Ipsilateral Lower-to-Upper Limb Cross-Transfer Effect on Muscle Strength, Mechanical Power, and Lean Tissue Mass after Accentuated Eccentric Loading

Potential Importance of Maximal Upper Body Strength-Generating Qualities and Upper Body Strength Training for Performance of High-Intensity Running and Jumping Actions: A Scoping Review

PURPOSE

To investigate the influence of upper body (UB) strength qualities and UB strength training on the performance of high-intensity running and jumping actions and to identify gaps and recommendations for future research.

METHODS

A systematic search using the PRISMA Scoping Review protocol was conducted in February 2024 using PubMed, Scopus, and ICTRP. Studies eligible for inclusion were those that reported associations between UB or trunk maximal strength qualities (e.g., absolute strength, forces, power) and high-intensity running or jumping actions or investigated the influence of an isolated UB strength training intervention on high-intensity running or jumping performances.

RESULTS

Of the 4730 articles, 7 studies met the inclusion criteria, reporting correlations for 16 high-intensity running or jumping tests. No intervention studies were identified. Preliminary findings of the limited number of studies highlight that greater UB maximal strength-generating capacity may positively influence repeated sprint ability. While a significant moderate correlation between greater absolute UB strength and faster "flying" sprint was also reported, mixed results were found for sprint acceleration. There is also evidence that change-of-direction performance may greatly benefit from high maximal isometric strength of all trunk muscles and that strong trunk extensors may enhance drop jumps.

CONCLUSIONS

This review identifies the potential of UB strength to contribute to high-intensity running and jumping actions. Future research is warranted to investigate this link via various UB strength tests and UB strength training protocols aimed at maximising neuromuscular adaptations.

Cross-education of lower limb muscle strength following resistance exercise training in males and females: A systematic review and meta-analysis

Cross-education describes the training of one limb that leads to performance enhancements in the contralateral untrained limb, driven by neural changes rather than muscle adaptation. In this systematic review and meta-analysis, we aimed to evaluate the efficacy of cross-education (vs. a control group) via resistance exercise training (RET) for improving muscle strength in the untrained lower limb of healthy males and females. A literature search from inception to September 2023 was conducted using MEDLINE (via PubMed), the Cochrane Library (CENTRAL), Web of Science (Core Database), Scopus, EBSCO-host, and Ovid-EMBASE. Independent screening, data extraction and quality assessment were conducted. The measured outcomes were change in one-repetition maximum (1-RM) load, maximum voluntary contraction (MVC), and concentric, eccentric and isometric peak torque. Change in muscle structure (pennation angle and muscle thickness) was also analysed. A total of 29 studies were included. The pooled effect size from the random-effects model shows that cross-education significantly increased 1-RM compared to the control group (standardised mean difference (SMD): 0.59, 95% CI: 0.22-0.97; P = 0.002). Cross-education also significantly improved MVC (SMD: 0.55, 95% CI: 0.16-0.94; P = 0.006), concentric (SMD: 0.61, 95% CI: 0.39-0.84; P < 0.00001), eccentric (SMD: 0.39, 95% CI: 0.13-0.64; P = 0.003) and isometric (SMD: 0.45, 95% CI: 0.26-0.64; P < 0.00001) peak torque, each compared to the control group. When RET was categorised as eccentric or concentric, subgroup analysis showed that only eccentric training was associated with significantly increased isometric peak torque via cross-education (SMD: 0.37, 95% CI: 0.13-0.61; P = 0.003) (concentric, SMD: 0.33, 95% CI: -0.09 to 0.74; P = 0.12). This systematic review and meta-analysis emphasise the potency of cross-education for improving lower limb muscle strength. These findings have potential implications for clinical situations of impaired unilateral limb function (e.g., limb-casting or stroke). Future work exploring the mechanisms facilitating these enhancements will help to develop optimised rehabilitation protocols.

Vertical Strength Transfer Phenomenon Between Upper Body and Lower Body Exercise: Systematic Scoping Review

BACKGROUND

There are a myriad of exercise variations in which upper body (UB) and lower body (LB) exercises have been intermittently used. However, it is still unclear how training of one body region (e.g. LB) affects adaptations in distant body areas (e.g. UB), and how different UB and LB exercise configurations could help facilitate physiological adaptations of either region; both referred to in this review as vertical strength transfer.

OBJECTIVE

We aimed to investigate the existence of the vertical strength transfer phenomenon as a response to various UB and LB exercise configurations and to identify potential mechanisms underpinning its occurrence.

METHODS

A systematic search using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) for Scoping Reviews protocol was conducted in February 2024 using four databases (Web of Science, MEDLINE, Scopus and CINAHL) to identify peer-reviewed articles that investigated the vertical strength transfer phenomenon.

RESULTS

Of the 5242 identified articles, 24 studies met the inclusion criteria. Findings suggest that the addition of UB strength training to LB endurance exercise may help preserve power-generating capacity for the leg muscle fibres. Furthermore, systemic endocrine responses to high-volume resistance exercise may beneficially modulate adaptations in precedingly or subsequently trained muscles from a different body region, augmenting their strength gains. Last, strength training for LB could result in improved strength of untrained UB, likely due to the increased central neural drive.

CONCLUSIONS

Vertical strength transfer existence is enabled by neurophysiological mechanisms. Future research should involve athletic populations, examining the potential of vertical strength transfer to facilitate athletic performance and preserve strength in injured extremities.

Ipsilateral transfer of motor skill from lower to upper limb in healthy adults: A randomized controlled trial

BACKGROUND AND PURPOSE

Whereas motor skills of the untrained upper limb (UL) can improve following practice with the other UL, it has yet to be determined if an UL motor skill can improve following practice of that skill with the lower limb (LL).

METHODS

Forty-five healthy subjects randomly participated in a 10-minute single-session intervention of (1) practicing 50 reaching movement (RM) sequences with the non-dominant left LL toward light switches (LL group); or (2) observing the identical 50 light switches sequences (Switches Observation (SO) group); or (3) observing nature films (Nature Observation (NO) group). RM sequence performance with the left UL toward the light switches was tested before and immediately after the intervention and retested after 24 h.

RESULTS

Reaching response time improved in the LL group more than in the SO and NO groups in the posttest (pBonferroni = 0.038 and pBonferroni < 0.001, respectively), and improved in the LL group more than in the NO group in the retest (pBonferroni = 0.004). Percentage of fails did not differ between groups across the timepoints.

CONCLUSIONS

It appears that the actual practice of the RM sequence skill with the UL together with the cognitive element embedded in the observation of the RM sequences contributes to ipsilateral transfer from LL to UL.

One-Year Handgrip Strength Change in Kindergarteners Depends upon Physical Activity Status

Free play in kindergarten can be roughly divided into fine and gross motor activities, but the effects of these activities on improving handgrip strength are unknown. Therefore, we aimed to compare one-year changes in handgrip strength and forearm flexor muscle size in children separated by preferred play in a kindergarten. One hundred and eleven children were recruited from a local kindergarten. They underwent handgrip strength and forearm muscle thickness measurements, and 95 (49 boys and 46 girls) underwent a second measurement one year after the first measurement. Class teachers assessed the physical activity of everyone in their class after the second measurement. Using three evaluation scores by the class teachers, we divided children into three groups based on the children's preference to play in kindergarten (fine movement vs. gross motor movement). Handgrip strength did not change differently between groups across one year. However, children who liked active playing outside (i.e., gross motor activity) were stronger than others. Furthermore, children who like playing outside observed greater changes than the other groups in the ulna (right hand) and radius muscle thickness (left hand), suggesting that changes in forearm muscle size might be incongruent with changes in handgrip strength among the three activity groups.

Effects of submaximal and supramaximal accentuated eccentric loading on mass and function

Introduction: Eccentric-overload (EO) resistance training emerges as an alternative to more optimally prescribe intensity relative to the force generation capabilities of the eccentric muscle contraction. Given the difficulties to individually prescribe absolute eccentric loads relative to each person's eccentric ability, setting the load relative to the concentric one-repetition maximum (1-RM) is the most used EO training approach. Therefore, we investigated the effects of submaximal and supramaximal (i.e., eccentric loads above 100% of 1-RM) accentuated eccentric training on changes in lean mass, anabolic hormonal responses and muscle function. Methods: Physically active university students (n = 27) were randomly assigned to two training groups. Participants in the training groups performed dominant leg isotonic training twice a week for 10 weeks (four sets of eight repetitions). Isotonic resistance was generated by an electric-motor device at two different percentages of 1-RM for the eccentric phase; 90% submaximal load, SUB group) and 120% (supramaximal load, SUPRA group). Concentric load was the same for both groups (30% of 1-RM). Changes in total thigh lean mass (TTLM), anabolic hormonal responses (growth hormone, IGF-1, IL-6, and total testosterone), unilateral leg-press 1-RM, maximal voluntary isometric contractions (MVIC), local muscle endurance (XRM), muscle power at 40 (PP40), 60 (PP60) and 80% (PP80) of the 1-RM, and unilateral vertical jump height before and after training were compared between groups. Results: After training, both SUB and SUPRA groups showed similar increases (p < 0.05) in MVIC (19.2% and 19.6%), XRM (53.8% and 23.8%), PP40 (16.2% and 15.7%), TTLM (2.5% and 4.2%), IGF-1 (10.0% and 14.1%) and IL-6 (58.6% and 28.6%). However, increases in 1-RM strength (16.3%) and unilateral vertical jump height (10.0%-13.4%) were observed for SUPRA only. Indeed, SUPRA was shown to be more favorable than SUB training for increasing 1-RM [ES = 0.77 (1.49-0.05)]. Unilateral muscle power at medium and high intensity (10.2% and 10.5%) also increased in SUB but without significant differences between groups. Discussion: Similar functional and structural effects were demonstrated after 10 weeks EO training with submaximal and supramaximal eccentric loads. Although supramaximal loading might be superior for increasing 1-RM, the use of this approach does not appear to be necessary in healthy, active individuals.

Children with Low Handgrip Strength: A Narrative Review of Possible Exercise Strategies to Improve Its Development

BACKGROUND

Handgrip strength (HGS) is a predictor of health in both children and adults. Evidence suggests that without a possible strategy, children with low HGS may become adults with low HGS. However, little is known about what strategies are effective for children with low HGS to achieve a higher baseline level in adulthood. This narrative review aimed to investigate whether physical exercise interventions could improve HGS in children.

METHODS

The relevant databases/search engine was searched using keywords related to the main topics discussed throughout this review.

RESULTS

Our findings suggest that it may not be possible to improve HGS over that observed from normal development with physical education or traditional resistance-training programs. However, if the training program includes exercises that directly stimulate the forearm/hand muscle groups to grip, it may be possible to obtain changes in HGS that exceed the changes due to normal developmental growth.

CONCLUSION

Although there are associations between HGS and markers of health, no research could be identified that examined whether increasing HGS would lead to an improvement in health. If an increase in HGS really does represent an improvement in long-term health, then gripping exercise may need to be included into physical activity programs during the growth/development phase.