High intensity interval training (HIIT) is widely used to improve VO_2max. The purpose of this study was to examine if lower extremity HIIT resulted in improved maximal oxygen uptake (VO_2max) and peak power output (PPO) of the upper extremities. Twenty healthy and trained participants (11 female and 9 male, VO_2max 3160±1175 ml/min) underwent a 6-week HIIT program of the lower extremities on a cycle ergometer. Before and after the training period a maximal cycle ergometry (CE) and a maximal hand crank ergometry (HCE) were conducted to determine VO_2max and PPO. Additionally, hematological parameters were determined. Increases in VO_2max of the lower extremities (3160±1175 to 3449±1231 ml/min, p<0.001, η²p=0.779) as well as of the upper extremities (2255±938 to 2377±1015 ml/min, p=0.010, η²p=0.356) from pre- to post-test were found. PPO of the lower extremities increased (243±95 to 257±93 W, p<0.001, η²p=0.491), whereas it remained unchanged for the upper extremities (103±50 to 108±54 W, p=0.209, η²p=0.150). All hematological parameters increased. The results demonstrate that VO_2max of the upper extremities increased after 6-weeks of cycling HIIT. However, upper body PPO was unchanged.

Purpose: This systematic review aimed to evaluate the effects of upper body endurance training (UBET) on oxygen uptake (VO₂) in healthy persons and derive evidence-based recommendations to improve upper body fitness and performance. Methods: Databases were systematically searched in accordance with PRISMA guidelines until 1 February 2023. Eligibility criteria included healthy male and female adults and older adults who underwent an UBET intervention. Outcomes of interest included physical fitness (VO_2peak and/ or VO_{2 submax}) and transfer effects (i.e., effects from trained (VO_{2peak ARM}) to untrained (VO_{2peak LEG}) musculature). Results: The search identified 8293 records, out of which 27 studies reporting on 29 interventions met our eligibility criteria. The average duration of interventions was 6.8 ± 2.6 weeks with 3.2 ± 0.8 training sessions per week. For 21 of 29 interventions, significant increases in VO_{2peak ARM} were reported following UBET (+16.4% ± 8.3%). Three of the nine studies that analyzed transfer effects of untrained legs after upper body training exhibited significant increases in VO_{2peak LEG} (+9.3% ± 2.6%). Conclusions: This review showed that UBET is a beneficial and useful training modality to increase the oxygen utilization in the upper body. Although UBET is an uncommon form of endurance training in healthy individuals, transfer effects to the untrained muscles can be observed in isolated cases only, rendering transfer effects in UBET inconclusive. Further research should focus on the peripheral changes in muscle morphology of the trained muscles and central changes in cardiovascular function as well as when transfer effects can occur after UBET in healthy people.

Background: Upper-body exercise is increasingly applied in athletic and exercise settings; however, acute physiological and perceptual differences compared to lower-body exercise remain insufficiently characterized. This study compared maximal performance parameters during incremental upper- and lower-body exercise in healthy adults. Methods: Seventeen moderately trained participants (eight females, nine males) completed randomized incremental tests on a hand crank ergometer (HCE) and a cycle ergometer (CE). Maximal fat oxidation (MFO), intensity at maximal fat oxidation (FAT_max), peak oxygen uptake (VO₂^peak), maximal heart rate (HR_peak), peak power output (PPO), immediate post-exercise lactate (LA_post), and differentiated ratings of perceived exertion (RPE_breathing and RPE_muscles) were assessed. Results: MFO was significantly lower during HCE compared with CE (0.26 vs. 0.55 g·min⁻¹, p < 0.001), occurring at a lower FAT_max (42.6% vs. 51.6% of VO₂^peak_, p = 0.016). Furthermore, relative VO₂^peak (34.1 vs. 48.9 mL·kg⁻¹·min⁻¹, p < 0.001), HR_peak (178 vs. 189 beats·min⁻¹, p < 0.001), and relative PPO (1.8 vs. 4.1 W·kg⁻¹, p < 0.001) were substantially reduced during HCE. While RPE_breathing was higher during CE (19.1 vs. 17.6, p < 0.001), RPE_muscles (19.4 vs. 19.8, p = 0.111) and LA_post (9.8 vs. 8.6 mmol·L⁻¹, p = 0.060) did not differ significantly between modalities. No significant modality-by-sex interactions were observed for any outcome. Conclusions: These findings demonstrate pronounced modality-specific differences in metabolic, cardiorespiratory, and perceptual responses. Exercise modality should therefore be carefully considered when interpreting maximal exercise tests and prescribing training or rehabilitation programs.