Specificity of Exercise and Specificity of Training: A Subcellular Review

Partial range of motion training elicits favorable improvements in muscular adaptations when carried out at long muscle lengths

The study compared changes in strength and regional muscle hypertrophy between different ranges of motion (ROM) in the knee extension exercise. Forty-five untrained women were randomized to either a control group or to perform the exercise in one of the following 4 groups (0°=extended knee): Full ROM (FULL_ROM: 100°-30° of knee flexion); Initial Partial ROM (INITIAL_ROM: 100°-65°); Final Partial ROM (FINAL_ROM: 65°-30°); Varied ROM (VAR_ROM: daily alternation between the ROM of INITIAL_ROM and FINAL_ROM). Pre- and post-training assessments included one repetition maximum (1RM) testing in the ROM corresponding to the initial, final and full ROM, and measurement of cross-sectional areas of the rectus femoris and vastus lateralis muscles at 40%, 50%, 60% and 70% of femur length in regard to regional muscle hypertrophy. Results showed that the INITIAL_ROM group presented a greater relative increase than all groups at 70%, and at 50% and 60% the increases were greater than FINAL_ROM, FULL_ROM, and non-training control (CON) groups. Moreover, FINAL_ROM group presented similar changes compared to the CON group at 60% and 70%. In regard to 1RM, FINAL_ROM and INITIAL_ROM groups presented greater relative increases at the ROM trained, and no group showed greater increases than VAR_ROM or INITIAL_ROM, regardless the ROM tested. In conclusion, partial ROM training in the initial phase of the knee extension exercise promoted greater relative hypertrophy in certain muscle regions than training in other ROM configurations, and no group promoted a greater 1RM increase than VAR_ROM group, which showed similar 1RM increases in the different ROMs tested.

Comparison of Peak Oxygen Uptake Between Upper-Body Exercise Modes: A Systematic Literature Review and Meta-Analysis

Purpose: To compare peak oxygen uptake (VO_2peak) between the asynchronous arm crank ergometry (ACE), and synchronous wheelchair ergometry (WERG), wheelchair treadmill (WTR), and upper-body poling (UBP) mode.

Methods: PubMed, Scopus, CINAHL, and SPORTDiscus™ were systematically searched, and identified studies screened based on title, abstract, and thereafter full-text. Studies comparing VO_2peak between ≥2 of the modes were included. A meta-analysis was performed by pooling the differences in VO_2peak between upper-body exercise modes. The quality of the included studies was assessed and the level of evidence (LoE) established for each mode comparison. Meta-regression analyses investigated the effect of total body mass and participant-related characteristics (% of able-bodied participants, % of participants with tetraplegia and % of participants who are wheelchair athletes) on differences in VO_2peak between modes.

Results: Of the 19 studies included in this review, 14 studies investigated the difference in absolute and body-mass normalized VO_2peak between ACE and WERG, and 5 studies examined the differences between ACE and WTR. No significant difference in absolute or body-mass normalized VO_2peak was found between ACE and WERG (overall effect ±95% CI: 0.01 ± 0.06 L·min⁻¹ and 0.06 ± 1.2 ml·kg⁻¹·min⁻¹, both p > 0.75; LoE: strong). No significant difference in absolute or body-mass normalized VO_2peak was found between ACE and WTR (overall effect ±95% CI: −0.10 ± 0.18 L·min⁻¹ and −1.8 ± 2.5 ml·kg⁻¹·min⁻¹, both p > 0.14; LoE: moderate). Absolute and/or body-mass normalized VO_2peak did not differ between WERG and WTR in one study with 13 participants (LoE: limited) and between ACE and UBP in one study with 18 participants (LoE: moderate). In the meta-regression analyses, there was no significant effect of the investigated factors on differences in VO_2peak.

Conclusions: The differences between the asynchronous ACE and synchronous WERG propulsion, including possible differences in trunk involvement, do not seem to influence VO_2peak. Therefore, ACE and WERG can be used interchangeably to test VO_2peak. Possible differences in VO_2peak in all other mode comparisons remain unclear due to the wide CIs and limited to moderate LoE.

Gait biomechanics of skipping are substantially different than those of running

The inherit injury risk associated with high-impact exercises calls for alternative ways to achieve the benefits of aerobic exercise while minimizing excessive stresses to body tissues. Skipping presents such an alternative, incorporating double support, flight, and single support phases. We used ground reaction forces (GRFs), lower extremity joint torques and powers to compare skipping and running in 20 healthy adults. The two consecutive skipping steps on each limb differed significantly from each other, and from running. Running had the longest step length, the highest peak vertical GRF, peak knee extensor torque, and peak knee negative and positive power and negative and positive work. Skipping had the greater cadence, peak horizontal GRF, peak hip and ankle extensor torques, peak ankle negative power and work, and peak ankle positive power. The second vs first skipping step had the shorter step length, higher cadence, peak horizontal GRF, peak ankle extensor torque, and peak ankle negative power, negative work, and positive power and positive work. The first skipping step utilized predominately net negative joint work (eccentric muscle action) while the second utilized predominately net positive joint work (concentric muscle action). The skipping data further highlight the persistence of net negative work performed at the knee and net positive work performed at the ankle across locomotion gaits. Evidence of step segregation was seen in distribution of the braking and propelling impulses and net work produced across the hip, knee, and ankle joints.

CONCLUSIONS

Skipping was substantially different than running and was temporally and spatially asymmetrical with successive foot falls partitioned into a dominant function, either braking or propelling whereas running had a single, repeated step in which both braking and propelling actions were performed equally.