The Effects of Eight Weeks of Leucine/Whey Protein Supplementation and Resistance Training on Isokinetic Peak Torque

Resistance training can lead to significant increases in muscle size and strength. Supplementing the diet with leucine and whey protein purportedly increases protein synthesis, potentially accelerating the processes involved with hypertrophy and strength increases. PURPOSE: To examine the effects of leucine and whey protein supplementation during 8 weeks of unilateral dynamic constant external resistance (DCER) training on isokinetic peak torque. METHODS: Thirty-five men (mean age ± SD = 22.3 ± 2.3 y) volunteered to participate in this investigation. Participants were randomly assigned to one of three groups: supplement (SUPP), placebo (PLA), or control (CON). The SUPP and PL participants then trained the leg extensors of the dominant limb (based on kicking preference) three times per week for eight weeks. Leg extension peak torque was determined for all participants pretraining and post training at 0, 60, 120, 180, 240, and 300°.s-1 using an isokinetic dynamometer. RESULTS: The results indicated there was no significant time × velocity × group interaction (p = 0.55). There was, however, a significant time × group interaction. Both the SUPP group (p \u3c 0.001) and the PLA group (p = 0.02) demonstrated significant increases in peak torque from pretraining to post training, while the CON group did not (p = 0.59). There was no difference in the magnitude of the gain in isokinetic peak torque between the SUPP and PLA groups (p = 0.62). CONCLUSION: Isokinetic peak torque increased significantly following 8 weeks of DCER training. However, the increase in peak torque was not augmented by leucine and whey protein supplementation

Mechanical Differences Between Sexes During A Jump Landing

Jump landings are a frequent occurrence in both male and female sports. However, aberrant landing mechanics, such as landing with smaller knee flexion angles (KFA), can increase the likelihood of knee joint injury. Previous research suggests males and females demonstrate different landing mechanics, which could explain the higher incidence of knee injuries in females, such as anterior cruciate ligament (ACL) injury. PURPOSE: The purpose of this study was to compare lower extremity landing biomechanics associated with ACL injury between males and females. We hypothesized that females would land with smaller KFA and greater knee abduction angles (KAA) compared to males. METHODS: Landing biomechanics were assessed in 15 males (23.46±2.75 yrs, 1.77±0.06 m, 77.81±14.01kg) and 15 females (21.24±1.99 yrs, 1.63±0.06 m, 63.15±12.19kg) during a jump landing task. All participants had experience playing sports that required jumping and landing. Separate independent samples t-tests were used to compare KFA at initial contact, knee abduction angle (KAA) at initial contact, peak KFA, and peak KAA between males and females. RESULTS: Males demonstrated larger KFA at initial contact compared to females (16.52±4.55o vs 12.85±4.91o, p=0.04), but smaller KAA at initial contact (3.13±2.07o vs 0.93±052o, po vs 91.88±10.71o, p=0.03) and smaller peak KAA (-2.97±2.0o vs -6.49±4.11o, p=0.004). CONCLUSION: The landing mechanics demonstrated by females may be problematic, as smaller KFA when landing have been associated with higher forces being absorbed, increasing the odds of ACL injury. Furthermore, females also demonstrated greater KAA, which have also been linked with traumatic knee injury. Therefore, females participating in sports involving landing from a jump could benefit from interventions that aim to improve landing kinematics

An Analysis of Horizontal Forces Between Sports

Different sports have various demands that athletes must meet to perform at the requisite level. For example, hockey athletes produce primarily horizontal forces due to skating. However, in basketball, there are a combination of horizontal forces from running and vertical forces from frequent jumping. Therefore, utilizing forces exclusively in one direction as a metric to compare athletes of different sports could provide a limited analysis. PURPOSE: The purpose of this investigation was to compare the relationship between horizontal and vertical forces between athletes who participate in the 4 major sports in the US by using a ratio of horizontal and vertical forces produced, called Fmax ratios. We hypothesized that athletes who move primary horizontally, like hockey players, would have greater Fmax ratios than athletes who participate in sports that involve jumping, like basketball. METHODS: Kinetic data were collected on 28 male athletes (8 baseball, 8 basketball, 6 hockey, 3 football, 22.4±4.53 yrs., 1.86±0.08m, 86.39±8.64kg) who participate in the 4 major US sports. All athletes had their horizontal forces measured using a DynaSpeed MUSCLELAB system. Athletes ran at various %’s of bodyweight using the DynaSpeed, and regression was used to predict peak horizontal forces. To measure vertical forces, athletes performed a countermovement jump on a force platform. Fmax ratios were calculated by dividing peak horizontal force by peak vertical force. A one-way ANOVA was used to compare Fmax ratios between athletes of the 4 major US sports. RESULTS: No differences were found in Fmax ratios between sports (Baseball = 0.22±0.03, Basketball = 0.20±0.02, Hockey = 0.21±0.02, Football = 0.20±0.01, p=0.34). CONCLUSION: Results contradict our hypothesis as no mean differences were found between any sports. Furthermore, an exploratory analysis found no differences in horizontal forces between groups. This suggests that regardless of predominant direction utilized in sport, athletes of different sports still produce the same magnitude of horizontal forces as well as ratios. Future studies that investigate Fmax ratios should aim to measure horizontal and vertical forces simultaneously rather than separately to best capture sport specificity

The Effects Of A Heel Lift On Squat Biomechanics

The barbell squat is an effective exercise for improving lower extremity function. During the descent of a squat, the hip and knee joints flex while the ankle joint dorsiflexes. The hip and knee joints then extend and the ankle joint plantarflexes when standing up. During the squat, some athletes use shoes with an elevated heel or other means of heel elevation to achieve lower squat depth. Research has suggested that use of heel elevation may improve range of motion (ROM) of the lower extremity joints and improve stability of the movement during deep squats, especially with an external load. PURPOSE: The purpose of this study was to compare lower extremity biomechanics during the back squat exercise in a heel-lift (HL) vs non-heel lift (NHL) condition. We hypothesized that the HL condition would result in greater peak knee flexion angles (KFA) and greater net knee joint moments (NJM). METHODS: 25 healthy participants (13 male, 12 female, 23.6±3.14 yrs., 1.70±0.08 m, 72.24±12.86kg) who had back squatted at least once per week for the last three months were recruited for data collection. 2 visits were required from each participant with the first visit involving back squat one-repetition-maximum (1RM) testing (101.62±41.40kg). During the second visit, participants underwent 3-D biomechanical analyses for the back squat with and without heel lift. Participants performed three repetitions at 75% 1RM for each condition in a randomized order, with a five-minute rest period. Squat velocity was controlled for by using a metronome set to 20 beats per minute. The 2nd of the three repetitions was used for analysis. Paired samples T-tests were used to compare peak knee NJM and peak KFA between the HL and NHL conditions. RESULTS: No differences were found between HL and NHL for knee NJM (2.79±0.96 Nm/kg-1vs 2.7±0.79 Nm/kg-1, p=0.72) or peak KFA (126.03±15.73o vs 125.8±15.39o, p=0.83) CONCLUSION: Results contradict our hypothesis, as the HL did not increase the participants KFA or knee NJM. These results suggest that shoe type used during the back squat exercise may be left up to user preference as to what is comfortable for them. Future studies may aim to see if adding a HL influences lower extremity biomechanics when the load is closer to 1RM, or in other squat variations

Effects of Percussive Massage Treatments on Symptoms Associated With Eccentric Exercise-Induced Muscle Damage

Percussive massage (PM) is an emerging recovery treatment, but the research on its effects post-eccentric exercise (post-EE) is limited. PURPOSE: To investigate the effects of PM on maximal isometric torque (MIT), range of motion (ROM), and an 11-point numerical rating scale (NRS) of soreness from 24-72 h post-EE. METHODS: Seventeen untrained, college-aged subjects (14 women and 3 men) performed 60 eccentric elbow flexion actions with their nondominant arms. Nine subjects received 1 minute of PM on their nondominant arm’s biceps brachii immediately, 24, 48, and 72 h post-EE, versus eight rested quietly (control [CON]). In order, the NRS, ROM, and MIT were collected pre-eccentric exercise (pre-EE) and after treatment (AT) at 24, 48, and 72 h post-EE. The NRS was also collected before treatment (BT). Electromyographic (EMG) amplitude was collected during the MIT and normalized to pre-EE. MIT was made relative to body mass. All measures were analyzed via separate two-way (group × time) mixed factorial ANOVAs. RESULTS: There was no interaction (p = 0.22) for MIT but a main effect for time (p \u3c 0.001), indicating an approximately (approx.) 12% decrease (p = 0.02) from pre-EE to 24 h post-EE. Values returned to pre-EE by 48 h (p = 0.47). There was no interaction (p = 0.55) or main effect of time (p = 0.47) for EMG. An interaction (p \u3c 0.001) for ROM showed that the PM group had higher values than the CON at 24 (p = 0.01), 48 (p = 0.01), and 72 h (p = 0.04) by approx. 8, 6, and 6°, respectively. The PM group returned to pre-EE (p \u3e 0.05) faster than the CON (PM: 48 h, CON: 72 h) and exceeded (p \u3c 0.001) their pre-EE at 72 h by approx. 4°. An interaction (p = 0.01) for NRS revealed that the groups did not differ BT at 24 (p = 0.11), 48 (p = 0.052), and 72 h (p = 0.10). However, the PM group’s NRS lowered from BT to AT within the 24 (p \u3c 0.001), 48 (p \u3c 0.001), and 72 h (p = 0.01) visits by approx. 1 point per visit. As a result, the PM group had lower values (p \u3c 0.001) than the CON AT at 24, 48, and 72 h by approx. 3, 2, and 2 points, respectively. Lastly, the PM group returned their NRS to pre-EE (p \u3e 0.05) faster than the CON (PM: BT 72 h, CON: never). CONCLUSION: The PM treatments improved ROM without affecting MIT or muscle activation 24-72 h post-EE. Although the PM did not enhance the recovery from soreness until 72 h, it consistently provided immediate, temporary relief when used 24-72 h post-EE

Effects of Acute Late Sleep Restriction on Strength, Power, and Running Speed in Recreationally Active Females

Previous research suggests that late sleep restriction (SR) paired with exercise in the morning does not have a significant impact on sport performance measures. However, this evidence is based on research conducted primarily in males. PURPOSE: To examine the effects of late sleep restriction on measures of strength, speed, and power among recreationally active females. METHODS: Twenty-three (23) recreationally active (aerobic physical activity and resistance exercise at least three times a week for six months) females participated in this study (mean age 21.5 years, BMI 23 kg/m2). A randomized, cross-over design was used under two conditions, recommended sleep (RS), and late SR. Participants performed three exercises to obtain measures; Isometric mid-thigh-pull (Relative Peak Force [RPF], Peak Force [PF], Rate of Force Development [RFD]), 20-yard sprint (time in seconds), and Counter-movement jump (Jump Height [JH], Relative Peak Power [RPP]). Conditions were separated with a 3-day resting period. For RS, participants were instructed to achieve 7h of sleep which align with the recommendation for healthy sleep length. For SR, participants subtracted three hours of sleep from the usual wake-up time with at least three hours of awake time before testing. RESULTS: No significant differences were found comparing RS and SR for all measures. CONCLUSION: Late SR did not affect measures of strength, speed, and power among recreationally active female athletes when compared to RS. These results support former research suggesting no evidence of impaired performance for strength, power, or speed with a single bout of late sleep restriction and exercise in the morning. Previous research suggests that psychomotor functioning may be affected in a greater way than gross motor functioning. Therefore, future research should consider effects of multiple, consecutive bouts of SR on performance measures as well as psychomotor functioning specifically in females

Povezanost između snage trupa i pokazatelja sportske uspješnosti

Development of core muscle strength and power to improve sport performance has been a controversial issue yielding mixed results. The purpose of this study was to investigate the relationship between two core field tests emphasizing power and measures of sport performance. Participants were twenty healthy, recreationally active males (age 23.40±1.88 yrs, height 174.63±5.81 cm, mass 76.08±7.67 kg). Participants were tested on four performance variables (40-yd sprint, shuttle run [5-10-5], vertical jump, and 1RM back squat) and two core field tests (front abdominal power throw [FAPT] and side abdominal power throw [SAPT]). Results demonstrated significant moderate correlations between the FAPT and 1RM back squat (r=.652) and relative back squat (r=.509). No other significant correlations were found. Results indicate that although the FAPT and SAPT tests are easy to perform in the field, most, but not all, performance measures were unrelated to core power. In order to properly assess the core and its role in human performance, it is necessary to evaluate sport-specific muscle actions and movements.Razvijanje mišićne jakosti i snage trupa kako bi se unaprijedila sportska izvedba i uspješnost jest kontroverzan znanstveni i stručni problem istraživanje kojega daje miješane rezultate. Cilj je ovoga istraživanja bilo utvrđivanje povezanosti između dva terenska testa za procjenu snage trupa i pokazatelja sportske uspješnosti. Uzorak ispitanika činilo je 20 zdravih, rekreativno aktivnih muškaraca (dob 23,40±1,88 godina, tjelesna visina 174,63±5,81 cm, tjelesna masa 76,08±7,67 kg). Sportska uspješnost ispitanika procijenjena je četirima testovima (sprint na 40 jarda, shuttle run: 5-10-5 jarda, vertikalni skok i maksimalni stražnji čučanj), a snaga njihova trupa (core) procijenjena je dvama terenskim testovima (eksplozivno bacanje medicinke prema naprijed – FAPT, i eksplozivno bacanje medicinke strance – SAPT). Rezultati analiza su pokazali značajne umjerene korelacije između FAPT i maksimalnoga stražnjega čučnja (r=,652) i relativnoga stražnjega čučnja (r=,509). Nisu utvrđene značajne korelacije između ostalih testova. Rezultati pokazuju da, iako je terenske testove FAPT i SAPT vrlo lako provoditi, većina, ali ne i sve varijable koje procjenjuju sportsku uspješnost nisu u korelaciji sa snagom trupa procijenjenom navedenim testovima. Da bi se adekvatno procijenila snaga trupa i njena uloga u sportskoj izvedbi i uspješnosti, potrebno je vrednovati sportu svojstvene mišićne akcije i kretnje

Povezanost između snage trupa i pokazatelja sportske uspješnosti

Development of core muscle strength and power to improve sport performance has been a controversial issue yielding mixed results. The purpose of this study was to investigate the relationship between two core field tests emphasizing power and measures of sport performance. Participants were twenty healthy, recreationally active males (age 23.40±1.88 yrs, height 174.63±5.81 cm, mass 76.08±7.67 kg). Participants were tested on four performance variables (40-yd sprint, shuttle run [5-10-5], vertical jump, and 1RM back squat) and two core field tests (front abdominal power throw [FAPT] and side abdominal power throw [SAPT]). Results demonstrated significant moderate correlations between the FAPT and 1RM back squat (r=.652) and relative back squat (r=.509). No other significant correlations were found. Results indicate that although the FAPT and SAPT tests are easy to perform in the field, most, but not all, performance measures were unrelated to core power. In order to properly assess the core and its role in human performance, it is necessary to evaluate sport-specific muscle actions and movements.Razvijanje mišićne jakosti i snage trupa kako bi se unaprijedila sportska izvedba i uspješnost jest kontroverzan znanstveni i stručni problem istraživanje kojega daje miješane rezultate. Cilj je ovoga istraživanja bilo utvrđivanje povezanosti između dva terenska testa za procjenu snage trupa i pokazatelja sportske uspješnosti. Uzorak ispitanika činilo je 20 zdravih, rekreativno aktivnih muškaraca (dob 23,40±1,88 godina, tjelesna visina 174,63±5,81 cm, tjelesna masa 76,08±7,67 kg). Sportska uspješnost ispitanika procijenjena je četirima testovima (sprint na 40 jarda, shuttle run: 5-10-5 jarda, vertikalni skok i maksimalni stražnji čučanj), a snaga njihova trupa (core) procijenjena je dvama terenskim testovima (eksplozivno bacanje medicinke prema naprijed – FAPT, i eksplozivno bacanje medicinke strance – SAPT). Rezultati analiza su pokazali značajne umjerene korelacije između FAPT i maksimalnoga stražnjega čučnja (r=,652) i relativnoga stražnjega čučnja (r=,509). Nisu utvrđene značajne korelacije između ostalih testova. Rezultati pokazuju da, iako je terenske testove FAPT i SAPT vrlo lako provoditi, većina, ali ne i sve varijable koje procjenjuju sportsku uspješnost nisu u korelaciji sa snagom trupa procijenjenom navedenim testovima. Da bi se adekvatno procijenila snaga trupa i njena uloga u sportskoj izvedbi i uspješnosti, potrebno je vrednovati sportu svojstvene mišićne akcije i kretnje

Acute Effect of Mini-Trampoline Jumping on Vertical Jump and Balance Performance

Jumping and balance are necessary skills for most athletes, and mini-trampoline training has been shown to improve them. Little is known about the acute effect of mini-trampoline jumping on jump performance and dynamic balance. Objectives: The purpose of this study is to investigate the effect of 6 maximal jumps on a mini-trampoline on countermovement vertical jump (CMVJ) variables and on balance parameters. Methods: Twenty one recreationally trained individuals participated in three testing sessions and were either allocated to a control group (N=10) or a trampoline group (N=11). All the participants performed a dynamic warm up prior to their assessments. Baseline CMVJ and balance assessments were measured. For the jump performance tests, the control group rested for 30s, and the trampoline group performed 6 maximal CMVJs on a mini-trampoline. Immediately following the trampoline jumps or the rest period, participants performed three jump trials. The jumping protocol was repeated every minute up to 5 minutes and balance was reassessed immediately after only. Results: There was no significant interaction of time by group and no group effects in all the jumping parameters, however, there was a significant increase in jump height (p 0.05) on the balance variables. Conclusion: These results do not support our hypothesis and show that trampoline jumping does not improve jump and balance performance acutely

Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency Versus Isometric Torque Relationships

This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?sid=e7a03093-e666-4634-b895-d6b4313857c2%40sessionmgr13&vid=1&hid=17&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=15943883This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 ± 3.5 yrs) and 8 women (mean 21.0 ± 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R2 = 0.983), where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r2 = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric torque relationship in both the men (r2 = 0.813) and women (r2 = 0.578). The results demonstrated gender differences in the MMG amplitude vs. isometric torque relationship, but similar torque-related patterns for MMG mean power frequency. These findings suggested that the plateau in MMG amplitude at high levels of isometric torque production for the biceps brachii in the men, but not the women, may have been due to greater isometric torque, muscle stiffness, and/or intramuscular fluid pressure in the men, rather than to differences in moto