Does Acute Fatigue Negatively Affect Intrinsic Risk Factors of the Lower Extremity Injury Risk Profile? A Systematic and Critical Review

Kinematics but not kinetics alterations to single-leg drop jump movements following a subject-tailored fatiguing protocol suggest an increased risk of ACL injury

Introduction

Neuromuscular fatigue causes a transient reduction of muscle force, and alters the mechanisms of motor control. Whether these alterations increase the risk of anterior cruciate ligament (ACL) injury is still debated. Here we compare the biomechanics of single-leg drop jumps before and after the execution of a fatiguing exercise, evaluating whether this exercise causes biomechanical alterations typically associated with an increased risk of ACL lesion. The intensity of the fatiguing protocol was tailored to the aerobic capacity of each participant, minimizing potential differential effects due to inter-individual variability in fitness.

Methods

Twenty-four healthy male volunteers performed single leg drop jumps, before and after a single-set fatiguing session on a cycle ergometer until exhaustion (cadence: 65-70 revolutions per minute). For each participant, the intensity of the fatiguing exercise was set to 110% of the power achieved at their anaerobic threshold, previously identified by means of a cardiopulmonary exercise test. Joint angles and moments, as well as ground reaction forces (GRF) before and after the fatiguing exercise were compared for both the dominant and the non-dominant leg.

Results

Following the fatiguing exercise, the hip joint was more extended (landing: Δ=-2.17°, p = 0.005; propulsion: Δ=-1.83°, p = 0.032) and more abducted (landing: Δ=-0.72°, p = 0.01; propulsion: Δ=-1.12°, p = 0.009). Similarly, the knee joint was more extended at landing (non-dominant leg: Δ=-2.67°, p < 0.001; dominant: Δ=-1.4°, p = 0.023), and more abducted at propulsion (both legs: Δ=-0.99°, p < 0.001) and stabilization (both legs: Δ=-1.71°, p < 0.001) hence increasing knee valgus. Fatigue also caused a significant reduction of vertical GRF upon landing (Δ=-0.21 N/kg, p = 0.003), but not during propulsion. Fatigue did not affect joint moments significantly.

Conclusion

The increased hip and knee extension, as well as the increased knee abduction we observed after the execution of the fatiguing exercise have been previously identified as risk factors for ACL injury. These results therefore suggest an increased risk of ACL injury after the execution of the participant-tailored fatiguing protocol proposed here. However, the reduced vertical GRF upon landing and the preservation of joint moments are intriguing, as they may suggest the adoption of protective strategies in the fatigued condition to be evaluated in future studied.

Female National Collegiate Athletic Association Division-I Athlete Injury Prediction by Vertical Countermovement Jump Force-Time Metrics

ABSTRACT

Merrigan, JJ, Stone, JD, Kraemer, WJ, Vatne, EA, Onate, J, and Hagen, JA. Female National Collegiate Athletic Association Division-I athlete injury prediction by vertical countermovement jump force-time metrics. J Strength Cond Res 38(4): 783-786, 2024-Vertical countermovement jump (CMJ) assessments on force plates have been purported to screen for musculoskeletal injury risk (MSKI) but with little scientific support. Thus, this study aimed to identify associations and noncontact lower-body injury predictability with CMJ force-time metrics in female athletes. The study entailed a retrospective analysis of routine injury and performance monitoring from 155 female National Collegiate Athletics Association Division I athletes. Noncontact lower-body injuries included in analysis were confirmed by medical staff, occurred during competition or training, resulted in time loss from training, and occurred within 3 months following CMJ testing (2 maximal effort, no arm swing, jumps on dual force plates). A total of 44 injuries occurred within 3 months following CMJ baseline testing and resulted in an average of 24.5 missed days from training. Those who sustained an injury were more likely to sustain another injury (15 of 44 injuries [33.1%]; odds ratio = 3.05 [95% CI = 1.31-6.99]). For every 1-unit increase from the mean in eccentric mean power and minimum eccentric force, there was a decrease in odds of sustaining a MSKI. Despite high overall model accuracy (85.6%), the receiving operating characteristic area under the curve (65.9%) was unacceptable and the true positive rate (recall) was 0.0%. Thus, no injuries in the testing data set were correctly classified by the logistic regression model with CMJ force-time metrics as predictors. Baseline CMJ assessment may not be useful for noncontact lower-body musculoskeletal injury screening or predictability in National Collegiate Athletics Association female athletes.

Analysis of Injuries in the Swiss U20 Elite Ice Hockey Season 2019/2020-A Retrospective Survey

(1) Background: In Switzerland, there is little data on injury characteristics in elite ice hockey players aged under 20 years (U20 Elite juniors). This study aimed to determine the injury rate and type of injury in Swiss U20 ice hockey players. (2) Methods: The present study was carried out in a retrospective, non-experimental design using an online questionnaire provided to the 314 elite players of the 12 Swiss U20 Elite ice hockey teams. The injury rate, rate ratios, injury location, type and severity of injury, and injury mechanism were reported. (3) Results: Seventy-three athletes from 11 teams volunteered (response rate = 24%). A total of 30 out of 45 recorded injuries led to time loss in practice and competition. Injury occurred once or twice during the 2019/2020 season. For each player, the injury rate was 0.66 per 1000 practice hours and 2.98 per 1000 competition hours (injury rate ratio = 4.5). The head/neck region was the most common injury location (45.5%). (4) Conclusions: Knowledge of injury characteristics in ice hockey is necessary for meaningful injury management and injury prevention. The results of the present study provide information on the injury rate, location, types, severity, and mechanism in elite Swiss U20 ice hockey players. Most injuries result from contact with another player. More strict sanctioning for irregular behavior and fair play can serve as preventive measures. Further studies should examine different preventive measures such as wearing full-face coverage.

Acute pre- and post-competitive soccer match-play changes in neuromuscular factors, physical performance, and muscle response in youth male players

There is a paucity of literature analyzing the impact of fatigue from actual competitive soccer match-play on measures of neuromuscular function and muscle damage markers in youth players. Aims The main purpose was to analyze the acute pre- and post-competitive soccer match-play changes in measures of landing mechanics, stretch-shortening cycle capability, physical performance, muscle damage, and match intensity. A secondary purpose was to explore whether the players' maturity status and chronological age were associated with post-soccer match-play responses. Methods Thirty-two male youth outfield soccer players from two chronological competition age groups (U14 and U16) were assessed pre-and post-competitive soccer match-play for 2D dynamic knee valgus at landing (DKV), leg stiffness, reactive strength index, 20 m sprint time, CMJ-Abalakov jump height, creatine kinase and urea activity and visual analogue scale for muscle soreness (VAS). Players' maturity status was also estimated using a previously validated regression equation. Results There were statistically significant (p < 0.05) post-competitive soccer match-play impairments in all measures of stretch-shortening cycle capability and muscle damage markers assessed irrespective of the age group. Likewise, significant post-match play alterations in landing mechanics (DKV of the dominant leg) and physical performance (sprint time and jump height) scores were documented for the U14 players. Significant interactions between maturity and landing mechanics and VAS responses to competitive soccer match-play were also found whereby more mature players demonstrated larger post-match changes. Conclusion The findings of this study suggest the existence of a negative influence of competitive match-play on neuromuscular function and muscle damage in youth soccer.

Higher Eccentric Hamstring Muscle Fatigue After Participation in a Soccer Match in Young Female Athletes

BACKGROUND

Hamstring (HS) strength deficits and imbalances have been identified as risk factors for sustaining anterior cruciate ligament (ACL) injuries and muscular strains, with HS injuries being the most prevalent muscle injuries in soccer athletes. The aim of this study was to investigate HS eccentric strength before and after a soccer match in both male and female soccer athletes.

HYPOTHESIS

Soccer athletes have changes in eccentric HS strength after a soccer game.

STUDY DESIGN

Cohort observational study.

LEVEL OF EVIDENCE

Level 3.

METHODS

HS eccentric strength (mean and absolute peak torque and total work) was measured in 64 healthy male and female competitive football athletes (14-25 years) with an automatic device during the execution of the Nordic hamstring exercise (NHE) test before and after a 90-minute soccer match. The anterior-knee laxity (AKL) was quantified with an arthrometer.

RESULTS

Mean and absolute eccentric HS peak torque decreased by 24.5 N.m (-12.34%; P < 0.01) and 21.9 N.m (-10.08%; P < 0.01) in female athletes, whereas their male peers improved by 19.9 N.m (+9.01%; P = 0.01) and by 20.9 N.m (+8.51%; P = 0.02), respectively. HS total work in female athletes decreased by 831.1 J (P < 0.01) compared with the male athlete reduction of 235.3 J. Both the pre- versus postmatch intersex mean and absolute eccentric HS peak torque changes were significant (P < 0.01), as were the changes in HS total work (P < 0.01). The pre- versus postmatch AKL difference and the dominant versus nondominant limb comparison of the strength parameters were not significantly different. Younger female athletes (14-19 years old) presented a greater decrease in mean and absolute peak HS eccentric strength compared with those in older female athletes and men.

CONCLUSION

HS eccentric strength and work differ based on athlete sex, as measured by the NHE test. Mean peak, absolute peak, and total work showed greater reductions in female athletes than those in their male peers. The subgroup of 14- to 19-year-old female athletes experienced the highest reduction in strength parameters.

Balance Training Under Fatigue: A Randomized Controlled Trial on the Effect of Fatigue on Adaptations to Balance Training

ABSTRACT

Keller, M, Lichtenstein, E, Roth, R, and Faude, O. Balance training under fatigue: a randomized controlled trial on the effect of fatigue on adaptations to balance training. J Strength Cond Res 38(2): 297-305, 2024-Balance training is an effective means for injury prevention in sports. However, one can question the existing practice of putting the balance programs at the start of a training session (i.e., train in an unfatigued state) because the occurrence of injuries has been associated with fatigue. Therefore, the aim of this study was to assess the influence of balance training in a fatigued or an unfatigued state on motor performance tested in fatigued and unfatigued conditions. Fifty-two, healthy, active volunteers (28.0 years; 19 women) were randomly allocated to 1 of 3 different training groups. The BALANCE group completed 6 weeks of balance training. The other 2 groups completed the identical balance tasks either before (BALANCE-high-intensity interval training [HIIT]) or after (HIIT-BALANCE) a HIIT session. Thus, these groups trained the balance tasks either in a fatigued or in an unfatigued state. In PRE and POST tests, balance (solid ground, soft mat, wobble board) and jump performance was obtained in fatigued and unfatigued states. Balance training resulted in reduced sway paths in all groups. However, the linear models revealed larger adaptations in BALANCE-HIIT and BALANCE when compared with HIIT-BALANCE ( d = 0.22-0.71). These small to moderate effects were-despite some uncertainties-consistent for the "unfatigued" and "fatigued" test conditions. The results of this study revealed for the first time that balance training under fatigue results in diminished adaptations, even when tested in a fatigued state. Therefore, the data indicate that balance training should be implemented at the start of a training session or in an unfatigued state.

Reliability and validation of the German Achilles tendon Total Rupture Score

PURPOSE

Patient-related outcome measures (PROMs) are important instruments to evaluate efficacy of orthopaedic procedures. The Achilles tendon Total Rupture Score (ATRS) is a PROM developed to evaluate outcomes after treatment of Achilles tendon ruptures (ATRs). Purpose of this study is to develop and culturally adapt the German version of the ATRS and to evaluate reliability and validity.

METHODS

The ATRS was translated by forward-backward translation based on common guidelines. In this retrospective study, 48 patients with a surgical intervention after ATR were recruited. Reliability was evaluated by intraclass correlation coefficient (ICC) and Cronbach's alpha. Construct validity was valued by determining Pearson correlation coefficient with the German version of the Foot and Ankle Outcome Score (FAOS) and the Victorian Institute of Sports Assessment-Achilles questionnaire (VISA-A).

RESULTS

The German Version of the ATRS has an excellent internal consistency (Cronbach's alpha 0.96) as well as an excellent test-retest-reliability (ICC 0.98). It has a moderately strong correlation with the VISA-A (r = 0.73) as well as with the FAOS subclasses (r = 0.6-0.79).

CONCLUSION

The German version of the ATRS demonstrated good psychometric properties. It proofed to be a valid and reliable instrument for use in patients with Achilles tendon Rupture.

LEVEL OF EVIDENCE

Level II.

Monitoring modifiable injury risk factors over an in-season mesocycle in semi-professional female field hockey players

OBJECTIVE

This study aimed to determine changes of modifiable injury risk factors and fatigue parameters during a mesocycle (4 months of the competitive season) in semi-professional female field hockey players (Spanish 2nd Division).

METHODS

Fourteen female field hockey players (age: 22.6 ± 4.9 years) participated in the study over 4 months of the competitive season (September-December 2019). The players were tested each month for their: maximal isometric knee flexion, hip adduction, and abduction muscle strength; passive straight leg raise and ankle dorsiflexion range of motion (ROM); countermovement jump height; and perceptual fatigue (through a perceived well-being questionnaire).

RESULTS

Statistical differences were reported in isometric knee flexion torque in the dominant and non-dominant limb (p = < 0.001, ηp2 = 0.629,0.786 respectively), non-dominant isometric hip abductors torque (p = 0.016, ηp2 = 0.266) and isometric hip adductors torque in dominant and non-dominant limbs (p = < 0.001, ηp2 = 0.441-546). Also, significant differences were reported in the straight leg raise test (p = < 0.001, ηp2 = 0-523, 0.556) and ankle dorsiflexion (p = 0.001, ηp2 = 0.376, 0.377) for the dominant and non-dominant limb respectively. Finally, the jump height measured showed significant differences (p = <.001, ηp2 = 0.490), while no differences were reported in perceived well-being parameters (p = 0.089-0.459).

CONCLUSION

Increments in isometric muscle strength and fluctuations in ROM values and vertical jumping capacity are reported over an in-season mesocycle (i.e., 4 months of the competitive season). This information can be used to target recovery strategies to make them more efficient.

Effect of Ginseng Intake on Muscle Damage Induced by Exercise in Healthy Adults

One of the most popular herbal supplements in the world is ginseng. Several studies have evaluated the capacity of ginseng as a protective element in the physiological response to exercise. The result produced by the exercise causes an increase in cellular biomarkers of damage in the skeletal muscle, mainly in the pro-inflammatory types. The different types of ginseng are composed of ginsenosides, which are active ingredients that act on the central nervous system and have antioxidant and anti-inflammatory properties, as well as effects on cortisol modulation. The use of ginseng as a nutritional supplement can help muscle regeneration and renewal. The objective of this review is to enrich the knowledge regarding the consumption of ginseng for a specific situation, such as exercise, which would cause an improvement in the tolerance to chronic load stimuli in sport, thus helping the subjects to recover between training sessions. Due to these benefits, it could also be an ideal food supplement for regenerative processes in muscle injuries in which inflammatory markers increase significantly. This review aims to summarise that biological factors can be attenuated after exercise due to the consumption of ginseng in healthy subjects, accelerating and improving muscle regeneration and, therefore, improving the ability to adapt to the stimuli generated by said exercise.

The effect of fatigue on spike jump biomechanics in view of patellar tendon loading in volleyball

BACKGROUND AND OBJECTIVE

Patellar tendinopathy (PT) is a highly prevalent overuse injury in volleyball and is often linked with overloading of the patellar tendon. Little is known, however, about whether and how patellar tendon loading is affected by fatigue during the most challenging jump activity in volleyball. Therefore, this study investigates the effect of a high-intensity, intermittent fatigue protocol on movement alterations in terms of patellar tendon loading during a volleyball spike jump.

METHODS

Forty-three male volleyball players participated in this study. Three-dimensional full-body kinematics and kinetics were collected when performing a spike jump before and after the fatigue protocol. Sagittal plane joint angles, joint work and patellar tendon loading were calculated and analyzed with curve analyses using paired sample t-tests to investigate fatigue effects (p < 0.05).

RESULTS

Fatigue induced a stiffer lower extremity landing strategy together with prolonged pelvis-trunk flexion compared to baseline (p = 0.001-0.005). Decreased patellar tendon forces (p = 0.001-0.010) and less eccentric knee joint work (-5%, p < 0.001) were observed after the fatigue protocol compared to baseline.

CONCLUSION

Protective strategies seem to be utilized in a fatigued state to avoid additional tensile forces acting on the patellar tendon, including proximal compensations and stiff lower extremity landings. We hypothesize that players might be more prone for developing PT if eccentric patellar tendon loads are high in the non-fatigued state and/or these loads are somehow not decreased after fatigue.

Males and females have similar neuromuscular coordination strategies of the quadriceps during fatiguing repeated all-out cycling

Introduction

An imbalance of vastus medialis (VM) and vastus lateralis (VL) muscle activation and patterns of dyscoordination may contribute to the sex discrepancy in the incidence of patellofemoral pain syndrome (PFPS). While some studies have examined sex-specific VM/VL coordination strategies in some tasks, no previous studies have examined sex-specific VM/VL coordination strategies during repeated sprint exercise (RSE).

Methods

In this study, asymptomatic young adults (N = 39, 19 females) completed a RSE protocol consisting of 10 × 10 s all-out cycling interspersed by 30 s of passive rest. Electromyographic (EMG) signals from the VM and VL muscles were recorded throughout exercise.

Results

VM:VL ratio did not change with fatigue and was not different between the sexes. From sprint 1 to 10, VM-VL onset delay increased from 9.62 to 16.95 ms and from 19.28 to 45.09 ms in males and females, respectively (p < 0.001); however, no sex difference was found (p = 0.524). Muscle activation amplitude plateaued at different sprint repetitions in males and females while mechanical work plateaued at similar repetitions.

Discussion

These findings suggest that sex differences in the incidence of PFPS may not be influenced by VM/VL muscle coordination as assessed by EMG.

Fatigue does not increase limb asymmetry or induce proximal joint power shift in habitual, multi-speed runners

During prolonged jogging, joint moment and work tend to decrease in the distal (ankle) joint but increase at proximal (hip/knee) joints as performance fatigue manifests, and such adaptations might be expected to occur in sprinting. Fatigue is also thought to increase inter-limb asymmetries, which is speculated to influence injury risk. However, the effects of fatigue on sprint running gait have been incompletely studied, so these hypotheses remain untested. Using statistical parametric mapping, we compared 3-D kinematics and ground reaction force production between the dominant (DL) and non-dominant (NDL) legs of 13 soccer players during both non-fatigued and fatigued sprint running. Contrary to the tested hypotheses, relative between-leg differences were greater in non-fatigued than fatigued sprinting. DL generated higher propulsive impulse due to increased ankle work, while NDL exhibited greater vertical impulse, potentially due to greater hip flexion prior to downward foot acceleration. Whilst few changes were detected in DL once fatigued, NDL shifted towards greater horizontal force production, largely resulting from an increase in plantar flexion (distal-joint) moments and power. After fatiguing running, inter-limb asymmetry was reduced and no distal-to-proximal shift in joint work was detected. These adaptations may attenuate decreases in running speed whilst minimising injury risk.

A Multidimensional Assessment of a Novel Adaptive Versus Traditional Passive Ankle Sprain Protection Systems

BACKGROUND

Ankle braces aim to reduce lateral ankle sprains. Next to protection, factors influencing user compliance, such as sports performance, motion restriction, and users' perceptions, are relevant for user compliance and thus injury prevention. Novel adaptive protection systems claim to change their mechanical behavior based on the intensity of motion (eg, the inversion velocity), unlike traditional passive concepts of ankle bracing.

PURPOSE

To compare the performance of a novel adaptive brace with 2 passive ankle braces while considering protection, sports performance, freedom of motion, and subjective perception.

STUDY DESIGN

Controlled laboratory study.

METHODS

The authors analyzed 1 adaptive and 2 passive (one lace-up and one rigid brace) ankle braces, worn in a low-cut, indoor sports shoe, which was also the no-brace reference condition. We performed material testing using an artificial ankle joint system at high and low inversion velocities. Further, 20 male, young, healthy team sports athletes were analyzed using 3-dimensional motion analysis in sports-related movements to address protection, sports performance, and active range of motion dimensions. Participants rated subjective comfort, stability, and restriction experienced when using the products.

RESULTS

Subjective stability rating was not different between the adaptive and passive systems. The rigid brace was superior in restricting peak inversion during the biomechanical testing compared with the passive braces. However, in the material test, the adaptive brace increased its stiffness by approximately 400% during the fast compared with the slow inversion velocities, demonstrating its adaptive behavior and similar stiffness values to passive braces. We identified minor differences in sports performance tasks. The adaptive brace improved active ankle range of motion and subjective comfort and restriction ratings.

CONCLUSION

The adaptive brace offered similar protective effects in high-velocity inversion situations to those of the passive braces while improving range of motion, comfort, and restriction rating during noninjurious motions.

CLINICAL RELEVANCE

Protection systems are only effective when used. Compared with traditional passive ankle brace technologies, the novel adaptive brace might increase user compliance by improving comfort and freedom of movement while offering similar protection in injurious situations.

The Effect of Fatigue on Trunk and Pelvic Jump-Landing Biomechanics in View of Lower Extremity Loading: A Systematic Review

Fatigue has often been considered a risk factor for developing sports injuries, modulating lower extremity jump-landing biomechanics. The impact of fatigue on proximal trunk and pelvic biomechanics has been suggested to play an important role in lower extremity loading and injury risk, yet the available evidence remains ambiguous as the trunk and pelvis were often not the primary focus of research. Therefore, the purpose of this systematic review was to determine how fatigue affects trunk and pelvic three-dimensional jump-landing biomechanics. PubMed (MEDLINE), Web of Science, Embase, CINAHL and SPORTDiscus were consulted up to and including April 2022 for potential studies investigating the effect of fatigue on trunk and pelvic kinematics, kinetics and/or muscular activity during jump-landing tasks in healthy, physically active populations. Methodological quality of the studies was assessed by the modified Downs and Black checklist. Twenty-one studies were included and methodological quality was moderate to high among these studies. The results indicate prevailing evidence for more trunk flexion during standardized jump-landing tasks after lower extremity muscle fatigue. Otherwise, lumbo-pelvic-hip muscle fatigue does not seem to elicit major detrimental changes to these jump-landing biomechanics. Although a wide variability of trunk and pelvic jump-landing strategies was observed, the results provide evidence for increased trunk flexion after lower extremity muscle fatigue. This proximal strategy is suggested to help unload fatigued lower extremity structures and lack of this compensation might increase knee injury risk.

Factors associated with patellofemoral pain in recreational road cyclists: A cross-sectional study in 59953 cyclists - SAFER XXXIII

OBJECTIVE

Patellofemoral pain (PFP) is a common cycling-related injury, and independent factors need to be identified to enable effective injury prevention strategies. We aim to determine factors associated with PFP in cyclists entering mass community-based events.

DESIGN

Cross-sectional study.

SETTING

2016-2020 Cape Town Cycle Tour.

PARTICIPANTS

Consenting race entrants.

MAIN OUTCOME MEASURES

62758 consenting race entrants completed a pre-race medical questionnaire, and 323 reported PFP. Selected factors associated with PFP (demographics, cycling experience and training, chronic disease history) were explored using multivariate analyses.

RESULTS

Prevalence ratio (PR) of PFP was similar for sex and age groups. Independent factors associated with PFP (adjusted for sex and age) were history of chronic disease [Composite Chronic Disease Score (0-10)(PR = 2.0, p < 0.0001) and any allergies (PR = 2.0, p < 0.0001)].

CONCLUSION

A history of chronic diseases and allergies is associated with PFP in cyclists. Practical clinical recommendations are: 1) that prevention programs for PFP be considered when cycling is prescribed as a physical activity intervention for patients with chronic disease, and 2) that older cyclists presenting with PFP be assessed for the presence of risk factors or existing chronic disease.

A Pilot Study of Plantar Mechanics Distributions and Fatigue Profiles after Running on a Treadmill: Using a Support Vector Machine Algorithm

The treadmill is widely used in running fatigue experiments, and the variation of plantar mechanical parameters caused by fatigue and gender, as well as the prediction of fatigue curves by a machine learning algorithm, play an important role in providing different training programs. This experiment aimed to compare changes in peak pressure (PP), peak force (PF), plantar impulse (PI), and gender differences of novice runners after they were fatigued by running. A support vector machine (SVM) was used to predict the fatigue curve according to the changes in PP, PF, and PI before and after fatigue. 15 healthy males and 15 healthy females completed two runs at a speed of 3.3 m/s ± 5% on a footscan pressure plate before and after fatigue. After fatigue, PP, PF, and PI decreased at hallux (T1) and second-fifth toes (T2-5), while heel medial (HM) and heel lateral (HL) increased. In addition, PP and PI also increased at the first metatarsal (M1). PP, PF, and PI at T1 and T2-5 were significantly higher in females than in males, and metatarsal 3-5 (M3-5) were significantly lower in females than in males. The SVM classification algorithm results showed the accuracy was above average level using the T1 PP/HL PF (train accuracy: 65%; test accuracy: 75%), T1 PF/HL PF (train accuracy: 67.5%; test accuracy: 65%), and HL PF/T1 PI (train accuracy: 67.5%; test accuracy: 70%). These values could provide information about running and gender-related injuries, such as metatarsal stress fractures and hallux valgus. Application of the SVM to the identification of plantar mechanical features before and after fatigue. The features of the plantar zones after fatigue can be identified and the learned algorithm of plantar zone combinations with above-average accuracy (T1 PP/HL PF, T1 PF/HL PF, and HL PF/T1 PI) can be used to predict running fatigue and supervise training. It provided an important idea for the detection of fatigue after running.

Acute effect of kinesio tape on postural control in individuals with functional ankle instability following ankle muscle fatigue

Background: Kinesio taping (KT) is one of the therapeutic interventions in sports medicine practice. The study aims to assess the acute effect of different KT methods on postural control in individuals with functional ankle instability (FAI) after ankle muscle fatigue.

Methods: Twenty-eight participants with FAI were recruited to complete maximum voluntary isometric contraction (MVIC) and proprioception of ankle using isokinetic dynamometer, dynamic postural control using Y-balance test and static postural control using a force platform after a fatigue protocol in four taping conditions: facilitatory KT (FKT), ankle balance taping (ABT), sham taping (ST) and no taping (NT).

Results: No significant difference was observed for the data MVIC and proprioception after ankle muscle fatigue amongst the four taping treatments. A significant difference in Y-Balance Test was observed amongst the four taping treatments at posterolateral direction (p < 0.001) and posteromedial direction (p < 0.001), suggesting that KT may significantly improve dynamic postural control following ankle muscle fatigue. For Center of pressure (COP) measurements, the mediolateral COP sway range of NT was significantly larger than that of FKT (p = 0.003) and ST (p < 0.001), suggesting that the placebo effect of KT was inevitable.

Conclusion: The effect of KT seems increased dynamic postural control in individuals with FAI after ankle muscle fatigue, and this effect is not strongly related to the taping methods. By preventing fatigue-related impairments of postural control, KT may help reduce the risk of injury in individuals with FAI.

Efficacy of Patellar Taping and Electromyographic Biofeedback Training at Various Knee Angles on Quadriceps Strength and Functional Performance in Young Adult Male Athletes with Patellofemoral Pain Syndrome: A Randomized Controlled Trial

Background

The severity of the articular lesion is the single most essential element in investigating the extent of flexion that is required for activities. However, a prior study found no differences in muscle strength gains of quadriceps muscles at different knee angles in people with patellofemoral pain syndrome (PFPS).

Objective

The effects of patellar taping and electromyographic biofeedback (EMG-BF)-guided isometric quadriceps strengthening at different knee angles (e.g., 30°, 60°, and 90° of knee flexion) on quadriceps strength and functional performance in people with PFPS were compared in this single-blind randomized controlled parallel trial.

Methods

Sixty adult male athletes with PFPS (age: 26.9 ± 1.4 years) were randomly divided into two groups. The experimental group (n = 30) received patellar taping and EMG-BF-guided isometric contraction exercise at 30°, 60°, and 90° angles, and the control group (n = 30) received sham patellar taping without EMG-BF-guided exercises for six weeks. Pain intensity, knee function, muscle strength, and the single-leg triple hop (SLTH) test were assessed.

Results

The pain intensity and SLTH scores between the groups were significantly different at the end of the trial (p ≤ 0.001). The EMG-BF and control groups had mean pain scores of 1.3 (0.8) and 4.5 (0.8), respectively. The EMG-BF and control groups had mean functional scores of 80.4 (5.1) and 69.1 (6.1), respectively. The mean SLTH score for the EMG-BF group was 540.7 (51.2) and for the control group it was 509.4 (49.8) after the trial. Quadriceps muscle strength was significantly higher in those who performed quadriceps strength training at 60° of knee flexion after six weeks than in those who performed strength training at 30° or 90° of knee flexion.

Conclusion

The findings indicated that individuals who trained their quadriceps at a 60° knee angle had significantly stronger quadriceps muscles than individuals who trained at 30° or 90° of knee flexion. Trial Registration. This trial is registered at Clinical Trials.gov under the identifier NCT05055284.

Complex Network Model Reveals the Impact of Inspiratory Muscle Pre-Activation on Interactions among Physiological Responses and Muscle Oxygenation during Running and Passive Recovery

Simple Summary

Different warm-ups can be used to improve physical and sports performance. Among these strategies, we can include the pre-activation of the inspiratory muscles. Our study aimed to investigate this pre-activation model in high-intensity running performance and recovery using an integrative computational analysis called a complex network. The participants in this study underwent four sessions. The first and second sessions were performed to explain the procedures, characterize them and determine the individualized pre-activation intensity (40% of the maximum inspiratory pressure). Subsequently, on different days, the subjects were submitted to high-intensity tethered runs on a non-motorized treadmill with monitoring of the physiological responses during and after this effort. To understand the impacts of the pre-activation of inspiratory muscles on the organism, we studied the centrality metrics obtained by complex networks, which help in the interpretation of data in a more integrated way. Our results revealed that the graphs generated by this analysis were altered when inspiratory muscle pre-activation was applied, emphasizing muscle oxygenation responses in the leg and arm. Blood lactate also played an important role, especially after our inspiratory muscle strategy. Our findings confirm that the pre-activation of inspiratory muscles promotes modulations in the organism, better integrating physiological responses, which could increase performance and improve recovery.

Abstract

Although several studies have focused on the adaptations provided by inspiratory muscle (IM) training on physical demands, the warm-up or pre-activation (PA) of these muscles alone appears to generate positive effects on physiological responses and performance. This study aimed to understand the effects of inspiratory muscle pre-activation (IM_PA) on high-intensity running and passive recovery, as applied to active subjects. In an original and innovative investigation of the impacts of IM_PA on high-intensity running, we proposed the identification of the interactions among physical characteristics, physiological responses and muscle oxygenation in more and less active muscle to a running exercise using a complex network model. For this, fifteen male subjects were submitted to all-out 30 s tethered running efforts preceded or not preceded by IM_PA, composed of 2 × 15 repetitions (1 min interval between them) at 40% of the maximum individual inspiratory pressure using a respiratory exercise device. During running and recovery, we monitored the physiological responses (heart rate, blood lactate, oxygen saturation) and muscle oxygenation (in vastus lateralis and biceps brachii) by wearable near-infrared spectroscopy (NIRS). Thus, we investigated four scenarios: two in the tethered running exercise (with or without IM_PA) and two built into the recovery process (after the all-out 30 s), under the same conditions. Undirected weighted graphs were constructed, and four centrality metrics were analyzed (Degree, Betweenness, Eigenvector, and Pagerank). The IM_PA (40% of the maximum inspiratory pressure) was effective in increasing the peak and mean relative running power, and the analysis of the complex networks advanced the interpretation of the effects of physiological adjustments related to the IM_PA on exercise and recovery. Centrality metrics highlighted the nodes related to muscle oxygenation responses (in more and less active muscles) as significant to all scenarios, and systemic physiological responses mediated this impact, especially after IM_PA application. Our results suggest that this respiratory strategy enhances exercise, recovery and the multidimensional approach to understanding the effects of physiological adjustments on these conditions.

Dynamic postural control and physical stress: an approach to determining injury risk in real sporting conditions

Dynamic postural control is one of the essential factors in situations where non-contact injuries mainly occur, i.e., landing, cutting, or stopping. Therefore, testing of dynamic postural control should be implemented in injury risk assessment. Moreover, non-contact injuries mainly occur under loaded conditions when the athlete is physically stressed. Therefore, risk factors and mechanisms of these injuries should also be regarded under loading conditions and not only when the athlete is recovered. Current studies examining the influence of physical load on risk factors, such as dynamic postural control, often use cycling protocols to stress the participants. Nevertheless, most types of sports require running as a central element and the induced internal load after cycling might not be the same after running. Therefore, the current study aimed to examine the influence of a running and a cycling protocol on dynamic postural control and to determine the potential injury risk under representative conditions. In total, 128 sport students (64 males and 64 females, age: 23.64 ± 2.44, height: 176.54 ± 8.96 cm, weight: 68.85 ± 10.98 kg) participated in the study. They were tested with the Y Balance Test before and after one loading protocol. A total of 64 participants completed a protocol on a cycle ergometer and the other 64 on a treadmill. A mixed ANOVA showed significant interactions of time and load type. Dynamic postural control was reduced immediately after cycling but did not change after running. These findings indicate a load type dependence of dynamic postural control that must be considered while assessing an athlete’s potential injury risk and they support the need for more representative designs.

Validation of Instrumented Football Shoes to Measure On-Field Ground Reaction Forces

Ground reaction forces (GRF) have been widely studied in football to prevent injury. However, ambulatory tools are missing, posing methodological limitations. The purpose of this study was to assess the validity of an innovative football shoe measuring normal GRF (nGRF) directly on the field through instrumented studs. A laboratory-based experiment was first conducted to compare nGRF obtained with the instrumented shoe (IS) to vertical GRF (vGRF) obtained with force platform (FP) data, the gold standard to measure vGRF. To this aim, three subjects performed 50 steps and 18 counter-movement jumps (CMJs). Secondly, eleven subjects completed running sprints at different velocities on a football field, as well as CMJs, while wearing the IS. Good to excellent agreement was found between the vGRF parameters measured with the FP and the nGRF measured by the IS (ICC > 0.75 for 9 out of 11 parameters). Moreover, on-field nGRF patterns demonstrated a progressive and significant increase in relation with the running velocity (p < 0.001). This study demonstrated that the IS is a highly valid tool to assess vGRF patterns on a football field. This innovative way to measure vGRF in situ could give new insights to quantify training load and detect neuromuscular fatigue.

Patellofemoral Pain Syndrome in Young Female Athletes: A Case-Control Study

Background

Patellofemoral pain syndrome (PFPS) is the most common cause of anterior knee pain in children and adolescents, and it is characterized by highly limiting, recurrent, frontal pain.

Objectives

The purpose of the study is to assess the incidence and onset of PFPS in the young female athletes and to compare it to healthy individuals.

Methods

Between 2017 and 2019, 51 subjects were reviewed and divided in three groups: rhythmic gymnastics athletes (RG; 21 individuals, mean age: 13.8 ± 3.6 years), basketball athletes (BG; 17 individuals, mean age: 14.2 ± 3.1 years), and control group (CG; 13 individuals, mean age: 14.5 ± 4.3 years). All patients underwent physical examination including patellar glide, tilt, grind and apprehension tests, tiptoe and jack tests, Coleman block, and navicular drop tests. The clinical and functional outcomes of the subjects were assessed using the Kujala patellofemoral score (KPS).

Results

In RG patients were recorded 66.7% of normal footprint (NF), 9.5% of cavus feet (FCF), and 23.8% of flatfeet (FFF); 14.8% patellar positive tests, KS = 98.6 ± 13.7. BG patients had 70.6% of NF, 11.8% FCF, and 17.6% of FFF; 23.5% patellar positive tests, KS = 98.3 ± 12.4. CG patients had 61.5% of NF, 7.7% of FCF and 30.8% of FFF; 15.4% patellar positive tests, KPS = 98,9 ± 15.3. No statistically significance was found between the three cohorts of patients.

Conclusions

PFPS is a common pathology; muscular imbalance and overuse could exacerbate pain and discomfort in young female athletes. Our findings show high type and level of sport activity are not related to increase frequency of clinical symptoms related to PFPS.

A New Tool for Rapid Assessment of Acute Exercise-Induced Fatigue

Background

There are limited sensitive evaluation methods to distinguish people's symptoms of peripheral fatigue and central fatigue simultaneously. The purpose of this study is to identify and evaluate them after acute exercise with a simple and practical scale.

Methods

The initial scale was built through a literature review, experts and athlete population survey, and a small sample pre-survey. Randomly selected 1,506 students were evaluated with the initial scale after exercise. Subjective fatigue self-assessments (SFSA) were completed at the same time.

Results

The Acute Exercise-Induced Fatigue Scale (AEIFS) was determined after performing a factor analysis. In the exploratory factor analysis, the cumulative variance contribution rate was 65.464%. The factor loadings of the total 8 questions were 0.661-0.816. In the confirmatory factor analysis, χ2/df = 2.529, GFI = 0.985, AGFI = 0.967, NFI = 0.982, IFI = 0.989, CFI = 0.989, and RMSEA = 0.048. The Cronbach's alpha coefficient for the scale was 0.872, and it was 0.833 for peripheral fatigue and 0.818 for central fatigue. The intra-class correlation coefficient for the scale was 0.536, and the intra-class correlation coefficients for peripheral fatigue and central fatigue were 0.421 and 0.548, respectively. The correlation coefficient between the total score of the AEIFS and the SFSA score was 0.592 (p < 0.01).

Conclusion

Our results demonstrate that the AEIFS can distinguish peripheral fatigue and central fatigue and can also reflect their correlation. This scale can be a useful evaluation tool not only for measuring fatigue after acute exercise but also for guiding reasonable exercise, choosing objective testing indicators, and preventing sports injuries resulting from acute exercise-induced fatigue.

Load-Induced Changes of Inter-Limb Asymmetries in Dynamic Postural Control in Healthy Subjects

Inter-limb asymmetries are associated with a higher potential risk for non-contact injuries. Differences in function or performance between the limbs might lead to imbalances and promote instability, increasing the potential risk for injuries. Consequently, an investigation of inter-limb asymmetries should be included in injury risk assessment. Furthermore, since non-contact injuries mainly occur under loaded conditions, an investigation of load-induced changes of inter-limb asymmetries can provide additional information on the athlete’s potential injury risk. Therefore, the current study aimed to investigate the influence of physical load on inter-limb asymmetries in dynamic postural control, which is essential in situations with a high risk for non-contact injuries such as landing, cutting, or stopping. In total, dynamic postural control of 128 active and healthy subjects (64 males and 64 females, age: 23.64 ± 2.44, height: 176.54 ± 8.96 cm, weight: 68.85 ± 10.98 kg) was examined. Dynamic postural control was tested with the Y-Balance Test (YBT) before and after a loading protocol on a bicycle ergometer or a treadmill. The results showed no significant increase of the inter-limb asymmetries in anterior direction [F_{(1, 126)} = 4.44, p = 0.04, η²_p = 0.03]. Moreover, there is high variation between the subjects regarding the magnitude and the direction of the asymmetries and the changes due to load. Therefore, a more individual analysis considering the magnitude and the direction of the asymmetries is required. Thereby, considering different modifying factors, e.g., sex, injury history, and baseline level of asymmetries, can be helpful. Moreover, an analysis of the changes during load might provide further insights, reveal possible differences, and help detect the reasons and mechanisms underlying inter-limb asymmetries and asymmetrical loading.

Foot tapping and unilateral vertical jump performance in athletes after knee surgery: an explorative cross-sectional study

Background

Guiding athletes through the rehabilitation process and judging the time at which return to sports can be enabled after anterior cruciate ligament (ACL) injuries are still challenging processes. The purpose of this explorative cross-sectional study was to retrospectively compare unilateral vertical jump as well as vertical foot tapping outcomes in athletes returned to sports after ACL reconstruction (ACLR) with uninjured athletes.

Methods

Seven-teen ACLR athletes (male/female: 12/5) were examined 11 (6–23) months after their ACL injury and after return to sport clearance together with 67 uninjured athletes (male/female: 51/16). Seventeen age and stature matched controls were selected from the sample of uninjured athletes. Participants unilaterally performed acyclic (squat jump, SJ; drop jump, DJ) and cyclic (foot tapping, FT) tests. SJ peak power, DJ take-off efficiency (TOE) and FT coefficients (FTC) were compared between ACLR and matched as well as unmatched control groups. Limb symmetry index (LSI) as well as performance score were calculated.

Results

Analyses of the SJ peak power revealed moderate effects of group (right: P < 0.09, η_p² = 0.06; left: P < 0.05, η_p² = 0.08). The TOE was largely affected by group (right: P < 0.01, η_p² = 0.12; left: P < 0.01, η_p² = 0.13). No effect of group was found on the FTC (P > 0.8, η_p² < 0.01). The SJ peak power LSI (r = 0.46, P < 0.07) and TOE LSI (r = 0.38, P = 0.13) were positively associated with the performance score of the ACLR group.

Conclusion

Although already returned to sports, the ACLR group underperformed the matched and unmatched control groups significantly. Unilaterally performed vertical jumps may provide additional information on athletes’ rehabilitation progress and help to manage the rehabilitation process and decisions on potential readiness after ACLR. More attention should be paid to the direction of the LSI results.

Concurrent Evolution of Biomechanical and Physiological Parameters With Running-Induced Acute Fatigue

Understanding the influence of running-induced acute fatigue on the homeostasis of the body is essential to mitigate the adverse effects and optimize positive adaptations to training. Fatigue is a multifactorial phenomenon, which influences biomechanical, physiological, and psychological facets. This work aimed to assess the evolution of these three facets with acute fatigue during a half-marathon. 13 recreational runners were equipped with one inertial measurement unit (IMU) on each foot, one combined global navigation satellite system-IMU-electrocardiogram sensor on the chest, and an Android smartphone equipped with an audio recording application. Spatio-temporal parameters for the running gait, along with the heart rate, its variability and complexity were computed using validated algorithms. Perceived fatigability was assessed using the rating-of-fatigue (ROF) scale at every 10 min of the race. The data was split into eight equal segments, corresponding to at least one ROF value per segment, and only level running parts were retained for analysis. During the race, contact time, duty factor, and trunk anteroposterior acceleration increased, and the foot strike angle and vertical stiffness decreased significantly. Heart rate showed a progressive increase, while the metrics for heart rate variability and complexity decreased during the race. The biomechanical parameters showed a significant alteration even with a small change in perceived fatigue, whereas the heart rate dynamics altered at higher changes. When divided into two groups, the slower runners presented a higher change in heart rate dynamics throughout the race than the faster runners; they both showed similar trends for the gait parameters. When tested for linear and non-linear correlations, heart rate had the highest association with biomechanical parameters, while the trunk anteroposterior acceleration had the lowest association with heart rate dynamics. These results indicate the ability of faster runners to better judge their physiological limits and hint toward a higher sensitivity of perceived fatigue to neuromuscular changes in the running gait. This study highlights measurable influences of acute fatigue, which can be studied only through concurrent measurement of biomechanical, physiological, and psychological facets of running in real-world conditions.

Internet Survey of Risk Factors Associated With Training and Competition in Dogs Competing in Agility Competitions

Objective: To describe risk factors associated with training and competition in relation to frequency and severity of injuries experienced by agility dogs.

Procedures: An internet-based survey collected data on competition level variables and training level variables. The primary outcome was history of any injury and a secondary outcome considered history of severe injury (injury lasting > 3 months). Logistic regression was used to estimate associations and final models were obtained via backward selection to identify the strongest associations within variables.

Results: There were 4,197 dogs included in this analysis. Injury was reported for 1,737 (41.4%) dogs and severe injury was reported for 629 (15.0%). In the model with competition level factors, jumping 4” (OR: 1.50) or 2–4” (OR: 1.31) over shoulder height compared to jumping 0–2” lower and competing at national events was associated with increased injury risk, while competing 6+ times on rubber matting was associated with lower risk (OR: 0.62). Training level variables associated with injury risk were age starting jump, teeter, and weave training, with the highest risk observed for dogs starting jump training between 3 and 18 months but starting weave and teeter training after 18 months of age.

Conclusion and Clinical Relevance: Many variables thought to be associated with injury risk were not significant in the final model. Starting jump training at an earlier age was associated with greater risk of injury relative to starting after 18 months. It is possible that the high impact of jump training before skeletal maturity may increase the risk of injuries or musculoskeletal conditions. The increased risk of injury in dogs that jump 2–4, or 4+ inches higher than shoulder height may be due to increased biomechanical forces during takeoff and landing. Faster dogs may be at higher risk of injury; handlers planning competition around big events or competing at the national level are likely to have faster dogs, and may be less likely to compete on rubber matting. These data provide valuable current insight into the possible effects that training and competition variables may have on injury risk in agility dogs.

Influence of invertor and evertor muscle fatigue on functional jump tests and postural control: A prospective cross-sectional study

OBJECTIVE

Fatigue of the ankle's stabilizing muscles may influence the performance of functional activities and postural control. The purpose of this study was to evaluate the performance of healthy young adults using functional jump tests and static posturography control under pre- and post-fatigue conditions of the ankle invertor and evertor muscles.

METHODS

Thirty physically active healthy male and female (15 male and 15 female) volunteers (24.3 years) were enrolled in this prospective cross-sectional study. Participants performed tests on one day under a non-fatigued state of invertor and evertor muscles and on the second day in a fatigued state. Tests included static posturography on a force platform in a bipedal stance with eyes open and closed and in one-legged support with eyes open and functional jump tests (figure-of-8, side hop, 6-m crossover hop, and square hop). Fatigue of the ankle invertor and evertor muscles was induced using isokinetic dynamometry with 30 repetitions at 120°/s.

RESULTS

Participants had an average age of 24.3 years (SD ± 2.08), the height of 1.73 m (SD ± 0.08), and a weight of 68.63 kg (SD ± 10.29). The average Body Mass Index (BMI) was 22.88 (SD ± 2.46). A decrease in performance was observed in functional activities and postural control under all conditions after the induction of muscle fatigue, except for the speed at a bipedal stance with eyes open.

CONCLUSIONS

Functional jump tests are low cost and useful for clinical practice and evaluation of the effects of muscle fatigue and could be used in clinical practice.

Effects of Maximal Effort Running on Special Agents' Loaded and Unloaded Drop Jump Performance and Mechanics

The purpose was to investigate the effect of load and fatigue on landing forces and mechanics. Thirteen Department of State special agents first completed drop jump testing, a maximal treadmill test, and another round of drop jump testing. During drop jump testing, agents performed 3 maximal effort drop jumps from 30 cm with body mass only (unloaded) or a 15 kg weight-vest (loaded). A force plate was used to collect force–time data, while two laptops were placed 3 m from the force plate from frontal and sagittal planes. Two-way analyses of variance were used to analyze the effect of load and fatigue on landing forces and Landing Error Scoring System (LESS) with alpha of p < 0.05. Dropping from 30 cm with 15 kg resulted in greater landing impulse, which was driven by increases in contact time. The loaded condition also resulted in lower jump height and reactive strength indexes. After the maximal graded treadmill test there were no further changes in drop jump ground reaction forces or performance. However, relative aerobic capacity was related to impulse changes following the treadmill test in unloaded (R² = 0.41; p = 0.018) and loaded conditions (R² = 0.32; p = 0.044). External loads of 15 kg increased impulse and contact time and resultantly decreased drop jump height and reactive strength indexes. It is encouraged that training protocols be aimed to concomitantly improve aerobic capacity and lower body power. Plyometric training with progressive overloading using external loads may be helpful, but further research is warranted.

Independent Risk Factors Predicting Gradual Onset Injury in 2824 Trail Running Race Entrants: SAFER XVIII Study

INTRODUCTION

Trail running is characterized by elevation changes, with uneven and varying running surfaces. Risk factors that may predict gradual-onset running-related injuries (GORRIs) in short-distance trail running have not been explored. The objective was to determine risk factors that predict GORRIs in trail running race entrants who entered mass community-based trail running events.

METHODS

In this descriptive cross-sectional study, data were collected prospectively from a prerace medical screening questionnaire over 4 trail run events held annually. Using a Poisson regression model, runner demographics, race distance, running training/racing variables, history of chronic diseases (number of chronic diseases reported as a cumulative "chronic disease composite score"), and allergies were investigated to determine factors predicting self-reported GORRI history in the previous 12 mo.

RESULTS

This study included 2824 race entrants (80% of entrants). The retrospective annual incidence for GORRIs was 13%. Independent risk factors predicting GORRIs were longer race distance (P<0.0001), increasing chronic disease composite score (P=0.0012), and a history of allergies (P=0.0056). The lower limb (94%) was the main anatomic region of GORRIs, and soft tissue injuries accounted for most (83%) GORRIs. Common specific GORRIs were iliotibial band syndrome (22%), Achilles tendon injury (10%), and hamstring injury (9%).

CONCLUSIONS

Independent risk factors predicting GORRIs among trail running entrants included longer race distance, a higher chronic disease composite score, and a history of allergies. This study has highlighted trail running race entrants at risk for sustaining GORRIs who could be targeted for future injury prevention interventions.

Fatigue Induced by Repeated Changes of Direction in Élite Female Football (Soccer) Players: Impact on Lower Limb Biomechanics and Implications for ACL Injury Prevention

Background

The etiology of Anterior Cruciate Ligament (ACL) injury in women football results from the interaction of several extrinsic and intrinsic risk factors. Extrinsic factors change dynamically, also due to fatigue. However, existing biomechanical findings concerning the impact of fatigue on the risk of ACL injuries remains inconsistent. We hypothesized that fatigue induced by acute workload in short and intense game periods, might in either of two ways: by pushing lower limbs mechanics toward a pattern close to injury mechanism, or alternatively by inducing opposed protective compensatory adjustments.

Aim

In this study, we aimed at assessing the extent to which fatigue impact on joints kinematics and kinetics while performing repeated changes of direction (CoDs) in the light of the ACL risk factors.

Methods

This was an observational, cross-sectional associative study. Twenty female players (age: 20-31 years, 1st-2nd Italian division) performed a continuous shuttle run test (5-m) involving repeated 180°-CoDs until exhaustion. During the whole test, 3D kinematics and ground reaction forces were used to compute lower limb joints angles and internal moments. Measures of exercise internal load were: peak post-exercise blood lactate concentration, heart rate (HR) and perceived exertion. Continuous linear correlations between kinematics/kinetics waveforms (during the ground contact phase of the pivoting limb) and the number of consecutive CoD were computed during the exercise using a Statistical Parametric Mapping (SPM) approach.

Results

The test lasted 153 ± 72 s, with a rate of 14 ± 2 CoDs/min. Participants reached 95% of maximum HR and a peak lactate concentration of 11.2 ± 2.8 mmol/L. Exercise duration was inversely related to lactate concentration (r = -0.517, p < 0.01), while neither%HR _max nor [La^-] _b nor RPE were correlated with test duration before exhaustion (p > 0.05). Alterations in lower limb kinematics were found in 100%, and in lower limb kinetics in 85% of the players. The most common kinematic pattern was a concurrent progressive reduction in hip and knee flexion angle at initial contact (10 players); 5 of them also showed a significantly more adducted hip. Knee extension moment decreased in 8, knee valgus moment increased in 5 players. A subset of participants showed a drift of pivoting limb kinematics that matches the known ACL injury mechanism; other players displayed less definite or even opposed behaviors.

Discussion

Players exhibited different strategies to cope with repeated CoDs, ranging from protective to potentially dangerous behaviors. While the latter was not a univocal effect, it reinforces the importance of individual biomechanical assessment when coping with fatigue.

Interval Return to Play Programs for the Tennis Athlete

PURPOSE OF REVIEW

General guidelines exist for return to sport after injury. The goal of these guidelines is to outline phases of recovery that will minimize the risk of reinjury and promote an optimal return to function for the athlete. This paper analyzes the current research pertaining to interval return to play programs with a special focus on the tennis athlete. The authors examine the different components of an interval tennis program and work to develop what they feel are the necessary elements of the optimal return to sport guidelines for tennis athletes. These criteria are based on the available literature, research, and preliminary data collection as well as the personal experiences and clinical observations of the authors.

RECENT FINDINGS

Interval sports programs are typically designed to guide the athlete back to competition after an injury. The current research reveals the obstacles present in implementing an appropriate interval sports program including a lack of consensus on which criteria is actually necessary and relevant. Limited research is present for interval tennis programs. Return to sport competition and sports science is continuously evolving. The authors highlight the necessary components in rehabilitation and performance principles for establishing a comprehensive interval tennis program. In addition, the role of technology in sports rehabilitation is assessed as it pertains to return to play. The authors proposed that interval sports program can help guide and direct future clinicians in their rehabilitation of the tennis athlete.

The interaction of acute physical fatigue with three traditional functional performance tests and the reactive balance test

OBJECTIVES

To assess the impact of acute physical fatigue on traditional and neurocognitive functional performance tests in recreational athletes.

DESIGN

randomized counterbalanced cross-over study, pre-post design SETTING: laboratory PARTICIPANTS: Twenty recreational athletes (age = 24 ± 3 years) MAIN OUTCOME MEASURES: We evaluated fatigue impairments following a 30 s all-out effort in three traditional and one neurocognitive functional performance test. The traditional functional performance tests encompassed the single leg hop for distance (SLH), countermovement jump (CMJ) and Y-balance test (YBT). The neurocognitive functional performance test encompassed the reactive balance test (RBT). A 30 s modified Wingate was used to induce acute physical fatigue.

RESULTS

Acute physical fatigue was successfully induced as indicated by a significant increase in heart rate, systolic blood pressure, blood lactate levels and rating of perceived exertion (p < 0.001). Acute physical fatigue induced significant decreases in RBT accuracy (p = 0.004) and SLH performance (p < 0.001). YBT, CMJ and RBT visuomotor reaction time remained unaffected by acute physical fatigue.

CONCLUSIONS

Acute physical fatigue impairs SLH performance and decreases accuracy in the RBT. YBT and CMJ performance remained unaffected by acute physical fatigue. Clinicians should be aware of this divergent neurocognitive functional impairments caused by one all-out effort to allow well-informed selection of functional performance tests.

Sports Injury Forecasting and Complexity: A Synergetic Approach

The understanding that sports injury is the result of the interaction among many factors and that specific profiles could increase the risk of the occurrence of a given injury was a significant step in establishing programs for injury prevention. However, injury forecasting is far from being attained. To be able to estimate future states of a complex system (forecasting), it is necessary to understand its nature and comply with the methods usually used to analyze such a system. In this sense, sports injury forecasting must implement the concepts and tools used to study the behavior of self-organizing systems, since it is by self-organizing that systems (i.e., athletes) evolve and adapt (or not) to a constantly changing environment. Instead of concentrating on the identification of factors related to the injury occurrence (i.e., risk factors), a complex systems approach looks for the high-order variables (order parameters) that describe the macroscopic dynamic behavior of the athlete. The time evolution of this order parameter informs on the state of the athlete and may warn about upcoming events, such as injury. In this article, we describe the fundamental concepts related to complexity based on physical principles of self-organization and the consequence of accepting sports injury as a complex phenomenon. In the end, we will present the four steps necessary to formulate a synergetics approach based on self-organization and phase transition to sports injuries. Future studies based on this experimental paradigm may help sports professionals to forecast sports injuries occurrence.

Does Mental Fatigue Negatively Affect Outcomes of Functional Performance Tests?

PURPOSE

Mental fatigue impairs psychomotor skill performance by affecting visuomotor reaction time, accuracy, and decision-making. Recently, neurocognitive functional performance tests (FPT) that integrate these outcomes have been developed. The aim of this study was to assess the effect of mental fatigue on traditional and neurocognitive FPT in healthy adults.

METHODS

Fourteen volunteers (four women; mean ± SD age, 22 ± 1 yr; height, 176.9 ± 8.4 cm; weight, 69.7 ± 10.4 kg) participated in a randomized counterbalanced crossover design. A 100% incongruent Stroop color word test of 90 min was used to induce mental fatigue and the control task encompassed watching a 90-min documentary. Traditional FPT comprised a single-leg hop for distance, countermovement jump, and Y-balance test, whereas the neurocognitive FPT encompassed the reactive balance test (RBT). All FPTs were evaluated pre-post the 90-min task. Mental fatigue was assessed using the Stroop task, visual analog scale for mental fatigue, and the Eriksen-Flanker task.

RESULTS

Mental fatigue was successfully induced, as shown by a significant increase in visual analog scale for mental fatigue (P < 0.001), with no decrease in performance on the Stroop and Eriksen-Flanker task. No interaction effect of mental fatigue was found for the Y-balance test, single-leg hop, and countermovement jump. For the RBT accuracy, a significant interaction effect of mental fatigue and time was observed (P = 0.024), with participants performing significantly worse when mentally fatigued. No interaction effect or main effect of condition and time was observed when considering the effect of mental fatigue on visuomotor reaction time in the RBT.

CONCLUSIONS

Mental fatigue negatively affects a neurocognitive FPT, indicated by a decreased accuracy in response to visual stimuli in the RBT. Traditional FPT remained unaffected by mental fatigue.

The Influence of Physical Load on Dynamic Postural Control-A Systematic Replication Study

Dynamic postural control is challenged during many actions in sport such as when landing or cutting. A decrease of dynamic postural control is one possible risk factor for non-contact injuries. Moreover, these injuries mainly occur under loading conditions. Hence, to assess an athlete's injury risk properly, it is essential to know how dynamic postural control is influenced by physical load. Therefore, the study's objective was to examine the influence of maximal anaerobic load on dynamic postural control. Sixty-four sport students (32 males and 32 females, age: 24.11 ± 2.42, height: 175.53 ± 8.17 cm, weight: 67.16 ± 10.08 kg) were tested with the Y-Balance Test before and after a Wingate Anaerobic Test on a bicycle ergometer. In both legs, reach distances (anterior) and composite scores were statistically significantly reduced immediately after the loading protocol. The values almost returned to pre-load levels in about 20 min post-load. Overall, findings indicate an acute negative effect of load on dynamic postural control and a higher potential injury risk during a period of about 20 min post-load. To assess an athlete's sports-specific injury risk, we recommend testing dynamic postural control under loaded conditions.

A Contemporary Approach to Patellofemoral Pain in Runners

Patellofemoral pain (PFP) is among the most common injuries in recreational runners. Current evidence does not identify alignment, muscle weakness, and patellar maltracking or a combination of these as causes of PFP. Rather than solely investigating biomechanics, we suggest a holistic approach to address the causes of PFP. Both external loads, such as changes in training parameters and biomechanics, and internal loads, such as sleep and psychological stress, should be considered. As for the management of runners with PFP, recent research suggested that various interventions can be considered to help symptoms, even if these interventions target biomechanical factors that may not have caused the injury in the first place. In this Current Concepts article, we describe how the latest evidence on education about training modifications, strengthening exercises, gait and footwear modifications, and psychosocial factors can be applied when treating runners with PFP. The importance of maintaining relative homeostasis between load and capacity will be emphasized. Recommendations for temporary or longer-term interventions will be discussed. A holistic, evidence-based approach should consist of a graded exposure to load, including movement, exercise, and running, while considering the capacity of the individual, including sleep and psychosocial factors. Cost, accessibility, and the personal preferences of patients should also be considered.

Effects of Aerobic and Anaerobic Fatigue Exercises on Postural Control and Recovery Time in Female Soccer Players

Sixteen female soccer players (age = 20.19 ± 1.52 years; body mass = 56.52 ± 4.95 kg; body height = 164.81 ± 4.21 cm) with no history of lower extremity injury participated in the study. The Biodex SD Balance system was used to determine the non-dominant single-leg stability. In anaerobic exercise, each subject performed four maximal cycling efforts against a resistance equivalent to 0.075 kg/body mass for 30 s with three-minute rest intervals. In aerobic exercise, subjects performed the Bruce protocol on a motorized treadmill. After each exercise, subjects subsequently performed a single-leg stability test and then repeated the same test for four times with five-minute passive rest periods. In accordance with the results, it was found that the impairment observed right after the aerobic loading was higher (p < 0.001) compared to the anaerobic one. However, the time-related deterioration in both aerobic and anaerobic loadings was similar. The B-pre value was lower than B_post and B₅ (p < 0.01) and B₁₀ (p < 0.05) in both conditions. Subjects could reach the initial balance level at B₁₅ after aerobic and anaerobic loadings. The lactate level did not reach resting value even after 20 min of both fatigue protocols. Although the fatigue after aerobic and aerobic exercise negatively affects a single-leg dynamic balance level, single leg balance ability returns to the baseline status after 10 min of passive recovery duration.