A vertical bar chart showing the time spent in each heart rate training zone (Z1–Z5) during a workout or training period. Each bar uses the conventional zone color semantics (grey for Z1 recovery, blue for Z2 endurance, green for Z3 aerobic, orange for Z4 threshold, red for Z5 maximum) and is annotated with its duration, making the distribution of training intensity immediately readable. This is the standard summary chart found in fitness platforms such as Garmin, Strava, and Polar, and it reveals at a glance whether a session was easy, balanced, or high-intensity.
""" anyplot.ai
bar-heart-rate-zones: Time in Heart Rate Zones Bar Chart
Library: matplotlib 3.11.0 | Python 3.13.13
Quality: 89/100 | Created: 2026-06-14
"""
import os
import pathlib
import sys
# Remove this script's directory from sys.path so `import matplotlib` resolves
# to the installed package, not this file (which shares the name).
_HERE = str(pathlib.Path(__file__).parent.resolve())
sys.path = [p for p in sys.path if p != _HERE]
import matplotlib.pyplot as plt
import numpy as np
# Save outputs next to this script regardless of CWD
_OUT = pathlib.Path(__file__).parent
# Theme tokens (Imprint palette — theme-adaptive chrome)
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
# Semantic zone colors — fitness convention: grey / blue / green / ochre / red
# Imprint palette members chosen by semantic exception (each zone has a strong hue convention)
ZONE_COLORS = [INK_MUTED, "#4467A3", "#009E73", "#BD8233", "#AE3030"]
# Data — 60-minute tempo run
zone_ids = ["Z1", "Z2", "Z3", "Z4", "Z5"]
zone_names = ["Recovery", "Endurance", "Aerobic", "Threshold", "Maximum"]
minutes = [8, 22, 15, 12, 3]
hr_ranges = ["< 115 bpm", "115–138 bpm", "138–156 bpm", "156–169 bpm", "> 169 bpm"]
bar_labels = [f"{m} min" for m in minutes]
tick_labels = [f"{zid} {name}\n{hr}" for zid, name, hr in zip(zone_ids, zone_names, hr_ranges, strict=True)]
# Plot
x = np.arange(len(zone_ids))
fig, ax = plt.subplots(figsize=(8, 4.5), dpi=400, facecolor=PAGE_BG)
ax.set_facecolor(PAGE_BG)
bars = ax.bar(x, minutes, color=ZONE_COLORS, width=0.55, zorder=2, edgecolor=PAGE_BG, linewidth=1.5)
# Emphasize the dominant Z2 bar (highest duration — 22 min)
dominant_idx = minutes.index(max(minutes))
bars[dominant_idx].set_edgecolor(INK)
bars[dominant_idx].set_linewidth(2.0)
bars[dominant_idx].set_zorder(3)
# Idiomatic bar labels via ax.bar_label() (available since matplotlib 3.4)
ax.bar_label(bars, labels=bar_labels, fontsize=9, fontweight="bold", padding=4, color=INK)
# Style
title = "bar-heart-rate-zones · python · matplotlib · anyplot.ai"
ax.set_title(title, fontsize=12, fontweight="medium", color=INK, pad=14)
ax.set_ylabel("Time (minutes)", fontsize=10, color=INK, labelpad=10)
ax.set_xlabel("Heart Rate Training Zone", fontsize=10, color=INK, labelpad=14)
ax.set_xticks(x)
ax.tick_params(axis="both", which="both", length=0, labelsize=9, labelcolor=INK_SOFT)
ax.set_xticklabels(tick_labels, fontsize=9, color=INK_SOFT)
ax.yaxis.grid(True, alpha=0.15, linewidth=0.8, color=INK, zorder=0)
ax.spines["top"].set_visible(False)
ax.spines["right"].set_visible(False)
ax.spines["left"].set_color(INK_SOFT)
ax.spines["bottom"].set_color(INK_SOFT)
ax.set_xlim(-0.6, 4.6)
ax.set_ylim(0, max(minutes) * 1.22)
# Total training time — anchors the workout narrative
ax.text(
0.98,
0.97,
"Total: 60 min",
ha="right",
va="top",
transform=ax.transAxes,
fontsize=9,
fontweight="medium",
color=INK_SOFT,
)
fig.subplots_adjust(left=0.12, right=0.97, top=0.88, bottom=0.24)
# Save
plt.savefig(_OUT / f"plot-{THEME}.png", dpi=400, facecolor=PAGE_BG)
plt.close()
Part of Time in Heart Rate Zones Bar Chart on anyplot.ai.