The effect of the menstrual cycle on collagen metabolism, growth hormones and strength in young physically active women.

This study aimed to investigate the effect of the menstrual cycle on strength, functioning of the GH/IGF-1 axis and collagen metabolism in physically active women. Twenty-four physically active and eumenorrheic women volunteered to participate in the study (body mass 60.3 ± 9.18 kg, age 21.8 ± 0.92 years). Blood samples were obtained between the 5th and 8th days (the follicular phase) and between the 19th and 22th days (the luteal phase) of the menstrual cycle to determine sex steroid concentrations (follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), oestradiol (E2) and progesterone (P)). Also insulin-like growth factor 1 (IGF-1) and collagen metabolism markers (synthesis (PICP) and breakdown (ICTP)) and maximum voluntary contraction (MVC) were measured. MVC was higher in the luteal phase 164.1 ± 34.77 [N m] (F(1.23) = 4.59; p = 0.043). The recorded collagen synthesis marker (PICP = 296.4 ± 35.61 [ng/ml]) was at the upper level of the reference range (30-300), with an insignificant decrease in the luteal phase (Z = 1.612; p = 0.107) and a significant increase in oestradiol concentration (Z = 4.286; p = 0.0001). The marker of collagen breakdown (ICTP = 4.16 ± 0.68 [µg/l]) was reduced by 6.8% in the same phase (Z = 1.764; p = 0.137). The variability of physical abilities (MVC) during the menstrual cycle showed that menstrual status should be taken into account in determination of the training loads. Increasing the load in the luteal phase seems to be favoured by a beneficial change in collagen metabolism (lower synthesis decrease, lower breakdown increase) observed in physically active women.

Effect of concentric vs. eccentric variant of lower limbs plyometric training on biomechanical and biochemical parameters.

AbstractThe study aimed to compare the effectiveness of two variants of 4 weeks plyometric training involving jumping up (dominance of concentric muscle work, UP) and jumping down (dominance of eccentric muscle work, DOWN) the stairs. Twenty-six young men were divided into two groups: UP (n = 13) and DOWN (n = 13). Control measurements of the muscle torques, vertical jumps, and creatine kinase (CK) activity were performed every week. The training resulted in significant changes (p < 0.001) in the muscle torques of the hip extensors (Δ ≈ 20% in both groups) and plantar flexors (ΔUP = 25%, ΔDOWN = 33%), but in the muscle torques of the knee extensors a significant (p < 0.001) increase occurred only in the group jumping down the stairs (ΔDOWN ≈ 15%). Furthermore, a significant increase (p < 0.001) of the height of the vertical jump was noted in the study only in the group jumping down (ΔDOWN = 8%). Training with the dominance of eccentric work caused greater weekly changes in the activity of creatine kinase in the plasma. The study confirmed that the exercise involving jumping on the stairs is viable in plyometric training, as it is an effective means of training the strength of the muscles of the lower limbs and vertical jump height, with a greater share assigned to jumping down consecutive steps.

Effect of a strength or hypertrophy training protocol, each performed using two different modes of resistance, on biomechanical, biochemical and anthropometric parameters.

The study aimed to analyse the effectiveness of two variants of 8-week strength training (hypertrophy, strength) with different modes of resistance. Healthy male subjects (n=75) were allocated to five groups of equal size: hypertrophy training with a variable cam (Hyp-Cam), hypertrophy training with disc plates (Hyp-Disc), maximal strength training with a variable cam (Str-Cam), maximal strength training with disc plates (Str-Disc), and a control group (CG). The Hyp-Cam and Str-Cam groups trained with a machine where the load was adjusted to the strength capabilities of the elbow flexors. The Hyp-Disc and Str-Disc groups trained on a separate machine in which a load was applied with disc plates. The CG did not train. All groups were assessed for changes and differences in one-repetition (1RM) lifts, isokinetic muscle torque, arm circumference and arm skinfold thickness, and plasma creatine kinase (CK) activity. Within the 8-week training period the 1RM increased (p<.001) in all groups by over 20%, without significant between-group differences. Muscle torque increased significantly (p<.001) only in the Hyp-Cam group (by 13.7%). Arm circumference at rest increased by 1.7 cm (p<.001) and 1.1 cm (p<.001) in the Hyp-Cam and Hyp-Disc groups, respectively, but not in the Str-Cam (0.3 cm; p>.05) or Str-Disc (0.2 cm; p>.05) group. Skinfold thickness of the biceps and triceps decreased more within the 8-week period in Str-Cam (by 1.1 and 2.1 cm; p<.001 and p<.001 respectively) and Str-Disc (0.7 and 1.5 cm; p<.001 and p<.01 respectively) than in Hyp-Cam (by 0.4 and 1.8 cm; p>.05 and p<.01 respectively) and Hyp-Disc groups (by 0.2 and 1.4 cm; p>.05 and p<.05 respectively). CK activity was significantly (p<.05) elevated in each training group except Hyp-Cam (p>.05). The 8-week hypertrophy training with a variable cam results in greater peak muscle torque improvement than in the other examined protocols, with an insignificant increase in training-induced muscle damage indices.

Postural stability pattern as an important safety factor of firefighters.

BACKGROUND: Firefighting is a hazardous profession that involves high fall risk and is crucial component for the safety of people. OBJECTIVE: The aim of this study was to identify factors that impact on postural stability patterns of firefighters. METHODS: The study examined 177 Polish firefighters from the National Firefighting and Rescue System (NFRS) aged 31.9±10.1 years, with body height of 179.6±5.93, body mass of 83.9±11.0 and BMI of 26.0±3.03. Postural stability was evaluated by means of the Balance System SD (Biodex USA) set at the level 12 of instability, in a sportswear, bunker gear, with and without visual input. The fall risk test (FRI) was also performed. Four indices were analysed: overall stability index (OSI), anterior-posterior stability index (APSI), medial-lateral stability index (MLSI), and fall risk index (FRI). RESULTS: Mean results for fall risk index (FRI) were in the normal range for all age groups regardless of the type of clothing the firefighters were wearing. Individual results obtained in the fall risk test, 128 firefighters were in the normal range for their age, furthermore, 10 firefighters obtained better results than the normal range, 34 firefighters had worse results and 5 people failed to complete the test. Postural stability with eyes closed was found to decline with age. Wearing bunker gear did not have an effect on postural stability. CONCLUSIONS: Balance tests should be integrated into the firefighting training routines in order to improve balance and support fall prevention. Exercises with reduced visual input should also be incorporated into the training methodology.

Comparison of changes in the load components for intense training on two machines: with a variable-cam and with a disc plate.

BACKGROUND: The object of the presented experiment was to construct a cam to provide the optimal load while training the muscles throughout the entire range of motion of a joint. The starting point for our consideration was the flexion of the elbow joint - based on its functioning, we wished to verify the efficacy of the cam during various workout routines. METHODS: The experiment was two-fold. In the first part, muscle flexion torque values were measured for 78 male participants, under static conditions and at four different angles of the elbow joint. Subsequently, the data was analyzed and based on the resulting graph the shape of a cam was determined. In the next stage, 75 men underwent training using two types of machines designed to exercise the elbow joint's flexors, one with a mounted cam and one with a disc plate. RESULTS: The strength and power changes were found to be more pronounced in the workouts conducted with the cam-equipped machine. CONCLUSIONS: Our conclusion stemming from this project is that a cam, designed specifically to customize and optimize the external load to the muscle strength potential during training, results in a safer, more efficient in terms of promoting the desired training effect and a more comfortable workout.

Comparison of ground reaction forces during the Basic Step on the Core Board platform at various levels of stability.

PURPOSE: The aim of this paper was to examine and compare the changes of ground reaction forces observed during the Basic Step on the Core Board fitness device at various levels of stability. MATERIAL AND METHOD: The study involved 10 female students. Participants stepped on and off the Core Board 10 times at 3 levels of stability. After completing a series of steps, the Core Board's stability was modified and the participant repeated the whole series. The measurement platform to examine three components of the reaction force (horizontal in the sagittal and frontal planes, and vertical) was used. RESULTS: The ground reaction force (GRF) observed on the Core Board, in the vertical and horizontal components is higher at all three levels of stability than on the platform without the device. Significant differences in GRF were observed in the horizontal component in the frontal plane (Fz) at all three levels of mobility as well as in impulse, measured on platforms with the device. CONCLUSION: The results on the Core Board training device present highest horizontal ground reaction forces in frontal plane at the highest level of Core Board mobility and this showing little medio-lateral stability and a more reactive way of movement regulation of the participants. As a consequence of the force patterns found it may be suggested that fitness training concepts should focus more possibly higher strains on the locomotor system most likely caused by changed ground reaction force patterns, an idea that has to be further analyzed with more complex measurement approaches.

Symmetry of proprioceptive sense in female soccer players.

PURPOSE: The purpose of the study was to assess the symmetry of proprioceptive sense among female soccer players when trying to reproduce isometric knee extensions (right and left) and to analyze the impact of a given level of muscle force on proprioception. METHODS: The study involved 12 soccer players aged 19.5 ± 2.65 years. Soccer players performed a control measurement of a maximum 3s (knee at the 90°) position in the joint. Subsequently, 70%, 50%, and 30% of the maximum voluntary contraction (MVC) were all calculated and then reproduced by each subject with feedback. Next, the players reproduced the predefined muscle contraction values in three sequences: A - 50%, 70%, 30%; B - 50%, 30%, 70%; C - 70%, 30%, 50% of MVC without visual control. RESULTS: In every sequence, the participants found obtaining the value of 30% of MVC the most difficult. The value they reproduced most accurately was 70% of MVC. Both trial II and trial III demonstrated that the symmetry index SI significantly differed from values considered acceptable (SIRa). In each successive sequence the largest asymmetry occurred while reproducing the lowest values of MVC (30%) (p < 0.05). CONCLUSION: High level of prioprioceptive sense is important to soccer players due to the extensive overload associated with dynamics stops or changes in direction while running. Special attention should be paid to develop skills in sensing force of varying levels. It was much harder to reproduce the predefined values if there was no feedback.

The sense of position and movement in the knee joint during voluntary movements.

The aim of the paper was to assess body position reproduction as well as jump height during an intended movement, together with an assessment of the influence of factors that disturb this process. Factors disturbing the jump were related to with the reproduction of different knee joint angles (90° or 120°); different muscle activity in performed jumps: SJ with no countermovement and CMJ with countermovement; as well as with and without visual (VC) of control movement (nVC) - eyes covered. Nineteen subjects aged twenty-one years participated in the experiment. Jump height (h) was calculated on the basis of a reaction force (R) of the base, as registered with a tensometric platform. Two-dimensional cinematographic analysis was used to assess the reproduction of angular position in the knee joint. A significant factor determining the level of position reproduction during voluntary movements was the imposed angle as well as the character of muscle activity. The biggest difficulty of developing maximum heights occurred during jumps with disturbed visual control (eyes shut).

Evaluation of the effectiveness of training on a machine with a variable-cam.

The aim of the study was to assess the effectiveness of the training of elbow flexors through the use of 2 machines, one of which was equipped with a disc plate of constant radius, the other one with a variable-cam having a radius adjustable to muscle strength. The experiment included 45 men divided into 3 equal groups: training group A (variable-cam), training group B (circle), and control group C. The training lasted for 8 weeks, 3 times a week. In order to control the effects, the values of peak torque and power of the flexor muscles of the elbow were isokinetically measured for the angular velocities of 30°/s and 60°/s. Also taken were anthropometric measurements of the arm and the creatine kinase (CK) activity in the blood plasma. As a result of the training, significant increases of biomechanical values were noted only in group A: power increased over 20%, the peak torque over 14%. After the training, significant increases of arm circumference in the relaxed position were noted in group A (17 mm), as well as in group B (11 mm). Also, some changes in CK activity were observed between Monday and Friday in a training week. On the basis of the experimental measurements, it may be ascertained that training elbow flexor muscles on a machine with a variable-cam is more efficient for increases in strength and power, as well as for some anthropometric parameters, than training on a machine with a disc plate.

Influence of time of rest on the power decrease during exercising on the inclined plane.

The aim of this paper is to investigate the influence of the time of rest on the change of maximal and average power as a function of time during training on an inclined plane. The values of power, developed during 7 series of 10 bounces with a 0.5 and 1 minute break, were analyzed. The research was conducted on 10 female students from the second year of master studies with a major of physical education. Taking into account the results obtained, which were compared to data from other sources, it is possible to conclude that the value of maximal power for the whole group examined during the training with a 0.5 minute break decreased by 22%, and for the training with a 1 minute break by 12%. One can assume that the training with a 0.5 minute break was more tiring, and for that reason students were not able to regenerate fully so as to bounce in the subsequent series. That is why one should say that the second method of training is more efficient for the evaluation of the maximal power of the contestant.