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Lower Leg Anterior and Lateral Intracompartmental Pressure Changes Before and After Classic Versus Skate Nordic Rollerskiing

Context

Chronic exertional compartment syndrome (CECS) is a debilitating condition resulting in loss of function and a decrease in athletic performance. Cases of CECS are increasing among Nordic skiers; therefore, analysis of intracompartmental pressures (ICPs) before and after Nordic skiing is warranted.

Objective

To determine if lower leg anterior and lateral ICPs and subjective lower leg pain levels increased after a 20-minute Nordic rollerskiing time trial and to examine if differences existed between postexercise ICPs for the 2 Nordic rollerskiing techniques, classic and skate.

Design

Crossover study.

Setting

Outdoor paved loop.

Patients or Other Participants

Seven healthy Division I Nordic skiers (3 men, 4 women; age = 22.71 ± 1.38 y, height = 175.36 ± 6.33 cm, mass = 70.71 ± 6.58 kg).

Intervention(s)

Participants completed two 20-minute rollerskiing time trials using the classic and skate technique in random order. The time trials were completed 7 days apart. Anterior and lateral ICPs and lower leg pain scores were obtained at baseline and at minutes 1 and 5 after rollerskiing.

Main Outcome Measure(s)

Anterior and lateral ICPs (mm Hg) were measured using a Stryker Quic STIC handheld monitor. Subjective measures of lower leg pain were recorded using the 11-point Numeric Rating Scale.

Results

Increases in both anterior (P = .000) and lateral compartment (P = .002) ICPs were observed, regardless of rollerskiing technique used. Subjective lower leg pain increased after the classic technique for the men from baseline to 1 minute postexercise and after the skate technique for the women. Significant 3-way interactions (technique × time × sex) were observed for the anterior (P = .002) and lateral (P = .009) compartment ICPs and lower leg pain (P = .005).

Conclusions

Postexercise anterior and lateral ICPs increased compared with preexercise ICPs after both classic and skate rollerskiing techniques. Lower leg pain is a primary symptom of CECS. The subjective lower leg pain 11-point Numeric Rating Scale results indicate that increases in lower leg ICPs sustained during Nordic rollerskiing may increase discomfort during activity. Our results therefore suggest that Nordic rollerskiing contributes to increases in ICPs, which may lead to the development of CECS.Key Words: chronic exertional compartment syndrome, compartment syndrome, anterior compartment, lower leg pain Nordic skiing

Key Points

• The exact cause of chronic exertional compartment syndrome is currently unknown.
• The diagnosis of chronic exertional compartment syndrome is increasing within the competitive Nordic skiing population.
• Increases in anterior and lateral intracompartmental pressures were observed after a 20-minute time trial using either the classic or skating Nordic rollerskiing technique.

Chronic exertional compartment syndrome (CECS) is a debilitating condition resulting in loss of function and a decrease in athletic performance. In general, a compartment syndrome occurs when the circulation and function of tissues within a closed space are compromised by increased pressure within that space.¹ An increase in tissue pressure within an enclosed space can threaten perfusion and tissue viability. In the case of CECS, this increase in tissue pressure within the confined space is reversible and will decrease after exercise ceases.² Common symptoms of CECS in the lower leg include burning, aching, paresthesia, weakness, and an inability to dorsiflex the foot. These symptoms are detrimental to performance and, if left untreated, have the potential to end an athlete''s career. Chronic exertional compartment syndrome has been reported among runners, cyclists, and military personnel.³ Recently, increasing anecdotal evidence of CECS among competitive Nordic skiers has been shown; however, no researchers have examined the relationship between Nordic skiing and intracompartmental pressures (ICPs).Rollerskiing is a typical dry-land method of Nordic ski training and may be performed using either the classic or the skate technique. Rollerskis are shortened Nordic skis with 1 wheel at each end designed to be used on smooth indoor or outdoor surfaces. Classic rollerskiing uses the same kick-and-glide motion as on snow. Classic rollerskis have wider wheels than skate rollerskis. A ratchet mechanism on 1 wheel only rolls forward, providing unidirectional travel and limiting negative gain. Skate rollerskiing uses the same lateral leg push as on snow. Skate rollerskis have narrower wheels, similar to in-line skates, and both wheels roll freely in either direction. For both techniques, boots and bindings are the same as those used for Nordic skiing on the snow.Anecdotally, some athletes complain that they experience more lower leg pain during classic rollerskiing than classic snow skiing, which could be attributed to the weight of the ski (approximately 2.5 kg per pair of classic rollerskis compared with approximately 1.18 kg per pair of classic snow skis). More recent anecdotal evidence has suggested that any increased pressure observed during the classic rollerskiing technique may be attributed to the quality of the rollerski wheels and the skier''s effort needed to maintain forward tracking and control of the ski while in motion. This suggestion is similar to anecdotal reports of increased lower leg pain while skate skiing in icy conditions, when one must sustain muscular contractions in the lower leg and foot to maintain control of the ski.It is unknown whether Nordic skiing causes chronic increases in anterior and lateral ICPs, which may contribute to the development of CECS. Combined with a thorough history and clinical examination, ICP testing is the gold standard used to diagnose CECS.⁴ In this study, if anterior and lateral ICPs increased during Nordic rollerskiing, the findings could point to Nordic rollerskiing as a possible contributor in the development of CECS. Coaches, athletes, and health care personnel may then seek modified skiing techniques and equipment to avoid increased ICPs during Nordic rollerskiing.The purpose of our study was to determine if ICPs of the anterior and lateral lower leg compartments increased among collegiate Nordic skiers after a 20-minute rollerskiing time trial. We also aimed to determine whether postexercise ICPs differed for the classic rollerskiing technique versus the skate rollerskiing technique. We hypothesized that the ICPs of both the anterior and lateral lower leg compartments would increase among collegiate Nordic skiers after the 20-minute time trial. We also hypothesized that postexercise anterior and lateral ICPs would be higher after the skate rollerskiing technique than the classic rollerskiing technique. Significant results will allow physicians, athletic trainers, coaches, and athletes to better understand CECS and the Nordic skiing population, which may lead to modified training methods or injury-prevention practices for both symptomatic and asymptomatic skiers.     

Selenium Cycling Across Soil-Plant-Atmosphere Interfaces: A Critical Review

Selenium (Se) is an essential element for humans and animals, which occurs ubiquitously in the environment. It is present in trace amounts in both organic and inorganic forms in marine and freshwater systems, soils, biomass and in the atmosphere. Low Se levels in certain terrestrial environments have resulted in Se deficiency in humans, while elevated Se levels in waters and soils can be toxic and result in the death of aquatic wildlife and other animals. Human dietary Se intake is largely governed by Se concentrations in plants, which are controlled by root uptake of Se as a function of soil Se concentrations, speciation and bioavailability. In addition, plants and microorganisms can biomethylate Se, which can result in a loss of Se to the atmosphere. The mobilization of Se across soil-plant-atmosphere interfaces is thus of crucial importance for human Se status. This review gives an overview of current knowledge on Se cycling with a specific focus on soil-plant-atmosphere interfaces. Sources, speciation and mobility of Se in soils and plants will be discussed as well as Se hyperaccumulation by plants, biofortification and biomethylation. Future research on Se cycling in the environment is essential to minimize the adverse health effects associated with unsafe environmental Se levels.     

Lipopolysaccharide-induced cytokine and receptor expression and neutrophil infiltration in the liver of osteopetrosis (op/op) mutant mice

BACKGROUND/AIMS: Mice homozygous for the osteopetrosis (op) mutation are genetically deficient in macrophage colony-stimulating factor (M-CSF/CSF-1) and are characterized by defective differentiation and function of macrophages. The aim of this study is to assess the contribution of M-CSF to lipopolysaccharide (LPS)-induced cytokine expression and neutrophil infiltration in the liver. Methods: We investigated the effects of LPS administration in M-CSF-deficient op/op mutant mice. The expression of cytokines and receptors in the liver was studied by immunohistochemistry and RT-PCR. Neutrophil infiltration in the liver was also examined. RESULTS: After LPS administration, cytokine production and expression of LPS receptors, such as CD14 and scavenger receptor class A (MSR-A), were induced at lower levels in op/op mice than those in littermate mice. Neutrophil infiltration in the liver of op/op mice did not differ significantly from that of littermate mice. Anti-IL-8 receptor homologue and anti-C5a receptor antibody reduced the number of infiltrating neutrophils. CONCLUSIONS: These findings indicate that deficient macrophage activation following LPS injection in op/op mice is associated with decreased expression of CD14 and MSR-A in the liver. Thus, M-CSF plays a critical role in LPS-induced macrophage activation but does not exert a dominant role in neutrophil infiltration in the liver.     

Lipopolysaccharide‐induced cytokine and receptor expression and neutrophil infiltration in the liver of osteopetrosis (op/op) mutant mice

Abstract: Background/Aims: Mice homozygous for the osteopetrosis (op) mutation are genetically deficient in macrophage colony‐stimulating factor (M‐CSF/CSF‐1) and are characterized by defective differentiation and function of macrophages. The aim of this study is to assess the contribution of M‐CSF to lipopolysaccharide (LPS)‐induced cytokine expression and neutrophil infiltration in the liver. Methods: We investigated the effects of LPS administration in M‐CSF‐deficient op/op mutant mice. The expression of cytokines and receptors in the liver was studied by immunohistochemistry and RT‐PCR. Neutrophil infiltration in the liver was also examined. Results: After LPS administration, cytokine production and expression of LPS receptors, such as CD14 and scavenger receptor class A (MSR‐A), were induced at lower levels in op/op mice than those in littermate mice. Neutrophil infiltration in the liver of op/op mice did not differ significantly from that of littermate mice. Anti‐IL‐8 receptor homologue and anti‐C5a receptor antibody reduced the number of infiltrating neutrophils. Conclusions: These findings indicate that deficient macrophage activation following LPS injection in op/op mice is associated with decreased expression of CD14 and MSR‐A in the liver. Thus, M‐CSF plays a critical role in LPS‐induced macrophage activation but does not exert a dominant role in neutrophil infiltration in the liver.     

Knee extensor strength differences in obese and healthy-weight 10-to 13-year-olds

The purpose of this study was to investigate if obese children have reduced knee extensor (KE) strength and to explore the relationship between adiposity and KE strength. An observational case–control study was conducted in three Australian states, recruiting obese [N = 107 (51 female, 56 male)] and healthy-weight [N = 132 (56 female, 76 male)] 10- to 13-year-old children. Body mass index, body composition (dual energy X-ray absorptiometry), isokinetic/isometric peak KE torques (dynamometry) and physical activity (accelerometry) were assessed. Results revealed that compared with their healthy-weight peers, obese children had higher absolute KE torques (P ≤ 0.005), equivocal KE torques when allometrically normalized for fat-free mass (FFM) (P ≥ 0.448) but lower relative KE torques when allometrically normalized for body mass (P ≤ 0.008). Adjustments for maternal education, income and accelerometry had little impact on group differences, except for isometric KE torques relative to body mass which were no longer significantly lower in obese children (P ≥ 0.013, not significant after controlling for multiple comparisons). Percent body fat was inversely related to KE torques relative to body mass (r = ?0.22 to ?0.35, P ≤ 0.002), irrespective of maternal education, income or accelerometry. In conclusion, while obese children have higher absolute KE strength and FFM, they have less functional KE strength (relative to mass) available for weight-bearing activities than healthy-weight children. The finding that FFM-normalized KE torques did not differ suggests that the intrinsic contractile properties of the KE muscles are unaffected by obesity. Future research is needed to see if deficits in KE strength relative to mass translate into functional limitations in weight-bearing activities.     

Viral Infection of Engrafted Human Islets Leads to Diabetes

Type 1 diabetes (T1D) is characterized by the destruction of the insulin-producing β-cells of pancreatic islets. Genetic and environmental factors both contribute to T1D development. Viral infection with enteroviruses is a suspected trigger for T1D, but a causal role remains unproven and controversial. Studies in animals are problematic because of species-specific differences in host cell susceptibility and immune responses to candidate viral pathogens such as coxsackievirus B (CVB). In order to resolve the controversial role of viruses in human T1D, we developed a viral infection model in immunodeficient mice bearing human islet grafts. Hyperglycemia was induced in mice by specific ablation of native β-cells. Human islets, which are naturally susceptible to CVB infection, were transplanted to restore normoglycemia. Transplanted mice were infected with CVB4 and monitored for hyperglycemia. Forty-seven percent of CVB4-infected mice developed hyperglycemia. Human islet grafts from infected mice contained viral RNA, expressed viral protein, and had reduced insulin levels compared with grafts from uninfected mice. Human-specific gene expression profiles in grafts from infected mice revealed the induction of multiple interferon-stimulated genes. Thus, human islets can become severely dysfunctional with diminished insulin production after CVB infection of β-cells, resulting in diabetes.