Warming-up before sporting activity improves knee position sense

Acute effects of Nordic hamstring exercise on hip and knee joints proprioception

BACKGROUND AND OBJECTIVES

Nordic Hamstring Exercise (NHE) is one of the best exercises proposed for injury prevention of hamstring muscles. However, its effects on lower extremity proprioception are unclear. The aim of this study was to investigate the immediate effects of a single bout of NHE on hip and knee joints' proprioception.

METHODS

Forty collegiate male soccer players participated in this study with a mean age of 22.85 ± 1.82 years and were randomized into either control (n = 20) or experimental (n = 20) groups. Each subject participated in pre-test measurements in which hip and knee active joints position sense (JPS) were assessed in standing and lying tasks using the image-capturing method. The experimental group then performed three sets of NHE with 10 repetitions in each set, while the control group rested for 10 min. Paired and independent t-tests were used for calculating the differences within and between groups on SPSS software, respectively. The level of significance was P ≤ 0.05.

RESULTS

Hip JPS in the lying task and knee JPS in both of the standing and lying tasks were impaired significantly after performing a single bout of NHE (P ≤ 0.05). However, the effects of this exercise on hip JPS in the standing task were not significant (P ≥ 0.05).

CONCLUSIONS

NHE performing with three sets of 10 repetitions can significantly impair hip and knee JPS immediately after exercise and reduce the proprioception acuity of the lower limbs. It is recommended to perform this exercise at a time rather than before training or match sessions.

Comparing shoulder proprioception, upper extremity dynamic stability, and hand grip strength in overhead athletes with and without scapular dyskinesis

INTRODUCTION

Scapular dyskinesis is prevalent among asymptomatic athletes, particularly those involved in overhead activities, and can significantly impact their neuromuscular control. These changes may impair upper extremity function and strength, elevating the risk of injury. Therefore, it is imperative to investigate how scapular dyskinesis affects shoulder proprioception, upper extremity dynamic stability, and hand grip strength in overhead athletes. This study compared these parameters between overhead athletes with and without scapular dyskinesis.

METHODS

The study included twenty asymptomatic professional overhead athletes with scapular dyskinesis and twenty without scapular dyskinesis, identified using the lateral scapular slide test. In this cross-sectional study, shoulder active joint position sense, serving as shoulder proprioception, was measured using an isokinetic dynamometer. Upper extremity dynamic stability and hand grip strength were evaluated using an upper quarter modified star excursion balance test (UQ-mSEBT) and a handheld dynamometer.

RESULTS

The study found that the shoulder active joint position sense was significantly lower in the scapular dyskinesis group compared to the group without scapular dyskinesis (PExternal Rotation = 0.003, PInternal Rotation < 0.001, and PForward Flexion = 0.002). However, the two groups had no significant differences in UQ-mSEBT and hand grip strength scores.

CONCLUSIONS

The results showed that scapular dyskinesis could affect the sense of shoulder active joint position among asymptomatic overhead athletes. However, it did not affect their upper extremity dynamic stability and hand grip strength.

Reference value of knee position sense in weight-bearing and non-weight-bearing conditions

BACKGROUND

Our study aimed to identify age-related changes in knee proprioception to provide reference values for weight-bearing (WB) and non-weight-bearing (NWB) conditions and to identify factors (age, WB condition, dominance, and sex) that can affect knee proprioception.

METHODS

A total of 84 healthy adult men and women were recruited. Active knee joint position sense (JPS) was measured using a digital inclinometer for knee proprioception. The participants performed the required movements actively, with verbal feedback from the examiner, slowly moving to the target angles (30° and 50°) and maintaining them for 5 s before returning to the starting position. Afterward, without assistance from the examiner, the participants actively moved back to the same angle, and the examiner confirmed the angles. This procedure was repeated twice for each target angle, and the average values were used as the data. The participants were barefoot, wearing shorts, and closed their eyes while the measurements were obtained. The measurements were first obtained on the dominant side under the NWB conditions. When a change in posture was needed during the measurement, the participants sat in a resting position for 2 min.

RESULTS

Except for age, all other factors (WB condition, dominance, sex) were not statistically significant. Age showed a significant difference in knee JPS, except for the non-dominant side at 30° and the dominant side at 50° in the NWB condition.

CONCLUSION

This study indicates that the WB condition, dominant side, and sex need not be considered when measuring and assessing knee JPS. Age shows a negative correlation with knee joint position sense, and the reference values presented in this study can be used as objective target values during the rehabilitation process.

Investigating post-mild traumatic brain injury neuromuscular function and musculoskeletal injury risk: A protocol for a prospective, observational, case-controlled study in service members and active individuals

INTRODUCTION

Musculoskeletal injury (MSKI) risk is increased following mild traumatic brain injury (mTBI). Increased MSKI risk is present up to 2 years following post-mTBI return-to-duty/activity relative to both non-mTBI peers and to their pre-mTBI selves across a range of populations, including military service members, and professional, college and high school athletes. Despite the well documented increased post-mTBI MSKI risk, the underlying neuromuscular mechanisms contributing to this increased risk have yet to be definitively determined. A number of potential mechanisms have been suggested (eg, aberrant kinematics, dynamic balance impairments, lower voluntary muscle activation), but none have been confirmed with a comprehensive, prospective study. This study aims to: (1) elucidate the neuromuscular control mechanisms following mTBI that contribute to increased MSKI risk, and (2) prospectively track patient outcomes (up to 12 months; MSKI occurrences and patient-reported outcomes (PRO)).

METHODS AND ANALYSIS

This is a multicentre prospective, case-matched control observational study to identify deficiencies in neuromuscular function following mTBI that may contribute to increased MSKI risk. Participants (aim to recruit 148, complete data collection on 124) will be classified into two cohorts; mTBI and control. All participants will undergo longitudinal (initial, 6 weeks post-initial, 12 weeks post-initial) comprehensive three-dimensional biomechanical (jump-landing; single leg hop; cut; gait), neuromuscular (interpolated twitch technique, muscular ramp contraction) and sensory (joint repositioning; light touch sensation) assessments to elucidate the underlying neuromuscular control mechanisms post-mTBI that may contribute to increased MSKI. Occurrences of MSKI and PROs (National Institutes of Health Patient-Reported Outcome Measurement Information System: Physical Function, Pain Interference, Depression, Anxiety; Brief Resilience Scale; Tampa Scale of Kinesiophobia), will be tracked monthly (up to 1 year) via electronic data capture platforms.

ETHICS AND DISSEMINATION

The study received approval from the Walter Reed National Military Medical Center Institutional Review Board. Results will be made available to the associated funding agency and other researchers via conference proceedings and journal articles.

TRIAL REGISTRATION NUMBER

NCT05122728.

The Clinical Benefits of a Dynamic vs. Static Component as Part of a Comprehensive Warm-Up for Recreational Sports Players with Clinical Histories of Hamstring Injuries: A Randomized Clinical Trial

Background: Few previous studies have analyzed the effects of certain specific static and dynamic warm-up components on recreational sports players with a previous hamstring injury. Therefore, the aim of this study was to analyze changes in some modifiable and external risk factors after (immediately and in a follow-up assessment after 10 min) a static or dynamic warm-up program on recreational sports players with a previous hamstring injury. Methods: A total of 62 participants were randomized into 2 groups: static warm-up (SW) (n = 31) or dynamic warm-up (DW) (n = 31). Range of movement (RoM), perceived pain, the pressure−pain threshold, and joint position sense were assessed at baseline, immediately after the intervention and 10 min afterwards. The intervention for the SW (hot pack procedures in both hamstring muscles) lasted 20 min. The DW intervention consisted of a running exercise performed on a treadmill for 10 min. Results: Both groups showed statistically significant changes (p ≤ 0.05) in the primary outcomes (perceived pain and the pressure−pain threshold) at the three measurement times (this was also true for RoM for the SW group, with statistically significant differences only between times from the baseline to the 10-min follow-up; p ≤ 0.05, d = 0.23). The intra-group secondary outcome showed no statistically significant changes (p > 0.05) in both groups (except for the period from the baseline−immediately after in the DW group; p ≤ 0.05, d = 0.53). The comparison between groups showed no statistically significant differences for any of the variables analyzed. (p ≥ 0.05). Conclusion: The present findings suggest that both specific warm-up modalities seem to positively influence perceived pain on stretching and the pressure threshold; however, the significant reduction in the joint repositioning error and the larger effect sizes observed in the DW group suggest that this method has a greater beneficial impact in recreational sports players with clinical histories of hamstring injuries.

The Effect of a Handball Warm-Up Program on Dynamic Balance among Elite Adolescent Handball Players

This study examined the effect of the handball warm-up program (HWP) on dynamic balance among elite adolescent handball players. In this case, 24 handball players were randomly assigned into experimental warm-up and control groups. The HWP was performed over 8 weeks (3 times per week). Dynamic balance before and after the intervention training programs were measured by the Biodex Balance System (BBS) and Y Balance test for the dominant (DL) and non-dominant legs (non-DL). After HWP training, BBS scores significantly improved in the overall (OSI) (30.4% and 31.1%), anterior-posterior (APSI) (44.6% and 35.2%), and medial-lateral stability indexes (MLSI) (38.8% and 43%) for both DL and non-DL. Post-training, the Y Balance test exhibited significant improvements in OSI (13.2% and 10.6%), anterior (17.2% and 12.6%), posteriolateral (12.8% and 11.3%), and posteriomedial stability indexes (9.2% and 7.9%) with DL and non-DL, respectively. In conclusion, dynamic balance improved overall after eight weeks of the HWP, with this improvement significantly greater with the trained versus the control group. Optimal balance during handball is an important factor to ensure coordinated and efficient movements and it is speculated that improved balance could positively impact injury prevention. Hence, the HWP program can be used as an alternative to a conventional warm-up program.

Acute Impact of Proprioceptive Exercise on Proprioception and Balance in Athletes

This study aimed to compare the acute effect of a proprioceptive exercise session and a non-specific exercise session on knee position sense, and the static and dynamic balance of athletes. Sixty male athletes (19.4 ± 1.2 years) participated in a within-subjects repeated-measures study. Knee position sense in closed kinetic chain, and static (BESS test) and dynamic balance (Y-balance test) were measured before and after two exercise sessions, consisting of 10 min of non-specific exercise in a cycle-ergometer or proprioceptive exercise with an unstable platform. Overall, both exercise sessions significantly improved knee position sense, BESS score, and YBT composite score, and no differences were detected between proprioceptive and non-specific sessions (knee position sense, −6.9 ± 65.2% vs. −11.5 ± 75.0%, p = 0.680; BESS, −19.3 ± 47.7% vs. −29.03 ± 23.5%, p = 0.121; YBT, 2.6 ± 2.7% vs. 2.2 ± 2.2%, p = 0.305). Twenty athletes did not improve knee position sense after the exercise session (non-responders). When analyzing only the exercise responders, both sessions improved knee position sense, but the improvement was greater after the proprioceptive exercise session (56.4 ± 25.6% vs. 43.8 ± 18.9%, p = 0.023). In conclusion, a single proprioceptive, as well as non-specific, exercise session increased knee position sense and balance. The proprioceptive exercise seems to be more effective in improving joint position sense when considering only athletes who respond to the intervention.

The effect of static stretching of agonist and antagonist muscles on knee joint position sense

Background/Aims

Proprioception acuity is important in sports activities and stretching is widely used in warm-up programmes. The main objective of this study was to evaluate if a warm-up programme with and without stretching flexors and extensors muscles could affect knee joint position sense.

Methods

The effects of different stretching regimens on joint position sense were examined. A total of 12 semi-professional football players completed four warm-up sessions over 4 weeks: standard warm-up programme; standard warm-up programme with quadriceps stretching; standard warm-up programme with hamstring stretching; and standard warm-up programme with stretching of both quadriceps and hamstrings. Open kinetic chain knee joint position sense was estimated from the ability to reproduce the three target angles (20°, 45° and 60° knee flexion) in the dominant limb before and after the intervention.

Results

In the absolute angular error, there was a statistically significant three-way interaction between the warm-up programme, target angle and time (F (6, 54)=6.88, P=0.001). Findings of post-hoc analysis demonstrated that there was a statistically significant difference between the pre- and post-stretching of hamstrings for the target angles of 20° (4.70 vs 1.57, P=0.01), 45° (1.70 vs 4.50, P=0.02), and 60° (1.93 vs 4.20, P=0.02). In the relative angular error, interaction of time by the warm-up programme was significant (F (3, 27)=3.41, P=0.03).

Conclusions

The warm-up programme with static stretching of hamstrings had a negative effect on open kinetic chain knee joint position sense during the flexion to extension repositioning task, which may not only have a negative effect on performance of athletes as a part of warm-up exercises, but may also lead to further injuries.

Does delayed onset muscle soreness affect the biomechanical variables of the drop vertical jump that have been associated with increased ACL injury risk? A randomised control trial

INTRODUCTION

Delayed onset muscle soreness (DOMS) and Anterior Cruciate Ligament (ACL) injuries are both prevalent in sport. It is currently unknown whether DOMS increases ACL injury risk.

AIM

This study aimed to provide preliminary insight on whether DOMS affects ACL injury risk by investigating whether DOMS affects the biomechanical variables of the DVJ that have been identified as risk factors for future ACL injury.

METHODS

This was a randomised control trial involving 32 active individuals aged 18-35 years, with no history of ACL injury. Participants underwent two sessions of force-plate testing and 3D motion analysis of the drop vertical jump (DVJ). The DVJ was chosen as it has been investigated prospectively for association with future ACL injury. Initial testing was followed by randomisation to DOMS or control group. The DOMS group underwent a DOMS-inducing exercise protocol, the control group did not. Both groups were re-tested 48 h after initial testing. Five variables of the DVJ that have been associated with future ACL injury were chosen for analysis - peak knee flexion angle, peak vertical ground reaction force, ground contact time, peak knee abduction angle & peak knee abduction moment. Between-group differences were compared using a two-way mixed analysis of variance; alpha level set to 0.05.

RESULTS

DOMS was successfully induced in all participants of the DOMS group however no statistically significant group x time interactions were found for any of the five variables analysed.

CONCLUSIONS

DOMS did not affect the biomechanical variables of the DVJ that have been associated with future ACL injury. By extension, this may suggest that DOMS might not affect ACL injury risk. However, it is also possible that certain attributes of the DVJ meant that any effect of DOMS was simply unable to be quantified, even if an effect existed. All considered, our position is that conclusion cannot be drawn from this study alone on whether DOMS affects ACL injury risk. Further research is required.

Effects of 2 Different External Loads on Joint Position Sense and the Relationship Between Muscle Strength and Force Sense

CONTEXT

Joint position sense (JPS) tests of proprioception lack ecological validity because the testing conditions are so different from the normal function that they can contribute little to understanding the role proprioception plays in daily and sporting activities.

OBJECTIVE

To evaluate the effect of low and high external load on the knee JPS and to investigate the relationship between maximum voluntary isometric contraction and force sense (FS).

DESIGN

Experimental study.

SETTING

Research laboratory.

PARTICIPANTS

A total of 47 volunteers with no history of knee pathology.

INTERVENTIONS

Three active JPS tests performed with no load, low load, and high load were compared at the 45° target angle. For isometric FS test, 50% load was used. For isotonic low load and high load JPS tests, 30% and 70% loads were applied, respectively.

MAIN OUTCOME MEASURES

To analyze obtained data set 2-way multiple analysis of variance, repeated measures of analysis of variance, paired sample t test, and the Pearson correlation coefficient were used.

RESULTS

JPS was not affected by gender (male and female) and activity levels (sedentary, recreational, and trained). Results of the repeated measure of analysis of variance demonstrated the significant main effect of loads (P = .001). Significant differences were found between no load, low load, and high load JPS (P = .001). A positive and significant correlation was found between maximum voluntary isometric contraction and FS error values (r = .41, P = .001).

CONCLUSIONS

The results suggest that as the load level increases, the knee JPS improves. Knee JPS assessed under external load may be a more appropriate alternative to the nature of the sport. Those with higher muscle strength have a worse FS.

Effects of Combining Running and Practical Duration Stretching on Proprioceptive Skills of National Sprinters

Romero-Franco, N, Párraga-Montilla, JA, Molina-Flores, EM, and Jiménez-Reyes, P. Effects of combining running and practical duration stretching on proprioceptive skills of national sprinters. J Strength Cond Res 34(4): 1158-1165, 2020-Practical duration stretching after aerobic activities is a recommended component of the first part of warm-up because of its effects on performance. However, its effects on proprioceptive skills are unknown. This study aimed to analyze the effects of running and practical duration static stretching (SS) and dynamic stretching (DS) on postural balance and the joint position sense (JPS) of national sprinters. Thirty-two national sprinters were randomly classified into a SS group (n = 11), DS group (n = 11), or control group (n = 10). Static stretching performed 5 minutes of running and short-duration (20 seconds) static stretches; DS performed 5 minutes of running and short-duration dynamic (20 seconds) stretches; and the control group performed 5 minutes of running. Before and after the intervention, unipedal static postural balance and knee JPS were evaluated. Static stretching exhibited a more centralized center of pressure in the medial-lateral plane for unipedal static postural balance in right-leg support after stretching (p = 0.005, d = 1.24), whereas DS showed values further from the center after stretching for the same unipedal support compared with baseline (p = 0.042, d = 0.49), and the control group remained stable (p > 0.05). Joint position sense did not show significant differences in any group (p > 0.05). In conclusion, combining running and practical duration SS may be beneficial for right-leg postural stabilization, whereas DS may be partly and slightly deleterious. Both SS and DS combined with running and running alone have neutral effects on knee JPS. Sports professionals should consider running and practical duration SS as part of the warm-up of sprinters to partly improve unipedal static postural balance.

Immediate effects of neurodynamic nerve gliding versus static stretching on hamstring neuromechanical properties

PURPOSE

We investigated the immediate effects of neurodynamic nerve gliding (ND) on hamstring flexibility, viscoelasticity, and mechanosensitivity, compared with traditional static stretching (ST).

METHODS

Twenty-two physically active men aged 21.9 ± 1.9 years were divided randomly into two equal intervention groups using ST or ND. An isokinetic dynamometer was used to measure the active knee joint position sense, perform passive knee extension, record the passive extension range of motion (ROM) and the passive-resistive torque of hamstrings. Stiffness was determined from the slope of the passive torque-angle relationship. A stress relaxation test (SRT) was performed to analyze the viscoelastic behavior of the hamstrings. The passive straight leg raise (SLR) test was used to evaluate hamstring flexibility.

RESULTS

A significant interaction was observed for ROM and passive ultimate stiffness, reflected by an increase in these indicators after ND but not after SD. SLR increased significantly in both groups. After ST, a significantly faster initial stress relaxation was observed over the first 4 s. than after ND. There was no significant change in the active knee joint position sense.

CONCLUSIONS

ND provided a slightly greater increase in hamstring extensibility and passive stiffness, possibly by decreasing nerve tension and increasing strain in connective tissues than ST. The ST mostly affected the viscoelastic behavior of the hamstrings, but neither intervention had a significant impact on proprioception.

Jogging and Practical-Duration Foam-Rolling Exercises and Range of Motion, Proprioception, and Vertical Jump in Athletes

CONTEXT

Foam-rolling exercises are frequently included in warmups due to their benefits for increasing range of motion (ROM). However, their effects on proprioception and vertical jump have not been analyzed and therefore remain unclear. Moreover, the effects of performing practical-duration foam-rolling exercises after typical warmup exercises such as jogging are unknown.

OBJECTIVE

To analyze the effects of jogging and practical-duration foam-rolling exercises on the ROM, knee proprioception, and vertical jump of athletes.

DESIGN

Randomized controlled study.

SETTING

Sports laboratory and university track.

PATIENTS OR OTHER PARTICIPANTS

Thirty athletes were randomly classified into an experimental group (EG) or control group (CG).

INTERVENTION(S)

The EG performed 8-minute jogging and foam-rolling exercises. The CG performed 8-minute jogging.

MAIN OUTCOME MEASURE(S)

Knee flexion, hip extension, active knee extension, ankle dorsiflexion (ADF), knee-joint position sense, and countermovement jump (CMJ) were evaluated before the intervention (baseline), after (post 0 min), and 10 minutes later.

RESULTS

The EG exhibited higher values for ADF and CMJ at post 0 min (ADF: P < .001, d = 0.88; CMJ: P < .001, d = 0.52) and 10 minutes later (ADF: P = .014, d = 0.41; CMJ: P = .006, d = 0.22) compared with baseline. Although the CG also showed increased CMJ at post 0 min (P = .044, d = 0.21), the EG demonstrated a greater increase (P = .021, d = 0.97). No differences were found in the remaining ROM variables (knee flexion, hip extension, active knee extension: P values > .05). For knee-joint position sense, no differences were found (P > .05).

CONCLUSIONS

Combining jogging and practical-duration foam rolling may increase ADF and CMJ without affecting knee proprioception and hip or knee ROM. Jogging by itself may slightly increase ADF and CMJ, but the results were better and were maintained after 10 minutes when foam rolling was added.

Effect of Force Sense to Active Joint Position Sense and Relationships between Active Joint Position Sense, Force Sense, Jumping and Muscle Strength

We aimed to investigate the effect of external load on the joint position sense (JPS) accuracy and its relation to the target jump height. The present study also aimed to explore the relationship between force sense (FS) and maximum voluntary isometric contraction (MVIC). Participants' MVIC levels were determined during the 45-degree knee extension task. Then, participants were asked to execute a knee JPS task with external load (EL-JPS) and with no-load (EL-JPS). To assess jumping accuracy participants were instructed to jump with their 50% of maximum jump height. Results indicated that EL-JPS error values were lower than NL-JPS. EL-JPS was correlated to jumping errors. However, the relationship between NL-JPS and jumping errors was not significant. A significant correlation was found between MVIC and FS errors.

Balance and proprioception responses to FIFA 11+ in amateur futsal players: Short and long-term effects

Background: The FIFA 11+ has shown positive effects on balance and proprioception parameters in football players. As there have been very few research studies involving futsal, we examined the short and long term effects of the FIFA 11+ on static and dynamic balance, as well as proprioception in male amateur futsal players. Methods: Seventy-one male futsal players were randomized to two groups (FIFA 11+: n = 37, age: 27.33 ± 4.33 years; Control: n = 34, age: 25.55 ± 4.65 years). Intervention lasted 10 weeks, 2 sessions per week, succeeded by a 10-week follow-up period. For balance testing, we assessed the single-legged postural sway with a force platform (static balance) and the Y balance test (dynamic balance). Proprioception was assessed with active joint position sense testing. Results: Complete pre-post intervention and follow-up tests were available for 61 players. The FIFA 11+ group showed higher training exposure and lower body mass index and body weight. After adjustment for baseline differences, no significant differences between groups were observed in the pre-post changes for centre of pressure measures, Y-balance and proprioception parameters both at short and long-term. Conclusions: Performing FIFA 11+ for 10 weeks did not improve static and dynamic balance as well as proprioception in amateur futsal players.

Validity and Reliability of a Digital Inclinometer to Assess Knee Joint Position Sense in an Open Kinetic Chain

Context: New methods are being validated to easily evaluate the knee joint position sense (JPS) due to its role in the sports movement and the risk of injury. However, no studies to date have considered the open kinetic chain (OKC) technique, despite the biomechanical differences compared with closed kinetic chain movements. Objective: To analyze the validity and reliability of a digital inclinometer to measure the knee JPS in the OKC movement. Design: The validity and intertester and intratester reliability of a digital inclinometer for measuring knee JPS were evaluated. Setting: Sports research laboratory. Participants: A total of 18 athletes (11 males and 7 females; 28.4 [6.6] y; 71.9 [14.0] kg; 1.77 [0.09] m; 22.8 [3.2] kg/m²) voluntary participated in this study. Main Outcomes Measures: Absolute angular error (AAE), relative angular error (RAE), and variable angular error (VAE) of knee JPS in an OKC. Results: Intraclass correlation coefficient (ICC) and standard error of the mean (SEM) were calculated to determine the validity and reliability of the inclinometer. Data showed excellent validity of the inclinometer to obtain proprioceptive errors compared with the video analysis in JPS tasks (AAE: ICC = .981, SEM = 0.08; RAE: ICC = .974, SEM = 0.12; VAE: ICC = .973, SEM = 0.07). Intertester reliability was also excellent for all the proprioceptive errors (AAE: ICC = .967, SEM = 0.04; RAE: ICC = .974, SEM = 0.03; VAE: ICC = .939, SEM = 0.08). Similar results were obtained for intratester reliability (AAE: ICC = .861, SEM = 0.1; RAE: ICC = .894, SEM = 0.1; VAE: ICC = .700, SEM = 0.2). Conclusions: The digital inclinometer is a valid and reliable method to assess the knee JPS in OKC. Sport professionals may evaluate the knee JPS to monitor its deterioration during training or improvements throughout the rehabilitation process.

A New Direction to Athletic Performance: Understanding the Acute and Longitudinal Responses to Backward Running

Backward running (BR) is a form of locomotion that occurs in short bursts during many overground field and court sports. It has also traditionally been used in clinical settings as a method to rehabilitate lower body injuries. Comparisons between BR and forward running (FR) have led to the discovery that both may be generated by the same neural circuitry. Comparisons of the acute responses to FR reveal that BR is characterised by a smaller ratio of braking to propulsive forces, increased step frequency, decreased step length, increased muscle activity and reliance on isometric and concentric muscle actions. These biomechanical differences have been critical in informing recent scientific explorations which have discovered that BR can be used as a method for reducing injury and improving a variety of physical attributes deemed advantageous to sports performance. This includes improved lower body strength and power, decreased injury prevalence and improvements in change of direction performance following BR training. The current findings from research help improve our understanding of BR biomechanics and provide evidence which supports BR as a useful method to improve athlete performance. However, further acute and longitudinal research is needed to better understand the utility of BR in athletic performance programs.

Effect of static and dynamic muscle stretching as part of warm up procedures on knee joint proprioception and strength

BACKGROUND

The importance of warm up procedures prior to athletic performance is well established. A common component of such procedures is muscle stretching. There is conflicting evidence regarding the effect of static stretching (SS) as part of warm up procedures on knee joint position sense (KJPS) and the effect of dynamic stretching (DS) on KJPS is currently unknown. The aim of this study was to determine the effect of dynamic and static stretching as part warm up procedures on KJPS and knee extension and flexion strength.

METHODS

This study had a randomised cross-over design and ten healthy adults (20±1years) attended 3 visits during which baseline KJPS, at target angles of 20° and 45°, and knee extension and flexion strength tests were followed by 15min of cycling and either a rest period (CON), SS, or DS and repeat KJPS and strength tests. All participants performed all conditions, one condition per visit.

RESULTS

There were warm up×stretching type interactions for KJPS at 20° (p=0.024) and 45° (p=0.018), and knee flexion (p=0.002) and extension (p<0.001) strength. The SS and DS improved KJPS but CON condition did not and SS decreased strength. No change in strength was present for DS or CON.

CONCLUSIONS

Both SS and DS improve KJPS as part of pre-exercise warm up procedures. However, the negative impact of SS on muscle strength limits the utility of SS before athletic performance. If stretching is to be performed as part of a warm up, DS should be favoured over SS.

Influence of warm-up duration and recovery interval prior to exercise on anaerobic performance

The purpose of the study was to determine the impact of different active warm-up (AWU) durations and the rest interval separating it from exercise on anaerobic performance. Eleven male physical education students (22.6 ± 2.52 years; 179.2 ± 4.3 cm; 82.5 ± 9.7 kg; mean ± SD) participated in a cross-over randomized study, and they all underwent the Wingate test after three AWU durations: 5 min (AWU5), 15 min (AWU15) and 20 min (AWU20), with recovery (WREC) or without a recovery interval (NREC) separating the AWU and anaerobic exercise performance. All the AWUs consisted of pedalling at a constant pace of 60 rpm at 50% of the maximal aerobic power. The rest interval between the end of warm-up and the beginning of exercise was set at 5 min. During the Wingate test, peak power (PP), mean power (MP) and the fatigue index (FI) were recorded and analysed. Oral temperature was recorded at rest and at the end of the warm-up. Likewise, rest, post-warm-up and post-Wingate heart rate (HR) and rating of perceived exertion (RPE) were recorded during each session. The ANOVA showed a significant effect of recovery interval, warm-up duration and measurement point on RPE scores (P<0.001). Although the effect of AWU duration on MP and PP was significant (P<0.05), the effect of the recovery interval on both parameters was not significant (P>0.05). Moreover, the analyses showed a significant interaction between recovery interval and AWU duration (P<0.001 and P<0.05 for MP and PP respectively). The AWU15 duration improves the MP and PP when associated with a recovery interval prior to exercise of 5 min. However, the AWU5 duration allows better improvement of power output when the exercise is applied immediately after the warm-up. Consequently, physically active males, as well as educators and researchers interested in anaerobic exercise, must take into account the duration of warm-up and the following recovery interval when practising or assessing activities requiring powerful lower limb muscle contractions.

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

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

Unipedal Postural Balance and Countermovement Jumps After a Warm-up and Plyometric Training Session: A Randomized Controlled Trial

The purpose of this study was to analyze the immediate effects of a plyometric training protocol on unipedal postural balance and countermovement jumps. In addition, we analyzed the effects of a warm-up on these parameters. Thirty-two amateur male sprinters (24.9 ± 4.1 years; 72.3 ± 10.7 kg; 1.78 ± 0.05 m; 22.6 ± 3.3 kg·m) were randomly sorted into a control group (n = 16) (they did not perform any physical activity) and a plyometric training group (n = 16) (they performed a 15-minute warm-up and a high-intensity plyometric protocol consisting of 10 sets of 15 vertical jumps). Before and after the warm-up, and immediately after and 5 minutes after the plyometric protocol, all athletes indicated the perceived exertion on calf and quad regions on a scale from 0 (no exertion) to 10 (maximum exertion). They also carried out a maximum countermovement jump and a unipedal postural balance test (athletes would remain as still as possible for 15 seconds in a left leg and right leg support stance). Results showed that, in the plyometric group, length and velocity of center-of-pressure movement in right leg support stance increased compared with baseline (p = 0.001 and p = 0.004, respectively) and to the control group (p = 0.035 and p = 0.029, respectively) immediately after the plyometric protocol. In addition, the countermovement jump height decreased right after the plyometric protocol (p < 0.001). The perceived exertion on calf and quad regions increased after the plyometry (p < 0.001). Five minutes later, these parameters remained deteriorated despite a slight recovery (length: p = 0.044; velocity: p = 0.05; countermovement jump height: p < 0.001; local exertion: p < 0.001). Data also showed that countermovement jump height improved after the warm-up (p = 0.021), but unipedal postural balance remained unaltered. As a conclusion, high-intensity plyometric exercises blunt unipedal postural balance and countermovement jump performance. The deterioration lasts at least 5 minutes, which may influence future exercises in the training session. Coaches should plan the training routine according to the immediate effects of plyometry on postural balance and vertical jumps, which play a role in injury prevention and sports performance.

Joint-position sense is altered by football pre-participation warm-up exercise and match induced fatigue

BACKGROUND

The demands to which football players are exposed during the match may augment the risk of injury by decreasing the sense of joint position. This study aimed to assess the effect of pre-participation warm-up and fatigue induced by an official football match on the knee-joint-position sense of football players.

METHODS

Fourteen semi-professional male football players (mean age: 25.9±4.6 years old) volunteered in this study. The main outcome measures were rate of perceived exertion and knee-joint-position sense assessed at rest, immediately after a standard warm-up (duration 25 min), and immediately after a competitive football match (90 minutes duration).

RESULTS

Perceived exertion increased significantly from rest to the other assessments (rest: 8.6±2.0; after warm-up: 12.1±2.1; after football match: 18.5±1.3; p<0.001). Compared to rest, absolute angular error decreased significantly after the warm-up (4.1°±2.2° vs. 2.0°±1.0°; p=0.0045). After the match, absolute angular error (8.7°±3.8°) increased significantly comparatively to both rest (p=0.001) and the end of warm-up (p<0.001). Relative error showed directional bias with an underestimation of the target position, which was higher after the football match compared to both rest (p<0.001) and after warm-up (p<0.001).

CONCLUSIONS

The results indicate that knee-joint-position sense acuity was increased by pre-participation warm-up exercise and was decreased by football match-induced fatigue.

CLINICAL RELEVANCE

Warm-up exercises could contribute to knee injury prevention, whereas the deleterious effect of match-induced fatigue on the sensorimotor system could ultimately contribute to knee instability and injury.

Comparison of the effect of weight-bearing and non-weight-bearing positions on knee position sense in patients with chronic stroke

[Purpose] The purpose of this study was to investigate the knee joint proprioception in weight-bearing (WB) and non-weight-bearing (NWB) positions and to study the difference between the methods in chronic stroke patients. [Subjects and Methods] The subjects were 15 stroke patients who were randomly scheduled to perform both positions by a physical therapist not involved in the study. The subjects performed the positions (WB and NWB) based on a randomized controlled cross-sectional design. WB subjects were positioned in one-leg standing to assess the knee joint position sense. NWB subjects were instructed to sit comfortably in a chair and maintain the knees at 90° of flexion with the leg out of the plinth. [Results] The results revealed that the WB position showed a significant difference in knee position sense. The proprioception sense in the WB position was a higher than that in the NWB position. [Conclusion] The knee proprioception of chronic stroke patients differs between the weight-bearing and non-weight-bearing positions.

Effect of different warm-up strategies on simulated laparoscopy performance: a randomized controlled trial

OBJECTIVE

The objective of this trial was to assess which type of warm-up has the highest effect on virtual reality (VR) laparoscopy performance. The following warm-up strategies were applied: a hands-on exercise (group 1), a cognitive exercise (group 2), and no warm-up (control, group 3).

DESIGN

This is a 3-arm randomized controlled trial.

SETTING

The trial was conducted at the department of surgery of the University Hospital Basel in Switzerland.

PARTICIPANTS

A total of 94 participants, all laypersons without any surgical or VR experience, completed the study.

RESULTS

A total of 96 participants were randomized, 31 to group 1, 31 to group 2, and 32 to group 3. There were 2 postrandomization exclusions. In the multivariate analysis, we found no evidence that the intervention had an effect on VR performance as represented by 6 calculated subscores of accuracy, time, and path length for (1) camera manipulation and (2) hand-eye coordination combined with 2-handed maneuvers (p = 0.795). Neither the comparison of the average of the intervention groups (groups 1 and 2) vs control (group 3) nor the pairwise comparisons revealed any significant differences in VR performance, neither multivariate nor univariate. VR performance improved with increasing performance score in the cognitive exercise warm-up (iPad 3D puzzle) for accuracy, time, and path length in the camera navigation task.

CONCLUSIONS

We were unable to show an effect of the 2 tested warm-up strategies on VR performance in laypersons. We are currently designing a follow-up study including surgeons rather than laypersons with a longer warm-up exercise, which is more closely related to the final task.

Agreement between weight bearing and non-weight bearing joint position replication tasks at the knee and hip

Peak joint angles assumed during the stance phase of running may indicate a runner's ability to sense limb position in space. Joint position sense can be assessed through weight bearing and non-weight bearing tasks. The purpose of this investigation was to determine if weight bearing and non-weight bearing knee and hip joint replication tasks elicited similar joint position sense test results. Absolute replication error was measured during sagittal plane knee and frontal plane hip conditions on 23 healthy runners. Three-dimensional kinematics was recorded during running. Intraclass correlation coefficients (ICCs) determined agreement between the two measures of joint position sense. Pearson's correlation coefficients measured the relationship between hip and knee absolute error and peak joint angles during running. Despite similar mean absolute error, ICCs indicated low agreement between weight bearing and non-weight bearing conditions at each joint. The results indicate the tests are not interchangeable. Absolute error for non-weight bearing hip replication was correlated with peak stance hip adduction during running. Weight bearing and non-weight bearing joint position sense tasks within the knee and hip joints measure joint position sense differently. Therefore, a task that is relevant to the activity of interest should be selected to measure joint position sense.

Lower extremity joint position sense in runners with and without a history of knee overuse injury

Kinematic and kinetic analyses are routinely implemented to determine if gait differences exist between runners with and without a history of knee injury. Hip and knee kinematic differences have been reported between knee injured and non-injured runners. Yet, there is no consensus on whether these differences are the primary variables contributing to knee injury. Furthermore, there may be additional underlying factors that contribute to the development of injury that cannot be determined by gait analysis. The purpose of this investigation was to determine if joint position sense differences exist in runners with and without a history of knee overuse injury. Sagittal plane knee and hip joint position sense was measured in 13 runners with a history of knee overuse injury and 13 runners with no history of knee overuse injury. Absolute joint position replication error was measured during both a weight bearing and a non-weight bearing condition. Joint position replication errors at each joint were compared among groups and task using a two-way ANOVA with joint task as the repeated measure. Knee and hip joint replication errors were similar between both groups. The weight bearing and non-weight bearing tasks resulted in similar joint position replication errors. There were no interaction effects. In conclusion, knee flexion and hip adduction joint position sense is similar in runners with and without a history of knee overuse injury. Therefore, joint position sense measured via weight bearing and non-weight bearing joint position replication tasks may not play an important role in the development of knee overuse injury.