A Comparison of Quadriceps-to-Hamstrings Ratios During Isokinetic Testing, Cutting, and Drop Landings in Male Soccer Players.

Collegiate soccer is not an unusual place to suffer a knee injury. The sport has many dynamic movements, such as cutting, jumping and shooting. Many professionals use quadriceps-to-hamstring (Q/H) ratios as a tool to determine when an injured player can to return to game play or use the ratio to investigate how predisposed a certain player is to sustaining a knee injury. However, many of these ratios are taken in isokinetic testing in a controlled environment and to our knowledge it is unknown if these ratios are similar to those measured during dynamic activity. Therefore, this study investigated if there was a relationship between Q/H ratios measured during isokinetic testing and drop landings and cutting. Fifteen Division 2 collegiate male soccer players (age: 19.79 ± 1.25 years; height: 176.74 ± 6.22 cm; weight: 77.24 ± 11.01 kg). Wearing Athlos© compression shorts participants performed isokinetic testing, drop landings and cutting drills while muscle activity was measured. A significant difference was found between the bilateral Q/H ratios during the drop landings (p = 0.04; η = 0.49). There were no significant bilateral differences measured during the cutting drills in either direction and isokinetic testing (p > 0.05). Additionally, there was so significant relationship in Q/H ratios between isokinetic testing and the dynamic movements (p > 0.05). This suggests that clinicians should use Q/H ratios during dynamic movements rather than isokinetic testing in a controlled environment to better assess player risk disposition and return-to-play criteria.

Gait Retraining as an Intervention for Patellofemoral Pain.

PURPOSE OF REVIEW: Movement retraining in rehabilitation is the process by which a motor program is changed with the overall goal of reducing pain or injury risk. Movement retraining is an important component of interventions to address patellofemoral pain. The purpose of this paper is to review the methods and results of current retraining studies that are aimed at reducing symptoms of patellofemoral pain. RECENT FINDINGS: The majority of studies reviewed demonstrated some improvement in patellofemoral pain symptoms and overall function. However, the degree of improvement as well as the persistence of improvement over time varied between studies. The greatest pain reduction and persistent changes were noted in those studies that incorporated a faded feedback design including between 8 and 18 sessions over 2-6 weeks, typically 3-4 sessions per week. Additionally, dosage in these studies increased to 30-45 min during later sessions, resulting in 177-196 total minutes of retraining. In contrast, pain reductions and persistence of changes were the least in studies where overall retraining volume was low and feedback was either absent or continual. Faulty movement patterns have been associated with patellofemoral pain. Studies have shown that strengthening alone does not alter these patterns, and that addressing the motor program is needed to effect these changes. Based upon the studies reviewed here, retraining faulty patterns, when present, appears to play a significant role in addressing patellofemoral pain. Therefore, movement retraining, while adhering to basic motor control principles, should be part of a therapist's intervention skillset when treating patients with PFP.

Intraindividual Variability and Validity in Smart Apparel Muscle Activity Measurements During Exercise in Men.

The purpose of the study was to compare smart apparel (SA) muscle activity measurements to surface electromyography (sEMG) muscle activity measurements during exercise, and determine if any systematic bias of the apparel exists. Thirty-five male participants (Ages 23.1±2.92 yrs, height 178±0.09 cm, mass 81.14±10.59 kg, body fat percentage 15.4±4.79%) provided informed consent for participation. During two separate exercise sessions, participants performed three sets of 12 bodyweight squats and pushups in both SA and sEMG. Conditions (sEMG or SA) were randomly counterbalanced. During sEMG, sensors were placed at selected anatomical locations on the right side. During SA, sEMG sensors were sewn into the fabric. Percent of maximal voluntary contractions (%MVC) were calculated. Paired t-test were used to analyze group mean differences in %MVC between conditions. Bland & Altman plots were created to determine any systematic bias. A Pearson's product correlation was run to determine any association with intertrial variability and body fat percentage. The alpha levels were set a p<0.05. It was determined that there were no significant differences between %MVC in the SA and sEMG for three of the selected muscles (p>0.05). There was a significant difference in %MVC measured in the SA and sEMG for the RDELT (p=0.02). Specifically, the %MVC for the deltoid during pushups was 11.8% greater compared to sEMG. Intertrial differences were not significantly correlated with %BF (p>0.05). The apparel appears to be valid in the recreational population and appears to have no systematic bias.

The effects of gait retraining in runners with patellofemoral pain: A randomized trial.

BACKGROUND: Running popularity has increased resulting in a concomitant increase in running-related injuries with patellofemoral pain most commonly reported. The purpose of this study was to determine whether gait retraining by modifying footstrike patterns from rearfoot strike to forefoot strike reduces patellofemoral pain and improves associated biomechanical measures, and whether the modification influences risk of ankle injuries. METHODS: Sixteen subjects (n=16) were randomly placed in the control (n=8) or experimental (n=8) group. The experimental group performed eight gait retraining running sessions over two weeks where footstrike pattern was switched from rearfoot strike to forefoot strike, while the control group performed running sessions with no intervention. Variables were recorded pre-, post-, and one-month post-running trials. FINDINGS: Knee pain was significantly reduced post-retraining (P<0.05; effect size=0.294) and one-month follow-up (P<0.05; effect size=0.294). Knee abduction was significantly improved post-retraining (P<0.05; effect size=0.291) and one-month follow-up (P<0.05; effect size=0.291). Ankle flexion was significantly different post-retraining (P<0.05; effect size=0.547), as well as ankle range of motion post-retraining (P<0.05; effect size=0.425) and one-month follow-up (P<0.05; effect size=0.425). INTERPRETATION: Findings suggest running with a forefoot strike pattern leads to reduced knee pain, and should be considered a possible strategy for management of patellofemoral pain in recreational runners. This trial is registered at the US National Institutes of Health (clinicaltrials.gov) #NCT02567123.

Intraindividual Variability in Test-Retest Air Displacement Plethysmography Measurements of Body Density for Men and Women.

Air displacement plethysmography (ADP) is a popular method for estimating body density (Db). Most ADP tests are performed once, with test-retest investigations scarce. Therefore, we investigated test-retest reliability of ADP. Active men (n = 25) and women (n = 25) volunteered and followed standard pretest guidelines. Participants wore dry, form-fitting swimwear and manufacturer-supplied swim caps. In a single session, two ADP trials with measured thoracic gas volume (TGV) were performed without repositioning participants. Separate 2 (sex) × 2 (ADP trial) repeated-measures ANOVAs were performed to investigate within-between comparisons of Db, TGV, body volume (Vb), and relative fatness (%BF). Paired t tests were used to investigate significant differences as appropriate. The Bland and Altman technique was used to depict individual intertrial variations. For all analyses, α =.05. A significant main effect for sex was found; men were lower in %BF and higher in all other variables compared with women. Individual variability was notable (ADP1-ADP2). The range of individual intertrial differences were larger for women than men, respectively, for Db (-0.0096-0.0045 g/cc; -0.0019-0.0054 g/cc), TGV (-0.623-1.325 L; -0.584-0.378 L), Vb (-0.249-2.10 L; -0.234-0.397 L), and %BF (-2.1-4.4%; -0.2-0.9%). When assessing body composition of women via ADP or using Db from ADP in a multicomponent model, at least two trials with measured TGV should be performed and the average of the values recorded and reported.

Rocker-bottom, profile-type shoes do not increase lower extremity muscle activity or energy cost of walking.

The purpose of this study was to determine if wearing rocker-bottom shoes with compliant midsoles (RB) influences muscle activity and metabolic cost of walking. Furthermore, we sought to determine if weight differences between shod conditions accounted for any potential change. Twenty-eight subjects (17 women, 11 men, age 22.8 ± 6.6 years; weight 72 ± 20 kg; height 170 ± 6.7 cm; percent body fat 23.0 ± 11.7) walked on a treadmill (0% grade) for 10 minutes at a self-selected speed plus 10% (1.3 ± 0.2 m·s) in each of the following laboratory-provided shoes: flat-bottomed shoe (W), flat-bottomed shoe weight-matched to RB (WM), and RB. Muscle activity of the right side biceps femoris (BF), rectus femoris (RF), gastrocnemius (GA), and tibalis anterior (TA) was recorded for 30 seconds at the beginning, middle, and ending of the 10-minute walk using an electromyography (EMG) system. The average (AVG) and root mean square (RMS) were calculated from full-wave rectified EMG data at each interval. The rate of oxygen consumption (V[Combining Dot Above]O2) was measured for 10 minutes during each condition. A 3 (shoe) × 3 (time) repeated-measures analysis of variance (ANOVA) was used to compare each EMG-dependent variable (AVG and RMS EMG of each muscle), and repeated measures ANOVA was used to test V[Combining Dot Above]O2. Muscle activity (for any muscle) was not influenced by the interaction of shoe and time (p > 0.05). The AVG and RMS for RF, BF, and GA, including V[Combining Dot Above]O2, were not different among shod conditions (W: 9.7 ± 0.6 ml·kg·min; WM: 10.0 ± 0.5 ml·kg·min; RB: 10.1 ± 0.5 ml·kg·min), whereas TA AVG and RMS were lower during RB (p < 0.05). It seems that there is no increase in muscle activity or metabolic cost while wearing RB beyond the flat-bottomed shoe despite there being the rocker-profile design and mass differences.