Recreational runners with Achilles tendinopathy have clinically detectable impairments: A case-control study

ObjectivesTo confirm what impairments are present in runners with Achilles tendinopathy (AT) and explore the variance of AT severity in an adequately powered study.DesignCase-control study.SettingTwo private physiotherapy clinics in Australia and Spain.ParticipantsForty-four recreational male runners with AT and 44 healthy controls matched by age, height, and weight.Main outcome measuresDemographics, activity (IPAQ-SF), pain and function (VISA-A), pain during hopping (Hop pain VAS), hopping duration, psychological factors (TSK-11, PASS20), and physical tests regarding lower-limb maximal strength and endurance.ResultsBody mass index (BMI), activity, VISA-A, pain, and duration of hopping, TSK-11, PASS20, standing heel raise to failure, seated heel raise and leg extension 6RM, hip extension and abduction isometric torque were significantly different between groups (P < 0.05) with varied effect sizes (V = 0.22, d range = 0.05–4.18). 46% of AT severity variance was explained by higher BMI (β = −0.41; p = 0.001), weaker leg curl 6RM (β = 0.32; p = 0.009), and higher pain during hopping (β = −0.43; p = 0.001).ConclusionRunners with AT had lower activity levels, lower soleus strength, and were less tall. BMI, pain during hopping, and leg curl strength explained condition severity. This information, identified with clinically applicable tools, may guide clinical assessment, and inform intervention development.     

Dynamic stability in runners with and without plantar fasciitis

BackgroundPlantar fasciitis (PF) is a common overuse injury experienced by runners. PF may decrease the ability of the plantar fascia to create tension and reduce stability of the foot. Stability of the foot is necessary for whole-body dynamic stability during running which consists of cyclical periods of single leg stance. Given that a major risk factor for running-related injury is previous injury, evaluating dynamic stability in runners with PF, runners with resolved PF, and healthy runners may elucidate differences between these individuals and clarify risk for secondary injury in these groups.Research questionIs dynamic stability reduced in runners with PF and runners with resolved PF compared to healthy runners?MethodsThirty runners were recruited for this retrospective comparative study based on mileage and injury status: current PF (PF), resolved PF (RPF), or healthy (CON). Kinematic and kinetic data were collected during running and dynamic stability was determined by time-to-contact (TtC) analysis for early, mid, and late stance to the anterior, posterior, medial, and lateral boundary of the foot. Dynamic stability was compared between groups one-way ANOVAs (α = 0.05) and Tukey post-hoc tests conducted when appropriate. Cohen’s d effect sizes (d) were reported for all TtC comparisons (small = 0.20, medium = 0.50, large = 0.80).ResultsTtC values were shorter in PF compared to the other groups to all boundaries during mid-stance. TtC was significantly greater in PF compared to RPF to the anterior boundary during late stance.SignificanceShorter TtC observed in PF compared to the other groups during midstance may indicate reduced dynamic stability during the most stable portion of running which may lead to increased injury risk.     

Development of a trail running injury screening instrument: A multiple methods approach

ObjectiveTo develop a trail running injury screening instrument (TRISI) for utilisation as clinical decision aid in determining if a trail runner is at an increased risk for injury.DesignMultiple methods approach.MethodsThe study utilised five phases 1) identification of injury risk factors 2) determining the relevance of each identified risk factor in a trail running context, 3) creating the content of the Likert scale points from 0 to 4, 4) rescaling the Likert scale points to determine numerical values for the content of each Likert scale point, and 5) determining a weighted score for each injury risk factor that contributes to the overall combined composite score.ResultsOf the 77 identified injury risk factors, 26 were deemed relevant in trail running. The weighted score for each injury risk factor ranged from 2.21 to 5.53 with the highest calculated score being 5.53. The final TRISI includes risk categories of training, running equipment, demographics, previous injury, behavioural, psychological, nutrition, chronic disease, physiological, and biomechanical factors.ConclusionThe developed TRISI aims to assist the clinician during pre-race injury screening or during a training season to identify meaningful areas to target in designing injury risk management strategies and/or continuous health education.     

The energy cost of walking or running on sand

Summary Oxygen uptake ( O₂) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3–7 km · h^–1) or running (7–14 km · h^–1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of O₂ to speed and expressed in J · kg^–1 · m^–1 assuming an energy equivalent of 20.9 J · ml O₂ ^–1. At the highest speedsC was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand,C increased linearly with speed from 3.1 J · kg^–1 · m^–1 at 3 km · h^–1 to 5.5 J · kg^–1 · m^–1 at 7 km · h^–1, whereas on a firm surfaceC attained a minimum of 2.3 J · kg^–1 · m^–1 at 4.5 km · h^–1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km · h^–1,C was about 1.8 times greater on sand than on compact terrain. When running on sandC was approximately independent of the speed, amounting to 5.3 J · kg^–1 · m^–1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.     

Physical activity and plasma interleukin-6 in humans – effect of intensity of exercise

The present study included data from three marathon races to investigate the hypothesis that a relationship exists between running intensity and elevated concentrations of interleukin (IL)-6 in plasma. The study included a total of 53 subjects whose mean age was 30.6 [95% confidence interval (CI) 1.4] years, mean body mass 77.7 (95%CI 2.0) kg, mean maximal oxygen uptake (V˙O_2max) 59.3 (95%CI 1.4) ml · min⁻¹ · kg⁻¹, and who had participated in the Copenhagen Marathons of 1996, 1997 or 1998, achieving a mean running time of 206 (95%CI 7) min. Running intensity was calculated as running speed divided by V˙O_2max. The concentration of IL-6 in plasma peaked immediately after the run. There was a negative correlation between peak IL-6 concentration and running time (r=−0.30, P < 0.05) and a positive correlation between peak IL-6 concentration and running intensity (r=0.32, P < 0.05). The IL-1 receptor antagonist (IL-1ra) plasma concentration peaked 1.5 h after the run and there was a positive correlation between the peak plasma concentrations of IL-6 and IL-1ra (r=0.39, P < 0.01). Creatine kinase (CK) plasma concentration peaked on the 1st day after the run, but no association was found between peak concentrations of IL-6 and CK. In conclusion, the results confirmed the hypothesized association between plasma IL-6 concentration and running intensity, but did not confirm the previous finding of a connection between IL-6 plasma concentration and muscle damage. Accepted: 6 August 2000     

Physical training and fasting erythrocyte activities of free radical scavenging enzyme systems in sedentary men

Summary Effects of 10 weeks of physical training on free radical scavenging enzyme systems in erythrocytes were investigated in 7 sedentary healthy male students. The training consisted of running over 5 km, 6 times/week. Their maximum oxygen uptake and 12 min walk-run performance increased significantly after training. Of the antioxidant enzyme systems examined in the erythrocytes, both catalase activity and concentration and total glutathione reductase (GR) activity also showed significant increases following the training. The erythrocyte GR activity coefficient also increased significantly. These results suggest that chronic aerobic exercise increases riboflavin requirements and has some positive effects on antioxidative processes.     

Blood lactate response to overtraining in male endurance athletes

Many physiological markers vary similarly during training and overtraining. This is the case for the blood lactate concentration ([La⁻]_b), since a right shift of the lactate curve is to be expected in both conditions. We examined the possibility of separating the changes in training from those of overtraining by dividing [La⁻]_b by the rating of perceived exertion ([La⁻]_b/RPE) or by converting [La⁻]_b into a percentage of the peak blood lactate concentration ([La⁻]_b,peak). Ten experienced endurance athletes increased their usual amount of training by 100% within 4 weeks. An incremental test and a time trial were performed before (baseline) and after this period of overtraining, and after 2 weeks of recovery (REC). The [La⁻]_b and RPE were measured during the recovery of each stage of the incremental test. We diagnosed overtraining in seven athletes, using both physiological and psychological criteria. We found a decrease in mean [La⁻]_b,peak from baseline to REC [9.64 (SD 1.17), 8.16 (SD 1.31) and 7.69 (SD 1.84) mmol · l⁻¹, for the three tests, respectively; P < 0.05] and a right shift of the lactate curve. Above 90% of maximal aerobic speed (MAS) there was a decrease of mean [La⁻]_b/RPE from baseline to REC [at 100% of MAS of 105.41 (SD 17.48), 84.61 (SD 12.56) and 81.03 (SD 22.64) arbitrary units, in the three tests, respectively; P < 0.05), but no difference in RPE, its variability accounting for less than 25% of the variability of [La⁻]_b/RPE (r=0.49). Consequently, [La⁻]_b/RPE provides little additional information compared to [La⁻]_b alone. Expressing [La⁻]_b as a %[La⁻]_b,peak resulted in a suppression of the right shift of the lactate curve, suggesting it was primarily the consequence of a decreased production of lactate by the muscle. Since the right shift of the curve induced by optimal training is a result of improved lactate utilization, the main difference between the two conditions is the decrease of [La⁻]_b,peak during overtraining. We propose retaining it as a marker of overtraining for long duration events, and repeating its measurement after a sufficient period of rest to make the distinction with overreaching. Accepted: 26 September 2000     

Effects of order of presentation of exercise intensities and of sauna baths on perceived exertion during treadmill running

Summary Thirteen male subjects performed a running test on the treadmill consisting of four standard exercise intensities [65%, 75%, 85%, 95% maximal O₂ uptake (VO_2max)] presented in ascending, descending or random order. At the end of each exercise intensity, O₂ consumption, heart rate (f _c), venous blood lactate concentration ([la]_b) and perceived exertion were assessed. This last variable was determined according to the Borg nonlinear CR-20 scale. The same variables were also determined during exercise at a standard intensity (65% or 95%VO_2max) performed before and after a Finnish sauna bath. Ratings of perceived exertion showed a good test-retest reliability (r=0.77); they were the same when the exercise intensity was expressed in relative (%VO_2max) or absolute (speed) terms, and were independent of the order of presentation of the exercise. The latter had no effect onf _c either but it did, however, influence [la]_b, which was significantly higher in the descending, as compared to the ascending or random modes of presentation. The sauna bath increasedf _c at a given exercise intensity, but left perceived exertion and [la]_b unchanged. It was concluded that at least under the present experimental conditions,f _c and venous [la]_b do not play a major role as determinants of perceived exertion.     

Glycolytic activity of rat aorta after exercise

Summary Activities of glycolytic enzymes in the aorta were investigated in female Wistar rats. There were two groups of rats; one served as the control (sedentary rats), while the other group was forced to run on a treadmill for 10 weeks. In the control animals, the activities of hexokinase, phosphofructokinase and aldolase were relatively lower than those of the other glycolytic enzymes (phosphoglucose isomerase, lactate dehydrogenase and pyruvate kinase). After exercise, the activity of phosphofructokinase increased by 15%, whereas the other enzymatic activities were much the same as in the controls. Within the limits of the experiments, the increased percentage of phosphofructokinase was statistically significant (p<0.05). Since phosphofructokinase is a putative rate limiting enzyme, this enzymatic activation may indicate that glycolytic activity in the rat aorta is enhanced during and after running exercise.     

Force-, power-, and elasticity-velocity relationships in walking,running, and jumping

Summary Ground reaction forces and mechanical power were investigated when the subjects walked normally, while they were racing or running at four speeds, and when they performed the running long jump take-off. In addition, the apparent spring constants of the support leg in eccentric and concentric phases were investigated at the four running speeds, during the running long jump take-off, and in the triple jump. Six club level track and field athletes, four national level long jumpers, and six national level triple jumpers took part in the study. Cinematographic technique and a mathematical model of hopping (Alexander and Vernon 1975) were employed in the analysis. Force and power values were found to vary in the following order (from highest to lowest): long jump take-off, maximal running speed, submaximal running (80, 60, and 40% of maximum speed), racing gait, and normal gait. The data disclosed that the measured parameters had the highest values in the long jump take-off performed by the long jump athletes. Their peak values were: resultant ground reaction force 3270±74 N and mechanical power 160.1±10.5 J×kg^–1×s^–1. For the track and field athletes the values were 2010±80 N and 126.0±12.6 J ×kg^–1×s^–1. The apparent spring constant values of the support leg in the national level jumper group were in eccentric phase 30.54±8.38 N×mm^–1 ×kg^–1 and in concentric phase 0.129±0.012 N×mm^–1×kg^–1. In the track and field athletes the values were 13.97±1.01 N×mm^–1×kg^–1 and 0.093±0.003 N×mm^–1×kg^–1, respectively. In general, the increase in force and mechanical power output was related to the value of the apparent spring constant of the support leg in the eccentric phase. The spring constant in the eccentric phase increased with the velocity of motion in running, the long jump take-off and the triple jump. This suggests that it may be possible to use this parameter as a measure of mechanical performance, as it may reflect the combined elasticity of muscles, tendons, and bones.