Donald C. McKenzie

A retrospective case-control analysis of 2002 running injuries

Objective: To provide an extensive and up to date database for specific running related injuries, across the sexes, as seen at a primary care sports medicine facility, and to assess the relative risk for individual injuries based on investigation of selected risk factors. Methods: Patient data were recorded by doctors at the Allan McGavin Sports Medicine Centre over a two year period. They included assessment of anthropometric, training, and biomechanical information. A model was constructed (with odds ratios and their 95% confidence intervals) of possible contributing factors using a dependent variable of runners with a specific injury and comparing them with a control group of runners who experienced a different injury. Variables included in the model were: height, weight, body mass index, age, activity history, weekly activity, history of injury, and calibre of runner. Results: Most of the study group were women (54%). Some injuries occurred with a significantly higher frequency in one sex. Being less than 34 years old was reported as a risk factor across the sexes for patellofemoral pain syndrome, and in men for iliotibial band friction syndrome, patellar tendinopathy, and tibial stress syndrome. Being active for less than 8.5 years was positively associated with injury in both sexes for tibial stress syndrome; and women with a body mass index less than 21 kg/m2 were at a significantly higher risk for tibial stress fractures and spinal injuries. Patellofemoral pain syndrome was the most common injury, followed by iliotibial band friction syndrome, plantar fasciitis, meniscal injuries of the knee, and tibial stress syndrome. Conclusions: Although various risk factors were shown to be positively associated with a risk for, or protection from, specific injuries, future research should include a non-injured control group and a more precise measure of weekly running distance and running experience to validate these results.

Stress fractures in athletes: A study of 320 cases

We analyzed cases of 320 athletes with bone scan- positive stress fractures (M = 145, F = 175) seen over 3.5 years and assessed the results of conservative management. The most common bone injured was the tibia (49.1 %), followed by the tarsals (25.3%), metatar sals (8.8%), femur (7.2%), fibula (6.6%), pelvis (1.6%), sesamoids (0.9%), and spine (0.6%). Stress fractures were bilateral in 16.6% of cases. A significant age difference among the sites was found, with femoral and tarsal stress fractures occurring in the oldest, and fibular and tibial stress fractures in the youngest. Run ning was the most common sport at the time of injury but there was no significant difference in weekly running mileage and affected sites. A history of trauma was significantly more common in the tarsal bones. The average time to diagnosis was 13.4 weeks (range, 1 to 78) and the average time to recovery was 12.8 weeks (range, 2 to 96). Tarsal stress fractures took the longest time to diagnose and recover. Varus alignment was found frequently, but there was no significant difference among the fracture sites, and varus alignment did not affect time to diagnosis or recovery. Radiographs were taken in 43.4% of cases at the time of presentation but were abnormal in only 9.8%. A group of bone scan- positive stress fractures of the tibia, fibula, and meta tarsals (N = 206) was compared to a group of clinically diagnosed stress fractures of the same bone groups (N = 180), and no significant differences were found. Patterns of stress fractures in athletes are different from those found in military recruits. Using bone scan for diagnosis indicates that tarsal stress fractures are much more common than previously realized. Time to diagnosis and recovery is site-dependent. Technetium99 bone scan is the single most useful diagnostic aid. Conservative treatment of stress fractures in athletes is satisfactory in the majority of cases.

A prospective study of running injuries: the Vancouver Sun Run “In Training” clinics

Objectives: Seventeen running training clinics were investigated to determine the number of injuries that occur in a running programme designed to minimise the injury rate for athletes training for a 10 km race. The relative contributions of factors associated with injury were also reported. Methods: A total of 844 primarily recreational runners were surveyed in three trials on the 4th, 8th, and 12th week of the 13 week programme of the “In Training” running clinics. Participants were classified as injured if they experienced at least a grade 1 injury—that is, pain only after running. Logistic regression modelling and odds ratio calculation were performed for each sex using the following predictor variables: age, body mass index (BMI), previous aerobic activity, running frequency, predominant running surface, arch height, running shoe age, and concurrent cross training. Results: Age played an important part in injury in women: being over 50 years old was a risk factor for overall injury, and being less than 31 years was protective against new injury. Running only one day a week showed a non-significant trend for injury risk in men and was a significant risk factor in women and overall injury. A BMI of > 26 kg/m2 was reported as protective for men. Running shoe age also significantly contributed to the injury model. Half of the participants who reported an injury had had a previous injury; 42% of these reported that they were not completely rehabilitated on starting the 13 week training programme. An injury rate of 29.5% was recorded across all training clinics surveyed. The knee was the most commonly injured site. Conclusions: Although age, BMI, running frequency (days a week), and running shoe age were associated with injury, these results do not take into account an adequate measure of exposure time to injury, running experience, or previous injury and should thus be viewed accordingly. In addition, the reason for the discrepancy in injury rate between these 17 clinics requires further study.

Markers of inflammation and myofibrillar proteins following eccentric exercise in humans

Abstract The purpose of this study was to examine the time-course and relationships of technetium-99m (99mTc) neutrophils in muscle, interleukin-6 (IL-6), myosin heavy chain fragments (MHC), eccentric torque, and delayed onset muscle soreness (DOMS) following eccentric exercise in humans. Twelve male subjects completed a pre-test DOMS questionnaire, performed a strength test and had 100 ml blood withdrawn for analysis of plasma IL-6 and MHC content. The neutrophils were separated, labelled with 99mTc, and re-infused into the subjects immediately before the exercise. Following 300 eccentric repetitions of the right quadriceps muscles on an isokinetic dynamometer, the subjects had 10 ml of blood withdrawn and repeated the eccentric torque exercise tests and DOMS questionnaire at 0, 2, 4, 6, 20, 24, 48, 72 h, and 6 and 9 days. Bilateral images of the quadriceps muscles were taken at 2, 4, and 6 h. Computer analysis of regions of interest was used to determine the average count per pixel. The 99mTc neutrophils and IL-6 increased up to 6 h post-exercise (P < 0.05). The neutrophils were greater in the exercised muscle than the non-exercised muscle (P < 0.01). The DOMS was increased from 0 to 48 h, eccentric torque decreased from 2 to 24 h, and MHC peaked at 72 h post-exercise (P < 0.001). Significant relationships were found between IL-6 at 2 h and DOMS at 24 h post-exercise (r=0.68) and assessment of the magnitude of change between IL-6 and MHC (r=0.66). These findings suggest a relationship between damage to the contractile proteins and inflammation, and that DOMS is associated with inflammation but not with muscle damage.

Effects of menstrual cycle phase on athletic performance.

The purpose of this study was to examine the effects of menstrual cycle phase on four selected indices of athletic performance: aerobic capacity, anaerobic capacity, isokinetic strength, and high intensity endurance. Sixteen eumenorrheic women (VO2max > or = 50 ml.kg-1.min-1) were tested during the early follicular (F) and midluteal (L) phases of the menstrual cycle. Cycle phases were confirmed by serum estradiol and progesterone assays. No significant differences were observed between F and L tests in weight, percent body fat, sum of skinfolds, hemoglobin concentration, hematocrit, maximum heart rate, maximum minute ventilation, maximum respiratory exchange ratio, anaerobic performance, endurance time to fatigue (at 90% of VO2max), or isokinetic strength of knee flexion and extension. Both absolute and relative VO2max, however, were slightly lower in L than in F (F = 3.19 +/- 0.09.min-1, L = 3.13 +/- 0.08.min-1, P = 0.04; and F = 53.7 +/- 0.9 ml.kg-1.min-1, L = 52.8 +/- 0.8 ml.kg-1.min-1, P = 0.06). These results suggest that the cyclic increases in endogenous female steroid hormones of an ovulatory menstrual cycle may have a slight, deleterious influence on aerobic capacity, with potential implications for individual athletes. Nevertheless, the cycle phase did not impact significantly on the majority of the other performance tests and cardiorespiratory variables measured in this study.

Running Shoes, Orthotics, and Injuries

SummaryRunning is the most visible expression of the continued interest in regular physical activities. Unfortunately injuries are common, primarily due to overuse, and a number of aetiological factors have been recognised. Of these, training errors can be responsible for up to 60% of injuries. The training surface, a lack of flexibility and strength, the stage of growth and development, poor footwear and abnormal biomechanical features have all been implicated in the development of running injuries. A thorough understanding of the biomechanics of running is a necessary prerequisite for individuals who treat or advise runners.Clinically, the configuration of the longitudinal arch is a valuable method of classifying feet and has direct implications on the development and management of running problems. The runner with excessively pronated feet has features which predispose him/her to injuries that most frequently occur at the medial aspect of the lower extremity: tibial stress syndrome; patellofemoral pain syndrome; and posterior tibialis tendinitis. These problems occur because of excessive motion at the subtalar joint and control of this movement can be made through the selection of appropriate footwear, plus orthotic foot control. The runner with cavusfeet often has a rigid foot and concomitant problems of decreased ability to absorb the force of ground contact. These athletes have unique injuries found most commonly on the lateral aspect of the lower extremity; iliotibial band friction syndrome; peroneus tendinitis; stress fractures; trochanteric bursitis; and plantar fasciitis. Appropriate footwear advice and the use of energy-absorbing materials to help dissipate shock will benefit these individuals. Running shoes for the pronated runner should control the excessive motion. The shoes should be board-lasted, straight-lasted, have a stable heel counter, extra medial support, and a wider flare than the shoes for the cavusfoot. For these athletes a slip-lasted, curve-lasted shoe with softer ethylene vinyl acetate (EVA) and a narrow flare is appropriate. Orthotic devices are useful in selected runners with demonstrated biomechanical abnormalities that contribute to the injury. Soft orthotics made of a commercial insole laminated with EVA are comfortable, easily adjusted, inexpensive, and more forgiving than the semirigid orthotics which are useful in cases where the soft orthotic does not provide adequate foot control.A review of injury data shows an alarming rise in the incidence of knee pain in runners — from 18% to 50% of injuries in 13 years. Errors in training judgement, with excessive loading, particularly in runners with compromised biomechanical features, represent the primary aetiological factors. These errors cannot be accommodated by running shoe design. Similarly, orthotic devices alone will not control the injury pattern of most runners. Although footwear and biomechanical control may represent a significant therapeutic intervention in some individuals, they must remain part of a comprehensive rehabilitation programme that considers the other aetiological factors that contribute to running injuries.

Respiratory mechanics during exercise in endurance-trained men and women.

The purpose of this study was to compare the mechanics of breathing including the measurement of expiratory flow limitation, end‐expiratory lung volume, end‐inspiratory lung volume, and the work of breathing in endurance‐trained men (n= 8) and women (n= 10) during cycle exercise. Expiratory flow limitation was assessed by applying a negative expiratory pressure at the mouth. End‐expiratory lung volume and end‐inspiratory lung volume were determined by having subjects perform inspiratory capacity manoeuvres. Transpulmonary pressure, taken as the difference between oesophageal and airway opening pressure, was plotted against volume and integrated to determine the work of breathing. Expiratory flow limitation occurred in nine females (90%) and three males (43%) during the final stage of exercise. Females had a higher relative end‐expiratory lung volume (42 ± 8 versus 35 ± 5% forced vital capacity (FVC)) and end‐inspiratory lung volume (88 ± 5 versus 82 ± 7% FVC) compared to males at maximal exercise (P < 0.05). Women also had a higher work of breathing compared to men across a range of ventilations. On average, women had a work of breathing that was twice that of men at ventilations above 90 l min−1. These data suggest that expiratory flow limitation may be more common in females and that they experience greater relative increases in end‐expiratory lung volume and end‐inspiratory lung volume at maximal exercise compared to males. The higher work of breathing in women is probably attributed to their smaller lung volumes and smaller diameter airways. Collectively, these findings suggest that women utilize a greater majority of their ventilatory reserve compared to men and this is associated with a higher cost of breathing.

Asthma and the elite athlete: Summary of the International Olympic Committee's Consensus Conference, Lausanne, Switzerland, january 22-24, 2008

Respiratory symptoms cannot be relied on to make a diagnosis of asthma and/or airways hyperresponsiveness (AHR) in elite athletes. For this reason, the diagnosis should be confirmed with bronchial provocation tests. Asthma management in elite athletes should follow established treatment guidelines (eg, Global Initiative for Asthma) and should include education, an individually tailored treatment plan, minimization of aggravating environmental factors, and appropriate drug therapy that must meet the requirements of the World Anti-Doping Agency. Asthma control can usually be achieved with inhaled corticosteroids and inhaled beta(2)-agonists to minimize exercise-induced bronchoconstriction and to treat intermittent symptoms. The rapid development of tachyphylaxis to beta(2)-agonists after regular daily use poses a dilemma for athletes. Long-term intense endurance training, particularly in unfavorable environmental conditions, appears to be associated with an increased risk of developing asthma and AHR in elite athletes. Globally, the prevalence of asthma, exercise-induced bronchoconstriction, and AHR in Olympic athletes reflects the known prevalence of asthma symptoms in each country. The policy of requiring Olympic athletes to demonstrate the presence of asthma, exercise-induced bronchoconstriction, or AHR to be approved to inhale beta(2)-agonists will continue.

The human spleen during physiological stress

AbstractMany mammals have the ability to autotransfuse a large quantity of red blood cells from the spleen into the active circulation during times of stress. This enhancement of the oxygen transport system has benefited the athletic mammal, that is, the thoroughbred horse, fox and greyhound in an improved aerobic performance. The role of the spleen in sequestering 50% of the total red cell volume in seals and horses, during times of inactivity, dramatically reduces the viscosity of the blood and therefore the work of the heart. In comparison, the human spleen contains only a small percentage of red blood cells, and has been primarily thought of as a lymphoid organ. Many mammals have the ability to autotransfuse a large quantity of red blood cells from the spleen into the active circulation during times of stress. This enhancement of the oxygen transport system has benefited the athletic mammal, that is, the thoroughbred horse, fox and greyhound in an improved aerobic performance. The role of the spleen in sequestering 50% of the total red cell volume in seals and horses, during times of inactivity, dramatically reduces the viscosity of the blood and therefore the work of the heart. In comparison, the human spleen contains only a small percentage of red blood cells, and has been primarily thought of as a lymphoid organ.The aim of this review is to emphasise the similarities between the human spleen and that of several athletic mammalian species during acute physiological stress. In the athletic mammalian model the expulsion of blood from the spleen is facilitated via the sympathetic nervous system resulting in contraction of smooth muscle within the splenic capsule. In comparison, the lack of smooth muscle contained within the human splenic capsule has meant that active contraction of the spleen has historically been viewed as unlikely, although evidence of contractile proteins within the red pulp have suggested otherwise.Exercise results in haemoconcentration, which has been attributed solely to a reduction in plasma volume. Indirect calculation of plasma volume changes utilise haemoglobin and haematocrit and assume that the circulating red cell volume remains constant. However, several studies have suggested that the human spleen could account for 30% of the increase in haematocrit. This would result in a substantial overestimation of the reduction in plasma volume, indicating that the expulsion of red blood cells from the spleen must not be overlooked when utilising these equations.

Inspiratory muscle training attenuates the human respiratory muscle metaboreflex.

We hypothesized that inspiratory muscle training (IMT) would attenuate the sympathetically mediated heart rate (HR) and mean arterial pressure (MAP) increases normally observed during fatiguing inspiratory muscle work. An experimental group (Exp, n= 8) performed IMT 6 days per week for 5 weeks at 50% of maximal inspiratory pressure (MIP), while a control group (Sham, n= 8) performed IMT at 10% MIP. Pre‐ and post‐training, subjects underwent a eucapnic resistive breathing task (RBT) (breathing frequency = 15 breaths min−1, duty cycle = 0.70) while HR and MAP were continuously monitored. Following IMT, MIP increased significantly (P < 0.05) in the Exp group (−125 ± 10 to −146 ± 12 cmH2O; mean ±s.e.m.) but not in the Sham group (−141 ± 11 to −148 ± 11 cmH2O). Prior to IMT, the RBT resulted in significant increases in HR (Sham: 59 ± 2 to 83 ± 4 beats min−1; Exp: 62 ± 3 to 83 ± 4 beats min−1) and MAP (Sham: 88 ± 2 to 106 ± 3 mmHg; Exp: 84 ± 1 to 99 ± 3 mmHg) in both groups relative to rest. Following IMT, the Sham group observed similar HR and MAP responses to the RBT while the Exp group failed to increase HR and MAP to the same extent as before (HR: 59 ± 3 to 74 ± 2 beats min−1; MAP: 84 ± 1 to 89 ± 2 mmHg). This attenuated cardiovascular response suggests a blunted sympatho‐excitation to resistive inspiratory work. We attribute our findings to a reduced activity of chemosensitive afferents within the inspiratory muscles and may provide a mechanism for some of the whole‐body exercise endurance improvements associated with IMT.