Relationship between training load and recovery in collegiate American football players during pre-season training.

Background: The purpose of this study was to examine the relationship between training load and next-day recovery in collegiate American football (AF) players during pre-season.Methods: Seventeen athletes (Linemen, n = 6; Non-linemen, n = 11) participated in the 14-day study wearing monitoring (accelerometer + heart rate) sensors during on-field practice sessions throughout pre-season to assess the physiological (PL), mechanical load (ML) and recording of session RPE (sRPE load) immediately post-practice. Prior to practice, participants completed a drop-jump reactive strength index (RSI) test and reported perceived recovery status (PRS). Loaded counter movement vertical jump was assessed before and after pre-season.Results: For every one unit increase in sRPE load, RSI declined by 0.03. Non-linemen had a lower RSI value of 73.1 units compared to linemen. For every one unit increase in ML, the PRS decreased by 0.01. Non-linemen recorded higher average ML during week 2 (ES = 1.17) compared to linemen. Non-linemen recorded higher RSI values in weeks 1 (ES = -1.41) and 2 (ES = -1.72) compared to linemen. All training load and recovery parameters were lower week 2 compared to week 1 (p < 0.05) for all players.Conclusions: Next-day RSI values were influenced by sRPE load while next-day PRS appears to be more influenced by ML. No difference in PL or sRPE load was observed been groups despite non-linemen completing a higher ML throughout the preseason. A combination of training load and recovery metrics may be needed to monitor the fatigue and state of readiness of each player.

Effects of One Versus Two Doses of a Multi-Ingredient Pre-Workout Supplement on Metabolic Factors and Perceived Exertion during Moderate-Intensity Running in Females.

The primary purpose of this study was to examine the acute effects of one versus two doses of a multi-ingredient pre-workout supplement on energy expenditure during moderate-intensity treadmill running. In addition, our second aim was to investigate the responses of associated metabolic factors (i.e., substrate utilization, measures of gas exchange), perceived exertion, and resting cardiovascular variables with one and two doses of the pre-workout supplement. Twelve females (mean ± SD: age = 25.3 ± 9.4 years; body mass = 61.2 ± 6.8 kg) completed three bouts of 30 min of treadmill running at 90% of their ventilatory threshold on separate days after consuming one dose of the pre-workout supplement (1-dose), two doses (2-dose), and a placebo. There were no differences among conditions for energy expenditure, fat or carbohydrate oxidation, respiratory exchange ratio, oxygen consumption, or heart rate across exercise time. The two-dose group, however, had lower (p = 0.036) ratings of perceived exertion (11.8 ± 1.7) than the one-dose (12.6 ± 1.7) and the placebo (12.3 ± 1.2) at the 20-min time point of exercise as well as greater resting systolic blood pressure (110 ± 10 mmHg) compared to the one-dose (106 ± 10 mmHg) and the placebo (104 ± 10 mmHg) conditions. Both the one-dose and two-dose conditions had greater increases in diastolic blood pressure compared to the placebo. Thus, our findings indicated that the present pre-workout supplement had no performance-enhancing benefits related to energy metabolism but did attenuate feelings of exertion.

A Methodological Report: Adapting the 505 Change-of-Direction Speed Test Specific to American Football.

Lockie, RG, Jalilvand, F, Orjalo, AJ, Giuliano, DV, Moreno, MR, and Wright, GA. A methodological report: Adapting the 505 change-of-direction speed test specific to American football. J Strength Cond Res 31(2): 539-547, 2017-The 505 involves a 10-m sprint past a timing gate, followed by a 180° change-of-direction (COD) performed over 5 m. This methodological report investigated an adapted 505 (A505) designed to be football-specific by changing the distances to 10 and 5 yd. Twenty-five high school football players (6 linemen [LM]; 8 quarterbacks, running backs, and linebackers [QB/RB/LB]; 11 receivers and defensive backs [R/DB]) completed the A505 and 40-yd sprint. The difference between A505 and 0 to 10-yd time determined the COD deficit for each leg. In a follow-up session, 10 subjects completed the A505 again and 10 subjects completed the 505. Reliability was analyzed by t-tests to determine between-session differences, typical error (TE), and coefficient of variation. Test usefulness was examined via TE and smallest worthwhile change (SWC) differences. Pearson's correlations calculated relationships between the A505 and 505, and A505 and COD deficit with the 40-yd sprint. A 1-way analysis of variance (p ≤ 0.05) derived between-position differences in the A505 and COD deficit. There were no between-session differences for the A505 (p = 0.45-0.76; intraclass correlation coefficient = 0.84-0.95; TE = 2.03-4.13%). Additionally, the A505 was capable of detecting moderate performance changes (SWC0.5 > TE). The A505 correlated with the 505 and 40-yard sprint (r = 0.58-0.92), suggesting the modified version assessed similar qualities. Receivers and defensive backs were faster than LM in the A505 for both legs, and right-leg COD deficit. Quarterbacks, running backs, and linebackers were faster than LM in the right-leg A505. The A505 is reliable, can detect moderate performance changes, and can discriminate between football position groups.

The acute effects of multi-ingredient pre-workout ingestion on strength performance, lower body power, and anaerobic capacity.

BACKGROUND: Multi-ingredient pre-workout supplements (MIPS) are popular among resistance trained individuals. Previous research has indicated that acute MIPS ingestion may increase muscular endurance when using a hypertrophy-based protocol but less is known in regard to their effects on strength performance and high intensity running capacity. Therefore, the purpose was to determine if short-term, MIPS ingestion influences strength performance and anaerobic running capacity. METHODS: In a double-blind, randomized, placebo controlled, crossover design; 12 males (19 ± 1 yrs.; 180 ± 12 cm; 89.3 ± 11 kg; 13.6 ± 4.9 %BF) had their body composition assessed followed by 5-repetition maximum (5RM) determination of back squat (BS; 119.3 ± 17.7 kg) and bench press (BP; 92.1 ± 17.8 kg) exercises. On two separate occasions subjects ingested a MIPS or a placebo (P) 30-minutes prior to performing a counter movement vertical jump test, 5 sets of 5 repetitions at 85 % of 5RM of BS and BP, followed by a single set to failure, and an anaerobic capacity sprint test to assess peak and mean power. Subjective markers of energy levels and fatigue were also assessed. Subjects returned one week later for a second testing session using counter treatment. RESULTS: MIPS resulted in a greater number of repetitions performed in the final set to failure in the BP (MIPS, 9.8 ± 1.7 repetitions; P, 9.1 ± 2; p = 0.03, d = 0.38), which led to a greater total volume load (set x repetitions x load) in the MIPS (753 ± 211 kg) compared to P (710 ± 226 kg; p =0.03, d = .20). MIPS ingestion improved subjective markers of fatigue (p = 0.01, d = 3.78) and alertness (p = 0.048, d = 2.72) following a bout of resistance training. An increase in mean power was observed in the MIPS condition (p = 0.03, d = 0.25) during the anaerobic sprint test. CONCLUSION: Results suggest that acute ingestion of a MIPS study may increase upper body muscular endurance. In addition, acute MIPS ingestion improved mean power output during an anaerobic capacity sprint test. However, the practical significance of these performance related outcomes may be minimal due to the small effect sizes observed. MIPS ingestion does appear to positively influence subjective markers of fatigue and alertness during high-intensity exercise.

Jump Shrug Height and Landing Forces Across Various Loads.

The purpose of this study was to examine the effect that load has on the mechanics of the jump shrug. Fifteen track and field and club/intramural athletes (age 21.7 ± 1.3 y, height 180.9 ± 6.6 cm, body mass 84.7 ± 13.2 kg, 1-repetition-maximum (1RM) hang power clean 109.1 ± 17.2 kg) performed repetitions of the jump shrug at 30%, 45%, 65%, and 80% of their 1RM hang power clean. Jump height, peak landing force, and potential energy of the system at jump-shrug apex were compared between loads using a series of 1-way repeated-measures ANOVAs. Statistical differences in jump height (P < .001), peak landing force (P = .012), and potential energy of the system (P < .001) existed; however, there were no statistically significant pairwise comparisons in peak landing force between loads (P > .05). The greatest magnitudes of jump height, peak landing force, and potential energy of the system at the apex of the jump shrug occurred at 30% 1RM hang power clean and decreased as the external load increased from 45% to 80% 1RM hang power clean. Relationships between peak landing force and potential energy of the system at jump-shrug apex indicate that the landing forces produced during the jump shrug may be due to the landing strategy used by the athletes, especially at lighter loads. Practitioners may prescribe heavier loads during the jump-shrug exercise without viewing landing force as a potential limitation.

Acute effects of an arginine-based supplement on neuromuscular, ventilatory, and metabolic fatigue thresholds during cycle ergometry.

The purpose of the present study was to examine the effects of an acute dose of an arginine-based supplement on the physical working capacity at the fatigue threshold (PWCFT), lactate threshold (LT), ventilatory threshold (VT), and peak oxygen uptake during incremental cycle ergometry. This study used a double-blinded, placebo-controlled, within-subjects crossover design. Nineteen untrained men (mean age ± SD = 22.0 ± 1.7 years) were randomly assigned to ingest either the supplement (3.0 g of arginine, 300 mg of grape seed extract, and 300 mg of polyethylene glycol) or placebo (microcrystalline cellulose) and performed an incremental test on a cycle ergometer for determination of PWCFT, LT, VT, and peak oxygen uptake. Following a 1-week period, the subjects returned to the laboratory and ingested the opposite substance (either supplement or placebo) prior to completing another incremental test to be reassessed for PWCFT, LT, VT, and peak oxygen uptake. The paired-samples t tests indicated there were significant (P < 0.05) mean differences between the arginine and placebo conditions for the PWCFT (192 ± 42 vs. 168 ± 53 W, respectively) and VT (2546 ± 313 vs. 2452 ± 342 mL·min(-1)), but not the LT (135 ± 26 vs. 138 ± 22 W), absolute peak oxygen uptake (3663 ± 445 vs. 3645 ± 438 mL·min(-1)), or relative peak oxygen uptake (46.5 ± 6.0 vs. 46.2 ± 5.0 mL·kg(-1)·min(-1)). These findings suggested that the arginine-based supplement may be used on an acute basis for delaying the onset of neuromuscular fatigue (i.e., PWCFT) and improving the VT in untrained individuals.

Development of an Anaerobic Sprint Running Test Using a Nonmotorized Treadmill.

The purpose of this study was to determine the test-retest reliability of a newly developed anaerobic sprint running test (ASRT) on a nonmotorized treadmill (NMT). Twenty-six collegiate male athletes (21.2 ± 2.1 years; 181.3 ± 6.5 cm; 79.0 ± 9.3 kg) completed 3 trials of a 25-second maximal effort sprint on an NMT against a workload set to 18% of their individual body mass. Anaerobic power was determined by relative peak power output (PP) and anaerobic capacity was determined by relative mean power output (MP) during the test. Blood lactate (BLa) responses and fatigue index (FI) were also determined. Test-retest reliability was assessed by intraclass correlation coefficients (ICCs) and coefficients of variation (CV%). Results indicated no significant difference between the 3 trials for PP (T1 = 29.95 ± 6.51 W·kg(-1), T2 = 28.57 ± 5.55 W·kg(-1), T3 = 29.47 ± 5.94 W·kg(-1)), MP (T1 = 20.97 ± 3.64 W·kg(-1), T2 = 20.50 ± 3.46 W·kg(-1), T3 = 21.17 ± 3.79 W·kg(-1), and FI (T1 = 55 ± 8%, T2 = 51 ± 8%, T3 = 52 ± 9%). Reliability between the 3 trials for PP (ICC: r = 0.96, CV: 7%) and MP (ICC: r = 0.97, CV: 6%) was considered high. Reliability for FI exhibited an ICC of r = 0.83 (CV: 6%). Postsprint BLa values were not significantly different (p = 0.49) between the 3 trials. Test-retest reliability for postsprint BLa was found to be good (r = 0.68, CV = 8.8%). The results of the study indicate that the ASRT is reliable for assessing PP and MP in highly motivated subjects. In addition, anaerobic testing using the ASRT may be a more sport-specific test to assess anaerobic performance for many coaches and athletes.

Development and assessment of reliability for a sandbag throw conditioning test for wrestlers.

The purpose of this study was to develop and analyze a sport-specific conditioning test for wrestling that will incorporate the physiological demands of a match. Sixteen D-III collegiate wrestlers performed 2 tests to assess physical conditioning. The developed test (sandbag test) used a bag filled with sand that was repeatedly thrown over a course of seven 1-minute rounds. Average time per throw (T/T) was determined each round. The sandbag test was compared with a previously established repeated sprint protocol of maximal effort arm cranking on an upper body ergometer (UBE). Mean power output was determined for each sprint. Both the UBE test and the sandbag test were compared using performance decrement (%fatigue), blood lactate (BLa), and peak heart rate (HRpeak) values. Test-retest reliability for the sandbag test was found to be almost perfect using T/T (intraclass correlation coefficient, r = 0.96). No significant differences in %fatigue were found between the UBE test and the sandbag test (p = 0.600), BLa (p = 0.283), and HRpeak (p = 0.214). Further analysis by weight class (light-weight class [LWC] and heavy-weight class [HWC]) found a significant interaction for %fatigue between groups for the sandbag test and UBE (p = 0.001), but no interactions were observed for BLa (p = 0.198) or HRpeak (p = 0.990). Although no significant differences were found in %fatigue between the 2 tests when the data were grouped together, a clear difference was found between the LWC and HWC groups only in the sandbag test, indicating that this test may be more sensitive than the UBE. Coaches can assess their wrestlers with this reliable, inexpensive, and time-efficient sandbag test.

Effect of various loads on the force-time characteristics of the hang high pull.

The purpose of this study was to investigate the effect of various loads on the force-time characteristics associated with peak power during the hang high pull (HHP). Fourteen athletic men (age: 21.6 ± 1.3 years; height: 179.3 ± 5.6 cm; body mass: 81.5 ± 8.7 kg; 1 repetition maximum [1RM] hang power clean [HPC]: 104.9 ± 15.1 kg) performed sets of the HHP at 30, 45, 65, and 80% of their 1RM HPC. Peak force, peak velocity, peak power, force at peak power, and velocity at peak power were compared between loads. Statistical differences in peak force (p = 0.001), peak velocity (p < 0.001), peak power (p = 0.015), force at peak power (p < 0.001), and velocity at peak power (p < 0.001) existed, with the greatest values for each variable occurring at 80, 30, 45, 80, and 30% 1RM HPC, respectively. Effect sizes between loads indicated that larger differences in velocity at peak power existed as compared with those displayed by force at peak power. It seems that differences in velocity may contribute to a greater extent to differences in peak power production as compared with force during the HHP. Further investigation of both force and velocity at peak power during weightlifting variations is necessary to provide insight on the contributing factors of power production. Specific load ranges should be prescribed to optimally train the variables associated with power development during the HHP.

The impact of load on lower body performance variables during the hang power clean.

This study examined the impact of load on lower body performance variables during the hang power clean. Fourteen men performed the hang power clean at loads of 30%, 45%, 65%, and 80% 1RM. Peak force, velocity, power, force at peak power, velocity at peak power, and rate of force development were compared at each load. The greatest peak force occurred at 80% 1RM. Peak force at 30% 1RM was statistically lower than peak force at 45% (p = 0.022), 65% (p = 0.010), and 80% 1RM (p = 0.018). Force at peak power at 65% and 80% 1RM was statistically greater than force at peak power at 30% (p < 0.01) and 45% 1RM (p < 0.01). The greatest rate of force development occurred at 30% 1RM, but was not statistically different from the rate of force development at 45%, 65%, and 80% 1RM. The rate of force development at 65% 1RM was statistically greater than the rate of force development at 80% 1RM (p = 0.035). No other statistical differences existed in any variable existed. Changes in load affected the peak force, force at peak power, and rate of force development, but not the peak velocity, power, or velocity at peak power.

Kinetic comparison of the power development between power clean variations.

The purpose of this study was to compare the power production of the hang clean (HC), jump shrug (JS), and high pull (HP) when performed at different relative loads. Seventeen men with previous HC training experience, performed 3 repetitions each of the HC, JS, and HP at relative loads of 30, 45, 65, and 80% of their 1 repetition maximum (1RM) HC on a force platform over 3 different testing sessions. Peak power output (PPO), peak force (PF), and peak velocity (PV) of the lifter plus bar system during each repetition were compared. The JS produced a greater PPO, PF, and PV than both the HC (p < 0.001) and HP (p < 0.001). The HP also produced a greater PPO (p < 0.01) and PV (p < 0.001) than the HC. Peak power output, PF, and PV occurred at 45, 65, and 30% 1RM, respectively. Peak power output at 45% 1RM was greater than PPO at 65% (p = 0.043) and 80% 1RM (p = 0.004). Peak force at 30% was less than PF at 45% (p = 0.006), 65% (p < 0.001), and 80% 1RM (p = 0.003). Peak velocity at 30 and 45% was greater than PV at 65% (p < 0.001) and 80% 1RM (p < 0.001). Peak velocity at 65% 1RM was also greater than PV at 80% 1RM (p < 0.001). When designing resistance training programs, practitioners should consider implementing the JS and HP. To optimize PPO, loads of approximately 30 and 45% 1RM HC are recommended for the JS and HP, respectively.

Blood ammonium and lactate accumulation response to different training protocols using the parallel squat exercise.

Three parallel squat protocols with equal total work volume were used to determine the metabolic response of resistance exercise with different practical training protocols combining program variables in the way that they are typically prescribed in field. Sixteen men able to back squat 1.5 times their body weight participated in the study. Individualized muscular endurance (ME), strength (STR), and hypertrophy (HYP) squat workouts were developed based on a 1 repetition maximum back squat. Each protocol was performed 3-7 days apart in random order. Venous blood was obtained after 5 minutes of seated rest both before and after each workout for ammonium and lactate analysis. The ME protocol (79.8 µM [SD = 45.4], 95% confidence interval [CI]: 55.7-104.0) produced a greater change of plasma ammonium than both the HYP (45.3 µM [SD = 34.5], 95% CI: 26.9-63.6, p = 0.017) and STR (31.7 µM [SD = 52.3], 95% CI: 3.9-59.6, p = 0.006) protocols. Change of blood lactate concentration from resting levels to postexercise levels was significantly different (p = 0.005) between ME (6.1 mM [SD = 2.9], 95% CI: 4.6-7.7) and STR (3.9 mM [SD = 2.5], 95% CI: 2.6-5.2) protocols. The main finding of this study is that blood ammonium and lactate seem to accumulate in response to an increasing number of repetitions with decreasing rest time between sets. As consequence, a greater number of repetitions should be added to a resistance workout, along with a shorter rest time between sets when training for events that induce a large metabolic load. The metabolic accumulation associated with high repetition exercise may represent the need for longer recovery time between these types of workouts compared with workouts using a low number of repetitions.

Effects of beta-alanine supplementation on sprint endurance.

Recent research has shown that beta-alanine (BA) supplementation can increase intramuscular carnosine levels. Carnosine is an intramuscular buffer, and it has been linked to improvements in performance, specifically during bouts of high-intensity exercise that are likely limited by muscle acidosis. Therefore, the purpose of this study was to examine the effect of BA supplementation on sprint endurance at 2 different supramaximal intensities. Twenty-one anaerobically trained (rugby players [n = 4], wrestlers [n = 11], and recreationally strength trained athletes [n = 6]) college-aged men participated in a double-blind, placebo controlled study. The subjects performed an incremental VO2max test and 2 sprint to exhaustion tests set at 115 and 140% of their VO2max on a motorized treadmill before (PRE) and after (POST) a 5-week supplementation period. During this time, the subjects ingested either a BA supplement or placebo (PLA) with meals. The subjects ingested 4 g·d(-1) of BA or PLA during the first week and 6 g·d(-1) the following 4 weeks. Capillary blood samples were taken before and after each sprint to determine blood lactate response to the sprint exercise. No significant group (BA, PLA) × intensity (115%, 140%; p = 0.60), group by time (PRE, POST; p = 0.72), or group × intensity × time (p = 0.74) interactions were observed for time to exhaustion. In addition, similar nonsignificant observations were made for lactate response to the sprints (group × intensity, p = 0.43; group × time, p = 0.33, group × intensity × time, p = 0.56). From the results of this study, it was concluded that beta-alanine supplementation did not have a significant effect on sprint endurance at supramaximal intensities.

Rapidity of response to hypoxic conditions during exercise.

UNLABELLED: Previous studies have found decreases in arterial oxygen saturation to be temporally linked to reductions in power output (PO) during time-trial (TT) exercise. The purpose of this study was to determine whether preexercise desaturation (estimated from pulse oximetry [SpO2]), via normobaric hypoxia, would change the pattern of PO during a TT. PURPOSE: The authors tested the hypothesis that the starting PO of a TT would be reduced in the EARLY trial secondary to a reduced SpO2 but would not be reduced in LATE until ~30 s after the start of the TT. METHODS: Eight trained cyclists/triathletes (4 male, 4 female) performed 3 randomly ordered 3-km TTs while breathing either room air (CONTROL) or hypoxic air administered 3 min before the start of the TT (EARLY) or at the beginning of the TT (LATE). RESULTS: There was no effect of hypoxia on PO during the first 0.3 km of either the EARLY or the LATE trial compared with CONTROL, although there was a significant decrease in pre-TT SpO2 in EARLY vs CONTROL and LATE. The time for PO to decrease was ~40 s after the start of the TT in both EARLY and LATE. CONCLUSIONS: The results support the strong effect of the preexercise template on the pattern of PO during simulated competition and suggest that reductions in SpO2 are not direct signals to decrease PO.

Strength training for athletes: does it really help sports performance?

The use of strength training designed to increase underlying strength and power qualities in elite athletes in an attempt to improve athletic performance is commonplace. Although the extent to which strength and power are important to sports performance may vary depending on the activity, the associations between these qualities and performance have been well documented in the literature. The purpose of this review is to provide a brief overview of strength training research to determine if it really helps improve athletic performance. While there is a need for more research with elite athletes to investigate the relationship between strength training and athletic performance, there is sufficient evidence for strength training programs to continue to be an integral part of athletic preparation in team sports.

Predicting lower body power from vertical jump prediction equations for loaded jump squats at different intensities in men and women.

The purpose of this study was to determine the efficacy of estimating peak lower body power from a maximal jump squat using 3 different vertical jump prediction equations. Sixty physically active college students (30 men, 30 women) performed jump squats with a weighted bar's applied load of 20, 40, and 60% of body mass across the shoulders. Each jump squat was simultaneously monitored using a force plate and a contact mat. Peak power (PP) was calculated using vertical ground reaction force from the force plate data. Commonly used equations requiring body mass and vertical jump height to estimate PP were applied such that the system mass (mass of body + applied load) was substituted for body mass. Jump height was determined from flight time as measured with a contact mat during a maximal jump squat. Estimations of PP (PP(est)) for each load and for each prediction equation were compared with criterion PP values from a force plate (PP(FP)). The PP(est) values had high test-retest reliability and were strongly correlated to PP(FP) in both men and women at all relative loads. However, only the Harman equation accurately predicted PP(FP) at all relative loads. It can therefore be concluded that the Harman equation may be used to estimate PP of a loaded jump squat knowing the system mass and peak jump height when more precise (and expensive) measurement equipment is unavailable. Further, high reliability and correlation with criterion values suggest that serial assessment of power production across training periods could be used for relative assessment of change by either of the prediction equations used in this study.

Hip-abductor fatigue and single-leg landing mechanics in women athletes.

CONTEXT: Reduced hip-abductor strength and muscle activation may be associated with altered lower extremity mechanics, which are thought to increase the risk for anterior cruciate ligament injury. However, experimental evidence supporting this relationship is limited. OBJECTIVE: To examine the changes in single-leg landing mechanics and gluteus medius recruitment that occur after a hip-abductor fatigue protocol. DESIGN: Descriptive laboratory study. PATIENTS OR OTHER PARTICIPANTS: Twenty physically active women (age  =  21.0 ± 1.3 years). INTERVENTION(S): Participants were tested before (prefatigue) and after (postfatigue) a hip-abductor fatigue protocol consisting of repetitive side-lying hip abduction. MAIN OUTCOME MEASURE(S): Outcome measures included sagittal-plane and frontal-plane hip and knee kinematics at initial contact and at 60 milliseconds after initial contact during 5 single-leg landings from a height of 40 cm. Peak hip and knee sagittal-plane and frontal-plane joint moments during this time interval were also analyzed. Measures of gluteus medius activation, including latency, peak amplitude, and integrated signal, were recorded. RESULTS: A small (<1°) increase in hip-abduction angle at initial contact and a small (<1°) decrease in knee-abduction (valgus) angle at 60 milliseconds after contact were observed in the postfatigue landing condition. No other kinematic changes were noted for the knee or hip at initial contact or at 60 milliseconds after initial contact. Peak external knee-adduction moment decreased 27% and peak hip adduction moment decreased 24% during the postfatigue landing condition. Gluteus medius activation was delayed after the protocol, but no difference in peak or integrated signal was seen during the landing trials. CONCLUSIONS: Changes observed during single-leg landings after hip-abductor fatigue were not generally considered unfavorable to the integrity of the anterior cruciate ligament. Further work may be justified to study the role of hip-abductor activation in protecting the knee during landing.

Kinematic and kinetic variations among three depth jump conditions in male NCAA division III athletes.

Our purpose was to provide an in-depth investigation of 2 commonly used depth jump variants: depth jumping over a hurdle and depth jumping while touching as high as possible using an overhead goal. Fourteen male athletes performed a series of depth jumps from a 45-cm box. Three types of jumping conditions were used. One type of depth jump was a control jump (DJ45-C), performed for maximal height with no external apparatus used to influence the jump. Another type of depth jump was performed over a hurdle (DJ45-H), which was set at an individualized height for each athlete based on their leaping ability. The final type of depth jump was performed for maximal touch height on a Vertec measuring device (DJ45-T). Timing, kinematics, and kinetics of the 3 jumping conditions were compared. The hurdle depth jumping condition demonstrated lower ground contact times and significantly less (p < 0.05) flexion in the hips (41.22 ± 8.10 degrees) and knees (67.47 ± 8.36 degrees) when compared to control (49.26 ± 10.90 degrees of hip flexion and 73.85 ± 10.68 degrees of knee flexion) and target (50.51 ± 9.51 degrees of hip flexion and 75.01 ± 9.97 degrees of knee flexion) conditions. Jumping conditions that used goals (DJ45-H, DJ45-T) produced significantly higher (p < 0.05) vertical velocity of the sacrum at toe-off (3.57 ± .34 m/s and 3.46 ± .36 m/s, respectively) than the control condition (3.32 ± .34 m/s). The hurdle depth jump condition had higher ground reaction forces (875.36 ± 135.66 N) and higher dorsiflexion (566.02 ± 402.45 W) and plantar flexion power (768.84 ± 192.19 W) at the ankle than the Vertec (409.83 ± 387.23 W for dorsiflexion and 622.54 ± 188.95 W for plantar flexion) and control conditions (425.60 ± 380.01 W for dorsiflexion and 643.35 ± 166.70 W for plantar flexion). Few differences were found to exist between the Vertec and control conditions. Hurdle jumping in particular may be superior for the development of short ground contact time (<0.3 s) sport movements requiring brief but powerful lower-extremity power production.

Effects of acute static stretching of the throwing shoulder on pitching performance of national collegiate athletic association division III baseball players.

Stretching is a common component of an athletic warm-up even though many studies have demonstrated that pre-event static stretching can decrease strength and power performance. The purpose of this study was to examine the effects of acute static stretching of the throwing shoulder on pitching velocity and accuracy of National Collegiate Athletic Association Division III baseball players. Twelve collegiate baseball players, including 6 pitchers and 6 position players, participated in the study. Each participant completed 2 separate testing protocols over a span of 4-6 days. In the experimental condition (SS), 6 static stretches were applied to the throwing shoulder after an active warm-up. After a rest period of 5-10 minutes, participants were allowed 5 warm-up pitches from a pitching mound. Participants then threw 10 pitches measured for velocity and accuracy. The control condition (NS) followed the same procedure but did not include the 6 static stretches. Testing was conducted in an indoor practice facility during normal team practice. No significant differences were found in average velocity, maximum velocity, or accuracy measures when comparing the SS and NS conditions. These results suggest that acute static stretching of the throwing shoulder does not have a significant impact on baseball pitching performance. Static stretching of the shoulder may be performed during a warm-up before a throwing activity.