1
Vol.:(0123456789)
Scientific Reports |         (2023) 13:4167  
| https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports
Progressive daily hopping exercise 
improves running economy 
in amateur runners: a randomized 
and controlled trial
Tobias Engeroff 1,6, Kristin Kalo 2,6*, Ryan Merrifield 3, David Groneberg 4 & Jan Wilke 4,5
This study investigated the effects of a daily plyometric hopping intervention on running economy 
(RE) in amateur runners. In a randomized, controlled trial, thirty-four amateur runners (29 ± 7 years, 27 
males) were allocated to a control or a hopping exercise group. During the six-week study, the exercise 
group performed 5 min of double-legged hopping exercise daily. To progressively increase loading, the 
number of hopping bouts (10 s each) was steadily increased while break duration between sets was 
decreased. Pre- and post-intervention, RE, peak oxygen uptake  (VO2peak), and respiratory exchange 
ratio (RER) were measured during 4-min stages at three running speeds (10, 12, and 14 km/h). 
ANCOVAs with baseline values and potential cofounders as cofactors were performed to identify 
differences between groups. ANCOVA revealed an effect of hopping on RE at 12 km/h (df = 1; F = 4.35; 
p < 0.05; η2 = 0.072) and 14 km/h (df = 1; F = 6.72; p < 0.05; η2 = 0.098), but not at 10 km/h (p > 0.05). 
Exercise did not affect  VO2peak (p > 0.05), but increased RER at 12 km/h (df = 1; F = 4.26; p < 0.05; 
η2 = 0.059) and 14 km/h (df = 1; F = 36.73; p < 0.001; η2 = 0.520). No difference in RER was observed 
at 10 km/h (p > 0.05). Daily hopping exercise is effective in improving RE at high running speeds in 
amateurs and thus can be considered a feasible complementary training program.
Clinical trial registration German Register of Clinical Trials (DRKS00017373).
Competitive runners are on the constant quest for maximal performance. However, after decades of significant 
improvements, a trend towards more marginal changes has been observed in several disciplines including endur-
ance  running1. Consequently, a “marginal gains” approach, which aims at combining multiple small performance 
improvements in different areas to create a significant advantage, is becoming increasingly popular in amateur 
and professional competitive sports. Aiming at such marginal gains, amateur runners adopt complementary 
training approaches such as plyometrics from professional sports with the aim to maximize performance and 
minimize injury  risk2.
Running performance is inherently dependent on the efficiency of locomotion, which is often referred to as 
running economy (RE). How efficient a human moves over the ground is not only influenced by metabolic fac-
tors, but also by the quality of movement patterns and the mechanical characteristics of the locomotor  system3. 
The concept of RE takes these metabolic, neural and tissue-specific factors into account. It is defined as the oxygen 
uptake required per distance at a given running speed and represents one of the key parameters to quantify the 
ability to transform aerobic capacity into endurance running  performance3,4. Studies in both,  amateurs5 and 
elite  athletes6, confirmed the relevance of RE as a crucial factor for endurance running performance. Therefore, 
strategies to improve RE are sought after by coaches, athletes, and sports  scientists7.
Resistance training, plyometrics, and stretching represent three popular methods used to target  RE7. A 
common facet of these interventions is that they all influence metabolic, biomechanical and neuromuscular 
OPEN
1Division Health and Performance, Institute of Occupational, Social and Environmental Medicine, Goethe 
University Frankfurt, Frankfurt Am Main, Germany. 2Department of Sports Medicine, Disease Prevention 
and Rehabilitation, Johannes Gutenberg University Mainz, Albert-Schweitzer-Straße 22, 55128 Mainz, 
Germany. 3Department of Sports Medicine and Exercise Physiology, Institute of Sports Sciences, Goethe 
University Frankfurt, Frankfurt Am Main, Germany. 4Institute of Occupational, Social and Environmental Medicine, 
Goethe University, Frankfurt, Frankfurt Am Main, Germany. 5Departement of Movement Sciences, University of 
Klagenfurt, Klagenfurt, Austria. 6These authors contributed equally: Tobias Engeroff and Kristin Kalo. *email: 
kkalo@uni-mainz.de
2
Vol:.(1234567890)
Scientific Reports |         (2023) 13:4167  | 
https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports/
 efficiency7. Since simply replacing endurance training by an RE intervention would limit the ability to main-
tain or increase maximal aerobic performance, a more promising approach to maximize running performance 
requires the maintenance of endurance training routines to which additional methods that may improve RE are 
added (e.g. explosive strength  exercises3). Popular contents of such additional training strategies include jumps, 
hops, or sprints and are suggested to improve muscle/tendon stiffness or to modify movement mechanics and 
the stretch-shorten cycle (SSC)3.
According to the available evidence, the Achilles tendon (AT) has been demonstrated to play a significant role 
in  RE8–10. Kunimasa et al.11 compared a variety of anatomical characteristics of Kenyan and Japanese elite distance 
runners. The Kenyans, superior in running performance, exhibited higher relative AT lengths and greater AT 
tendon moment arms. This is of importance because both factors are positively associated with  RE9,10. In addi-
tion to morphological features, RE is also influenced by the mechanical properties of the AT. Arampatzis et al.8 
showed that RE is positively associated with normalized AT stiffness. Following a 14-week resistance exercise 
intervention, a 7%-increase in plantar flexor strength and a 16%-increase in tendon stiffness resulted in a 4% 
reduction of oxygen  consumption12.
In a pioneering study, Kawakami et al.13 found that muscle fibers, contrary to earlier beliefs, act almost iso-
metrically during stretch–shortening cycles (SSC). Conversely, the tendon undergoes significant length changes, 
storing and releasing kinetic energy. While the AT contributes more than 50% of the positive work even at low 
running speeds of ~ 2 m/s, this proportion increases to about 75% during  sprinting14. In view of the accumulat-
ing evidence supporting the importance of the AT in RE, numerous studies have investigated the effectiveness 
of related exercise interventions. Plyometric training, often using reactive jumps, hops or, bounces when applied 
in the lower limb, is a popular strategy aiming to improve SSC performance. It hence seems particularly suited 
to trigger morphological and functional adaptation of the tendon. However, so far, only a limited number of 
studies examined the effect of explosiveness training interventions on RE, and only a few of them used exclu-
sively plyometric  exercises3. Furthermore, most available trials used one to three sessions per week, but none 
studied higher  frequencies3. This is of importance because it has been shown that collagen production, which 
is paramount for tendon stiffness, is most effectively triggered by intermittent, progressive loading paradigms 
with relatively short durations and  intervals15,16. Finally, most of the available evidence of exercise interventions 
and RE focusses on athletes with moderate to high-performance  levels17. The present study therefore aimed to 
investigate the effects of a daily plyometric hopping intervention on RE in amateur runners. We defined amateur 
runners as persons who compete in sports without striving for financial reward (as opposed to professional 
athletes), thus do running as a hobby.
Methods
Study design and survey procedure. 
A two-arm randomized controlled trial was performed. Active 
amateur runners were allocated to a hopping exercise (HE) or control (CON) group. Randomization was coun-
terbalanced and conducted using BiAS for Windows version 11.10 (Goethe University Frankfurt, Germany). 
The study was approved by the local ethics committee (Ethikkommission FB 05, Goethe University Frankfurt; 
reference number: 2018-17b) and registered at the German Register of Clinical Trials (DRKS00017373, date of 
registry: 03/09/2019). All participants provided written informed consent.
Healthy adults were recruited using word of mouth, printed flyers, and social media advertising. To ensure a 
specific fitness level and thus that participants are able to complete the running protocol, individuals had to be 
amateur runners with a 10 km time < 55 min and younger than 40 years of age. Exclusion criteria encompassed 
contraindications for engagement in physical activity (tested by means of the Physical Activity Readiness Ques-
tionnaire), severe cardiovascular, metabolic, endocrine, neural, and psychiatric diseases, unhealed orthopaedic 
injuries and overuse disorders (particularly with regard to the knee and ankle region), local inflammation, 
pregnancy, self-reported use of supplements containing stimulants and anabolic–androgenic steroids.
Intervention. 
The CON and the HE groups continued their regular exercise regimes. While the CON group 
did not engage in an additional specific exercise intervention, the HE group completed a six-week plyometric 
hopping protocol. Each day, the individuals randomized to HE performed a variable amount of double-legged 
10-s hopping bouts (Table 1). While total session duration (5 min) was constant, the number of sets (and with 
this, net training time) was increased weekly in order to ensure safe functional and mechanical adaptation. 
When hopping, participants were instructed to start with both feet no wider than hip width apart and to hop 
as high as possible with both legs, keeping the knees extended and aiming to minimize ground contact time. 
Table 1.  Protocol of the hopping intervention. s seconds.
Week
Sets
Set duration [s]
Net hopping duration [s]
Rest between sets [s]
1
5
10
50
50
2
6
10
60
40
3
8
10
80
30
4
10
10
100
20
5
15
10
150
10
6
15
10
150
10
3
Vol.:(0123456789)
Scientific Reports |         (2023) 13:4167  | 
https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports/
To ensure safe and correct execution, participants received a 1-to-1 explanation by a coach holding a bachelor’s 
degree in Sports Science, who additionally monitored the first three training sessions of each individual. When 
later exercising alone, the HE participants provided the instructor with video recordings in order to allow super-
vision and, if needed, correction. Moreover, participants completed a hopping diary. If at least 70% of the jumps 
were completed, the subjects were considered compliant.
All participants completed a training diary, documenting weekly running activity (number of sessions, hours 
per session, pace) as well as other exercises in hours/ week (see Table 2) and (in case of the HE group) adherence 
to the hopping intervention. 
Measures. 
Before and after the intervention period, all exercise tests were performed on an electronically 
driven treadmill (mercury® med, h/p/cosmos sports & medical gmbh, Traunstein, Germany) without using a 
safety belt. To reduce intrasubject variability, the time of the day, the test equipment, as well as the type of run-
ning shoes worn were standardized for both, baseline and post-exercise tests. Participants were instructed to 
avoid exercise for 24 h and strenuous exercise for 48 h prior to testing. In addition, participants were asked to eat 
about 1.5 to 2 h before exercise testing, not to drink alcohol the day before, and not to consume any alcohol or 
cigarettes on the day of the test. Temperature was controlled by air conditioning and the difference in tempera-
ture between the baseline and post measurement did not exceed ± 0.5° Celsius.
In accordance with Saunders et al.18, RE was determined by measuring submaximal oxygen uptake  (VO2) 
during 4-min stages at three constant running speeds and an inclination of 0°. After a standardized warm-up of 
3 min walking at 5 km/h, participants ran at 10, 12, and 14 km/h,  respectively7. Peak oxygen uptake  (VO2peak) was 
determined during a ramp protocol performed 2 min after the last submaximal running stage. For this purpose, 
speed was increased by 1 km/h every minute from 12 km/h and to 20 km/h, treadmill inclination was increased 
by 1% until volitional  exhaustion19.
A breath-by-breath gas analyser was used to monitor gas exchange during exercise testing (Metalyzer, COR-
TEX Biophysik GmbH, Leipzig, Germany). Calibration of the gas as well as the flow sensor was performed 
according to manufacturer recommendations. Meyer et al.20 showed an excellent test–retest reliability for the 
used system  (VO2: 0.969,  VCO2: 0.964,  VE 0.953). Recorded data was stored and processed using a spiroergometry 
software (MetaSoft® Studio, CORTEX Biophysik GmbH, Leipzig, Germany). At the end of each running stage, the 
participants prepared themselves to step off the treadmill by gripping the side handles of the treadmill. Therefore, 
for each step, the last 10 s of  VO2 data was cut off and RE was determined as the V̇O2 collected during the last 
valid 60 s (i. e., seconds 170 to 230) of each 4-min running stage. Respiratory exchange ratio (RER,  VCO2/VO2) 
was calculated for these 60 s as well. During the ramp protocol, the highest individual V̇O2 recorded over a 30 s 
period within the testing time (floating mean) was defined as  VO2peak.
Statistical analysis. 
All analyses were performed using Jamovi 1.8 (The jamovi project, https:// www. jam-
ovi. org) and the significance level was set to α = 0.05. After variance homogeneity was confirmed using Levene´s 
Test, analyses of covariance (ANCOVA) with baseline values as a cofactor were performed to test for inter-
vention effects (between subjects/groups) on running economy and secondary outcomes  (VO2peak, respiratory 
exchange ratio). Sex was analysed as potential confounder. Further confounders (weight, frequency of regular 
running sessions and other exercises) were tested for between group differences using Kruskal–Wallis Tests. In 
case of significance, a second ANCOVA for intervention effects on running economy including baseline values 
for running economy and the potential confounding outcomes was carried out. For the estimates of effect sizes, 
eta squared (η2) was used and interpreted according to  Cohen21: 0.01 (small effect), 0.06 (medium effect) and 
0.14 (large effect).
Ethics approval and patient consent. 
The study was conducted according to the ethical guidelines of 
the Helsinki Declaration and was approved by the local ethical review board (Ethikkommission FB 05, Goethe 
University Frankfurt), number: 2018-17b. All participants provided written informed consent.
Table 2.  Description of the sample (mean values and standard deviations). n number, kg kilograms, m meter, 
h hours, km kilometers.
HE group (n = 15)
CON group (n = 19)
Total (n = 34)
Sex
11♂ ♀4
16♂ ♀3
27♂ ♀7
Age [years]
29.1 (7.6)
28.2 (5.9)
28.6 (6.6)
Weight [kg]
73.8 (10.4)
78.6 (9.01)
76.5 (9.8)
Height [m]
1.78 (0.07)
1.80 (0.07)
1.80 (0.08)
Exercise [h/week]
8.0 (3.0)
8.2 (3.4)
8.1 (3.2)
Running duration [h/week]
3.3 (2.4)
2.37 (2.2)
2.8 (2.3)
Running frequency [n/week]
2.7 (1.5)
1.89 (1.3)
2.2 (1.4)
Running experience [years]
6.2 (4.7)
8.21 (5.6)
7.3 (5.3)
Running speed [km/h]
10.9 (1.8)
11.15 (1.5)
11.0 (1.6)
4
Vol:.(1234567890)
Scientific Reports |         (2023) 13:4167  | 
https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports/
Results
From n = 46 recruited individuals, a total of n = 34 adults (29 ± 7 years, 27 males) completed the study. Overall, 
n = 12 participants dropped out of our study. Reasons were illness (n = 4), injury (n = 4), lack of time to follow-up 
(n = 2), and < 70% compliant with the hopping protocol (n = 2). A detailed indication of the dropouts per group 
is depicted in Fig. 1.
Descriptive data of sample characteristics are presented in Table 2. None of the potential confounders includ-
ing weight (df = 1; F = 0.0468; p = 0.830; η2 = 0.001), running frequency (df = 1; χ2 = 0.0305; p = 0.861), and general 
training volume (df = 1; χ2 = 0.8605; p = 0.354) showed significant differences between the two groups. Pre and 
post values of  VO2peak, RE and RER per stage and group are presented in Table 3.
Levene´s test indicated variance homogeneity for primary and secondary outcomes. ANCOVA revealed that 
hopping significantly improves running economy at 12 km/h (df = 1; F = 4.35; p = 0.045; η2 = 0.072) and 14 km/h 
(df = 1; F = 6.72; p = 0.015; η2 = 0.098) running speed. In contrast, no difference between the HE and CON group 
was found at a low (10 km/h) running speed (df = 1; F = 3.11; p = 0.088; η2 = 0.043). HE did not lead to higher 
Figure 1.  Flow chart of the study.
Table 3.  Spiroergometric values (mean values and standard deviations). n number, kg kilograms, h hours, km 
kilometers, ml milliliters, min minutes, VO2 oxygen intake, RE running economy, RER respiratory exchange 
ratio, VCO2 carbon dioxide production.
HE group (n = 15)
CON group (n = 19)
Total (n = 34)
Pre
Post
Pre
Post
Pre
Post
VO2peak [ml/min/kg]
51.4 (6.0)
51.1 (5.6)
48.26 (4.3)
50.2 (4.5)
49.7 (5.2)
50.6 (5.0)
RE (ml/min/kg), 10 km/h
35.2 (2.97)
33.9 (2.95)
34.8 (3.07)
34.8 (2.79)
35.0 (2.99)
34.4 (2.86)
RE (ml/min/kg), 12 km/h
41.1 (2.57)
40.2 (2.67)
40.4 (3.35)
41.3 (2.86)
40.7 (3.01)
40.9 (2.79)
RE (ml/min/kg), 14 km/h
47.1 (3.04)
46.1 (3.31)
45.3 (3.33)
46.9 (2.79)
46.1 (3.29)
46.5 (3.01)
RER  (VCO2/VO2), 10 km/h
0.90 (0.04)
0.93 (0.05)
0.92 (0.05)
0.93 (0.05)
0.91 (0.05)
0.93 (0.05)
RER  (VCO2/VO2), 12 km/h
0.95 (0.04)
0.98 (0.05)
0.97 (0.05)
0.97 (0.05)
0.96 (0.05)
0.98 (0.05)
RER  (VCO2/VO2), 14 km/h
1.01 (0.06)
1.05 (0.07)
1.02 (0.05)
1.02 (0.05)
1.02 (0.06)
1.03 (0.06)
5
Vol.:(0123456789)
Scientific Reports |         (2023) 13:4167  | 
https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports/
 VO2peak values in the HE group compared to the CON group (df = 1; F = 2.83; p = 0.102; η2 = 0.025). However, after 
six weeks of training, the respiratory exchange ratios during 12 km/h (df = 1; F = 4.26; p = 0.047; η2 = 0.059) and 
14 km/h (df = 1; F = 36.73; p < 0.001; η2 = 0.520) running speed were significantly higher in the HE group. RER 
at 10 km/h running speed remained unchanged (df = 1; F = 0.490; p = 0.489; η2 = 0.011). Sex showed no impact 
on ANCOVA results. Figure 2 shows group differences in the estimated marginal means of the post-values for 
RE and RER (generated considering the pre-values) at all three running speeds.
Discussion
The present study yielded three key findings. Firstly, six weeks of daily hopping exercise improve running econ-
omy and increase respiratory exchange ratio at higher running speeds (12 and 14 km/h) in amateur runners. 
Secondly, maximal aerobic capacity remains unaltered by hopping if regular running and exercise habits are 
maintained. Our findings are in line with earlier studies examining plyometric interventions in amateur  athletes22 
and highly trained  runners18. They also corroborate the observation of Saunders et al.18 that the effects of plyomet-
rics on running economy are more pronounced at higher running speeds. However, in contrast to the previous 
trials which used three weekly sessions with durations of up to 30 min as well as multiple jump  exercises18,22, this 
study applied short daily bouts (net duration 5 min) consisting of one simple and easy-to-learn hopping exercise 
only. Our results suggest that regular endurance and concurrent plyometric training can be performed jointly by 
amateur runners, without complex programs and at a high frequency without leading to adverse events such as 
overuse injuries or pain. Finally, third, performing a progressive hopping protocol with a high exercise density 
seems to be safe in amateur athletes as no injury or other side effects related to the interventions were reported.
Although the present trial strengthens the evidence that plyometric exercise improves running economy, the 
relative contributions of factors driving the observed changes are still a matter of debate. Tendon stiffness has 
been shown to significantly correlate with running  economy23. Earlier findings reported that the contribution 
of AT energy storage to the positive work performed during running increases with locomotion  speed14. Our 
data show significant improvements in RE at 12 and 14 km/h but not at 10 km/h which would provide support 
for the hypothesis that tendon stiffness was one of the driving factors for improvements in RE.
Our hypothesis assumed that repeated hopping would elicit morphological and functional adaptation in the 
tissue, which in turn improve energy storage capacity. The daily loading paradigm was chosen based on research 
elucidating optimal loading paradigms for collagenous connective  tissues15,16. For instance, Paxton et al.15 used 
engineered ligaments to study the effect of cyclic stretch on the phosphorylation of the extracellular signal-
regulated kinase 1/2 (ERK1/2), an enzyme associated with collagen synthesis. Maximal ERK 1/2 levels were 
observed after 10 min of cyclic stretch and up to 6 h, cells were refractory to new stretching bouts. As these data 
suggest that repeated short loading periods may be optimal for tissue adaptation, the authors compared a daily 
intermittent stretch program (10 min each 6 h) to continuous tissue lengthening and confirmed the superiority 
of the physiology-specific paradigm. In our trial, tissue loading was of similar duration (8–14 min). Yet, as three 
training bouts per day with 6-h-intervals are not feasible due to nocturnal sleep, we decided for one exercise 
Figure 2.  Group differences in the estimated marginal means of the post intervention values of RE and RER at 
three running speeds. Means (dots) and 95% confidence intervals (vertical lines) are displayed.
6
Vol:.(1234567890)
Scientific Reports |         (2023) 13:4167  | 
https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports/
session per day. The intervention was well tolerated and just two participants report pain (shin and ball of the 
foot), which might be related to the intervention. Upcoming trials may therefore consider further increasing 
the frequency, e.g., to twice daily. Also, it has to be noted that we did not measure tendon stiffness (e.g., using an 
instrumented treadmill). Future studies should hence be geared to combine both, assessments of stiffness and RE.
In addition to adaptations in the tendon, metabolic factors may have caused the alterations of  RE3. One often 
discussed adaptation is increased aerobic carbohydrate utilisation for oxidative  phosphorylation24. A shift in 
substrate use could have led to better running economy based on a lower oxygen cost for adenosine triphosphate 
(ATP) synthesis if a greater share of carbohydrates is used instead of fatty acids. Since RER values in our study 
exceeded 1.0 at higher running speed, another explanation for decreased oxygen uptake might be an increase in 
anaerobic  metabolism5. The assumption that a change in substrate use might have caused alterations in running 
economy is supported by an increase in respiratory exchange ratios in the hopping training group. Due to the 
applied method, which is based on oxygen uptake, running economy in our analysis reflects only aerobic energy 
metabolism. Based on our data, we thus are not able to delineate which of the aforementioned mechanisms led 
to the increase in RER. Furthermore, we did not control if all participants were able to maintain a metabolic 
steady state over a larger timeframe than 4 min during all tested running speeds and did not assess running 
performance using a time trial or a fixed distance. Consequently, further studies are necessary to prove, that 
differences in oxygen costs of running govern improvements in running performance. A third pathway for hop-
ping induced improvements in RE could be based on changes in movement  patterns3. Alterations in running 
mechanics are discussed as a possible mechanism for RE improvements induced by plyometric and explosive 
resistance  training7. However, evidence on specific adaptations is scarce so far and further studies investigating 
running mechanics are needed. Moreover, we did not investigate the subjective acceptance and feasibility of our 
hopping protocol to daily (exercise) routines using structured interviews.
Our findings have implications for clinical practice and may open new avenues for future research. As indi-
cated earlier, previous training paradigms predominantly focussed on complex and more time consuming inter-
ventions which are particularly used by professional  athletes3. This trial provided first evidence that short daily 
regimes consisting of just one jump exercise are effective in improving RE in amateurs. Such regimes become 
more relevant as many people run and compete for fun and social aspects, but also report musculoskeletal pain 
caused by  running25. In addition, the “marginal gains” approach, is becoming increasingly popular in amateur 
 sports2. Therefore, hopping can be considered as short and feasible program for amateur runners to optimize 
performance and minimize the risk for musculoskeletal pain and injuries. Although direct comparison of a) short 
daily and b) longer but less frequently applied training approaches are lacking, based on current evidence, the 
choice could be left to individual preference. In regard to applicability, further studies should analyse if plyometric 
exercises can be executed in a fatigued and non-fatigued state. As an example, it is unknown whether hopping 
interventions performed in direct proximity to regular training (immediately before or after) would thwart the 
beneficial effects achieved by endurance or hopping exercises. Finally, besides endurance runners, athletes in 
other sports might also benefit from increased RE. Team sports such as basketball or soccer are characterized 
by periods of moderate intensity running which are disrupted by short bouts of high-intensity  actions26. Con-
sequently, RE is discussed as a relevant factor for athletic  performance26 and training regimes might contribute 
to enhanced endurance and running speed in team sport athletes.
Perspective. 
This study provides first evidence that 5 min of daily hopping improve RE at moderate and high 
running speed without compromising maximal aerobic capacity in amateur runners. This is in line with previous 
studies using less frequent jump exercises with higher  duration18,22. The more frequent units nevertheless appear 
to be feasible and safe. However, the factors that lead to an improvement in RE are still debated. Upcoming trials 
should focus on comparisons of amateur and elite athletes, further increases of exercise frequency (e.g., twice 
daily), and the specific mechanisms underlying hopping induced RE improvements, inter alia including altered 
tendon stiffness and substrate utilisation.
Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable 
request.
Received: 25 November 2022; Accepted: 1 March 2023
References
 1. Weiss, M., Newman, A., Whitmore, C. & Weiss, S. One hundred and fifty years of sprint and distance running—Past trends and 
future prospects. Eur. J. Sport Sci. 16(4), 393–401. https:// doi. org/ 10. 1080/ 17461 391. 2015. 10425 26 (2016).
 2. García-Pinillos, F. et al. Strength training habits in amateur endurance runners in Spain: Influence of athletic level. Int. J. Environ. 
Res. Pub. Health 17(21), 8184. https:// doi. org/ 10. 3390/ ijerp h1721 8184 (2020).
 3. Denadai, B. S., de Aguiar, R. A., de Lima, L. C. R., Greco, C. C. & Caputo, F. Explosive training and heavy weight training are 
effective for improving running economy in endurance athletes: A systematic review and meta-analysis. Sports Med. (Auckland, 
N.Z.) 47(3), 545. https:// doi. org/ 10. 1007/ s40279- 016- 0604-z (2017).
 4. Jones, A. M. & Carter, H. The effect of endurance training on parameters of aerobic fitness. Sports Med. 29(6), 373–386. https:// 
doi. org/ 10. 2165/ 00007 256- 20002 9060- 00001 (2000).
 5. Engeroff, T. et al. Intensity related changes of running economy in recreational level distance runners. J. Sports Med. Phys. Fitness 
57(9), 1111–1118. https:// doi. org/ 10. 23736/ S0022- 4707. 16. 06403-3 (2017).
 6. Conley, D. L. & Krahenbuhl, G. S. Running economy and distance running performance of highly trained athletes. Med. Sci. Sports 
Exerc. 12(5), 357–360 (1980).
7
Vol.:(0123456789)
Scientific Reports |         (2023) 13:4167  | 
https://doi.org/10.1038/s41598-023-30798-3
www.nature.com/scientificreports/
 7. Barnes, K. R. & Kilding, A. E. Strategies to improve running economy. Sports Med. 45(1), 37–56. https:// doi. org/ 10. 1007/ s40279- 
014- 0246-y (2015).
 8. Arampatzis, A. et al. Influence of the muscle-tendon unit’s mechanical and morphological properties on running economy. J. Exp. 
Biol. 209(17), 3345–3357. https:// doi. org/ 10. 1242/ jeb. 02340 (2006).
 9. Hunter, G. R. et al. Tendon length and joint flexibility are related to running economy. Med. Sci. Sports Exerc. 43(8), 1492–1499. 
https:// doi. org/ 10. 1249/ MSS. 0b013 e3182 10464a (2011).
 10. Kovács, B., Kóbor, I., Sebestyén, Ö. & Tihanyi, J. Longer Achilles tendon moment arm results in better running economy. Phys. 
Int. 107(4), 527–541. https:// doi. org/ 10. 1556/ 2060. 2020. 10000 (2021).
 11. Kunimasa, Y. et al. Specific muscle-tendon architecture in elite Kenyan distance runners: Achilles tendon moment arm for Kenyan 
runners. Scand. J. Med. Sci. Sports 24(4), e269–e274. https:// doi. org/ 10. 1111/ sms. 12161 (2014).
 12. Albracht, K. & Arampatzis, A. Exercise-induced changes in triceps surae tendon stiffness and muscle strength affect running 
economy in humans. Eur. J. Appl. Physiol. 113(6), 1605–1615. https:// doi. org/ 10. 1007/ s00421- 012- 2585-4 (2013).
 13. Kawakami, Y., Muraoka, T., Ito, S., Kanehisa, H. & Fukunaga, T. In vivo muscle fibre behaviour during counter-movement exercise 
in humans reveals a significant role for tendon elasticity. J. Physiol. 540(2), 635–646. https:// doi. org/ 10. 1113/ jphys iol. 2001. 013459 
(2002).
 14. Lai, A., Schache, A. G., Lin, Y.-C. & Pandy, M. G. Tendon elastic strain energy in the human ankle plantar-flexors and its role with 
increased running speed. J. Exp. Biol. https:// doi. org/ 10. 1242/ jeb. 100826 (2014).
 15. Paxton, J. Z., Hagerty, P., Andrick, J. J. & Baar, K. Optimizing an intermittent stretch paradigm using ERK1/2 phosphorylation 
results in increased collagen synthesis in engineered ligaments. Tissue Eng. Part A 18(3–4), 277–284. https:// doi. org/ 10. 1089/ ten. 
tea. 2011. 0336 (2012).
 16. Schmidt, J. B., Chen, K. & Tranquillo, R. T. Effects of intermittent and incremental cyclic stretch on ERK signaling and collagen 
production in engineered tissue. Cell. Mol. Bioeng. 9(1), 55–64. https:// doi. org/ 10. 1007/ s12195- 015- 0415-6 (2016).
 17. Ramirez-Campillo, R. et al. Effects of jump training on physical fitness and athletic performance in endurance runners: A meta-
analysis. J. Sports Sci. 39(18), 2030–2050. https:// doi. org/ 10. 1080/ 02640 414. 2021. 19162 61 (2021).
 18. Saunders, P. U. et al. Short-term plyometric training improves running economy in highly trained middle and long distance run-
ners. J. Strength Cond. Res. 20(4), 947. https:// doi. org/ 10. 1519/R- 18235.1 (2006).
 19. Saunders, P. U., Pyne, D. B., Telford, R. D. & Hawley, J. A. Reliability and variability of running economy in elite distance runners. 
Med. Sci. Sports Exerc. 36(11), 1972–1976. https:// doi. org/ 10. 1249/ 01. MSS. 00001 45468. 17329. 9F (2004).
 20. Meyer, T., Georg, T., Becker, C. & Kindermann, W. Reliability of gas exchange measurements from two different spiroergometry 
systems. Int. J. Sports Med. 22(8), 593–597. https:// doi. org/ 10. 1055/s- 2001- 18523 (2001).
 21. Cohen J. (2013) Statistical power analysis for the behavioral sciences: Routledge
 22. Turner, A. M., Owings, M. & Schwane, J. A. Improvement in running economy after 6 weeks of plyometric training. J. Strength 
Cond. Res. 17(1), 60. https:// doi. org/ 10. 1519/ 1533- 4287(2003) 017% 3c0060: IIREAW% 3e2.0. CO;2 (2003).
 23. Fletcher, J. R., Esau, S. P. & MacIntosh, B. R. Changes in tendon stiffness and running economy in highly trained distance runners. 
Eur. J. Appl. Physiol. 110(5), 1037–1046. https:// doi. org/ 10. 1007/ s00421- 010- 1582-8 (2010).
 24. Saunders, P. U., Pyne, D. B., Telford, R. D. & Hawley, J. A. Factors affecting running economy in trained distance runners. Sports 
Med. 34(7), 465–485. https:// doi. org/ 10. 2165/ 00007 256- 20043 4070- 00005 (2004).
 25. Wilke, J., Vogel, O. & Vogt, L. Why are you running and does it hurt? Pain, motivations and beliefs about injury prevention among 
participants of a large-scale public running event. Int. J Environ. Res Pub Health 16(19), 3766. https:// doi. org/ 10. 3390/ ijerp h1619 
3766 (2019).
 26. Boone, J., Deprez, D. & Bourgois, J. Running economy in elite soccer and basketball players: Differences among positions on the 
field. Int. J. Perform. Anal. Sport 14(3), 775–787. https:// doi. org/ 10. 1080/ 24748 668. 2014. 11868 757 (2014).
Author contributions
Conception and design: K.K., J.W.; Acquisition of data: K.K., R.M.; Analysis and interpretation of the data: T.E., 
J.W.; Drafting of the article: T.E., K.K., J.W.; Critical revision of the article for important intellectual content: 
R.M., D.G.; Final approval of the article: all authors.
Funding
Open Access funding enabled and organized by Projekt DEAL.
Competing interests 
The authors declare no competing interests.
Additional information
Correspondence and requests for materials should be addressed to K.K.
Reprints and permissions information is available at www.nature.com/reprints.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and 
institutional affiliations.
Open Access  This article is licensed under a Creative Commons Attribution 4.0 International 
License, which permits use, sharing, adaptation, distribution and reproduction in any medium or 
format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the 
Creative Commons licence, and indicate if changes were made. The images or other third party material in this 
article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the 
material. If material is not included in the article’s Creative Commons licence and your intended use is not 
permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from 
the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.
© The Author(s) 2023

Progressive daily hopping exercise improves running economy in amateur runners: a randomized and controlled trial.
Engeroff, Tobias,Kalo, Kristin,Merrifield, Ryan,Groneberg, David,Wilke, Jan