Moderate volume of sprint bouts does not induce muscle damage in well-trained athletes

The effects of training based on Nordic hamstring and sprint exercises on measures of physical fitness and hamstring injury prevention in U19 male soccer players

This study analysed the effects of a training program based on Nordic hamstring and sprint exercises on physical performance and hamstring injuries in young male soccer players. Forty-nine U19 players were randomly assigned to a control (CG; n = 26) or experimental group (EG; n = 23). Linear sprint and with change of direction (COD) were assessed before and after a 14-week training period. Hamstring injuries were collected during the intervention period. Between-groups analysis revealed differences in linear sprint performance (p = 0.012-0.001) in favour of the EG. Pre-to-post performance increased significantly in the EG for 20 m (effect size [ES] = -0.56) and 30 m (ES = -0.62) sprints, but a significant reduction in some COD parameters was observed (ES = 0.45-0.57). In CG, only a significant reduction in COD with dominant leg was found (ES = 0.63). Significant differences in injury burden in favour of the EG was reported such as (27.87 [CG] vs. 3.82 [EG] absence days/1000 h of exposure, rate ratio = 7.30, 95% CI 3.34-15.99). While injury incidence was not different between the EG and CG. These findings suggest that the training program implemented can improve sprint performance and reduce injury burden.

The Addition of Sprint Interval Training to Field Lacrosse Training Increases Rate of Torque Development and Contractile Impulse in Female High School Field Lacrosse Players

Field lacrosse requires sudden directional changes and rapid acceleration/deceleration. The capacity to perform these skills is dependent on explosive muscle force production. Limited research exists on the potential of sprint interval training (SIT) to impact explosive muscle force production in field lacrosse players. The purpose of this study is to examine SIT, concurrent to field-lacrosse-specific training, on the rate of torque development (RTD), contractile impulse, and muscle function in female high school field lacrosse players (n = 12; 16 ± 1 yrs.). SIT was performed three times per week, concurrent to field-lacrosse-specific training, for 12 weeks. Right lower-limb muscle performance was assessed pre-, mid-, and post-SIT training via isometric and isokinetic concentric knee extensor contractions. Outcomes included RTD (Nm·s^-1), contractile impulse (Nm·s), and peak torque (Nm). RTD for the first 50 ms of contraction improved by 42% by midseason and remained elevated at postseason (p = 0.004, effect size (ES) = -577.3 to 66.5). Contractile impulse demonstrated a training effect across 0-50 ms (42%, p = 0.004, ES = -1.4 to 0.4), 0-100 ms (33%, p = 0.018, ES = 3.1 to 0.9), and 0-200 ms (22%, p = 0.031, ES = -7.8 to 1.6). Isometric (0 rad·s^-1) and concentric (3.1 rad·s^-1) strength increased by 20% (p = 0.002, ES = -60.8 to -20.8) and 9% (p = 0.038, ES = -18.2 to 0.0) from SIT and field-lacrosse-specific training, respectively (p < 0.05). SIT, concurrent to field-lacrosse-specific training, enhanced lower-limb skeletal muscle performance, which may enable greater sport-specific gains.

Microdosing Sprint Distribution as an Alternative to Achieve Better Sprint Performance in Field Hockey Players

Introduction: The implementation of optimal sprint training volume is a relevant component of team sport performance. This study aimed to compare the efficiency and effectiveness of two different configurations of within-season training load distribution on sprint performance over 6 weeks. Methods: Twenty male professional FH players participated in the study. Players were conveniently assigned to two groups: the experimental group (MG; n = 11; applying the microdosing training methodology) and the control group (TG; n = 9; traditional training, with players being selected by the national team). Sprint performance was evaluated through 20 m sprint time (T20) m and horizontal force−velocity profile (HFVP) tests before (Pre) and after (Post) intervention. Both measurements were separated by a period of 6 weeks. The specific sprint training program was performed for each group (for vs. two weekly sessions for MG and TG, respectively) attempting to influence the full spectrum of the F-V relationship. Results: Conditional demands analysis (matches and training sessions) showed no significant differences between the groups during the intervention period (p > 0.05). No significant between-group differences were found at Pre or Post for any sprint-related performance (p > 0.05). Nevertheless, intra-group analysis revealed significant differences in F0, Pmax, RFmean at 10 m and every achieved time for distances ranging from 5 to 25 m for MG (p < 0.05). Such changes in mechanical capabilities and sprint performance were characterized by an increase in stride length and a decrease in stride frequency during the maximal velocity phase (p < 0.05). Conclusion: Implementing strategies such as microdosed training load distribution appears to be an effective and efficient alternative for sprint training in team sports such as hockey.

Branched-Chain Amino Acids Supplementation Does Not Accelerate Recovery after a Change of Direction Sprinting Exercise Protocol

BCAAs supplementation has been widely used for post-exercise recovery. However, no evidence is currently available to answer the question of whether BCAAs supplementation can attenuate muscle damage and ameliorate recovery after a bout of change of direction (COD) sprinting, which is an exercise motion frequently used during team sport actions. This study aimed to assess the effect of BCAAs supplementation on muscle damage markers, subjective muscle soreness, neuromuscular performance, and the vascular health of collegiate basketball players during a 72 h recovery period after a standardized COD protocol. Participants orally received either BCAAs (0.17 g/kg BCAAs + 0.17 g/kg glucose) or placebo (0.34 g/kg glucose) supplementation before and immediately after a COD exercise protocol in a randomized, crossover, double-blind, and placebo-controlled manner. Creatine kinase increased immediately after exercise and peaked at 24 h, muscle soreness remained elevated until 72 h, whilst arterial stiffness decreased after exercise for both supplemented conditions. A negligibly lower level of interleukin-6 was found in the BCAAs supplemented condition. In conclusion, the results of this study do not support the benefits of BCAAs supplementation on mitigating muscle damage and soreness, neuromuscular performance, and arterial stiffness after COD for basketball players.

Prabhakar A, Eapen C, Keogh JW. Ability of functional performance assessments to discriminate athletes with and without chronic ankle instability : a case-control study

Background

The decline in motor function associated with chronic ankle instability (CAI) can be assessed using Functional Performance tests. Ankle muscular strength, endurance and range of motion (ROM) has been assessed in previous studies but functional activities such as sprinting and change of direction are less well studied in athletes with CAI. Hence the aim of this study was to determine how sprint, change of direction, ankle isometric strength, endurance and ROM measures may be associated with discriminate athletes with and without CAI.

Methods

One hundred and six participants (CAI: n = 53 or no CAI: n = 53) provided informed consent to participate in this study. Participants performed three functional performance tests, (30-m sprint test, Modified Illinois change of direction test (MICODT)) and change of direction test. Range of motion for dorsiflexion was measured using weight bearing lunge test and inversion, eversion and plantarflexion using Saunders® digital inclinometer. Strength was assessed using Baseline® hand-held dynamometer for plantarflexors, dorsiflexors, invertors and evertors. Muscular endurance was assessed by single heel raise test and Modified single heel raise test. Between-group comparisons utilised Student's t-test and Mann-Whitney U-tests, with a number of unique variable and multivariable binomial logistic regression performed to determine which performance measures may discriminate participants with CAI.

Results

The CAI participants performed significantly worse in the three functional performance tests as well as multiple measures of ankle ROM, isometric strength and muscular endurance (p < 0.008). While several measures of ROM (plantarflexion and dorsiflexion), strength (inversion and eversion) and both muscular endurance tests were significantly associated with CAI in the univariable analysis, the strongest association was the functional performance tests, especially MICDOT time (odds ratio (95% CI): 0.06 [0.02-0.17], sensitivity 94.3%, specificity 88.7%). Multivariable regression analyses indicated that performance across the functional performance tests were more strongly associated with CAI than any ankle ROM, muscular strength or endurance test. Further, the inclusion of the best ankle range of motion, strength or muscular endurance tests did not significantly improve upon the association of the MICDOT with CAI.

Conclusions

Chronic ankle instability in athletic populations appears to be highly associated with declines in functional performance and to a somewhat lesser extent, ankle range of motion, strength and muscle endurance measures. This may suggest that optimal rehabilitation for athletes with CAI may require a greater focus on improving sprinting speed and change of direction ability in the mid to latter stages of rehabilitation, with regular assessments of these functional performance tests necessary to guide the progression and overload of this training.

Functional and Anthropometrical Screening Test among High Performance Female Football Players: A Descriptive Study with Injury Incidence Analysis, the Basque Female Football Cohort (BFFC) Study

The main objectives of the present study were to describe the injury incidence and to analyze the anthropometric and physical characteristics of players from three high-level women's football teams. The present study involved 54 female football players (21.9 ± 4.9 years old) from three different teams competing in the Spanish Reto Iberdrola-Segunda División PRO league. A battery of tests was carried out to determine the anthropometric and physical performance characteristics of the players along with an injury incidence record during a full competitive season. The obtained results showed that there was a high incidence of injury, as 38% of the players suffered some type of injury during the season (range 1-5; 1.75 ± 1.02 injuries per player). Injuries occurred in both matches and during training at a similar percentage (48.6 vs. 51.4%), and the majority of the registered episodes were graded as moderate or severe injury types (60%). Players suffering from an injury accumulated a total of 1587 chronological days off work due to injury during the season, with a recurrence rate of 55%. Considering the high incidence of injury, and the injury burden and the reinjure rate observed in this research, it seems necessary to apply the most efficient prevention and recovery measures possible in these female football teams. These descriptive data could serve athletic trainers and medical staff of female football teams to better understand their own screening procedure-derived data.

Effects of the 5-m Shuttle Run Test on Markers of Muscle Damage, Inflammation, and Fatigue in Healthy Male Athletes

Physical exercise is often associated with increases in muscle damage markers and inflammation. However, biomarkers of muscle damage and inflammation responses to the 5-m shuttle run test (5mSRT) have not yet been evaluated. The aim of the present study was to investigate effects of the 5mSRT on muscle damage markers, inflammation, and perception of fatigue and recovery in healthy male athletes. Fifteen male amateur team sports players (age: 20 ± 3 yrs, height: 173 ± 7 cm, body-mass: 67 ± 7 kg) participated in this study. Blood biomarkers were collected at rest, 5 min after, and 72 h after the 5mSRT to measure muscle damage (i.e., creatinine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), and alanine aminotransferase (ALAT)) and inflammation (i.e., C-reactive protein (CRP)). Best distance (BD), total distance (TD), fatigue index (FI), and percentage decrement (PD) during the 5mSRT were assessed. Perceived recovery (PRS) and delayed onset muscle soreness (DOMS) were recorded before, 5 min after, and 72 h after the 5mSRT; perceived exertion (RPE) was recorded before, during, and 72 h after the 5mSRT. Muscle damage biomarkers post 5mSRT showed a significant increase compared to pre 5mSRT (p < 0.001) levels ((i.e., CK (190.6 ± 109.1 IU/L vs. 234.6 ± 113.7 IU/L), LDH (163.6 ± 35.1 IU/L vs. 209.9 ± 50.8 IU/L), ASAT (18.0 ± 4.4 IU/L vs. 21.7 ± 6.2 IU/L), and ALAT (10.2 ± 3.4 IU/L vs. 12.7 ± 3.8 IU/L)) and 72 h post 5mSRT (p < 0.001) levels ((CK (125.3 ± 80.5 IU/L vs. 234.6 ± 113.7 IU/L), LDH (143.9 ± 36.6 IU/L vs. 209.9 ± 50.8 IU/L), ASAT (15.0 ± 4.7 IU/L vs. 21.7 ± 6.2 IU/L), and ALAT (8.6 ± 2.4 IU/L vs. 12.7 ± 3.8 IU/L)). CRP was also significantly higher post 5mSRT compared to pre 5mSRT (2.1 ± 2.5 mg/L vs. 2.8 ± 3.3 mg/L, p < 0.001) and 72 h post 5mSRT (1.4 ± 2.3 mg/L vs. 2.8 ± 3.3 mg/L, p < 0.001). Significant correlations were reported between (i) physical performance parameters (i.e., PD, FI, TD, and BD), and (ii) markers of muscle damage (i.e., CK, LDH, ASAT, and ALAT) and inflammation (i.e., CRP). Similarly, DOMS and RPE scores were significantly higher post 5mSRT compared to pre 5mSRT (2.4 ± 1.0UA vs. 6.7 ± 1.1UA and 2.1 ± 0.6 UA vs. 8.1 ± 0.6 UA, respectively p < 0.001) and 72 h post 5mSRT (1.9 ± 0.7 UA vs. 6.7 ± 1.1 UA and 1.5 ± 0.6 UA vs. 8.1 ± 0.6 UA, respectively p < 0.001). PRS scores were significantly lower post 5mSRT as compared to pre 5mSRT (6 ± 1 UA vs. 3 ± 1 UA, p < 0.001) and 72 h post 5mSRT (7 ± 1 UA vs. 3 ± 1 UA, p < 0.001). Significant correlations existed between (i) performance parameters (PD, FI, TD, and BD) and (ii) RPE, PRS, and DOMS. The 5mSRT increased biomarkers of muscle damage and inflammation, as well as the DOMS and RPE and reduced the PRS. Seventy-two hours was sufficient for fatigue recovery induced by the 5mSRT. PD is better than FI for the calculation of performance decrements during the 5mSRT to represent fatigue.

Exercise induced changes in echo intensity within the muscle: a brief review

Echo intensity is the mean pixel intensity of a specific region of interest from an ultrasound image. This variable has been increasingly used in the literature as a physiological marker. Although there has been an increased interest in reporting changes in echo intensity in response to exercise, little consensus exists as to what a change in echo intensity represents physiologically. The purpose of this paper is to review some of the earliest, as well as the most up to date literature regarding the changes in echo intensity in response to exercise. Echo intensity has been used to measure muscle quality, muscle damage, acute swelling, and intramuscular glycogen. The changes in echo intensity, however, are not consistent throughout the literature and often times lead to conclusions that seem contrary to the physiologic effects of exercise. For example, echo intensity increases in conjunction with increases in strength, contrary to what would be expected if echo intensity was a marker of muscle quality/muscle damage. It is conceivable that a change in echo intensity represents a range of physiologic effects at different time points. We recommend that these effects should be determined experimentally in order to rule out what echo intensity might and might not represent. Until this is done, caution should be employed when interpreting changes in echo intensity with acute and chronic exercise.