Are unilateral and bilateral patellar tendinopathy distinguished by differences in anthropometry, body composition, or muscle strength in elite female basketball players?

Background: Overuse injury to the patellar tendon (patellar tendinopathy) is a major reason for interrupted training and competition for elite athletes. In both sexes, the prevalence of unilateral and bilateral tendinopathy has been shown to differ. It has been proposed that bilateral pathology may have a different aetiology from unilateral pathology. Investigation of risk factors that may be unique to unilateral and bilateral patellar tendinopathy in female athletes may reveal insights into the aetiology of this condition.
Objectives: To examine whether anthropometry, body composition, or muscle strength distinguished elite female basketball players with unilateral or bilateral patellar tendinopathy.
Methods: Body composition, anthropometry, and muscle strength were compared in elite female basketball players with unilateral (n = 8), bilateral (n = 7), or no (n = 24) patellar tendinopathy. Body composition was analysed using a dual energy x ray absorptiometer. Anthropometric measures were assessed using standard techniques. Knee extensor strength was measured at 180°/s using an isokinetic dynamometer. z scores were calculated for the unilateral and bilateral groups (using the no tendinopathy group as controls). z scores were tested against zero.
Results: The tibia length to stature ratio was approximately 1.3 (1.3) SDs above zero in both the affected and non-affected legs in the unilateral group (p<0.05). The waist to hip ratio was 0.66 (0.78) SD above zero in the unilateral group (p<0.05). In the unilateral group, leg lean to total lean ratio was 0.42 (0.55) SD above zero (p<0.07), the trunk lean to total lean ratio was 0.63 (0.68) SD below zero (p<0.05), and leg fat relative to total fat was 0.47 (0.65) SD below zero (p<0.09). In the unilateral group, the leg with pathology was 0.78 (1.03) SD weaker during eccentric contractions (p<0.07).
Conclusions: Unilateral patellar tendinopathy has identifiable risk factors whereas bilateral patellar tendinopathy may not. This suggests that the aetiology of these conditions may be different. However, interpretation must respect the limitation of small subject numbers.

Reliability of surface EMG measurements of the quadriceps during maximal isometric contractions following water immersion

Background: The influence of water immersion on neuromuscular function is of importance to a number of disciplines; however, the reliability of surface electromyography (SEMG) following water immersion is not known. This study examined the reliability of SEMG amplitude during maximal voluntary isometric contractions (MVICs) of the vastus lateralis following water immersion.

Methods: Using a Biodex isokinetic dynamometer and in a randomized order, 12 healthy male subjects performed four MVICs at 60° knee flexion on both the dominant and nondominant kicking legs, and the SEMG was recorded. Each subject's dominant and nondominant kicking leg was then randomly assigned to have SEMG electrodes removed or covered during 15 min of water immersion (20°C–25°C). Following water immersion, subjects performed a further four MVICs.

Results: Intraclass correlation coefficient (ICC) and the relative standard error of measurement (%SEM) of SEMG amplitude showed moderate to high trial-to-trial reliability when electrodes were covered (0.93% and 2.79%) and removed (0.95% and 2.10%, respectively).

Conclusions: The results of the this study indicate that SEMG amplitude of the vastus lateralis may be accurately determined during maximal voluntary contractions following water immersion if electrodes are either removed or covered with water-resistive tape during the immersion.

Examination of EMG normalisation methods for the study of the posterior and posterolateral neck muscles in healthy controls

The purpose of this study was to examine the reliability of normalisation methods used in the study of the posterior and posterolateral neck muscles in a group of healthy controls. Six asymptomatic male subjects performed a total of 12 maximum voluntary isometric contractions (MVIC) and 60%-submaximal isometric contractions (60%-MVIC) against the torque arm of an isokinetic dynamometer whilst surface and intramuscular electromyography (EMG) was recorded unilaterally from representative posterior and posterolateral locations. Reliability was calculated using intra-class correlation coefficient (ICC), relative standard error of measurement (%SEM) and relative coefficient of variation (%CV). Maximal torque output was found to be highly reliable in the directions of extension and right lateral bending when the first of three MVIC contractions was excluded. When averaged across contraction direction, high reliability was found for both surface (MVIC: ICC = 0.986, %SEM = 7.5, %CV = 9.2; 60%-MVIC: ICC = 0.975, %SEM = 10, %CV = 13.7) and intramuscular (MVIC: ICC = 0.910, %SEM = 20, %CV = 19.1; 60%-MVIC: ICC = 0.952, %SEM = 16.5, %CV = 13.5) electrodes. Intramuscular electrodes displayed the least reliability in right lateral bending. The use of visual feedback markedly increased the reliability of 60%-MVIC contractions.

Effects of long-term tennis playing on the muscle-bone relationship in the dominant and non-dominant forearms

The relationship between muscle strength and bone mineral density illustrates the positive effect of mechanical loading on bone. But local and systemic factors may affect both muscle and bone tissues. This study investigated the effects of long-term tennis playing on the relationship between lean tissue mass and bone mineral content in the forearms, taking the body dimensions into account. Fifty-two tennis players (age 24.2 +/- 5.8 yrs, 16.2 +/- 6.1 yrs of practice) were recruited. Lean tissue mass (LTM), bone area, bone mineral content (BMC), and bone mineral density were measured at the forearms from a DXA whole-body scan. Grip strength was assessed with a dynamometer. A marked side-to-side difference (p < 0.0001) was found in favor of the dominant forearm in all parameters. Bone area and BMC correlated with grip strength on both sides (r = 0.81 - 0.84, p < 0.0001). The correlations were still significant after adjusting for whole-body BMC body height, or forearm length. This result reinforced the putative role of the muscles in the mechanical loading on bones. In addition, forearm BMC adjusted to LTM or grip strength was higher on the dominant side, suggesting that tennis playing exerts a direct effect on bone.

Bone geometry in response to long-term tennis playing and its relationship with muscle volume : a quantitative magnetic resonance imaging study in tennis players

The benefit of impact-loading activity for bone strength depends on whether the additional bone mineral content (BMC) accrued at loaded sites is due to an increased bone size, volumetric bone mineral density (vBMD) or both. Using magnetic resonance imaging (MRI) and dual energy X-ray absorptiometry (DXA), the aim of this study was to characterize the geometric changes of the dominant radius in response to long-term tennis playing and to assess the influence of muscle forces on bone tissue by investigating the muscle–bone relationship. Twenty tennis players (10 men and 10 women, mean age: 23.1 ± 4.7 years, with 14.3 ± 3.4 years of playing) were recruited. The total bone volume, cortical volume, sub-cortical volume and muscle volume were measured at both distal radii by MRI. BMC was assessed by DXA and was divided by the total bone volume to derive vBMD. Grip strength was evaluated with a dynamometer. Significant side-to-side differences (P < 0.0001) were found in muscle volume (+9.7%), grip strength (+13.3%), BMC (+13.5%), total bone volume (+10.3%) and sub-cortical volume (+20.6%), but not in cortical volume (+2.6%, ns). The asymmetry in total bone volume explained 75% of the variance in BMC asymmetry (P < 0.0001). vBMD was slightly higher on the dominant side (+3.3%, P < 0.05). Grip strength and muscle volume correlated with all bone variables (except vBMD) on both sides (r = 0.48–0.86, P < 0.05–0.0001) but the asymmetries in muscle parameters did not correlate with those in bone parameters. After adjustment for muscle volume or grip strength, BMC was still greater on the dominant side. This study showed that the greater BMC induced by long-term tennis playing at the dominant radius was associated to a marked increase in bone size and a slight improvement in volumetric BMD, thereby improving bone strength. In addition to the muscle contractions, other mechanical stimuli seemed to exert a direct effect on bone tissue, contributing to the specific bone response to tennis playing.

Reliability of normalisation methods for EMG analysis of neck muscles

Acceptable reliability of normalisation contractions in electromyography (EMG) is paramount for testing conducted over a number of days or if normal laboratory strength testing equipment is unavailable. This study examined the reliability of maximal voluntary isometric contractions (MVIC) and sub-maximal (60%) isometric contractions for use in neck muscle EMG studies. Surface EMG was recorded bilaterally from eight sites around the neck at C4/5 level from five healthy male subjects. Subjects performed MVIC and sub-maximal normalisation contractions using an isokinetic dynamometer (ID) and a portable cable dynamometer with attached strain gauge (PCD) in addition to a MVIC against a manual resistance (MR). Subjects were tested in flexion, extension, left and right lateral bending and were retested by the same tester within a two-week period. Intra class correlation co-efficients (ICC) were calculated for each testing method and contraction direction and a mean ICC was calculated across all contraction directions. All normalisation methods produced excellent within-day reliability (mean ICC >0.80) but only the MVICs using the ID and PCD had acceptable reliability when assessed between-days. This study confirmed the validity of using MVICs elicited using the ID and PCD as reliable reference contractions for the normalisation of neck EMG.

Neck strength recovery after a single bout of specific strengthening exercise

Objective : To determine the level of neck strength decrement and the rate of strength recovery of the neck muscles after a single bout of specific neck conditioning exercise in both males and females.

Hypothesis : A decrement in neck strength may be evident after a bout of strengthening exercise.

Design : Intervention study with pre-and-post design.

Setting : Biomechanics laboratory.

Participants : Twenty healthy participants (10 male and 10 female, mean ± standard deviation age 22 ± 1.2 years).

Main Outcome Measures : Participants performed a single bout of neck strengthening exercise. Neck strength testing using an isokinetic dynamometer was performed pre and at five time points (1 h, one, three, five and seven days) post-exercise to assess the level of neck strength decrement and neck strength recovery rate from pre-exercise levels.

Results : Statistically significant (p ≥ 0.036) decreases in neck extension strength were recorded in all participants 1 h and one day post-exercise. The level of neck extension strength returned to pre-exercise levels three days post-exercise and surpassed pre-exercise levels five and seven days post-exercise. The male participants' neck flexion strength decrement and recovery followed a similar pattern to that displayed in neck extension but more variability in neck flexion strength recovery rates were recorded in the female participants in this study.

Conclusion : The consistent strength recovery times for the male participants recorded in this study idealise the prescription of neck strengthening exercises in a periodised fashion. More investigation needs to be instigated for the female neck musculature as consistent strength recovery rates were not identified in this study.

A new method to warm up lubricating oil to improve the fuel efficiency during cold start

Cold start driving cycles exhibit an increase in friction losses due to the low temperatures of metal and media compared to normal operating engine conditions. These friction losses are responsible for up to 10% penalty in fuel economy over the official drive cycles like the New European Drive Cycle (NEDC), where the temperature of the oil even at the end of the 1180 s of the drive cycle is below the fully warmed up values of between 100°C and 120°C. At engine oil temperatures below 100°C the water from the blow by condensates and dilutes the engine oil in the oil pan which negatively affects engine wear. Therefore engine oil temperatures above 100°C are desirable to minimize engine wear through blow by condensate. The paper presents a new technique to warm up the engine oil that significantly reduces the friction losses and therefore also reduces the fuel economy penalty during a 22°C cold start NEDC. Chassis dynamometer experiments demonstrated fuel economy improvements of over 7% as well as significant emission reductions by rapidly increasing the oil temperature. Oil temperatures were increased by up to 60°C during certain parts of the NEDC. It is shown how a very simple sensitivity analysis can be used to assess the relative size or efficiency of different heat transfer passes and the resulting fuel economy improvement potential of different heat recovery systems system. Due to its simplicity the method is very fast to use and therefore also very cost effective. The method demonstrated a very good correlation for the fuel consumption within ±1% compared to measurements on a vehicle chassis roll.

Hip adductor muscle strength is reduced preceding and during the onset of groin pain in elite junior Australian football players

Groin pain is a condition with a high prevalence in young Australian football players. It is considered that early identification of this condition allows for optimal management. Eighty-six players from two elite under-age Australian football sides were screened weekly for hip adductor muscle strength, using a hand-held dynamometer and for the onset of groin pain. The maximum variation in the average hip adductor muscle strength values of the sample was a 2.6% decrease from baseline in week 7 of the study. Twelve players (14% of the sample studied) reported groin pain for two consecutive weeks and were considered to have an onset of groin injury. The mean hip adductor muscle strength of these players was decreased significantly from baseline by an average of 11.75 ± 2.50% at the week of pain onset (F = 264.76 (1,11), p < 0.001), and 5.82 ± 5.16% in the week preceding the onset of pain (F = 14.03 (1,10), p = 0.004). These results confirm that hip adductor muscle strength is decreased both preceding and during the onset of groin injury in elite under-age Australian footballers.

Investigating the predictive ability of gait speed and quadriceps strength for incident falls in community-dwelling older women at high risk of fracture

Gait speed is a recommended geriatric assessment of physical performance, but may not be regularly examined in clinical settings. We aimed to investigate whether quadriceps strength tests demonstrate similar predictive ability for incident falls as gait speed in older women. We investigated 135 female volunteers aged mean±SD 76.7±5.0 years (range 70-92) at high risk of fracture. Participants completed gait speed assessments using the GAITRite Electronic Walkway System, and quadriceps strength assessments using a hand-held dynamometer (HHD). Participants reported incident falls monthly for 3.7±1.2 years. N=99 (73%) participants fell 355 times during the follow-up period (mean fall rate 83 per 100 person years). We observed a reduced odds ratio for multiple falls (0.83, 95% CI 0.70-0.98) and a reduced hazard ratio for time to first fall (0.90, 95% CI 0.83-0.98), according to quadriceps strength. There was also a significantly shorter time to first fall for those with low quadriceps strength (<7.0 kg; lowest tertile) compared with those with normal quadriceps strength (estimated means [95% CI] 1.54 [1.02, 2.06] vs. 2.23 [1.82, 2.64] years; P=0.019), but not for those with low (<1.0 m/s) vs. normal gait speed (P=0.15). Quadriceps strength is a significant predictor of incident falls over three years amongst community-dwelling older women at high risk of fracture. Quadriceps strength tests may be an acceptable alternative to gait speed for geriatric assessments of falls risk.

Muscle strength and areal bone mineral density at the hip in women: a cross-sectional study

BACKGROUND: Muscle strengthening exercises are promoted for building and maintaining a healthy skeleton. We aimed to investigate the relationship between muscle strength and areal bone mineral density (BMD) at the hip in women aged 26-97 years.

METHODS: This cross-sectional study utilises data from 863 women assessed for the Geelong Osteoporosis Study. Measures of hip flexor and abductor strength were made using a hand-held dynamometer (Nicholas Manual Muscle Tester). The maximal measure from three trials on each leg was used for analyses. BMD was measured at the hip using dual energy x-ray absorptiometry (DXA; Lunar DPX-L). Total lean mass, body fat mass and appendicular lean mass were determined from whole body DXA scans. Linear regression techniques were used with muscle strength as the independent variable and BMD as the dependent variable. Models were adjusted for age and indices of body composition.

RESULTS: Measures of age-adjusted hip flexor strength and hip abductor strength were positively associated with total hip BMD. For each standard deviation (SD) increase in hip flexor strength, the increase in mean total hip BMD (SD) was 10.4 % (p = 0.009). A similar pattern was observed for hip abductor strength, with an increase in mean total hip BMD of 22.8 % (p = 0.025). All associations between hip muscle strength and total hip BMD were independent of height, but were nullified after adjusting for appendicular lean mass or total lean mass.

CONCLUSIONS: There was a positive association observed between muscle strength and BMD at the hip. However, this association was explained by measures of lean mass.

A preliminary study on machinability of super austenitic stainless steel

Stainless steel is the most widely used alloys of steel. The reputed variety of stainless steel having customised material properties as per the design requirements is Duplex Stainless Steel and Austenitic Stainless Steel. The Austenite Stainless Steel alloy has been developed further to be Super Austenitic Stainless Steel (SASS) by increasing the percentage of the alloying elements to form the half or more than the half of the material composition. SASS (Grade-AL-6XN) is an alloy steel containing high percentages of nickel (24%), molybdenum (6%) and chromium (21%). The chemical elements offer high degrees of corrosion resistance, toughness and stability in a large range of hostile environments like petroleum, marine and food processing industries. SASS is often used as a commercially viable substitute to high cost non-ferrous or non-metallic metals. The ability to machine steel effectively and efficiently is of utmost importance in the current competitive market. This paper is an attempt to evaluate the machinability of SASS which has been a classified material so far with very limited research conducted on it. Understanding the machinability of this alloy would assist in the effective forming of this material by metal cutting. The novelty of research associated with this is paper is reasonable taking into consideration the unknowns involved in machining SASS. The experimental design consists of conducting eight milling trials at combination of two different feed rates, 0.1 and 0.15 mm/tooth; cutting speeds, 100 and 150 m/min; Depth of Cut (DoC), 2 and 3 mm and coolant on for all the trials. The cutting tool has two inserts and therefore has two cutting edges. The trial sample is mounted on a dynamometer (type 9257B) to measure the cutting forces during the trials. The cutting force data obtained is later analyzed using DynaWare supplied by Kistler. The machined sample is subjected to surface roughness (Ra) measurement using a 3D optical surface profilometer (Alicona Infinite Focus). A comprehensive metallography process consisting of mounting, polishing and etching was conducted on a before and after machined sample in order to make a comparative analysis of the microstructural changes due to machining. The microstructural images were capture using a digital microscope. The microhardness test were conducted on a Vickers scale (Hv) using a Vickers microhardness tester. Initial bulk hardness testing conducted on the material show that the alloy is having a hardness of 83.4 HRb. This study expects an increase in hardness mostly due to work hardening may be due to phase transformation. The results obtained from the cutting trials are analyzed in order to judge the machinability of the material. Some of the criteria used for machinability evaluation are cutting force analysis, surface texture analysis, metallographic analysis and microhardness analysis. The methodology followed in each aspect of the investigation is similar to and inspired by similar research conducted on other materials. However, the novelty of this research is the investigation of various aspects of machinability and drawing comparisons between each other while attempting to justify each result obtained to the microstructural changes observed which influence the behaviour of the alloy. Due to the limited scope of the paper, machinability criteria such as chip morphology, Metal Removal Rate (MRR) and tool wear are not included in this paper. All aspects are then compared and the optimum machining parameters are justified with a scope for future investigations