Changes in hamstring flexibility and muscle strength during the menstrual cycle in healthy young females

The Influence of Menstrual Cycle Phases on Maximal Strength Performance in Healthy Female Adults: A Systematic Review with Meta-Analysis

Maximal strength is a significant factor in achieving peak performance and injury prevention in athletes. In individualization strategies for the efficient development of athletes, it is necessary to consider the respective components separately. The purpose of this study was to systematically examine the effects of the different cycle phases on isometric, isokinetic, and dynamic maximum strength. A systematic literature review was conducted; databases were searched from January 1960 to September 2023. The included studies focused on the expression of maximal strength in the earlier follicular phase as well as at least one comparative phase. Of the initial 707 articles identified, 22 met the selection criteria and were included. The studies considered a total of 433 subjects. Our results revealed medium effects (weighted mean standardized mean difference (SMD) = 0.60; seven studies) for isometric maximal strength in favor of the late follicular phase, small effects (weighted mean SMD = 0.39; five studies) for isokinetic maximal strength in favor of the ovulation phase, and small effects (weighted mean SMD = 0.14; three studies) for dynamic maximal strength in favor of the late follicular phase. The results indicate that the early follicular phase is unfavorable for all strength classes. Peak performance in isometric strength is seen in the late follicular phase, whereas isokinetic strength peaks during ovulation. Dynamic strength is optimal in the late follicular phase.

Alterations of postural control across the menstrual cycle - A systematic review

BACKGROUND

Postural control is a vital component of injury prevention and prediction and plays a critical role in sports performance. Its relationship with the phases of the menstrual cycle (MC) is not yet fully understood and requires further investigation.

RESEARCH QUESTION

Does postural control alter between high hormone and low hormone phases of the MC?

METHODS

Five electronic databases were searched by two reviewers between 30th November and 2nd December 2022. Included were studies that investigated the effects of the MC on static and dynamic postural control in naturally cycling (NC) women by comparing the early follicular phase (EFP) with at least one high hormone phase of the MC. Two reviewers conducted the literature search, selection of eligible studies, data extraction, methodological quality assessment utilizing a modified Downs and Black Checklist, GRADE guidelines and SIGN grading, and synthesis of results.

RESULTS

Nine studies examined the effects of the MC on static (n = 7), dynamic (n = 1), or both forms of postural control (n = 1) in 148 NC women. Included studies were of very low to moderate quality. Level of evidence was either 2 + (n = 1) or 2- (n = 8). Limited evidence of five very low-quality studies indicated decreased static postural control during the ovulatory phase of the MC, compared to the EFP. The decrements were present in balance tasks that altered sensory input of at least two sensory systems of postural control.

SIGNIFICANCE

This systematic review is the first compiling evidence on the effect of the MC on postural control. Evidence that the MC influences postural control is unclear. However, a trend towards decrements in postural control form EFP to OP was observed in balance tasks that eliminated or altered sensory input. Hence, compensatory strategies might be less effective during the OP.

Effects of Low-Intensity Torque-Matched Isometric Training at Long and Short Muscle Lengths of the Hamstrings on Muscle Strength and Hypertrophy: A Randomized Controlled Study

ABSTRACT

Nakao, S, Ikezoe, T, Taniguchi, M, Motomura, Y, Hirono, T, Nojiri, S, Hayashi, R, Tanaka, H, and Ichihashi, N. Effects of low-intensity torque-matched isometric training at long and short muscle lengths of the hamstrings on muscle strength and hypertrophy: A randomized controlled study. J Strength Cond Res 37(10): 1978-1984, 2023-This study investigated the effects of low-intensity torque-matched isometric training on muscle hypertrophy and strengthening at long (LL) and short muscle lengths (SL). Twenty-eight young subjects completed an 8-week hamstring isometric training program (30% of maximal voluntary contraction (MVC) × 5 s × 20 repetitions × 5 sets × 3 times/week) at 30° knee flexion (LL) or 90° knee flexion (SL). The cross-sectional area (CSA) of the hamstrings and MVC were measured before and after the intervention. The active torque because of muscle contraction was calculated by subtracting the passive torque at rest from the total torque (30% MVC). The active torque was significantly lower in the LL training group than in the SL training group (p < 0.01), whereas there was no between-group difference in total torque during training. For CSA and MVC at 30° knee flexion, the split-plot analysis of variance (ANOVA) showed no significant time × group interaction; however, it did show a significant main effect of time (p < 0.05), indicating a significant increase after training intervention. As for MVC at 90° knee flexion, there was a significant time × group interaction (p < 0.05) and a significant simple main effect of time in both the LL (p < 0.01; Cohen's d effect size [ES] = 0.36) and SL (p < 0.01; ES = 0.64) training groups. Therefore, low-intensity isometric training at LL can induce hypertrophy and strengthening, even in cases where the active torque production is lower than that at SL, whereas the training at SL may be more effective for muscle strengthening at SL.

The Effects of Static Stretching Intensity on Range of Motion and Strength: A Systematic Review

The aim of this study was to systematically review the evidence on the outcomes of using different intensities of static stretching on range of motion (ROM) and strength. PubMed, Web of Science and Cochrane controlled trials databases were searched between October 2021 and February 2022 for studies that examined the effects of different static stretching intensities on range of motion and strength. Out of 6285 identified records, 18 studies were included in the review. Sixteen studies examined outcomes on ROM and four on strength (two studies included outcomes on both ROM and strength). All studies demonstrated that static stretching increased ROM; however, eight studies demonstrated that higher static stretching intensities led to larger increases in ROM. Two of the four studies demonstrated that strength decreased more following higher intensity stretching versus lower intensity stretching. It appears that higher intensity static stretching above the point of discomfort and pain may lead to greater increases in ROM, but further research is needed to confirm this. It is unclear if high-intensity static stretching leads to a larger acute decrease in strength than lower intensity static stretching.

Relationship between Muscle Flexibility and Characteristics of Muscle Contraction in Healthy Women during Different Menstrual Phases

OBJECTIVE

Skeletal muscle function is vital for preventing injury during exercise. It has been reported that skeletal muscle function fluctuates with the menstrual cycle and is considered one of the causes of injury. This study aimed to clarify the relationship between muscle flexibility and muscle contraction characteristics and their changes with the menstrual cycle.

METHODS

The subjects were healthy women who voluntarily participated in the study through recruitment posters. Muscle flexibility was measured with the passive knee extension (PKE) test, isokinetic knee flexor strength, and the maximum muscle strength exertion angle under two conditions of 60°/s and 120°/s in dominant hamstrings. Additionally, their correlations were analyzed and compared between the menstrual and ovulatory phases.

RESULTS

Sixteen subjects (mean age: 20.56 ± 0.73 years; body mass index: 20.21 ± 1.60) participated in the study. Correlation analysis showed a significant negative correlation between PKE and the maximum muscle strength exertion angle under the condition of 60°/s during the menstrual phase (r = -0.54; p = 0.03). No significant difference was observed in the two-group comparison of the variables measured during the menstrual and ovulatory phases.

CONCLUSION

This study confirmed that the more flexible muscles generate the maximum strength at a more contracted position during the menstrual phase in women. In the future, it is necessary to examine the relationship between the results of this study and exercise performance and injury occurrence.