Investigation into the Effects of Backrest Angle and Stick Location on Female Strength

Objectives: The purpose of this study was to investigate the effects of backrest angle and hand maneuver direction on maximum hand strength and to recommend a strength value for the hand-controlled stick of an aircraft. Methods: Forty-eight female subjects were recruited to perform simulated forward–backward and adduction–abduction maneuvers using control sticks. Each subject was free from musculoskeletal disorders and pain. The independent variables included four control maneuvers (forward, backward, adduction, abduction), two right-hand control stick locations (central, side), and three backrest angles (90°, 103°, 108°). The dependent variable was maximum hand strength. Results: The maximum strength for forward maneuvers with both central and side sticks was strongest at a 90° backrest angle (p < 0.001). The maximum strength for adduction maneuvers with both central and side sticks was also strongest at a 90° backrest angle (p < 0.001). On the other hand, the highest strength was observed at a 108° backrest angle when pulling the stick backward (p < 0.001). The abduction strength was significantly stronger than the adduction strength with a central stick (p < 0.001), but the adduction strength was significantly stronger than the abduction strength with a side stick (p < 0.001–p = 0.017). The forward and abduction strength were significantly different in different locations (p < 0.001). The recommended strength in the Code of Federal Regulations (CFR) by the US FAA is higher than the strength values observed in this study. Conclusions: The backrest angle, directions, and location affected the muscular strength. The recommended values should be reevaluated and adjusted for Taiwanese pilots.

The prevention of injuries among youth basketballers according to the “Sequence of Prevention’’: a systematic review

Background: Basketball is played by the youth worldwide, and various injuries occur in youth basketball. There is currently no overview of the incidence, the risk factors and preventive measures of musculoskeletal injuries among youth basketball players. Objective: This systematic review describes the most common injuries among youth basketball players. The most common risk factors and various preventive measures and interventions have also been reported and discussed. Methods: Search strategies were built based on groups of keywords, namely ‘injury’, ‘youth basketball’, and ‘cohort’. Search strategies were entered into Medline and SPORTDiscus. Titles, abstracts and full text articles were screened by two researchers. Data from the included articles were extracted by one researcher and checked by another researcher. Results: Twenty-seven studies showed that the overall injury rate ranged from 2.64 to 3.83 per 1 000 hours of exposure. Ankle- (22%-37%) and knee injuries (5%-41%) were the most common injuries. Risk factors for knee injuries included ankle dorsiflexion with a range less than 36.5 degrees and female athletes with greater hip abduction strength. High variations of postural sway corresponded to occurrences of ankle injuries (p=0.01, OR =1.22; p<0.001, OR =1.22). A core intervention (rate = 4.99/1 000 athlete exposure (AEs)) focused on the trunk and lower extremity led to a reduction in injuries compared to a sham intervention (rate =7.72/1 000 AEs) (p=0.02). Wearing a McDavid Ultralight 195 brace reduced ankle injuries compared to the controls (HR 0.30; 95 % CI 0.17 0.90; p=0.03). Conclusion: Ankle and knee injuries are the most common injuries among youth basketball players. Poor postural control, reduced ankle dorsiflexion and high hip abduction strength are the main risk factors. A neuromuscular warm-up, in combination with strength and stability exercises, seems to be the best training method to prevent injuries. Ankle injuries can be reduced by wearing a lace-up ankle brace.

Validity and reliability of the DiCI for the measurement of shoulder flexion and abduction strength in asymptomatic and symptomatic subjects

Background A higher risk of shoulder injury in the athletic and non-athletic population is frequently associated with strength deficits. Therefore, shoulder strength assessment can be clinically useful to identify and to quantify the magnitude of strength deficit. Thus, the aim of this study was to evaluate the validity and reliability of a DiCI (a new hand-held dynamometer) for the measurement of shoulder flexion and abduction strength in asymptomatic and symptomatic subjects. Methods Forty-three recreational athletes (29 males and 14 females; age: 22.1 ± 0.47 years; body mass: 68.7 ± 13.1 kg; height = 173.3 ± 9.7 cm) and 40 symptomatic subjects (28 males and 12 females; age: 49.9 ± 8.1 years; body mass: 70.6 ± 14.3 kg; height = 171.7 ± 9.0 cm) completed shoulder flexion and abduction strength tests in two identical sessions one-week apart. Both types of movement were evaluated at 45º and 90º. Results Relative reliability analysis showed excellent intra-class correlation coefficients (ICC) for all evaluated movements (ICC range = 0.90 to 0.99). Absolute reliability analysis showed a standard error of measurement (SEM) ranging from 1.36% to 2.25%, and minimal detectable change (MDC) ranging from 3.93% to 6.25%. In conclusion, the DiCI is a valid and reliable device for assessing shoulder strength both in recreational athletes and in subjects with restricted mobility and loss of strength.

Incidence, prevalence, severity, and risk factors for hip and groin problems in Swedish male ice hockey – A one-season prospective cohort study

ABSTRACT Context: The epidemiological focus on time loss may underestimate the true magnitude of hip and groin problems in male ice hockey players. Objective: To describe the prevalence, incidence and severity of hip and groin problems (time loss and non-time-loss) in Swedish ice hockey players over the course of a season and to explore potential pre-season risk factors for these problems. Design: Prospective one-season cohort study Setting: Professional and semi-professional Swedish ice hockey Patients or other participants: Twelve professional and semi-professional male ice hockey teams were invited to participate. Nine teams agreed to participate, and 163 players were included in analyses. Main outcome measures: Hip and groin problems in the previous season (time loss; non-time-loss), isometric adduction and abduction strength, and five-second squeeze test were recorded prior to the season and served as independent variables in the risk factor analysis. Main outcome measures were cumulative incidence of hip and groin problems, average prevalence, and odds ratios for groin problems in-season Results: Cumulative incidence for all problems was 45.4 % (95% CI 37.6–53.4) and 19% (13.3–25.9) for substantial problems. Average prevalence was 14.1% (10.8–17.5) for all and 5.7% (4.3–7.2) for substantial problems. Among reported problems, 69.2% had gradual onset; where only 17% lead to time loss. Players with non-time-loss problems in the previous season had significantly higher odds for new problems [All: OR 3.3 (1.7–6.3); Substantial: OR 3.6 (1.8–8.4)]. Pre-season strength was not significantly associated with the odds for subsequent problems. Conclusion: Hip and groin problems are common in ice hockey and may lead to substantial impairments in performance. Only one in five problems led to time loss and 7 out of 10 had gradual onset. Non-time-loss problems in the previous season were found to be a significant risk factor for new problems whereas preseason hip adduction and abduction strength was not.

The Effects of Gluteal Strength and Activation on the Relationship Between Femoral Alignment and Functional Valgus Collapse During a Single-Leg Landing

Context: A bias toward femoral internal rotation is a potential precursor to functional valgus collapse. The gluteal muscles may play a critical role in mitigating these effects. Objective: Determine the extent to which gluteal strength and activation mediate associations between femoral alignment measures and functional valgus collapse. Design: Cross-sectional. Setting: Research laboratory. Patients or Other Participants: Forty-five females (age = 20.1 [1.7] y; height = 165.2 [7.6] cm; weight = 68.6 [13.1] kg) and 45 males (age = 20.8 [2.0] y; height = 177.5 [8.7] cm; weight = 82.7 [16.5] kg), healthy for 6 months prior. Intervention(s): Femoral alignment was measured prone. Hip-extension and abduction strength were obtained using a handheld dynamometer. Three-dimensional biomechanics and surface electromyography were obtained during single-leg forward landings. Main Outcome Measures: Forward stepwise multiple linear regressions determined the influence of femoral alignment on functional valgus collapse and the mediating effects of gluteus maximus and medius strength and activation. Results: In females, less hip abduction strength predicted greater peak hip adduction angle (R2 change = .10; P = .02), and greater hip-extensor activation predicted greater peak knee internal rotation angle (R2 change = .14; P = .01). In males, lesser hip abduction strength predicted smaller peak knee abduction moment (R2 change = .11; P = .03), and the combination of lesser hip abduction peak torque and lesser gluteus medius activation predicted greater hip internal rotation angle (R2 change = .15; P = .04). No meaningful mediation effects were observed (υadj < .01). Conclusions: In females, after accounting for femoral alignment, less gluteal strength and higher muscle activation were marginally associated with valgus movement. In males, less gluteal strength was associated with a more varus posture. Gluteal strength did not mediate femoral alignment. Future research should determine the capability of females to use their strength efficiently.

Intrasession and Intersession Reliability of Isometric Trunk and Hip Strength Measurements Using the Portable Tension Dynamometer

Context: The trunk/pelvis is an important link between the upper- and lower-extremities. Therefore, assessing strength of the trunk and hip muscles that control the segments is clinically meaningful. While an isokinetic dynamometer can be used to measure trunk strength, the equipment is expensive and not portable. Objective: To test the reliability of simple trunk and hip strength measures that utilize a bar, straps, and a portable tension dynamometer. Design: Test–retest reliability study. Setting: Biomechanics research laboratory. Patients (or Other Participants): Twenty college-age individuals (10 males/10 females, age = 20.9 [3.7] y) participated. Intervention(s): The participants attended 2 testing sessions, 1 week apart. The participants’ trunk-flexion, rotation, and hip abduction strength were measured at each session. Main Outcome Measures: Peak trunk flexion, rotation, and hip abduction forces were normalized to the participant’s body weight (BW). In addition, hip-abduction torque was calculated by multiplying the force times the leg length and normalized to BW. The trial data from both sessions were used to calculate the intrasession reliability, and the averages from the 2 sessions were used to calculate the intersession reliability. Intraclass correlation coefficients, SEM, and minimal detectable change were calculated to evaluate reliability of measures. Results: The intrasession intraclass correlation coefficients (SEM) for trunk flexion, rotation, hip abduction, and hip abduction torque were .837 (5.2% BW), .978 (1.3% BW), .955 (1.0% BW), and .969 (5.8 N·m/BW), respectively. The intersession reliability for trunk flexion, rotation, hip abduction, and hip abduction torque were .871 (4.3% BW), .801 (3.8% BW), .894 (1.5% BW), and .968 (5.9 N·m/BW), respectively. Conclusions: The measures of trunk and hip abduction strength are highly repeatable within a session. The reliability of the measures between sessions was also good/excellent with relatively small SEM and minimal detectable change. The tests described in this study can be used to assess changes in trunk/hip strength over time.

Relationship between upper limb injuries and hip range of motion and strength in high school baseball pitchers

We aimed to examine the relationship between hip range of motion (ROM) and abduction strength and throwing-related shoulder/elbow injuries in high school baseball pitchers. The study included 135 baseball pitchers. We asked them to fill out a questionnaire at the checkups, that included the dominant arm and the years of baseball experience. To avoid a confirmation bias, the examiners were blinded to the participants’ hand dominance. All players underwent physical function measurements, such as height, weight, shoulder and hip strength, and shoulder and hip ROM. Shoulder and elbow injury was defined as shoulder and elbow pain that the patient had been aware of in the past 3 years. The results of injured and non-injured pitchers were compared. Eighty-five pitchers had experienced a shoulder or elbow injury in the past 3 years. The shoulder ROM and strength in the injured and non-injured groups did not differ to a statistically significant extent. The hip external rotation ROM on the dominant side, the hip abduction strength on the non-dominant side, and the hip abduction strength on the dominant side were significantly lower in the injured group than in the non-injured group. The results may contribute to reducing the incidence of these injuries.

Asymmetry Thresholds for Common Screening Tests and Their Effects on Jump Performance in Professional Soccer Players

Context Arbitrary asymmetry thresholds are regularly used in professional soccer athletes, notwithstanding the sparse literature available to examine their prevalence. Objective To establish normative and positional asymmetry values for commonly used screening tests and investigate their relationships with jumping performance. Design Cross-sectional study. Setting Elite soccer screening. Patients or Other Participants A total of 203 professional male soccer players. Main Outcome Measure(s) Bilateral and unilateral jumping; range of motion; and hamstrings (HAM), quadriceps (QUAD), and hip-adductor and -abductor strength tests were used to quantify asymmetry. Players were divided into 4 quartiles (Q1–Q4) based on the magnitude of their asymmetry for each test. Single composite scores were also developed to group tests by range of motion and HAM, QUAD, hip-adduction, and hip-abduction strength, and differences in jump performance were examined among players in each quartile. Results Large variability (range = 5.2%–14.5%) was evident in asymmetry scores across the different tests and physical qualities. Forwards displayed greater asymmetry in concentric quadriceps and eccentric hip-abduction strength (P &lt; .05). The HAM and QUAD composite scores indicated that Q4 players jumps were shorter than than in other quartiles during a single-legged countermovement jump and 10-second hop (P &lt; .05). No decrements in unilateral jump performance were shown among players in each quartile for range of motion or hip-adduction and -abduction strength, and no composite measures of asymmetry affected bilateral jump performance. Conclusions No single asymmetry threshold was present for all tests; the outcomes were task, variable, and population specific. Larger asymmetries in HAM and QUAD strength appeared to be detrimental to unilateral jump performance.