Biomedical subjects

Mark P Rayson

Publications and source records attributed to Mark P Rayson.

4 recordsLinked to original sources

PubMed2006

Can simple anthropometric and physical performance tests track training-induced changes in load-carriage ability?

The objective of this research was to determine whether tests of strength, endurance, and anthropometry could be used to assess training-induced changes (delta) in load-carriage performance. Eighty-four British Army recruits completed a 10-week training program. Strength, endurance, body composition, and 3.2-km load carriage with 15 kg and 25 kg were assessed before and after training. Training significantly increased load-carriage performance (7-16%), back extension and dynamic lifting strengths, endurance and fat-free mass, and reduced body fat. Statistically significant regression models (adjusted R2 of 0.063-0.797) were produced that predicted delta load-carriage performance. However, the 95% limits of agreement between observed and predicted delta load-carriage data showed margins of error (11-15%) comparable to the average training-induced gains in performance. Training-induced changes in load-carriage performance appear to be highly specific, which suggests that both training and testing procedures should also be specific to load-carriage performance.

Adolescent↗

PubMed2004

Training diagnosis for a load carriage task.

To explore the possibility of training diagnosis for a 3.2-km loaded march with a 25 kg load, 50 men trained for 10 weeks using either running, marching, and endurance-based circuit training (Circuits), or running, marching, and resistance training (Resistance). The march was performed before and after training, and other measurements related to loaded marching were conducted before training only. Each group was ranked by improvement in the loaded march, and divided into significantly different subgroups of 'good' and 'poor' responders (improvements of approximately 20% vs. 10%). For Circuits, there were significant differences between good and poor responders to training in the pretraining ratios of shuttle run: isometric lift strength (p = 0.031) and shuttle run: isometric back extension strength (p = 0.033). Stronger subjects with lower endurance responded better to Circuits. Resistance tended to show the opposite effect (p < 0.2). These are the first objective data on which to prescribe training for load carriage on an individual basis.

Adolescent↗

PubMed2003

Venous obstruction in healthy limbs: a model for chronic compartment syndrome?

PURPOSE: Chronic exertional compartment syndrome (CECS) in the anterior tibial (AT) compartment is generally believed to be the result of reduced venous blood flow caused by restrictive compartments and increased intramuscular pressures. If this is so, then restricting venous flow in the muscles of healthy subjects during exercise should mimic CECS. METHODS: This hypothesis was tested in 10 control subjects (aged 19-41 yr, five males) with and without external venous occlusion induced by a sphygmomanometer cuff fitted just below the knee and inflated to 80 mm Hg. Twenty CECS patients (20-39 yr, 16 males) were studied without external occlusion. Subjects performed intermittent, isometric maximal voluntary contractions (MVC) of the AT for 20 min (1.6-s contractions, 0.5 duty cycle). MVC, tetanic force (2 s at 50 Hz), muscle thickness (ultrasound imaging), and pain were measured during exercise and 10 min of recovery. RESULTS: Venous occlusion in the controls induced greater pain, fatigue, and increase in muscle thickness (P < 0.01). Initially the patients fatigued more slowly than the occluded controls, but at the end of exercise, the fatigue and pain were similar in these two groups. The controls showed a greater increase in muscle size (P = 0.01). Recovery was similar in all three groups, although the size of the patients' muscles recovered rather more slowly. CONCLUSION: External venous occlusion of the AT muscles in control subjects induces changes very similar to those of CECS patients, although the different time courses indicate that different processes are involved. The AT compartment of CECS patients is capable of distension.

Adult↗

PubMed2002

Chronic exertional compartment syndrome: muscle changes with isometric exercise.

UNLABELLED: Chronic exertional compartment syndrome (CECS) is a well-documented cause of lower leg pain in active individuals. The pathophysiology is unclear, although it is generally believed to be associated with increased intramuscular pressure, but there is very little information about muscle function in relation to the onset of pain. PURPOSE: To investigate strength, fatigue, and recovery of the anterior tibial muscles in CECS patients and healthy subjects during an isometric exercise protocol. METHODS: Twenty patients and 22 control subjects (mean age 27.6 yr and 33.0 yr, respectively) performed a 20-min isometric exercise protocol consisting of intermittent maximal voluntary contractions (MVC). Central fatigue was evaluated by comparing changes in electrically stimulated (2 s at 50 Hz) and voluntary contraction force before and during the exercise, and then throughout 10 min of recovery. Muscle size was measured by ultrasonography. Pain and cardiovascular parameters were also examined. RESULTS: The absolute MVC forces were similar, but MVC:body mass of the patients was lower (P < 0.05) as was the ratio of MVC to muscle cross-sectional area (P < 0.01). The extent of central and peripheral fatigue was similar in the two groups. The patients reported significantly higher levels of pain during exercise (P < 0.05 at 4 min) and after the first minute of recovery (P < 0.001). An 8% increase in muscle size after exercise was observed for both groups. There were no differences in the cardiovascular responses of the two groups. CONCLUSIONS: CECS patients were somewhat weaker than normal but fatigued at a similar rate during isometric exercise. Patients reported higher pain than controls despite comparable changes in muscle size, suggesting that abnormally tight fascia are not the main cause of CECS symptoms.

Adult↗