gms | German Medical Science

Objective: Overweight and its severe consequences are known as activator and accessory symptom of lifestyle diseases [1]. As a part of exercise interventions of the current guidelines for the prevention of cardiovascular disease and type-II-diabetes strength training is a major topic [2]. Because of elevated blood pressure during strength training new exercise interventions are necessary to gain all benefits of strength training without possible harm. Three different types of muscle activity are known. Concentric exercise (CE) as a consequence of active motion where the muscle strength exceeds external force, eccentric exercise (EE) as a consequence of passive motion, where external force exceeds internal strength and isometric exercise without visible motion, where external force is equal to internal strength [3]. Daily exercise is a mixture of concentric and eccentric exercise for movement and isometric exercise for static work. Concentric exercise is needed more in hiking upwards, whereas hiking downwards includes eccentric exercise more. Eccentric endurance training mixes high muscle force loads with low cardiovascular effort [4]. Therefore we investigated the effects of eccentric endurance training on strength parameters in overweight healthy individuals.

Material/Methods: After acceptance from the institutional review board and the Ethics Committee of Vorarlberg physical examination 55 individuals (gender: 36f/19m; age: 50±10.8a; BMI: 28.4±4.5kg/m²) absolved an 8-week intervention of downhill walking with hiking poles with a minimum of three bouts per week (distance: 4.2km; height: 636m). Participants therefore used a cable car connection for reaching the beginning of the track. Usage of cable-car connection also recorded compliance. Pre- and post intervention testing was made for isometric strength on isometric leg press test device (CTT-isoLegPress TITAN; BFMC, Germany) with a computer-supported ankle adjustment at 110° of knee flexion. Further testing for isometric trunk strength was performed with CTT Kolossos (BFMC, Germany), which provides measurement of anatomic directions of thoracic and lumbar spine in frontal, sagittal and transversal direction. Therefore six measurements including sagittal flexion and extension, lateral flexion and rotation in both directions were recorded. Ten seconds after one attempt measurement started sequentially, beginning with the left side. Two attempts over 7 seconds with maximum effort were logged for each person pre and post interventional. Leg strength was given in Newton [N] whereas trunk strength was given in Newton meter [Nm] as torque. For statistical analysis the higher value was used. For interval scaled parameters with normal distribution students t-test was used to perform a comparison of means. Further analyses were made for correlations with training frequency. A statistical level of significance was accepted with 5% using SPSS 15.0 (IBM Corporation, USA).

Results: After exclusion of 3 participants because of missing hiking times compliance was 94.5%. Change in Body Mass Index was not reported for both gender (f: p=0.149; m: p=0.450). No difference in hiking times was reported (p=0.325). Because of a statistically significant difference in pretested strength parameters for male and female participants (p=0.035) further calculations were made separated for both groups. Improvement in isometric strength in lower extremities performing leg press was statistically significant only in women (left: 183.5 N [13.6 %], p=0.002; right: 161.3 [11.0 %], p=0.005). The improvement of leg strength in men was not given significantly (left: 93.8 N [5.5%], p=0.103; right: 37.1 N [2.0%], p=0.240). No statistically significant change in sagittal trunk flexion was recorded (p=0.567) for both sexes. Measurement for lateral flexion showed a decrease of isometric strength in both sides and for both sexes, but only statistically significant for women in right direction (12.4 Nm [11.7%], p=0.026). Changes in rotational strength parameters showed significance only for women in the left direction (5.6 Nm [8.1%], p=0.016). Correlation of hiking times showed significance with age (r²= 0.171; p<0.001).

Conclusion: Despite lower cardiovascular stress eight weeks of eccentric endurance exercise show benefits in isometric leg and trunk muscle strength parameters in healthy overweight individuals. Therefore we recommend this exercise modality to sedentary overweight individuals.