Eccentric versus Concentric - Which Is the Most Stressful Cardiovascularly and Metabolically?

Acute and chronic cardiovascular responses to concentric and eccentric exercise in older adults with knee osteoarthritis

PURPOSE

Muscle contraction type in resistance exercise training may confer benefits besides strength in individuals with osteoarthritis and cardiovascular disease (CVD) risks. The purpose of the study was to explore whether Eccentric-resistance training (RT) improved hemodynamic responses to acute walking exercise stress compared to Concentric-RT among individuals with knee OA over four months.

METHODS

This was a secondary analysis from a randomized, controlled, single-blinded study. Participants (N = 88; 68.3 ± 6.4 yrs; 67.4% female) were randomized to one of two work-matched resistance training (RT) programs against a non-RT control group. Pre-training and month four, participants completed a self-paced Six-Minute Walk Test (6MWT) and progressive treadmill exercise test. Heart rates, blood pressures and mean arterial pressures (MAP) were captured during each test. Antihypertensive medications use was documented at each time point.

RESULTS

Leg strength improved in both training groups by month four (p < .05). Changes in 6MWT distance and progressive treadmill test time were not different across groups over four months. Neither Concentric or Eccentric RT produced different hemodyamic responses during the 6MWT compared to the control group post-training. However, Concentric RT was associated with 6.0%-7.4% reductions in systolic blood pressure during the graded treadmill walking test at 50%, 75% and 100% of the test time compared to Eccentric RT and the controls (p = .045). MAP values were lower at 75% and 100% of the treadmill test after Concentric RT (5.7%-6.0% reductions) compared to Eccentric RT (1.0%-2.4% reductions) and controls (1.5% and 4.0% elevations) post-training (p = .024). Antihypertensive medication use did not change in any group.

CONCLUSIONS

The repeated, progressive exposures of Concentric RT-induced blunted the hypertensive responses to acute exercise compared to Eccentric-RT. Among people with knee OA, Concentric-RT may confer strength benefits to manage OA and possibly reduce cardiovascular stress during exercise.

Skeletal muscle and cerebral oxygenation levels during and after submaximal concentric and eccentric isokinetic exercise

The aim was to investigate the potential differences in muscle (vastus lateralis) and cerebral (prefrontal cortex) oxygenation levels as well as in the number of repetitions and total work output between isokinetic eccentric and concentric exercise at a moderate relative intensity until exhaustion. Ten recreationally active young men underwent two isokinetic exercise sessions either concentric or eccentric, one on each randomly selected leg. The protocols were performed at 60°/s and an intensity corresponding to 60% of the maximal voluntary contraction (MVC) of each contraction type. Concentric torque was significantly lower compared to eccentric torque in both peak values and at values corresponding to 60% of MVC [230 ± 18 Nm vs. 276 ± 19 Nm (P = .014) and 137 ± 12 Nm vs. 168 ± 11 Nm, respectively (P = .010)]. The participants performed 40% more contractions during eccentric compared to concentric exercise [122 ± 15 vs. 78 ± 7, respectively]. No differences were found in the levels of oxyhaemoglobin, deoxyhemoglobin, total haemoglobin and tissue saturation index when eccentric and eccentric exercise regimes were compared (all P > .05). Our results demonstrate that eccentric exercise of moderate intensity leads to greater resistance to fatigue and more work output compared to concentric exercise, despite the comparable muscle and cerebral oxygenation levels.

The Effects of High-Intensity Interval Exercise on Skeletal Muscle and Cerebral Oxygenation during Cycling and Isokinetic Concentric and Eccentric Exercise

The aim of the present study was to study the effects of cycling and pure concentric and pure eccentric high-intensity interval exercise (HIIE) on skeletal muscle (i.e., vastus lateralis) and cerebral oxygenation. Twelve healthy males (n = 12, age 26 ± 1 yr, body mass 78 ± 2 kg, height 176 ± 2 cm, body fat 17 ± 1% of body mass) performed, in a random order, cycling exercise and isokinetic concentric and eccentric exercise. The isokinetic exercises were performed on each randomly selected leg. The muscle and the cerebral oxygenation were assessed by measuring oxyhemoglobin, deoxyhemoglobin, total hemoglobin, and tissue saturation index. During the cycling exercise, participants performed seven sets of seven seconds maximal intensity using a load equal to 7.5% of their body mass while, during isokinetic concentric and eccentric exercise, they were performed seven sets of five maximal muscle contractions. In all conditions, a 15 s rest was adopted between sets. The cycling HIIE caused greater fatigue (i.e., greater decline in fatigue index) compared to pure concentric and pure eccentric isokinetic exercise. Muscle oxygenation was significantly reduced during HIIE in the three exercise modes, with no difference between them. Cerebral oxygenation was affected only marginally during cycling exercise, while no difference was observed between conditions. It is concluded that a greater volume of either concentric or eccentric isokinetic maximal intensity exercise is needed to cause exhaustion which, in turn, may cause greater alterations in skeletal muscle and cerebral oxygenation.

Exercise-induced muscle damage: mechanism, assessment and nutritional factors to accelerate recovery

There have been a multitude of reviews written on exercise-induced muscle damage (EIMD) and recovery. EIMD is a complex area of study as there are a host of factors such as sex, age, nutrition, fitness level, genetics and familiarity with exercise task, which influence the magnitude of performance decrement and the time course of recovery following EIMD. In addition, many reviews on recovery from exercise have ranged from the impact of nutritional strategies and recovery modalities, to complex mechanistic examination of various immune and endocrine signaling molecules. No one review can adequately address this broad array of study. Thus, in this present review, we aim to examine EIMD emanating from both endurance exercise and resistance exercise training in recreational and competitive athletes and shed light on nutritional strategies that can enhance and accelerate recovery following EIMD. In addition, the evaluation of EIMD and recovery from exercise is often complicated and conclusions often depend of the specific mode of assessment. As such, the focus of this review is also directed at the available techniques used to assess EIMD.

Effects of Different Inter-Set Rest Intervals during the Nordic Hamstring Exercise in Young Male Athletes

CONTEXT

The Nordic hamstring exercise (NHE) is known to reduce hamstrings injury (HIS) risk in athletes. In order to optimise the NHE it is important to understand how acute resistance training variables influence its performance.

OBJECTIVE

To examine the effects of different inter-set rest intervals (ISRI) on force indices during performance of the NHE. Design: Crossover Study.

SETTING

Laboratory based.

PATIENTS OR PARTICIPANTS

Ten (age = 20.7 ± 2.3 years; height = 179.4 ± 5.5 cm; body mass = 83.9 ± 12.4 kg) well-trained young male team-sport athletes.

INTERVENTION

Participants performed 2 x 6 repetitions of the NHE with either a SHORT (one-minute) or LONG (three-minute) ISRI. All sets were performed on the NordBord.

MAIN OUTCOMES MEASURE(S)

Peak force (N), average force (N), percent maintenance (%) and percent decline (%) were recorded for both dominant and non-dominant limbs as well as inter-limb force asymmetries (%) calculated.

RESULTS

Analyses revealed no statistically significant interactions or main effects (p > 0.05) between conditions and sets in all variables. However, analysis of individual repetitions showed significant reductions (p < 0.05, ES = 0.58-1.28) in peak force from repetition four onwards.

CONCLUSIONS

Our findings suggest that a one-minute ISRI is sufficient to maintain force production qualities and inter-limb asymmetries between sets during the NHE in well-trained athletes. However, practitioners should be aware of the potentially high decrements in peak force production that may occur within the set.