines subjected to leaf removal were characterized by higher solid soluble sugars (SSC), titratable acidity (TA), tartaric acid, and ammonium nitrogen contents, while this was not the case for assimilable amino nitrogen (primary amino nitrogen). A total of 75 compounds were identified and quantified, including aliphatic alcohols, benzenic compounds, phenols, vanillins, monoterpenes, and C13 -norisoprenoids. Leaf removal led to enhanced amounts of glycosylated aroma compounds, mainly monoterpenes, and C13 -norisoprenoids. Chemometric analysis, used through FT-NIR and E-nose, showed that the aromatic patterns detected were well associated to the grape ripening trend and differences between leaf removal-treated and control grapes were detectable during fully ripe stage. CONCLUSION: Leaf removal at fruit set resulted in an overall induction of secondary metabolism, with special reference to glycosylated aroma compounds, namely monoterpenes and C13 -norisoprenoids. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Feasibility, Psychosocial Effects, Influence, and Perception of Elastic Band Resistance Balance Training in Older Adults.

This study utilised feedback from older adults during balance-challenging, elastic band resistance exercises to design a physical activity (PA) intervention. METHODS: Twenty-three active participants, aged 51-81 years, volunteered to perform a mini balance evaluation test and falls efficacy scale, and completed a daily living questionnaire. Following a 10 min warm-up, participants performed eight pre-selected exercises (1 × set, 8-12 repetitions) using elastic bands placed over the hip or chest regions in a randomised, counterbalanced order with 15 min seated rests between interventions. Heart rate (HR) and rate of perceived exertion (RPE) were measured throughout. Participant interview responses were used to qualify the experiences and opinions of the interventions including likes, dislikes, comfort, and exercise difficulty. RESULTS: Similar significant (p < 0.01) increases in HR (pre- = 83-85 bpm, mid- = 85-88 bpm, post-intervention = 88-89 bpm; 5-6%) and RPE (pre- = 8-9, mid- = 10, post-intervention = 10-11) were detected during the PA interventions (hip and chest regions). Interview data revealed that participants thought the PA interventions challenged balance, that the exercises would be beneficial for balance, and that the exercises were suitable for themselves and others. Participants reported a positive experience when using the PA interventions with an elastic band placed at the hip or chest and would perform the exercises again, preferably in a group, and that individual preference and comfort would determine the placement of the elastic band at either the hip or chest. CONCLUSION: These positive outcomes confirm the feasibility of a resistance band balance program and will inform intervention design and delivery in future studies.

Metataxonomic Analysis of Grape Microbiota During Wine Fermentation Reveals the Distinction of Cyprus Regional terroirs.

Wine production in Cyprus has strong cultural ties with the island's tradition, influencing local and foreign consumers' preferences and contributing significantly to Cyprus' economy. A key contributor to wine quality and sensorial characteristics development is the microbiota that colonizes grapes and performs alcoholic fermentation. Still, the microbial patterns of wines produced in different geographic regions (terroir) in Cyprus remain unknown. The present study investigated the microbial diversity of five terroirs in Cyprus, two from the PGI Lemesos region [Kyperounta (PDO Pitsilia) and Koilani (PDO Krasochoria)], and three from the PGI Pafos region [Kathikas (PDO Laona Akamas), Panayia, and Statos (PDO Panayia)], of two grape varieties, Xynisteri and Maratheftiko, using high-throughput amplicon sequencing. Through a longitudinal analysis, we examined the evolution of the bacterial and fungal diversity during spontaneous alcoholic fermentation. Both varieties were characterized by a progressive reduction in their fungal alpha diversity (Shannon index) throughout the process of fermentation. Additionally, the study revealed a distinct separation among different terroirs in total fungal community composition (beta-diversity) for the variety Xynisteri. Also, Kyperounta terroir had a distinct total fungal beta-diversity from the other terroirs for Maratheftiko. Similarly, a significant distinction was demonstrated in total bacterial diversity between the PGI Lemesos region and the PGI Pafos terroirs for grape juice of the variety Xynisteri. Pre-fermentation, the fungal diversity for Xynisteri and Maratheftiko was dominated by the genera Hanseniaspora, Aureobasidium, Erysiphe, Aspergillus, Stemphylium, Penicillium, Alternaria, Cladosporium, and Mycosphaerella. During and post-fermentation, the species Hanseniaspora nectarophila, Saccharomyces cerevisiae, Hanseniaspora guilliermondii, and Aureobasidium pullulans, became the predominant in most must samples. Regarding the bacterial diversity, Lactobacillus and Streptococcus were the predominant genera for both grape varieties in all stages of fermentation. During fermentation, an increase was observed in the relative abundance of some bacteria, such as Acetobacter, Gluconobacter, and Oenococcus oeni. Finally, the study revealed microbial biomarkers with statistically significant higher relative representation, associated with each geographic region and each grape variety, during the different stages of fermentation. The present study's findings provide an additional linkage between the grape microbial community and the wine terroir.

Altered Drop Jump Landing Biomechanics Following Eccentric Exercise-Induced Muscle Damage.

Limited research exists in the literature regarding the biomechanics of the jump-landing sequence in individuals that experience symptoms of muscle damage. The present study investigated the effects of knee localized muscle damage on sagittal plane landing biomechanics during drop vertical jump (DVJ). Thirteen regional level athletes performed five sets of 15 maximal eccentric voluntary contractions of the knee extensors of both legs at 60°/s. Pelvic and lower body kinematics and kinetics were measured pre- and 48 h post-eccentric exercise. The examination of muscle damage indicators included isometric torque, muscle soreness, and serum creatine kinase (CK) activity. The results revealed that all indicators changed significantly following eccentric exercise (p < 0.05). Peak knee and hip joint flexion as well as peak anterior pelvic tilt significantly increased, whereas vertical ground reaction force (GRF), internal knee extension moment, and knee joint stiffness significantly decreased during landing (p < 0.05). Therefore, the participants displayed a softer landing pattern following knee-localized eccentric exercise while being in a muscle-damaged state. This observation provides new insights on how the DVJ landing kinematics and kinetics alter to compensate the impaired function of the knee extensors following exercise-induced muscle damage (EIMD) and residual muscle soreness 48 h post-exercise.

Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up.

Studies examining acute, high-speed movement performance enhancement following intense muscular contractions (frequently called "post-activation potentiation"; PAP) often impose a limited warm-up, compromizing external validity. In the present study, the effects on countermovement vertical jump (CMJ) performance of back squat exercises performed with or without elastic bands during warm-up were compared. After familiarization, fifteen active men visited the laboratory on two occasions under randomized, counterbalanced experimental squat warm-up conditions: (a) free-weight resistance (FWR) and (b) variable resistance (VR). After completing a comprehensive task-specific warm-up, three maximal CMJs were performed followed by three back squat repetitions completed at 85% of 1-RM using either FWR or VR Three CMJs were then performed 30 seconds, 4 minutes, 8 minutes, and 12 minutes later. During CMJ trials, hip, knee, and ankle joint kinematics, ground reaction force data and vastus medialis, vastus lateralis, and gluteus maximus electromyograms (EMG) were recorded simultaneously using 3D motion analysis, force platform, and EMG techniques, respectively. No change in any variable occurred after FWR (P > 0.05). Significant increases (P < 0.05) were detected at all time points following VR in CMJ height (5.3%-6.5%), peak power (4.4%-5.9%), rate of force development (12.9%-19.1%), peak concentric knee angular velocity (3.1%-4.1%), and mean concentric vastus lateralis EMG activity (27.5%-33.4%). The lack of effect of the free-weight conditioning contractions suggests that the comprehensive task-specific warm-up routine mitigated any further performance augmentation. However, the improved CMJ performance following the use of elastic bands is indicative that specific alterations in force-time properties of warm-up exercises may further improve performance.

Stretch imposed on active muscle elicits positive adaptations in strain risk factors and exercise-induced muscle damage.

INTRODUCTION: Stretching highly-contracted plantar flexor muscles (isokinetic eccentric contractions) results in beneficial adaptations in muscle strain risk factors; however its effects in other muscle groups, and on architectural characteristics and exercise-induced muscle damage (EIMD), are unknown. METHODS: The influence of a 6-week knee extensor training program was studied in 26 volunteers (13 control; 13 experimental). Before and after the training program, passive and maximal isometric and eccentric knee extensor moments and range of motion (ROM) were recorded on an isokinetic dynamometer with simultaneous ultrasound imaging of vastus lateralis (VL). On a separate day, EIMD markers (creatine kinase [CK], delayed onset muscle soreness [DOMS]) were measured before and 24 hours after a 20-minute downhill run. The 6-week training program was performed twice-weekly where five sets of 12 stretches (3 seconds per stretch) were imposed on maximally contracted knee extensor muscles. RESULTS: Significant (P < 0.05) increases in eccentric (29.5%) and isometric (17.4%) moments, ROM (5.2°), stretch tolerance (55.4%), elastic energy storage (73.0%), VL thickness (7.8%), pennation angle (9.0%), and tendon stiffness (8.7%) occurred. No change (P > 0.05) in passive muscle-tendon stiffness (-9.4%) or resting fascicle length (-0.7%) occurred. The downhill run resulted in substantial DOMS and significant increase in CK concentration before the training program (107.6%); however, DOMS was eliminated from the knee extensors and a significantly smaller increase in CK (-70.0%) occurred post-training. CONCLUSION: Positive adaptations in functional and physiological variables confirm that imposing stretch on maximally contracted muscle provides beneficial adaptations likely to mitigate EIMD and injury risk and enhance functional performance.

A sled push stimulus potentiates subsequent 20-m sprint performance.

OBJECTIVES: The objective of this study was to examine the potentiating effects of performing a single sprint-style sled push on subsequent unresisted 20m sprint performance. DESIGN: Randomized crossover design. METHODS: Following a familiarization session, twenty rugby league players performed maximal unresisted 20m sprints before and 15s, 4, 8 and 12min after a single sled push stimulus loaded with either 75 or 125% body mass. The two sled push conditions were performed in a randomized order over a one-week period. The fastest sprint time recorded before each sled push was compared to that recorded at each time point after to determine the post-activation potentiation (PAP) effect. RESULTS: After the 75% body mass sled push, sprint time was 0.26±1.03% slower at the 15s time point (effect size [ES]=0.07) but faster at the 4 (-0.95±2.00%; ES=-0.22), 8 (-1.80±1.43%; ES=-0.42) and 12 (-1.54±1.54%; ES=-0.36)min time points. Sprint time was slower at all the time points after the 125% body mass sled (1.36±2.36%-2.59±2.90%; ESs=0.34-0.64). CONCLUSIONS: Twenty-meter sprint performance is potentiated 4-12min following a sled push loaded with 75% body mass while it is impaired after a 125% body mass sled. These results are of great importance for coaches seeking to potentiate sprint performance with the sled push exercise.

Chain-loaded variable resistance warm-up improves free-weight maximal back squat performance.

The acute influence of chain-loaded variable resistance exercise on subsequent free-weight one-repetition maximum (1-RM) back squat performance was examined in 16 recreationally active men. The participants performed either a free-weight resistance (FWR) or chain-loaded resistance (CLR) back squat warm-up at 85% 1-RM on two separate occasions. After a 5-min rest, the participants attempted a free-weight 1-RM back squat; if successful, subsequent 5% load additions were made until participants failed to complete the lift. During the 1-RM trials, 3D knee joint kinematics and knee extensor and flexor electromyograms (EMG) were recorded simultaneously. Significantly greater 1-RM (6.2 ± 5.0%; p < .01) and mean eccentric knee extensor EMG (32.2 ± 6.7%; p < .01) were found after the CLR warm-up compared to the FWR condition. However, no difference (p > .05) was found in concentric EMG, eccentric or concentric knee angular velocity, or peak knee flexion angle. Performing a CLR warm-up enhanced subsequent free-weight 1-RM performance without changes in knee flexion angle or eccentric and concentric knee angular velocities; thus a real 1-RM increase was achieved as the mechanics of the lift were not altered. These results are indicative of a potentiating effect of CLR in a warm-up, which may benefit athletes in tasks where high-level strength is required.

Stretching of Active Muscle Elicits Chronic Changes in Multiple Strain Risk Factors.

INTRODUCTION: The muscle stretch intensity imposed during "flexibility" training influences the magnitude of joint range of motion (ROM) adaptation. Thus, stretching while the muscle is voluntarily activated was hypothesized to provide a greater stimulus than passive stretching. The effect of a 6-wk program of stretch imposed on an isometrically contracting muscle (i.e., qualitatively similar to isokinetic eccentric training) on muscle-tendon mechanics was therefore studied in 13 healthy human volunteers. METHODS: Before and after the training program, dorsiflexion ROM, passive joint moment, and maximal isometric plantarflexor moment were recorded on an isokinetic dynamometer. Simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. Training was performed twice weekly and consisted of five sets of 12 maximal isokinetic eccentric contractions at 10°·s. RESULTS: Significant increases (P < 0.01) in ROM (92.7% [14.7°]), peak passive moment (i.e., stretch tolerance; 136.2%), area under the passive moment curve (i.e., energy storage; 302.6%), and maximal isometric plantarflexor moment (51.3%) were observed after training. Although no change in the slope of the passive moment curve (muscle-tendon stiffness) was detected (-1.5%, P > 0.05), a significant increase in tendon stiffness (31.2%, P < 0.01) and a decrease in passive muscle stiffness (-14.6%, P < 0.05) were observed. CONCLUSION: The substantial positive adaptation in multiple functional and physiological variables that are cited within the primary etiology of muscle strain injury, including strength, ROM, muscle stiffness, and maximal energy storage, indicate that the stretching of active muscle might influence injury risk in addition to muscle function. The lack of change in muscle-tendon stiffness simultaneous with significant increases in tendon stiffness and decreases in passive muscle stiffness indicates that tissue-specific effects were elicited.

Postactivation Potentiation of Horizontal Jump Performance Across Multiple Sets of a Contrast Protocol.

Seitz, LB, Mina, MA, and Haff, GG. Postactivation potentiation of horizontal jump performance across multiple sets of a contrast protocol. J Strength Cond Res 30(10): 2733-2740, 2016-This study determined whether a postactivation potentiation (PAP) effect could be elicited across multiple sets of a contrast PAP protocol. Fourteen rugby league players performed a contrast PAP protocol comprising 4 sets of 2 paused box squats accommodated with bands alternated with 2 standing broad jumps. The rest period between the squats and the jumps and between the sets was 90 seconds. A control protocol with standing broad jumps only was performed on a separate session. A standing broad jump was performed ∼2 minutes before each protocol and served as a baseline measurement. Standing broad jump distance was significantly greater (4.0 ± 3.4% to 5.7 ± 4.7%) than baseline during the 4 sets of the contrast PAP protocol with the changes being medium in the first, second, and fourth sets (effect size [ES]: 0.58, 0.67, and 0.69, respectively) and large for the third set (ES: 0.81). Conversely, no PAP effect was observed in the control protocol. Additionally, the stronger players displayed a larger PAP effect during each of the 4 sets of the contrast PAP protocol (Cohen's d: 0.28-1.68) and a larger mean effect across these 4 sets (Cohen's d: 1.29). Horizontal jump performance is potentiated after only 90 seconds of rest after an accommodating exercise, and this PAP effect can be elicited across 4 sets. Additionally, the PAP response is largely mediated by the individual's strength level. These results are of great importance for coaches seeking to incorporate PAP complexes involving horizontal jumps in their training programs.

Influence of variable resistance loading on subsequent free weight maximal back squat performance.

The purpose of the study was to determine the potentiating effects of variable resistance (VR) exercise during a warm-up on subsequent free-weight resistance (FWR) maximal squat performance. In the first session, 16 recreationally active men (age = 26.0 ± 7.8 years; height = 1.7 ± 0.2 m; mass = 82.6 ± 12.7 kg) were familiarized with the experimental protocols and tested for 1 repetition maximum (1RM) squat lift. The subjects then visited the laboratory on 2 further occasions under either control or experimental conditions. During these conditions, 2 sets of 3 repetitions of either FWR (control) or VR (experimental) squat lifts at 85% of 1RM were performed; during the experimental condition, 35% of the load was generated from band tension. After a 5-minute rest, 1RM, 3D knee joint kinematics, and vastus medialis, vastus lateralis, rectus femoris, and semitendinosus electromyogram (EMG) signals were recorded simultaneously. No subject increased 1RM after FWR, however, 13 of 16 (81%) subjects increased 1RM after VR (mean = 7.7%; p < 0.01). Lower peak and mean eccentric (16-19%; p ≤ 0.05) and concentric (12-21%; p ≤ 0.05) knee angular velocities were observed during the 1RM following VR when compared with FWR, however, no differences in knee flexion angle (1.8°; p > 0.05) or EMG amplitudes (mean = 5.9%; p > 0.05) occurred. Preconditioning using VR significantly increased 1RM without detectable changes in knee extensor muscle activity or knee flexion angle, although eccentric and concentric velocities were reduced. Thus, VR seems to potentiate the neuromuscular system to enhance subsequent maximal lifting performance. Athletes could thus use VR during warm-up routines to maximize squat performance.