Effects of plyometric training on muscle-tendon mechanical properties and behavior of fascicles during jumping.

The purpose of this study was to investigate the effects of plyometric training on the muscle-tendon mechanical properties and behavior of fascicles during jumping in order to elucidate the mechanisms of improved jump performance due to plyometric training. Eleven subjects completed a 12-week unilateral training program for plantar flexors. Active muscle stiffness with (100°·s-1 ) and without (250°·s-1 ) stretch reflex were calculated according to changes in muscle force and fascicle length during fast stretching after submaximal isometric contractions. Stiffness and hysteresis of tendon were measured using ultrasonography during ramp and ballistic contractions. Three kinds of unilateral jump heights using only ankle joint (no counter-movement jump: no-CMJ; counter-movement jump: CMJ; drop jump: DJ) on sledge apparatus were measured. During jumping, electromyographic activities (mEMG) of plantar flexors and fascicle length of the medial gastrocnemius muscle were measured. Active muscle stiffness at 250 and 100°·s-1 and maximal tendon elongation during ballistic contraction significantly increased after training. Tendon hysteresis during ballistic contraction significantly decreased after training, whereas that during ramp contraction did not. The heights of three jump tests, the ratio of mEMG during eccentric to that during concentric phases for CMJ, and the amount of fascicle shortening and shortening velocity during eccentric phase of DJ significantly increased after training. These results suggest that an increase in CMJ height was associated with changes in the muscle-tendon mechanical properties and muscle activation strategy, whereas an increase in DJ height could be explained by changes in the muscle-tendon mechanical properties, but not muscle activation strategy.

Protective and Recovery Effects of Resveratrol Supplementation on Exercise Performance and Muscle Damage following Acute Plyometric Exercise.

Plyometric exercise (PE) is an effective training method to increase muscle mass and strength. However, excessive or inappropriate conditions might cause exercise-induced muscle damage (EIMD). Resveratrol (RES) is a natural polyphenol plant antitoxin, which improves exercise performance, and exhibits anti-oxidation, anti-inflammatory, and anti-cancer effects. Therefore, this study investigated the effect of RES supplementation on the recovery of muscle damage, inflammation, soreness, muscle power, and anaerobic performance following plyometric-exercise-induced muscle damage (PEIMD). The present study was a double-blind, placebo-controlled research trial. Thirty-six young, untrained males were enrolled into the placebo (n = 12), RES-500 (500 mg RES/day, n = 12), or RES-1000 (1000 mg RES/day, n = 12) group by a jumping height-counterbalanced grouping design. At baseline, to pre-PEIMD, supplements were pre-loaded 7 days before they conducted PEIMD, and the exercise performance, delayed-onset muscle soreness (DOMS) and muscle damage biomarkers were measured over the experimental period at baseline, pre-PEIMD, and post-PEIMD at 2, 24, 48, and 72 h. As a result, we found that, at 72 h post-EIMD, the force peak (FP) and rate of force development (RFD) of the counter movement jump (CMJ) in RES groups showed no significant difference compared to that at baseline but was significantly greater than the placebo group. In the Wingate anaerobic test (WAnT), supplementation in the RES group had a better recovery effect on the relative peak power (RPP), relative mean power (RMP) and fatigue index (FI) (p < 0.05), especially in the high-dose group. For the detection of muscle pain after PEIMD, the RES supplement group was significantly better than the placebo group (p < 0.05). In addition, for muscle damage indexes, such as creatine kinase (CK) and lactate dehydrogenase (LDH), after PEIMD, supplementation with RES could significantly reduce and accelerate recovery (p < 0.05). In addition, the blood biochemical indicators of blood count, liver function, and kidney function showed that RES will not cause adverse risks to the human body. Our results suggest that replenishing RES in advance could effectively reduce muscle pain, increase exercise performance, and decrease muscle damage indicators caused by PEIMD, and the recovery was faster. Therefore, plyometric exercises combined with suitable RES supplementation could be an effective candidate for controlling muscle damage, improving physical adaption, and recovering anaerobic capacity.

Effect of D-ribose supplementation on delayed onset muscle soreness induced by plyometric exercise in college students.

OBJECTIVE: Previous investigations suggest that appropriate nutritional interventions may reduce delayed onset muscle soreness (DOMS). This study examined the effect of D-ribose supplementation on DOMS induced by plyometric exercise. METHODS: For the purpose of inducing DOMS, 21 untrained male college students performed a lower-limb plyometric exercise session that involved 7 sets of 20 consecutive frog hops with 90-s of rest between each set. Muscle soreness was measured with a visual analogue scale 1-h before, 24-h after, and 48-h after exercise. Subjects were then randomly placed into the D-ribose group (DRIB, n = 11) and the placebo group (PLAC, n = 10) to assure equivalent BMI and muscle soreness. After a 14-d washout/recovery period, subjects performed the same exercise session, with DRIB ingesting a 200 ml solution containing 15 g D-ribose 1-h before, 1-h, 12-h, 24-h, and 36-h after exercise, and PLAC ingesting a calorically equivalent placebo of the same volume and taste containing sorbitol and ß-cyclodextrin. Muscle soreness and isokinetic muscle strength were measured, and venous blood was assessed for markers of muscle damage and oxidative stress 1-h before, 24-h and 48-h after exercise. RESULTS: In DRIB, muscle soreness after 24-h and 48-h in the second exercise session were significantly lower (p < 0.01) than was experienced in the first exercise session. In the second exercise, blood-related markers of muscle soreness, including creatine kinase, lactate dehydrogenase (LDH), myoglobin and malondialdehyde (MDA) in DRIB after 24-h were lower in DRIB after 24-h than in PLAC (MDA, p < 0.05; rest outcomes, p < 0.01). In addition, LDH and MDA in DRIB were significantly lower (p < 0.01) after 24-h in DRIB than in PLAC. No difference was found in isokinetic muscle strength and oxidative stress markers, including superoxide dismutase and total antioxidant capacity, between DRIB and PLAC after 24-h and 48-h. CONCLUSION: D-ribose supplementation reduces muscle soreness, improves recovery of muscle damage, and inhibits the formation of lipid peroxides. Young adult males performing plyometric exercise are likely to realize a DOMS reduction through consumption of D-ribose in 15 g/doses both before (1-h) and after (1-h, 12-h, 24-h, 36-h) exercise. These results suggest that appropriately timed consumption of D-ribose may induce a similar alleviation of exercise-induced DOMS in the general public.

Part II: Comparison of Crossfit-Related Injury Presenting to Sports Medicine Clinic by Sex and Age.

OBJECTIVE: To examine CrossFit-related injuries based on sex and age. DESIGN: Retrospective case series. SETTING: A tertiary-level pediatric sports medicine clinic. PARTICIPANTS: CrossFit athletes. MAIN OUTCOME MEASURES: CrossFit-related injuries by sex (males vs females) and age groups (≤19 years vs >19 years) using a χ analysis with P = 0.05, odds ratio (OR), and 95% confidence interval (95% CI). RESULTS: Among injured CrossFit athletes, female athletes sustained lower extremity injuries more frequently than male athletes (P = 0.011; OR, 2.65; 95% CI, 1.25-5.65). In observed CrossFit injuries, shoulder injuries were more frequently observed in male athletes compared with female athletes (P = 0.049; OR, 2.79; 95% CI, 0.98-7.95). Additionally, a greater proportion of CrossFit athletes aged 19 years and younger suffered trunk/spine injuries than those older than 19 years (P = 0.027; OR, 2.61; 95% CI, 1.10-6.21) in injured CrossFit athletes. CONCLUSIONS: The current results indicated sex- and age-specific susceptibility to CrossFit-related injuries based on body parts and diagnoses. The presented information may be useful to develop a safer exercise program, especially for pediatric and adolescent CrossFit participants.

Stretch-shortening cycle exercise produces acute and prolonged impairments on endurance performance: is the peripheral fatigue a single answer?

OBJECTIVE: This study aimed to verify the acute and prolonged effects of stretch-shortening cycle exercise (SSC) on performance and neuromuscular function following a 4-km cycling time trial (4-km TT). METHODS: On separate days, individuals performed a 4-km TT without any previous exercise (CON), immediately (ACUTE) and 48 h after (PROL) SSC protocol (i.e., 100-drop jumps). Neuromuscular function was measured at baseline SSC (baseline), before (pre-TT) and after (post-TT) 4-km TT. Muscle soreness and inflammatory responses also were assessed. RESULTS: The endurance performance was impaired in both ACUTE (- 2.3 ± 1.8%) and PROL (- 1.8 ± 2.4%) compared with CON. The SSC protocol caused also an acute reduction in neuromuscular function, with a greater decrease in potentiated quadriceps twitch-force (Qtw.pot - 49 ± 16%) and voluntary activation (VA - 6.5 ± 7%) compared for CON and PROL at pre-TT. The neuromuscular function was fully recovered 48 h after SSC protocol. Muscle soreness and IL-10 were elevated only 48 h after SSC protocol. At post-TT, Qtw.pot remained lower in ACUTE (- 52 ± 14%) compared to CON (- 29 ± 7%) and PROL (- 31 ± 16%). CONCLUSION: These findings demonstrate that impairment in endurance performance induced by prior SSC protocol was mediated by two distinct mechanisms, where the acute impairment was related to an exacerbated degree of peripheral and central fatigue, and the prolonged impairment was due to elevated perceived muscle soreness.

Satellite cell activation and mTOR signaling pathway response to resistance and combined exercise in elite weight lifters.

PURPOSE: Our aim was to compare the effects of a single exercise training mode (resistance exercise) with a combined exercise training (resistance and plyometric exercise) mode on satellite cell activity and anabolic signaling at the molecular level. METHODS: Eighteen male weight lifters (20 ± 4 years, BMI 27 ± 6 kg/m2) were randomly assigned to either a series of resistance exercise or a series of combined exercise group. The intensity of the exercise was set at 60% of their 1 RM weight and subjects completed three sets each of six repetitions. The combined exercise group performed three different types of resistance exercise alternating with three different types of plyometric exercise, whereas the resistance exercise group performed only the three different types of resistance exercise which was repeated twice. Muscle biopsies were obtained the vastus lateralis muscle immediately before and 3 h after one bout of exercise. RESULTS: Exercise induced increases in satellite cell activation and myofibrillar protein synthesis following both exercise modes, but the resistance exercise group was superior compared to the combined exercise group in satellite cell activity expressed by Ki67/CD56 (165 vs 232%) and PI3K/Akt protein expression (121 vs 157%), mTOR protein expression (117 vs 288%), p70S6K protein expression (253 vs 809%), and 4E-BP1 protein expression (70 vs 139%) of anabolic signaling pathway. CONCLUSIONS: These results suggest that the previous findings showing a greater effect of combined as opposed to a single exercise mode could be the effect of a greater training volume rather than a true-training effect of a combined exercise program.

Effects of Warm-Up and Fatigue on Knee Joint Position Sense and Jump Performance.

The purpose of this study was to evaluate the effects of a warm-up and fatigue protocol on the vertical jump and knee joint position sense of sprinters. Thirty-two sprinters were randomly allocated to either a control group (CONT) or a plyometric group (PLYO) that performed a warm-up, followed by a high-intensity plyometric protocol. Absolute (AAE), relative (RAE), and variable (VAE) angular errors and vertical jump were evaluated before and after the warm-up, as well as after the plyometric protocol and again 5 min later. After the warm-up, athletes improved RAE and jump performance. After the plyometric protocol, scores on the RAE, VAE, and the vertical jump performance worsened compared to the control group and to the values obtained after the warm-up. Five minutes later, RAE and vertical jump continued to be impaired. AAE did not show significant differences. The vertical jump is improved after the warm-up, although it is deteriorated after high-intensity plyometry. Regarding knee proprioception, the lack of impairments in the AAE make unclear the effects of the plyometric exercises on knee proprioception.

Effects of low-level laser therapy applied before or after plyometric exercise on muscle damage markers: randomized, double-blind, placebo-controlled trial.

Promising effects of phototherapy on markers of exercise-induced muscle damage has been already demonstrated in constant load or isokinetic protocols. However, its effects on more functional situations, such as plyometric exercises, and when is the best moment to apply this treatment (pre- or post-exercise) remain unclear. Therefore, the purpose of this study was to investigate the effect of low-level laser therapy (LLLT) before or after plyometric exercise on quadriceps muscle damage markers. A randomized, double-blinded, placebo-controlled trial was conducted with 24 healthy men, 12 at pre-exercise treatment group and 12 at post-exercise treatment group. Placebo and LLLT (810 nm, 200 mW per diode, 6 J per diode, 240 J per leg) were randomly applied on right/left knee extensor muscles of each volunteer before/after a plyometric exercise protocol. Muscular echo intensity (ultrasonography images), soreness (visual analogue scale - VAS), and strength impairment (maximal voluntary contraction - MVC) were assessed at baseline, 24, 48, and 72 h post-exercise. Legs treated with LLLT before or after exercise presented significantly smaller increments of echo intensity (values up to 1 %) compared to placebo treatments (increased up to ∼7 %). No significant treatment effect was found for VAS and MVC, although a trend toward better results on LLLT legs have been found for VAS (mean values up to 30 % lesser than placebo leg). In conclusion, LLLT applied before or after plyometric exercise reduces the muscle echo intensity response and possibly attenuates the muscle soreness. However, these positive results were not observed on strength impairment.

Neuromuscular Fatigue and Physiological Responses After Five Dynamic Squat Exercise Protocols.

This aimed to analyze neuromuscular, physiological and perceptual responses to a single bout of 5 different dynamic squat exercise protocols. In a randomized and counterbalanced order, 15 male resistance-trained athletes (mean ± SD; age: 23.1 ± 1.9 years, body mass: 77.4 ± 8.0 kg) completed traditional multiple sets (MS: 4 × 6, 85% 1 repetition maximum [RM]), drop sets (DS: 1 × 6, 85% 1RM + 3 drop sets), eccentric overload (EO: 4 × 6, 70% 1RM concentric, 100% 1RM eccentric), flywheel YoYo squat (FW: 4 × 6, all-out), and a plyometric jump protocol (PJ: 4 × 15, all-out). Blood lactate (La), ratings of perceived exertion (RPE), counter movement jump height (CMJ), multiple rebound jump (MRJ) performance, maximal voluntary isometric contraction force, serum creatine kinase (CK) and delayed onset muscle soreness were measured. Immediately post exercise, La was significantly (p < 0.001) higher in FW (mean ± 95% confidence limit; 12.2 ± 0.9 mmol·L) and lower in PJ (3.0 ± 0.8 mmol·L) compared with MS (7.7 ± 1.5 mmol·L), DS (8.5 ± 0.6 mmol·L), and EO (8.2 ± 1.6 mmol·L), accompanied by similar RPE responses. Neuromuscular performance (CMJ, MRJ) significantly remained decreased (p < 0.001) from 0.5 to 48 hours post exercise in all protocols. There was a significant time × protocol interaction (p ≤ 0.05) in MRJ with a significant lower performance in DS, EO, and FW compared with PJ (0.5 hours post exercise), and in EO compared with all other protocols (24 hours post exercise). A significant main time effect with peak values 24 hours post exercise was observed in CK serum concentrations (p < 0.001), but there was no time × protocol interaction. In conclusion, (a) metabolic and perceptual demands were higher in FW and EO compared with MS, DS and PJ, (b) neuromuscular fatigue was consistent up to 48 hours post exercise in all protocols, and

Effects of estrogen fluctuation during the menstrual cycle on the response to stretch-shortening exercise in females.

The aim of this study was to investigate whether variation in estrogen levels during the menstrual cycle influences susceptibility to exercise-induced muscle damage after stretch-shortening cycle exercise. Physically active women (n = 18; age = 20.2 ± 1.7 yr) participated in this research. The subjects performed one session of 100 maximal drop jumps on day 1 or 2 of the follicular phase and another identical session on day 1 or 2 of the ovulatory phase; the order of the sessions was randomized. Quadriceps femoris muscle peak torque evoked by electrical stimulation and maximal voluntary contraction, muscle pain, and CK activity were measured before and at various times up to 72 h after exercise. It was found that the high estrogen level during the ovulatory phase might be related to an earlier return to baseline muscle strength after strenuous stretch-shortening cycle exercise in that phase compared with the follicular phase. The estrogen effect appears to be highly specific to the damaged site because the differences in most EIMD markers (CK, soreness, and low-frequency fatigue) between the two menstrual cycle phases were small.

Changes in metabolic and muscle damage indicators following a single bout of jump training on stair versus at level.

UNLABELLED: We hypothesized that stair-jump exercise would induce less muscle damage and greater acute metabolic responses than level-jumps. METHODS: Trained males executed 100 unilateral jumps on stairs with one leg, and at level with the other leg, with two weeks hiatus. Maximal isometric voluntary torque (MVC) and rate of torque development (RTD)in the quadriceps, and unilateral vertical jump height (VJ) were determined in the trained leg at pre-exercise,immediately at post- (IP), 24 h and 48 h after exercise. Serum creatine kinase (CK) level and delayed onset muscle soreness (DOMS) were evaluated at pre-exercise, 24 h and 48 h. Acute lactate and heart rate responses were also measured. RESULTS: Lactate and heart rate at IP increased similarly under the two conditions. CK was elevated and MVC was depressed while RTD and VJ remained unchanged at 24 h in both types of training. MVC recovered at 48 h only after stair-jump exercise. DOMS developed only after level-jumps. Except DOMS, no effects of condition were found in any other variables. CONCLUSIONS: We conclude that vigorous stair-jump exercise highly stresses the aerobic and the anaerobic energy system, and it preserves power and rapid torque generating ability 24 h after exercise. Stair-jump could be one alternative exercise to prevent muscle soreness.